Title:
Refigeration system
Kind Code:
A1
Abstract:
In a refrigeration system having a refrigerant circuit (20) that is constructed in such a way that a plurality of lines of refrigeration circuits (70, 80) having refrigeration heat exchangers (72, 84) respectively are connected to an outdoor circuit (30) provided with an outdoor heat exchanger (32) and a compression mechanism (31) and conducts a vapor compression type refrigeration cycle, at least one of the lines of refrigeration circuits (80) having an auxiliary compressor (85) connected in series to the refrigeration heat exchanger (84), in order to respond to a variety of patterns of defrosting operations without providing a defrosting mechanism other than the refrigerant circuit (20), there is provided a hot gas introduction passage (46, 89) for selectively introducing gas refrigerant discharged from the compression mechanism (31) of the outdoor circuit (30) into at least one of the plurality of refrigeration heat exchangers (72, 84) and a defrosting operation of conducting a refrigeration cycle by using the refrigeration heat exchanger (72, 84) as a condenser can be performed.


Inventors:
Takegami, Masaai (Osaka, JP)
Application Number:
11/921499
Publication Date:
05/21/2009
Filing Date:
05/30/2006
Primary Class:
International Classes:
F25B1/10
View Patent Images:
Attorney, Agent or Firm:
BIRCH STEWART KOLASCH & BIRCH (PO BOX 747, FALLS CHURCH, VA, 22040-0747, US)
Claims:
1. A refrigeration system having a refrigerant circuit (20) that is constructed in such a way that a plurality of lines of refrigeration circuits (70, 80) having refrigeration heat exchangers (72, 84) respectively are connected to an outdoor circuit (30) provided with an outdoor heat exchanger (32) and a compression mechanism (31) and conducts a vapor compression type refrigeration cycle, at least one of the lines of refrigeration circuits (80) having an auxiliary compressor (85) connected in series to the refrigeration heat exchanger (84), the refrigeration system comprising: a hot gas introduction passage (46, 89), (100, 102) for selectively introducing gas refrigerant discharged from the compression mechanism (31) of the outdoor circuit (30) into at least one of the plurality of refrigeration heat exchangers (72, 84); and a defrosting path (25) capable of performing a defrosting operation of conducting a refrigeration cycle by using that refrigeration heat exchanger (72, 84) as a condenser.

2. The refrigeration system according to claim 1, wherein the outdoor circuit (30) has a first refrigeration circuit (70) and a second refrigeration circuit (80) connected thereto in parallel, the first refrigeration circuit (70) having a first refrigeration heat exchanger (72), the second refrigeration circuit (80) having a second refrigeration heat exchanger (84) and the auxiliary compressor (85).

3. The refrigeration system according to claim 1, wherein the outdoor circuit (30) has a plurality of refrigeration circuits (80) connected thereto in parallel, each of the plurality of refrigeration circuits (80) having the refrigeration heat exchanger (84) and the auxiliary compressor (85).

4. The refrigeration system according to claim 1, wherein: the outdoor circuit (30) has an air heat exchanger circuit (60) connected thereto, the air heat exchanger circuit (60) having an air heat exchanger (62) for adjusting temperature of air; and a first defrosting operation and a second defrosting operation can be performed, the first defrosting operation using the refrigeration heat exchangers (72, 84) as condensers and using the air heat exchanger (62) as an evaporator, the second defrosting operation using the refrigeration heat exchangers (72, 84) as condensers and using the outdoor heat exchanger (32) as an evaporator.

5. The refrigeration system according to claim 1, wherein the hot gas introduction passage (46, 89) has a high stage side hot gas passage (46) and a low stage side hot gas passage (89), the high stage side hot gas passage (46) being connected to a discharge line (45) of the compression mechanism (31) of the outdoor circuit (30) and to a base pipe (42) of a low-pressure gas line of the respective refrigeration circuits (70, 80) and allowing a refrigerant flow to the respective refrigeration heat exchangers (72, 84) from the discharge line (45) of the compression mechanism (31) at a time of a defrosting operation, the low stage side hot gas passage (89) being connected to a discharge line (22b) and a suction line (88) of the auxiliary compressor (85) and allowing a refrigerant flow to the refrigeration heat exchanger (84) connected to the auxiliary compressor (85) from the discharge line (22b) of the auxiliary compressor (85) at the time of the defrosting operation.

6. The refrigeration system according to claim 5, wherein: the compression mechanism (31) of the outdoor circuit (30) includes: a first compressor (31a), a second compressor (31b), and a third compressor (31c), which are connected in parallel; a four-way switching valve (37) connected to an suction side of the compression mechanism (31); a high stage side opening/opening valve (SV1) disposed in the high stage side hot gas passage (46); and a low stage side opening/opening valve (SV2) disposed in the low stage side hot gas passage (89), the first compressor (31a) having its suction pipe (41a) connected to a first port (P1) of the four-way switching valve (37) via a check valve (CV1) for prohibiting a refrigerant flow to the first compressor (31a), the second compressor (31b) having its suction pipe (41b) connected to a second port (P2) of the four-way switching valve (37), the third compressor (31c) having its suction pipe (41c) connected to a third port (P3) of the four-way switching valve (37) via a check valve (CV2) for prohibiting a refrigerant flow to the third compressor (31c), the compression mechanism (31) having its high-pressure introduction pipe (47) communicating with a high pressure line connected to a fourth port (P4) of the four-way switching valve (37); the high stage side hot gas passage (46) is connected to the suction pipe (41a) of the first compressor (31a); and the four-way switching valve (37) is constructed so as to be able to switch between a first state in which the first port (P1) communicates with the second port (P2) and in which the third port (P3) communicates with the fourth port (P4) and a second state in which the first port (P1) communicates with the fourth port (P4) and in which the second port (P2) communicates with the third port (P3).

7. The refrigeration system according to claim 5, wherein: the compression mechanism (31) of the outdoor circuit (30) includes: a first compressor (31a), a second compressor (31b), and a third compressor (31c), which are connected in parallel; a four-way switching valve (37) connected to a suction side of the compression mechanism (31); and a low stage side opening/opening valve (SV2) disposed in the low stage side hot gas passage (89), the first compressor (31a) having its suction pipe 41a connected to a first port (P1) of the four-way switching valve (37), the second compressor (31b) having its suction pipe (41b) connected to a second port (P2) of the four-way switching valve (37), the third compressor (31c) having its suction pipe (41c) connected to a third port (P3) of the four-way switching valve (37) via a check valve (CV2) for prohibiting a refrigerant flow to the third compressor (31c); the high stage side hot gas passage (46) is connected to a fourth port (P4) of the four-way switching valve (37); and the four-way switching valve (37) is constructed so as to be able to switch between a first state in which the first port (P1) communicates with the fourth port (P4) and in which the second port (P2) communicates with the third port (P3) and a second state in which the first port (P1) communicates with the second port (P2) and in which the third port (P3) communicates with the fourth port (P4).

8. The refrigeration system according to claim 1, wherein the hot gas passage (46, 89) includes a first introduction passage (96) and a second introduction passage (97), the first introduction passage (96) introducing gas refrigerant discharged from the compression mechanism (31) of the outdoor circuit (30) into the auxiliary compressor (85), the second introduction passage (97) introducing gas refrigerant discharged from the auxiliary compressor (85) into the refrigeration heat exchanger (84).

9. The refrigeration system according to claim 8, wherein: the second introduction passage (97) is connected to the compression mechanism (31) of the outdoor circuit (30) and to the refrigeration heat exchanger (84); the first introduction passage (96) is branched from the second introduction passage (97) and is connected to the auxiliary compressor (85) so as to introduce part of gas refrigerant discharged from the compression mechanism (31) of the outdoor circuit (30) into the auxiliary compressor 85; and the second introduction passage (97) has a discharge pipe (98) of the auxiliary compressor (85) connected to its portion closer to the compression mechanism (31) of the outdoor circuit (30).

10. The refrigeration system according to claim 9, comprising a liquid injection passage (99) for introducing part of liquid refrigerant flowing out of the refrigeration heat exchanger (84) into the auxiliary compressor (85).

11. The refrigeration system according to claim 9, wherein the auxiliary compressor (85) is constructed of a variable displacement compressor.

12. The refrigeration system according to claim 1, wherein the hot gas introduction passage (100, 102) is directly connected to a discharge line (45) of the compression mechanism (31) of the outdoor circuit (30) and to at least one of gas side piping (110, 112) of the refrigeration heat exchangers (72, 84).

13. The refrigeration system according to claim 12, wherein the hot gas introduction passage (100, 102) is connected to the discharge line (45) of the compression mechanism (31) of the outdoor circuit (30) and to the gas side piping (110, 112) of the plurality of refrigeration heat exchangers (72, 84) and is provided with a switching mechanism (103) capable of switching or selecting the plurality of refrigeration heat exchangers (72, 84).

14. The refrigeration system according to claim 12, wherein the hot gas introduction passage (100, 102) is provided with a flow control mechanism (101).

Description:

TECHNICAL FIELD

The present invention relates to a refrigeration system having a refrigerant circuit of a vapor compression type refrigeration cycle such that plural lines of refrigeration circuits each having a refrigeration heat exchanger are connected in parallel to an outdoor circuit provided with an outdoor heat exchanger and a compression mechanism, and in particular, to a refrigeration system such that at least one line of refrigeration circuit has an auxiliary compressor connected in series to a refrigeration heat exchanger.

BACKGROUND ART

A refrigeration system for conducting a refrigeration-cycle has been known and has been widely used as a refrigeration unit of a chiller unit or a freezer unit (or a chiller showcase or a freezer showcase) for storing foods and the like. For example, patent document 1 discloses a refrigeration system provided with plural heat exchangers for refrigerating the interior of a chiller unit or the like. In this refrigeration system, a chiller heat exchanger for chilling the interior of a chiller showcase of a chiller unit and a freezer heat exchanger for freezing the interior of a freezer showcase of a freezer unit are connected in parallel to one outdoor unit. Moreover, in this refrigeration system, an auxiliary compressor is interposed between the freezer heat exchanger and the outdoor unit in addition to a compression mechanism (main compressor) of the outdoor unit. In this refrigeration system, a single-stage refrigeration cycle, which uses the chiller heat exchanger as an evaporator, and a two-stage refrigeration cycle, which uses the freezer heat exchanger as an evaporator and uses the auxiliary compressor as a low-stage compressor, are conducted by one refrigerant circuit.

The refrigeration system of this kind presents a problem that when moisture in air adheres to a chiller heat exchanger or a freezer heat exchanger and freezes there, the refrigeration of air in the refrigerator is impaired by the adhering frost. For this reason, it is necessary to melt the frost adhering to these heat exchangers, that is, to defrost the refrigeration heat exchangers.

Here, in the refrigeration system disclosed in the patent document 1, the evaporation temperature of refrigerant in the freezer heat exchange is set comparatively low and hence the problem of the frost developed in the freezer heat exchanger becomes particularly serious. For this reason, the refrigeration system conducts a refrigeration cycle for circulating refrigerant through the auxiliary compressor, the freezer heat exchanger, an expansion valve for the chiller heat exchanger, and the chiller heat exchanger in this order to defrost the freezer heat exchanger.

To this end, the refrigerant circuit of the refrigeration system is provided with a switching mechanism capable of switching between a first operation for a cooling operation in which the auxiliary compressor sucks refrigerant from the freezer heat exchanger and discharges the refrigerant to the suction side of the compression mechanism of the outdoor unit and a second operation for a defrosting operation in which the auxiliary compressor sucks refrigerant from the chiller heat exchanger and discharges the refrigerant to the freezer heat exchanger.

During the defrosting operation for defrosting the freezer heat exchanger, the refrigerant circuit sends the refrigerant from the freezer heat exchanger to the chiller heat exchanger while performing the second operation. During the defrosting operation, the refrigerant absorbs heat from air in the chiller showcase by the chiller heat exchanger, thereby being evaporated, and is sucked by the auxiliary compressor and is compressed by the auxiliary compressor and is sent to the freezer heat exchanger. The refrigerant dissipates heat in the freezer heat exchanger, thereby being condensed, and the heat melts the frost. The condensed refrigerant is expanded by an expansion valve before the chiller heat exchanger and then is returned to the chiller heat exchanger and absorbs heat from the air in the chiller showcase, thereby being evaporated. In this manner, in the refrigeration system, the freezer heat exchanger is defrosted by the use of heat that the refrigerant recovers from the air in the chiller showcase when the refrigerant flows through the auxiliary compressor, the freezer heat exchanger, the expansion valve, and the chiller heat exchanger in this order.

[Patent document 1] Japanese Unexamined Patent Publication No. 2004-353995

However, in the refrigeration system, when there arises a problem that moisture in air adheres to a chiller heat exchanger and freezes there to develop frost, whereby the refrigeration of air in the refrigerator is impaired, it is impossible to defrost the chiller heat exchanger by the heat of the refrigerant. Thus, to defrost the chiller heat exchanger, the refrigeration system needs to be provided with a defrosting mechanism such as an electric heater in addition to the refrigerant circuit, which presents a problem that the construction of the refrigeration system becomes complex.

Moreover, in the above-mentioned refrigeration system, the freezer heat exchanger is defrosted by using the chiller heat exchanger as a heat source, so it is necessary to bring the chiller heat exchanger and the freezer heat exchanger into a good balance between heat absorption and heat dissipation at the time of the defrosting operation. There is presented also a problem that this imposes a restriction on design.

The present invention has been made in view of these problems. The object of the present invention is to provide a refrigeration system capable of responding to a variety of patterns of defrosting operations without providing a defrosting mechanism except for a refrigerant circuit and of preventing the action of defrosting a refrigeration heat exchanger such as a chiller heat exchanger and a freezer heat exchanger from imposing a restriction on the design of these heat exchangers.

DISCLOSURE OF THE INVENTION

A first aspect of the invention is predicated on a refrigeration system having a refrigerant circuit 20 that is constructed in such a way that a plurality of lines of refrigeration circuits 70, 80 having refrigeration heat exchangers 72, 84 respectively are connected to an outdoor circuit 30 provided with an outdoor heat exchanger 32 and a compression mechanism 31 and conducts a vapor compression type refrigeration cycle, at least one of the lines of refrigeration circuits 80 having an auxiliary compressor 85 connected in series to the refrigeration heat exchanger 84.

This refrigeration system is characterized by including: a hot gas introduction passage 46, 89, 100, 102 for selectively introducing gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into at least one of the plurality of refrigeration heat exchangers 72, 84; and a defrosting path 25 capable of performing a defrosting operation of conducting a refrigeration cycle by using that refrigeration heat exchanger 72, 84 as a condenser.

In this first aspect of the invention, at the time of the defrosting operation, high-temperature refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is introduced into at least one of the plurality of refrigeration heat exchangers 72, 84 via the hot gas introduction passage 46, 89, 100, 102 and the operation of a refrigeration cycle using that refrigeration heat exchanger 72, 84 as a condenser is performed. Thus, frost adhering to that refrigeration heat exchanger 72, 84 is melted by heat absorbed by the heat exchanger used as an evaporator at that time and by heat produced by compressing the refrigerant in the compression mechanism 31. This defrosting operation can be performed by selecting the refrigeration heat exchanger 72, 84 because the hot gas introduction passage 46, 89, 100, 102 is provided.

A second aspect of the invention is characterized in that in the first aspect of the invention, the outdoor circuit 30 has a first refrigeration circuit 70 and a second refrigeration circuit 80 connected thereto in parallel, the first refrigeration circuit 70 having a first refrigeration heat exchanger 72, the second refrigeration circuit 80 having a second refrigeration heat exchanger 84 and the auxiliary compressor 85. The first refrigeration circuit 70 can be made a chiller circuit for chilling a chiller or a chiller showcase. The second refrigeration circuit 80 can be made a freezer circuit for freezing a freezer or a freezer showcase, for example.

In this second aspect of the invention, in the refrigeration system provided with the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84, by using the hot gas introduction passage 46, 89, the defrosting operation can be performed by a refrigeration cycle using at least one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 as a condenser. For example, the operation of defrosting only one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 can be performed or the operation of defrosting both of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 at the same time can be performed.

A third aspect of the invention is characterized in that in the first aspect of the invention, the outdoor circuit 30 has a plurality of refrigeration circuits 80 connected thereto in parallel, each of the plurality of refrigeration circuits 80 having the refrigeration heat exchanger 84 and the auxiliary compressor 85. This refrigeration circuit can be made a freezer circuit for freezing a freezer or a freezer showcase, for example.

In this third aspect of the invention, in the refrigeration system provided with a plurality of refrigeration heat exchangers 84, by using the hot gas introduction passage 46, 89, the defrosting operation can be performed by a refrigeration cycle using at least one of the plural refrigeration heat exchangers 84 as a condenser. For example, when there are provided two refrigeration heat exchangers 84, the operation of defrosting only one of the refrigeration heat exchangers 84 can be performed or the operation of defrosting both of the refrigeration heat exchangers 84 at the same time can be performed.

A fourth aspect of the invention is characterized in: that in any one of the first aspect of the invention to the third aspect of the invention, the outdoor circuit 30 has an air heat exchanger circuit (e.g., air-conditioning circuit) 60 connected thereto, the air heat exchanger circuit 60 having an air heat exchanger (e.g., air-conditioning heat exchanger) 62 for adjusting temperature of air; and that a first defrosting operation and a second defrosting operation can be performed, the first defrosting operation using the refrigeration heat exchangers 72, 84 as condensers and using the air heat exchanger 62 as an evaporator, the second defrosting operation using the refrigeration heat exchangers 72, 84 as condensers and using the outdoor heat exchanger 32 as an evaporator.

In this fourth aspect of the invention, in the refrigeration system provided with the plurality of refrigeration heat exchangers 72, 84 and the air heat exchanger 62, by using the hot gas introduction passage 46, 89, a defrosting operation can be performed by a refrigeration cycle using at least one of the plural refrigeration heat exchangers 72, 84 as a condenser. Specifically, the first defrosting operation using at least one of the plural refrigeration heat exchangers 72, 84 as a condenser and using the air heat exchanger 62 as an evaporator and the second defrosting operation using at least one of the refrigeration heat exchangers 72, 84 as a condenser and using the outdoor heat exchanger 32 as an evaporator can be performed.

A fifth aspect of the invention is characterized in that in any one of the first aspect of the invention to the fourth aspect of the invention, the hot gas introduction passage 46, 89 has a high stage side hot gas passage 46 and a low stage hot gas passage 89, the high stage side hot gas passage 46 being connected to a discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to a base pipe 42 of a low-pressure gas line of the respective refrigeration circuits 70, 80 and allowing a refrigerant flow to the respective refrigeration heat exchangers 72, 84 from the discharge line 45 of the compression mechanism 31 at the time of a defrosting operation, the low stage side hot gas passage 89 being connected to a discharge line 22b and a suction line 88 of the auxiliary compressor 85 and allowing a refrigerant flow to the refrigeration heat exchanger 84 connected to the auxiliary compressor 85 from the discharge line 22b of the auxiliary compressor 85 at the time of the defrosting operation.

In this fifth aspect of the invention, at the time of the defrosting operation, gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30, first, flows through the base pipe 42 of the low-pressure gas line of the respective refrigeration circuits 70, 80 from high stage side hot gas passage 46 to the respective refrigeration heat exchangers 72, 84. Then, for example, in a first refrigeration circuit (for example, chiller circuit) 70 not provided with the auxiliary compressor 85, the discharged gas refrigerant flows into a first refrigeration heat exchanger (for example, chiller heat exchanger) 72 and the refrigeration heat exchanger 72 functions as a condenser. Moreover, in a second refrigeration circuit (for example, freezer circuit) 80 provided with the auxiliary compressor 85, the discharged gas refrigerant flows through the low stage side hot gas passage 89 and flows into a second refrigeration heat exchanger (for example, freezer heat exchanger) 84 and the refrigeration heat exchanger 84 functions as a condenser.

Then, by selectively introducing the discharged gas refrigerant into the respective refrigeration heat exchangers 72, 84, frost adhering to at least one of the refrigeration heat exchangers 72, 84 is melted. For example, in the construction of the second aspect of the invention, the operation of defrosting only one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 can be performed or the operation of defrosting both of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 at the same time can be performed. When two refrigeration heat exchangers 84 are provided in the construction of the third aspect of the invention, the operation of defrosting only one of the refrigeration heat exchangers 84 can be performed or the operation of defrosting both of the refrigeration heat exchangers 84 at the same time can be performed. At this time, in the refrigeration heat exchanger 84 having the auxiliary heat exchanger 85 connected thereto, by stopping introducing the discharged gas refrigerant through the low stage side hot gas passage 89, there can be brought about a state in which the defrosting operation is not performed.

A sixth aspect of the invention is characterized in: that in the fifth aspect of the invention, the compression mechanism 31 of the outdoor circuit 30 includes: a first compressor 31a, a second compressor 31b, and a third compressor 31c, which are connected in parallel; a four-way switching valve 37 connected to an suction side of the compression mechanism 31; a high stage side opening/opening valve SV1 disposed in the high stage side hot gas passage 46; and a low stage side opening/opening valve SV2 disposed in the low stage side hot gas passage 89, the first compressor 31a having its suction pipe 41a connected to a first port P1 of the four-way switching valve 37 via a check valve CV1 for prohibiting a refrigerant flow to the first compressor 31a, the second compressor 31b having its suction pipe 41b connected to a second port P2 of the four-way switching valve 37, the third compressor 31c having its suction pipe 41c connected to a third port P3 of the four-way switching valve 37 via a check valve CV2 for prohibiting a refrigerant flow to the third compressor 31c, the compression mechanism 31 having its high-pressure introduction pipe 47 communicating with a high pressure line connected to a fourth port P4 of the four-way switching valve 37; that the high stage side hot gas passage 46 is connected to the suction pipe 41a of the first compressor 31a; and that the four-way switching valve 37 is constructed so as to be able to switch between a first state in which the first port P1 communicates with the second port P2 and in which the third port P3 communicates with the fourth port P4 and a second state in which the first port P1 communicates with the fourth port P4 and in which the second port P2 communicates with the third port P3.

In this sixth aspect of the invention, at the time of the defrosting operation, the four-way switching valve 37 is set to the second state and the high stage side opening/opening valve SV1 and the low stage side opening/opening valve SV2 are opened and two or one of the second compressor 31b and the third compressor 31c of the compression mechanism 31 is actuated. In this state, the gas refrigerant discharged from the compression mechanism 31 passes first from the high stage side hot gas passage 46 through the base pipe 42 of the low pressure line of the respective refrigeration circuits 70, 80 to the respective refrigeration heat exchangers 72, 84. Next, for example, in the first refrigeration circuit (for example, chiller circuit) 70 not provided with the auxiliary compressor 85, the discharged gas refrigerant flows into the first refrigeration heat exchangers (for example, chiller heat exchanger) 72 and the heat exchanger 72 functions as a condenser. Moreover, in the second refrigeration circuit (for example, freezer circuit) 80 provided with the auxiliary compressor 85, the discharged gas refrigerant flows through the low stage side hot gas passage 89 and flows into the second refrigeration heat exchanger (for example, freezer heat exchanger) 84 and the heat exchanger 84 functions as a condenser.

By selectively introducing the discharged gas refrigerant into the respective refrigeration heat exchangers 72, 84, frost adhering to at least one of the respective refrigeration heat exchangers 72, 84 is melted. For example, in the construction of the second aspect of the invention, the operation of defrosting only one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 can be performed or the operation of defrosting both of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 at the time can be performed. When two refrigeration heat exchangers 84 are provided in the construction of the third aspect of the invention, the operation of defrosting only one of the first refrigeration heat exchangers 84 can be performed or the operation of defrosting both of the refrigeration heat exchangers 84 at the time can be performed. At that time, in the refrigeration heat exchanger 84 having the auxiliary compressor 85 connected thereto, by closing the low stage side opening/opening valve SV2 to stop introducing the discharged gas refrigerant through the low stage side hot gas passage 89, there can be brought about a state in which the defrosting operation is not performed. Moreover, the low-pressure gas refrigerant having finished an expansion process and an evaporation process after a condensation process in the refrigeration heat exchangers 72, 84 passes through the four-way switching valve 37, the suction pipe 41b, and the suction pipe 41c and then is sucked by the second compressor 32b and the third compressor 31c.

A seventh aspect of the invention is characterized in: that in the fifth aspect of the invention, the compression mechanism 31 of the outdoor circuit 30 includes: a first compressor 31a, a second compressor 31b, and a third compressor 31c, which are connected in parallel; a four-way switching valve 37 connected to a suction side of the compression mechanism 31; and a low stage side opening/closing valve SV2 disposed in the low stage side hot gas passage 89, the first compressor 31a having its suction pipe 41a connected to a first port P1 of the four-way switching valve 37, the second compressor 31b having its suction pipe 41b connected to a second port P2 of the four-way switching valve 37, the third compressor 31c having its suction pipe 41c connected to a third port P3 of the four-way switching valve 37 via a check valve CV2 for prohibiting a refrigerant flow to the third compressor 31c; that the high stage side hot gas passage 46 is connected to a fourth port P4 of the four-way switching valve 37; and that the four-way switching valve 37 is constructed so as to be able to switch between a first state in which the first port P1 communicates with the fourth port P4 and in which the second port P2 communicates with the third port P3 and a second state in which the first port P1 communicates with the second port P2 and in which the third port P3 communicates with the fourth port P4.

In this seventh aspect of the invention, at the time of the defrosting operation, the four-way switching valve 37 is set to the second state and the low stage side opening/closing valve SV2 is opened and two or one of the second compressor 31b and the third compressor 31c of the compression mechanism 31 is actuated. In this state, the gas refrigerant discharged from the compression mechanism 31 passes first from the high stage side hot gas passage 46 and the four-way switching valve 37 through the base pipe 42 of the low pressure line of the respective refrigeration circuits 70, 80 to the respective refrigeration heat exchangers 72, 84. Next, for example, in the first refrigeration circuit (for example, chiller circuit) 70 not provided with the auxiliary compressor 85, the discharged gas refrigerant flows into the first refrigeration heat exchanger (for example, chiller heat exchanger) 72 and the heat exchanger 72 functions as a condenser. Moreover, in the second refrigeration circuit (for example, freezer circuit) 80 provided with the auxiliary compressor 85, the discharged gas refrigerant flows through the low stage side hot gas passage 89 and flows into the second refrigeration heat exchanger (for example, freezer heat exchanger) 84 and the heat exchanger 84 functions as a condenser.

By selectively introducing the discharged gas refrigerant into the respective refrigeration heat exchangers 72, 84, frost adhering to at least one of the respective refrigeration heat exchangers 72, 84 is melted. For example, in the construction of the second aspect of the invention, the operation of defrosting only one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 can be performed or the operation of defrosting both of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 at the same time can be performed. When two refrigeration heat exchangers 84 are provided in the construction of the third aspect of the invention, the operation of defrosting only one of the refrigeration heat exchangers 84 can be performed or the operation of defrosting both of the refrigeration heat exchangers 84 at the same time can be performed. At that time, in the refrigeration heat exchanger 84 having the auxiliary compressor 85 connected thereto, by closing the low stage side opening/closing valve SV2 to stop introducing the discharged gas refrigerant through the low stage side hot gas passage 89, there can be brought about a state in which the defrosting operation is not performed. Moreover, the low-pressure gas refrigerant having finished an expansion process and an evaporation process after a condensation process in the refrigeration heat exchangers 72, 84 passes through the four-way switching valve 37, the suction pipe 41b, and the suction pipe 41c and then is sucked by the second compressor 32b and the third compressor 31c.

An eighth aspect of the invention is characterized in that in the first aspect of the invention, the hot gas passage 46, 89 includes a first introduction passage 96 and a second introduction passage 97, the first introduction passage 96 introducing gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into the auxiliary compressor 85, the second introduction passage 97 introducing gas refrigerant discharged from the auxiliary compressor 85 into the refrigeration heat exchanger 84.

In this eighth aspect of the invention, the gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is introduced into the auxiliary compressor 85 via the first introduction passage 96 and is compressed by the auxiliary compressor 85 and then the gas refrigerant discharged from the auxiliary compressor 85 is introduced into the refrigeration heat exchanger 84 via the second introduction passage 97 and is used for defrosting the refrigeration heat exchanger 84. As described above, at the time of defrosting operation of this eighth aspect of the invention, the refrigerant is compressed by both of the compression mechanism 31 of the outdoor circuit 30 and the auxiliary compressor 85, so heat given to the refrigerant at the time of the defrosting operation can be increased.

A ninth aspect of the invention is characterized in: that in the eighth aspect of the invention, the second introduction passage 97 is connected to the compression mechanism 31 of the outdoor circuit 30 and to the refrigeration heat exchanger 84; that the first introduction passage 96 is branched from the second introduction passage 97 and is connected to the auxiliary compressor 85 so as to introduce part of gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into the auxiliary compressor 85; and that the second introduction passage 97 has a discharge pipe 98 of the auxiliary compressor 85 connected to its portion closer to the compression mechanism 31 of the outdoor circuit 30.

In this ninth aspect of the invention, part of the gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is introduced into the auxiliary compressor 85 via the first introduction passage 96 and is further compressed by the auxiliary compressor 85. Then, the gas refrigerant discharged from the auxiliary compressor 85 is merged with the gas refrigerant discharged from the compression mechanism 31 and flowing through the second introduction passage 97 and the refrigerant after merging is introduced into the refrigeration heat exchanger 84 and is used for defrosting the refrigeration heat exchanger 84. As described above, at the time of the defrosting operation of this ninth aspect of the invention, in the nearly same manner in the eighth aspect of the invention, the refrigerant is compressed by both of the compression mechanism 31 of the outdoor circuit 30 and the auxiliary compressor 85, so heat given to the refrigerant at the time of the defrosting operation can be increased.

A tenth aspect of the invention is characterized in that the ninth aspect of the invention, there is provided a liquid injection passage 99 for introducing part of liquid refrigerant flowing out of the refrigeration heat exchanger 84 into the auxiliary compressor 85.

In this tenth aspect of the invention is performed a liquid injecting operation for supplying the auxiliary compressor 85 with part of the refrigerant condensed by the refrigeration heat exchanger 84 and brought into a liquid state in the ninth aspect of the invention. As a result, the refrigerant sucked by the auxiliary compressor 85 is refrigerated. For this reason, it is possible to prevent the temperature of the gas refrigerant discharged from the auxiliary compressor 85 from being increased excessively as compared with a case where the liquid injecting operation is not performed.

An eleventh aspect of the invention is characterized in that in the ninth aspect of the invention, the auxiliary compressor 85 is constructed of a variable displacement compressor.

When the defrosting operation is performed in the ninth aspect of the invention, the temperature of the gas refrigerant discharged from the auxiliary compressor 85 is easily increased. However, in this eleventh aspect of the invention, the control of lowering an operating capacity is performed to prevent the temperature of the gas refrigerant discharged from the auxiliary compressor 85 from being excessively increased.

A twelfth aspect of the invention is characterized in that in the first aspect of the invention, the hot gas introduction passage 100, 102 is directly connected to a discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to at least one of gas side piping 110, 112 of the refrigeration heat exchangers 72, 84.

In this twelfth aspect of the invention, the high-temperature gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is introduced into at least one of the refrigeration heat exchangers 72, 84 from the gas side. Thus, the defrosting operation can be performed by using this refrigeration heat exchanger 72, 84 as a condenser and by using the other refrigeration heat exchanger as an evaporator.

A thirteenth aspect of the invention is characterized in that in the twelfth aspect of the invention, the hot gas introduction passage 100, 102 is connected to a discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to gas side piping 110, 112 of the plurality of refrigeration heat exchangers 72, 84 and is provided with a switching mechanism 103 capable of switching or selecting the plurality of refrigeration heat exchangers 72, 84.

In this thirteenth aspect of the invention, the defrosting operation can be performed by switching or selecting the plurality of refrigeration heat exchangers 72, 84.

A fourteenth aspect of the invention is characterized in that in the twelfth aspect of the invention or the thirteenth aspect of the invention, the hot gas introduction passage 100, 102 is provided with a flow control mechanism 101.

In this fourteenth aspect of the invention, the flow of the high-temperature gas refrigerant flowing through the hot gas introduction passage 100, 102 can be controlled.

EFFECTS OF THE INVENTION

According to the present invention, in the refrigeration system in which at least one line of refrigeration circuit 80 of the plurality of lines of refrigeration circuits 70, 80 connected in parallel to each other has the auxiliary compressor 85 connected in series to the refrigeration heat exchanger 84, there is provided the hot gas introduction passage 46, 89, 100, 102 for selectively introducing the gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into at least one of the plurality of refrigeration heat exchangers 72, 84 and the defrosting operation by the refrigeration cycle using the refrigeration heat exchanger 72, 84 as the condenser can be performed. Thus, the refrigeration heat exchangers 72, 84 can be defrosted by the use of heat absorbed by the outdoor heat exchanger 32 and heat produced by compressing the refrigerant by the compression mechanism 31. Further, when the refrigeration system is provided with an air-conditioning circuit, the refrigeration heat exchangers 72, 84 can be defrosted by the use of heat absorbed by the air-conditioning heat exchanger 62 at the time of the cooling operation and heat produced by compressing the refrigerant by the compression mechanism 31.

For this reason, even if the refrigeration system is not provided with a dedicated defrosting mechanism such as an electric heater in addition to the refrigerant circuit 20, the refrigeration system can perform a variety of patterns of defrosting operations. Thus, it is possible to prevent the construction of the refrigeration system from becoming complex. Moreover, unlike a refrigeration system in the related art in which a freezer heat exchanger is defrosted by using a chiller heat exchanger as a heat source, in this refrigeration system, it is not always necessary to bring the plural refrigeration heat exchangers 72, 84 into a good balance between heat absorption and heat dissipation at the time of the defrosting operation, so it is possible to enhance the degree of flexibility in designing the refrigeration system.

According to the second aspect of the invention, in the refrigeration circuit, the first refrigeration circuit 70 and the second refrigeration circuit 80 are connected in parallel to the outdoor circuit 30, the first refrigeration circuit 70 having the first refrigeration heat exchanger 72, the second refrigeration circuit 80 having the second refrigeration heat exchanger 84 and an auxiliary compressor 85. Thus, the operation of defrosting only one of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 can be performed or the operation of defrosting both of the first refrigeration heat exchanger 72 and the second refrigeration heat exchanger 84 at the same time can be performed. For this reason, it is possible to perform a variety of patterns of defrosting operations.

According to the third aspect of the invention, the plurality of refrigeration circuits 80 each having a refrigeration heat exchanger 84 and an auxiliary compressor 85 are connected in parallel to the outdoor circuit 30 in the refrigeration circuit, so for example, when there are provided two refrigeration heat exchangers 84, the operation of defrosting only one of the refrigeration heat exchangers 84 can be performed or the operation of defrosting both of the refrigeration heat exchangers 84 at the same time can be performed.

For this reason, it is possible to perform a variety of patterns of defrosting operations. According to the fourth aspect of the invention, the plurality of refrigeration circuits 70, 80 and the air heat exchange circuit 60 are connected to the outdoor circuit 30, and the first defrosting operation using at least one of the plurality of refrigeration heat exchangers 72, 84 as a condenser and using the air heat exchanger 62 as an evaporator and the second defrosting operation using at least one of the refrigeration heat exchangers 72, 84 as a condenser and using the outdoor heat exchanger 32 as an evaporator can be performed. Thus, it is possible to perform a more variety of patterns of defrosting operations.

According to the fifth aspect of the invention, the hot gas introduction passage 46, 89 is constructed of the high stage side hot gas passage 46 and the low stage hot gas passage 89, the high stage side hot gas passage 46 allowing a refrigerant flow to the respective refrigeration heat exchangers 72, 84 from the discharge line 45 of the compression mechanism 31 at the time of the defrosting operation, the low stage side hot gas passage 89 allowing a refrigerant flow to the refrigeration heat exchanger 84 connected to the auxiliary compressor 85 from the discharge line 22b of the auxiliary compressor 85 at the time of the defrosting operation. Thus, the operation of selectively introducing the gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into the respective refrigeration heat exchangers 72, 84 at the time of the defrosting operation can be performed with reliability. Moreover, by selectively introducing the gas refrigerant discharged from the compression mechanism 31 into the respective refrigeration heat exchangers 72, 84 from the high stage side hot gas passage 46 and the low stage hot gas passage 89, it is possible to respond to a variety of patterns of defrosting operations.

According to the sixth aspect of the invention, in the refrigerant circuit 20 using three compressors 31a, 31b, 31c as the compression mechanism 31 of the outdoor circuit 30 and using the four-way switching valve 37 on the suction side and having the plurality of refrigeration heat exchangers 72, 84, it is possible to respond to a variety of patterns of defrosting operations without making the construction of the refrigerant circuit 20 complex.

According to the seventh aspect of the invention, just as with the sixth aspect of the invention, in the refrigerant circuit 20 using three compressors 31a, 31b, 31c as the compression mechanism 31 of the outdoor circuit 30 and using the four-way switching valve 37 on the suction side and having the plurality of refrigeration heat exchangers 72, 84, it is possible to respond to a variety of patterns of defrosting operations without making the construction of the refrigerant circuit 20 complex.

According to the eighth aspect of the invention, heat given to the refrigerant at the time of the defrosting operation can be increased, so the defrosting capacity of the refrigeration heat exchanger 84 can be increased. Thus, when the defrosting capacity is not sufficient, by performing the control of the present invention, the refrigeration heat exchanger 84 can be effectively defrosted.

According to the ninth aspect of the invention, just as with the eighth aspect of the invention, heat given to the refrigerant at the time of the defrosting operation can be increased, so the defrosting capacity of the refrigeration heat exchanger 84 can be increased. Thus, when the defrosting capacity is not sufficient, by performing the control of the present invention, the refrigeration heat exchanger 84 can be effectively defrosted.

According to the tenth aspect of the invention, by performing the liquid injecting operation at the time of defrosting operation in the ninth aspect of the invention, it is possible to avoid the temperature of the gas refrigerant discharged from the auxiliary compressor 85 from being abnormally increased and hence to protect the auxiliary compressor 85 with reliability.

According to the eleventh aspect of the invention, by decreasing the operating capacity of the auxiliary compressor 85 at the time of the defrosting operation in the ninth aspect of the invention, it is possible to avoid the temperature of the gas refrigerant discharged from the auxiliary compressor 85 from being abnormally increased and hence to protect the auxiliary compressor 85 with reliability.

According to the twelfth aspect of the invention, the hot gas introduction passage 100, 102 is directly connected to the discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to at least one of the gas side piping 110, 112 of the refrigeration heat exchangers 72, 84. Thus, the high-temperature gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is introduced into at least one of the refrigeration heat exchangers 72, 84 from the gas side. Thus, the defrosting operation can be performed by using this refrigeration heat exchanger 72, 84 as a condenser and by using the other refrigeration heat exchanger as an evaporator.

According to the thirteenth aspect of the invention, the hot gas introduction passage 100, 102 is connected to the discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to the gas side piping 110, 112 of the plurality of refrigeration heat exchangers 72, 84 and is provided with the switching mechanism 103 capable of switching or selecting the plurality of refrigeration heat exchangers 72, 84. Thus, the defrosting operation can be performed by switching or selecting the plurality of refrigeration heat exchangers 72, 84.

According to the fourteenth aspect of the invention, the hot gas introduction passage 100, 102 is provided with the flow control mechanism 101, so the flow of the high-temperature gas refrigerant flowing through the hot gas introduction passage 100, 102 can be controlled. Here, when the flow of the gas refrigerant flowing through the hot gas introduction passage 100, 102 is large, frost adhering to the refrigeration heat exchangers 72, 84 is melted at a stretch and hence the block of the frost around the refrigeration heat exchangers 72, 84 might be dropped. However, by decreasing the flow of the refrigerant, the frost can be gradually melted and hence it is possible to prevent the block of the frost from being dropped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram of a refrigeration system according to an embodiment 1.

FIG. 2 is a refrigerant circuit diagram showing an operation at the time of a cooling operation in the embodiment 1.

FIG. 3 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the cooling operation in the embodiment 1.

FIG. 4 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the cooling operation in the embodiment 1.

FIG. 5 is a refrigerant circuit diagram showing an operation at the time of a heating operation in the embodiment 1.

FIG. 6 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the heating operation in the embodiment 1.

FIG. 7 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the heating operation in the embodiment 1.

FIG. 8 is a refrigerant circuit diagram of a refrigeration system according to an embodiment 2.

FIG. 9 is a refrigerant circuit diagram showing an operation at the time of a cooling operation in the embodiment 2.

FIG. 10 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the cooling operation in the embodiment 2.

FIG. 11 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the cooling operation in the embodiment 2.

FIG. 12 is a refrigerant circuit diagram showing an operation at the time of a heating operation in the embodiment 2.

FIG. 13 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the heating operation in the embodiment 2.

FIG. 14 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the heating operation in the embodiment 2.

FIG. 15 is a refrigerant circuit diagram of a refrigeration system according to an embodiment 3.

FIG. 16 is a refrigerant circuit diagram showing an operation at the time of a cooling operation in the embodiment 3.

FIG. 17 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the cooling operation in the embodiment 3.

FIG. 18 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the cooling operation in the embodiment 3.

FIG. 19 is a refrigerant circuit diagram showing an operation at the time of a heating operation in the embodiment 3.

FIG. 20 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of the heating operation in the embodiment 3.

FIG. 21 is a refrigerant circuit diagram showing another example of the defrosting operation at the time of the heating operation in the embodiment 3.

FIG. 22 is a refrigerant circuit diagram showing an example of a defrosting operation at the time of a cooling operation in an embodiment 4.

FIG. 23 is a refrigerant circuit diagram of a refrigeration system according to an embodiment 5.

REFERENCE NUMERAL

  • 10 refrigeration system
  • 20 refrigerant circuit
  • 22b discharge line (freezer side branch gas pipe)
  • 25 defrosting path
  • 30 outdoor circuit
  • 31 compression mechanism
  • 31a DC inverter compressor (first compressor)
  • 31b first non-inverter compressor (second compressor)
  • 31c second non-inverter compressor (third compressor)
  • 32 outdoor heat exchanger
  • 37 third four-way switching valve
  • 41a first suction pipe (suction pipe)
  • 41b second suction pipe (suction pipe)
  • 41c third suction pipe (suction pipe)
  • 41c first low-pressure gas pipe (base pipe of a low-pressure gas line)
  • 45 discharge line (high-pressure gas pipe)
  • 46 high stage side hot gas passage (hot gas introduction passage)
  • 47 high-pressure introduction pipe
  • 48 air-conditioning circuit
  • 60 air-conditioning heat exchanger
  • 62 chiller circuit (refrigeration circuit)
  • 72 chiller heat exchanger (refrigeration heat exchanger)
  • 80 freezer circuit (refrigeration circuit)
  • 84 freezer heat exchanger (refrigeration heat exchanger)
  • 85 booster compressor (auxiliary compressor)
  • 88 suction line
  • 89 low stage side hot gas passage (hot gas introduction passage)
  • 96 first introduction passage
  • 97 second introduction passage
  • 98 discharge pipe
  • 99 liquid injection passage
  • 100 hot gas introduction passage
  • 101 flow control mechanism
  • 102 branch pipe (hot gas introduction passage)
  • 110 gas side piping
  • 112 gas side piping
  • CV1 check valve
  • CV2 check valve
  • P1 first port
  • P2 second port
  • P3 third port
  • P4 fourth port
  • SV1 high stage side opening/closing valve
  • SV2 low stage side opening/closing valve

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 of the Invention

An embodiment 1 of the present invention will be described. A refrigeration system 10 of this embodiment is installed in a convenience store or the like and air-conditions the store and refrigerates the interior of a showcase.

As shown in FIG. 1, the refrigeration system 10 of this embodiment has an outdoor unit 11, an air-conditioning unit 12, a chiller showcase 13 as a chiller unit, a freezer showcase 14 as a freezer unit. The outdoor unit 11 is installed outdoors. On the other hand, all of the air-conditioning unit 12, the chiller showcase 13, and the freezer showcase 14 are installed in the convenience store or the like.

The outdoor unit 11 is provided with an outdoor circuit 30. The air-conditioning unit 11 is provided with an air-conditioning circuit (air heat exchanger circuit) 60. The chiller showcase 13 is provided with a chiller circuit (first refrigeration circuit) 70. The freezer showcase 14 is provided with a freezer circuit (second refrigeration circuit) 80. In this refrigeration system 10, these circuits 30, 60, 70, and 80 are connected by piping to construct a refrigerant circuit 20. The refrigerant circuit 20 includes a chiller/freezer circuit and an air-conditioning circuit.

On the chiller/freezer side of the refrigerant circuit 20, the chiller circuit 70 and the freezer circuit 80 both of which are the refrigeration circuits are connected in parallel to the outdoor circuit 30. Specifically, the chiller circuit 70 and the freezer circuit 80 are connected to the outdoor circuit 30 via first liquid side connection piping 21 and first gas side connection piping 22. The first liquid side connection piping 21 has its one end connected to the outdoor circuit 20. The first liquid side connection piping 21 has its other end branched into two parts and has one (chiller side branch liquid pipe 21a) of the branched parts connected to the liquid side end of the chiller circuit 70 and has the other (freezer side branch liquid pipe 21b) of the branched parts connected to the liquid side end of the freezer circuit 80. The first gas side connection piping 22 has its one end connected to the outdoor circuit 30. The first gas side connection piping 22 has its other end branched into two parts and has one (chiller side branch gas pipe 22a) of the branched parts connected to the gas side end of the chiller circuit 70 and has the other (freezer side branch gas pipe 22b) of the branched parts connected to the gas side end of the freezer circuit 80.

Moreover, on the air-conditioning side of the refrigerant circuit 20, the air-conditioning circuit 60 is connected to the outdoor circuit 30 via second liquid side connection piping 23 branched from the first liquid side connection piping 21 and second gas side connection piping 24. The second liquid side connection piping 23 has its one end connected to the outdoor circuit 30 via the first liquid side connection piping 21 and has its other end connected to the liquid side end of the air-conditioning circuit 60. The second gas side connection piping 24 has its one end connected to the outdoor circuit 30 and has its other end connected to the gas side end of the air-conditioning circuit 60.

(Outdoor Unit)

As described above, the outdoor unit 11 is provided with the outdoor circuit 30. The outdoor circuit 30 is provided with a compression mechanism 31, an outdoor heat exchanger 32, a receiver 33, and an outdoor expansion valve 34. Moreover, the outdoor circuit 30 is provided with a first four-way switching valve 35, a second four-way switching valve 36, a third four-way switching valve 37, a liquid side stop valve 38, a first gas side stop valve 39a, and a second gas side stop valve 39b. In this outdoor circuit 30, the liquid side stop valve 38 has the first liquid side connection piping 21 connected thereto and the first gas side stop valve 39a has the first gas side connection piping 22 connected thereto and the second gas side stop valve 39b has the second gas side connection piping 24 connected thereto.

The compression mechanism 31 is constructed of a DC inverter compressor 31a of a first compressor, a first non-inverter compressor 31b of a second compressor, and a second non-inverter compressor 31c of a third compressor, which are connected in parallel to each other. The respective compressors 31a, 31b, and 31c are scroll compressors of a hermetic high-pressure dome type, respectively. The DC inverter compressor 31a is supplied with electric power via an inverter. By changing the output frequency of the inverter of the DC inverter compressor 31a to change the rotation speed of its electric motor, the operation capacity of the DC inverter compressor 31a can be adjusted. On the other hand, the first non-inverter compressor 31b and the second non-inverter compressor 31c have their electric motors driven always at their specified rotation speeds and hence have their operation capacities kept constant.

The DC inverter compressor 31a has one end of a first suction pipe 41a connected to its suction side. The first non-inverter compressor 31b has one end of a second suction pipe 41b connected to its suction side. The second non-inverter compressor 31c has one end of a third suction pipe 41c connected to its suction side.

The other end of the first suction pipe 41a is connected to a first low-pressure gas pipe 42 of the base pipe of a chiller/freezer line low-pressure gas line and a first communication pipe 43a and the first low-pressure gas pipe 42 is connected to the first gas side stop valve 39a. The first suction pipe 41a is connected to a first port P1 of the third four-way switching valve 37 via the first communication pipe 43a. The first communication pipe 43a is provided with a check valve CV1 for prohibiting a refrigerant flow to the DC inverter compressor 31a. The other end of the second suction pipe 41a is connected to a second port P2 of the third four-way switching valve 37. The other end of the third suction pipe 41c is connected to a second low-pressure gas pipe 44 and a second communication pipe 43b and the second low-pressure gas pipe 44 is connected to a second four-way switching valve 36. The third suction pipe 41c is connected to a third port P3 of the third four-way switching valve 37 via the second communication pipe 43b. The second communication pipe 43b is provided with a check valve CV2 for prohibiting a refrigerant flow to the second non-inverter compressor 31c.

The compression mechanism 31 has a high-pressure gas pipe (discharge line) 45 connected to its discharge side. The high-pressure gas pipe 45 has one end of a high stage side hot gas passage 46 connected thereto and the other end of the high stage side hot gas passage 46 is connected to the first suction pipe 41a. The high stage side hot gas passage 46 has a first solenoid valve SV1 as a high stage side opening/opening valve. The high stage side hot gas passage 46 is a passage which is connected to the discharge line 45 of the compression mechanism 31 of the outdoor circuit 30 and to the first low-pressure gas pipe 42 of the base pipe of the low-pressure gas line of the respective refrigeration circuits 70, 80 and allows a refrigerant flow to the respective refrigeration heat exchangers 72, 84 from the discharge line 45 of the compression mechanism 31 at the time of the defrosting operation.

The high stage side hot gas passage 46 has one end of a high-pressure introduction pipe 47 connected between the discharge side of the compression mechanism 31 and the first solenoid valve SV1. The high-pressure introduction pipe 47 communicates with the high pressure line of the compression mechanism 31 via the high stage side hot gas passage 46 and has its other end connected to a fourth port P4 of the third four-way switching valve 37.

This third four-way switching valve 37 can switch between a first state (state shown by a solid line in FIG. 1) in which the first port P1 and the second port P2 communicate with each other and in which the third port P3 and the fourth port P4 communicate with each other and a second state (state shown by a broken line in FIG. 1) in which the first port P1 and the fourth port P4 communicate with each other and in which the second port P2 and the third port P3 communicate with each other.

The DC inverter compressor 31a has a first discharge pipe 48a connected to its discharge side and the first non-inverter compressor 31b has a second discharge pipe 48b connected to its discharge side and the second non-inverter compressor 31c has a third discharge pipe 48c connected to its discharge side. The first discharge pipe 48a is provided with a check valve CV3 for prohibiting a refrigerant flow to the DC inverter compressor 31a and the second discharge pipe 48b is provided with a check valve CV4 for prohibiting a refrigerant flow to the first non-inverter compressor 31b and the third discharge pipe 48c is provided with a check valve CV5 for prohibiting a refrigerant flow to the second non-inverter compressor 31c. The first discharge pipe 48a, the second discharge pipe 48b, and the third discharge pipe 48c are merged with each other and connected to the high-pressure gas pipe 45. The third discharge pipe 48c has a discharge connection pipe 49 connected between the point where the third discharge pipe 48c is connected to the high pressure pipe 45 and the check valve CV5.

In the first four-way switching valve 35, the first port P1 is connected to the high-pressure gas pipe 45 and the second port P2 is connected to the outdoor heat exchanger 32 via a first gas pipe 50 and the third port P3 is connected to the second four-way switching valve 36 via a gas connection pipe 52 and the fourth port P4 is connected to the second gas side stop valve 39b via a second gas pipe 51. The first four-way switching valve 35 can switch between a first state (state shown by a solid line in FIG. 1) in which the first port P1 and the second port P2 communicate with each other and in which the third port P3 and the fourth port P4 communicate with each other and a second state (state shown by a broken line in FIG. 1) in which the first port P1 and the fourth port P4 communicate with each other and in which the second port P2 and the third port P3 communicate with each other.

In the second four-way switching valve 36, the first port P1 is connected to the discharge connection pipe 49 and the third port P3 is connected to the second low-pressure gas pipe 44 and the fourth port P4 is connected to the gas connection pipe 52. Moreover, the second four-way switching valve 36 has its second port P2 closed. This second four-way switching valve 36 can switch between a first state (state shown by a solid line in FIG. 1) in which the first port P1 and the second port P2 communicate with each other and in which the third port P3 and the fourth port P4 communicate with each other and a second state (state shown by a broken line in FIG. 1) in which the first port P1 and the fourth port P4 communicate with each other and in which the second port P2 and the third port P3 communicate with each other.

The outdoor heat exchanger 32 is a fin-and-tube heat exchanger of a cross fin type and constructs a heat source side heat exchanger. An outdoor fan 32a is disposed near the outdoor heat exchanger 32. Outdoor air is sent to the outdoor heat exchanger 32 by the outdoor fan 32a and heat is exchanged between the refrigerant and the outdoor air in the outdoor heat exchanger 32. The outdoor heat exchanger 32, as described above, has its one end connected to the first four-way switching valve 35. On the other hand, the outdoor heat exchanger 32 has its other end connected to the top of a receiver 33 via a first liquid pipe 53. The first liquid pipe 53 is provided with a check valve CV6 that allows a refrigerant flow to the receiver 33 from the outdoor heat exchanger 32 and prohibits a back flow.

The receiver 33 has one end of a second liquid pipe 54 connected to its bottom. The second liquid pipe 54 has its other end connected to a liquid side stop valve 38. The second liquid pipe 54 is provided with a check valve CV7 that allows a refrigerant flow to a liquid side stop valve 38 from the receiver 33 and prohibits a back flow.

In the second liquid pipe 54, one end of a third liquid pipe 55 is connected between the check valve CV7 and the liquid side stop valve 38. The other end of the third liquid pipe 55 is connected to the top of the receiver 33. The third liquid pipe 55 is provided with a check valve CV8 that allows a refrigerant flow to the receiver 33 from the liquid side stop valve 38 and prohibits a back flow.

One end of a fourth liquid pipe 56 is connected between the receiver 33 and the check valve CV7 in the second liquid pipe 54. The other end of the fourth liquid pipe 56 is connected between the outdoor heat exchanger 32 and check valve CV6 in the first liquid pipe 53. Moreover, the fourth liquid pipe 56 is provided with an outdoor expansion valve 34.

The outdoor circuit 30 is provided with also various sensors and pressure switches. For example, the high-pressure gas pipe 45 is provided with a discharge temperature sensor 57 and a discharge pressure sensor (not shown). Each of the first discharge pipe 48a and the third discharge pipe 48c is provided with a high-pressure pressure sensor 58. Moreover, each of the suction pipes 41a, 41b, and 41c is provided with a suction temperature sensor and a suction pressure sensor although they are not shown. Furthermore, an outdoor air temperature sensor 59 is disposed near the outdoor fan 32a.

(Air-Conditioning Unit)

As described above, the air-conditioning unit 12 has an air-conditioning circuit (air heat exchange circuit) 60. In the air-conditioning circuit 60, an air-conditioning expansion valve 61 and an air heat exchanger 62 are disposed in this order from a liquid side end to a gas side end. The air heat exchanger 62 is constructed of a fin-and-tube heat exchanger of a cross fin type. In this air heat exchanger 62, heat is exchanged between the refrigerant and the indoor air. On the other hand, the air-conditioning expansion valve 61 is constructed of an electronic expansion valve.

The air-conditioning unit 12 is provided with a heat exchanger temperature sensor 63 and a refrigerant temperature sensor 64. The heat exchanger temperature sensor 63 is disposed in a heat exchanger tube of the air heat exchanger 62. The refrigerant temperature sensor 64 is disposed near a gas side end in the air-conditioning circuit 60. Moreover, the air-conditioning unit 12 is provided with an indoor air temperature sensor 65 and an air-conditioning fan 66. Indoor air in the store is sent to the air heat exchanger 62 by the air-conditioning fan 66.

(Chiller Showcase)

As described above, the chiller showcase 13 has a chiller circuit 70. In the chiller circuit 70, a chiller expansion valve 71 and a chiller heat exchanger (first refrigeration heat exchanger) 72 are disposed in this order from its liquid side end to a gas side end. The chiller heat exchanger 72 is constructed of a fin-and-tube heat exchanger of a cross fin type. In this chiller heat exchanger 72, heat is exchanged between the refrigerant and the air in the chiller showcase 13. On the other hand, the chiller expansion valve 71 is constructed of an electronic expansion valve.

The chiller showcase 13 is provided with a heat exchanger temperature sensor 73 and refrigerant temperature sensors 74, 75. The heat exchanger temperature sensor 73 is disposed in a heat exchanger tube of the chiller heat exchanger 72. A gas refrigerant temperature sensor 74 is disposed near a gas side end in the chiller circuit 70 and a liquid refrigerant temperature sensor 75 is disposed near a liquid side end in the chiller circuit 70. Moreover, the chiller showcase 13 is provided with a chiller temperature sensor 76 and a chiller fan 77. Air in the chiller showcase 13 is sent to the chiller heat exchanger 72 by the chiller fan 77.

(Freezer Showcase)

As described above, the freezer showcase 14 has a freezer circuit 80. In the freezer circuit 80, a refrigerant heat exchanger 81, a drain pan heater 82, a freezer expansion valve 83, a freezer heat exchanger (second refrigeration heat exchanger) 84, and a DC inverter compressor used as a booster compressor (auxiliary compressor) 85 are disposed in this order from its liquid side end to a gas side end. The freezer heat exchanger 84 is constructed of a fin-and-tube heat exchanger of a cross fin type. In this freezer heat exchanger 84, heat is exchanged between the refrigerant and the air in the freezer showcase 14. On the other hand, the freezer expansion valve 83 is constructed of an electronic expansion valve. The freezer expansion valve 83 is an expansion valve that is disposed in a freezer circuit 80 and can change the degree of opening.

The refrigerant heat exchanger 81 is a heat exchanger in which the refrigerants exchange heat between them and is constructed of a plate heat exchanger, for example. This refrigerant heat exchanger 81 has a high pressure side passage 81a connected to a freezer side branch liquid pipe 21b and a low pressure side passage 81b connected to a branch pipe 86 branched from the downstream side of the high pressure side passage 81a in the freezer side branch liquid pipe 21b. The branch pipe 86 has an electronic expansion valve disposed upstream of the low pressure side passage 81b and has the downstream side of the low pressure side passage 81b connected to an intermediate-pressure position of the booster compressor 85. An economizer is constructed of the refrigerant heat exchanger 81 and the electronic expansion valve 87.

A check valve CV9 that allows refrigerant to be discharged from the booster compressor 85 and prohibits the back flow of the refrigerant is disposed in a freezer side branch gas pipe 22b of the discharge line of the booster compressor 85. A low stage side hot gas passage 89 is connected between a downstream position of the check valve CV9 in the freezer side branch gas pipe 22b and a suction pipe 88 of the suction line of the booster compressor 85. The low stage side hot gas passage 89 is a passage, which is connected to the freezer side branch gas pipe 22b and the suction pipe 88 and allows a refrigerant flow to the freezer heat exchanger 84 from the freezer side branch gas pipe 22b at the time of the defrosting operation, and is provided with a second solenoid valve SV2 of a low stage side opening/opening valve.

The freezer showcase 14 is provided with a heat exchanger temperature sensor 90 and refrigerant temperature sensors 91, 92. The heat exchanger temperature sensor 90 is fixed to a heat exchanger tube of the freezer heat exchanger 84. A gas refrigerant temperature sensor 91 is disposed near a gas side end in the freezer circuit 80. A liquid refrigerant temperature sensor 92 is disposed near a liquid side end in the freezer circuit 80. A drain pan heater temperature sensor 93 is disposed near the drain pan heater 82. Moreover, the freezer showcase 14 is provided with a freezer temperature sensor 94 and a freezer fan 95. Air in the freezer showcase 14 is sent to the freezer heat exchanger 84 by the freezer fan 95.

(Entire Construction of Refrigerant Circuit)

As described above, the refrigerant circuit 20 of this embodiment has the chilling/freezer line side circuit and the air-conditioning line side circuit. In the chilling/freezer line side circuit, the plural refrigeration circuits (chiller circuit 70 and freezer circuit 80), which have refrigeration heat exchangers 72, 84 respectively, are connected in parallel to the outdoor circuit 30 provided with the outdoor heat exchanger 32 and the compression mechanism 31. In at least the freezer circuit 30 of one line refrigeration circuit, the booster compressor 85 is connected in series to the freezer heat exchanger 84.

The refrigerant circuit 20 of this embodiment has a high stage side hot gas passage 46 and a low stage side hot gas passage 89 as hot gas introduction passages 46, 89 for selectively introducing the gas refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into at least one of the plural refrigeration heat exchangers 72, 84 and is constructed so as to perform the defrosting operation of conducting the refrigeration cycle by using the refrigeration heat exchangers 72, 84 as condensers.

Moreover, the refrigerant circuit 20 includes the air-conditioning circuit 60 that has the air-conditioning heat exchanger 62 and air-conditions the room. As will be described later, the refrigerant circuit 20 is constructed so as to perform the defrosting operation (first defrosting operation) at the time of a cooling operation in which the refrigeration heat exchangers 72, 84 are used as condensers and in which the air-conditioning heat exchanger 62 is used an evaporator and the defrosting operation (second defrosting operation) at the time of a heating operation in which the refrigeration heat exchangers 72, 84 are used as condensers and in which the outdoor heat exchanger 32 is used an evaporator.

—Operation—

Of operations performed by the refrigeration system, main operations will be described below.

(Cooling Operation)

A cooling operation is the operation of refrigerating air in the chiller showcase 13 and the freezer showcase 14 and refrigerating air in the store by the air-conditioning unit 12 to cool the interior of the store.

As shown in FIG. 2, in the refrigerant circuit 20, the first four-way switching valve 35, the second four-way switching valve 36, and the third four-way switching valve 37 are set to the first state. Moreover, the outdoor expansion valve 34 is totally closed, and the air-conditioning expansion valve 61, the chiller expansion valve 71, and the freezer expansion valve have their degrees of opening suitably adjusted, and the first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerants discharged from the DC inverter compressor 31a, the first non-inverter compressor 31b, and the second non-inverter compressor 31c pass through the respective discharge pipes 48a, 48b, and 48c and merge with each other in the high-pressure gas pipe 45. Then, the refrigerant after merging passes through the first four-way switching valve 35 and is sent to the outdoor heat exchanger 32. In the outdoor heat exchanger 32, the refrigerant dissipates heat to the outdoor air, thereby being condensed.

The refrigerant condensed in the outdoor heat exchanger 32 passes through the receiver 33 and flows to the first liquid side connection piping 21 and is distributed to the chiller side branch liquid pipe 21a, the freezer side branch liquid pipe 21b, and the second liquid side connection piping 23.

The refrigerant flowing into the chiller circuit 70 from the chiller side branch liquid pipe 21a has its pressure reduced when the refrigerant passes the chiller expansion valve 71 and then is introduced into the chiller heat exchanger 72. In the chiller heat exchanger 72, the refrigerant absorbs heat from the air in the chiller showcase 13, thereby being evaporated. At this time, in the chiller heat exchanger 72, the evaporation temperature of the refrigerant is set to about −5° C., for example. The refrigerant evaporated in the chiller heat exchanger 72 flows through the chiller side branch gas pipe 22a and flows into the first gas side connection piping 22. In the chiller showcase 13, the air refrigerated by the chiller heat exchanger 72 is supplied into the chiller showcase 13, whereby the temperature in the chiller showcase 13 is kept at about 5° C., for example.

The refrigerant flowing from the freezer side branch liquid pipe 21b into the freezer circuit 80 passes through the refrigerant heat exchanger 81 and the drain pan heater 82. Then, when the refrigerant passes through the freezer expansion valve 83, the refrigerant has its pressure reduced and then is introduced into the freezer heat exchanger 84. In the freezer heat exchanger 84, the refrigerant absorbs heat from the air in the freezer showcase 14, thereby being evaporated. At this time, in the freezer heat exchanger 84, the evaporation temperature of the refrigerant is set at about −30° C., for example. In the freezer showcase 14, the air in the freezer showcase 14 refrigerated by the freezer heat exchanger 84 is supplied into the freezer showcase 14, whereby the temperature in the freezer showcase 14 is kept at about −20° C., for example.

The refrigerant evaporated in the freezer heat exchanger 84 passes through the suction pipe 88 and is sucked into the booster compressor 85. The refrigerant compressed by the booster compressor 85 passes through the discharge pipe 98 and the freezer side branch gas pipe 22b and flows into the first gas side connection piping 22.

In the first gas side connection piping 22, the refrigerant sent from the chiller circuit 70 and the refrigerant sent from the freezer circuit 80 merge with each other. These refrigerants pass through the first gas side connection piping 22 and the first low-pressure suction pipe 42 and flow into the first suction pipe 41a and the second suction pipe 41b and then are sucked by the DC inverter compressor 31a and the first non-inverter compressor 31b. The DC inverter compressor 31a and the first non-inverter compressor 31b compress the sucked refrigerants and discharge the refrigerants to the first discharge pipe 48a and the second discharge pipe 48b.

On the other hand, the refrigerant flowing into the second liquid side connection piping 23 is supplied to the air-conditioning circuit 60. The refrigerant flowing into the air-conditioning circuit 60 has its pressure reduced when the refrigerant passes through the air-conditioning expansion valve 61. Then, the refrigerant is introduced into the air-conditioning heat exchanger 62. In the air-conditioning heat exchanger 62, the refrigerant absorbs heat from the indoor air, thereby being evaporated. In the air-conditioning unit 12, the indoor air cooled by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant evaporated in the air-conditioning heat exchanger 62 passes through the second gas side connection piping 24 and flows into the outdoor circuit 30 and passes through the second gas pipe 51, the first four-way switching valve 35, and the second four-way switching valve 36 in sequence and then passes through the second low-pressure gas pipe 44 and the third suction pipe 41c and then is sucked by the second non-inverter compressor 31c. The second non-inverter compressor 31c compresses the sucked refrigerant and discharges the refrigerant to the third discharge pipe 48c.

At the time of the cooling operation shown in FIG. 2, by setting the third four-way switching valve 37 to the first state, two compressors 31a, 31b are used for the chilling/freezer line side circuit and one compressor 31c is used for the air-conditioning line side circuit. However, by switching the third four-way switching valve 37 to the second state, it is also possible to use one compressor 31a for the chilling/freezer line side circuit and to use two compressors 31b, 31c for the air-conditioning line side circuit. Moreover, by stopping one of three compressors 31a, 31b, and 31c in a state in which the third four-way switching valve 37 is set to either the first state or the second state, it is also possible to use one compressor for each of the chilling/freezer line side circuit and the air-conditioning line side circuit.

(Defrosting Operation at the Time of the Cooling Operation)

As for the defrosting operation at the time of the cooling operation, the defrosting operation shown in FIG. 3 in which the chiller heat exchanger 72 and the freezer heat exchanger 84 are defrosted at the same time and the defrosting operation shown in FIG. 4 in which the chiller heat exchanger 72 is defrosted while the freezer heat exchanger 84 performs a freezing operation can be performed. Here, a refrigerant flow at the time of the defrosting operation (defrosting path) is designated by a reference symbol 25. First, the defrosting operation shown in FIG. 3 will be described.

As shown in FIG. 3, in the refrigerant circuit 20, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the chiller expansion valve 71 and the freezer expansion valve 83 are fully opened, whereas the air-conditioning expansion valve 61 has its degree of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant discharged from the first non-inverter compressor 31b and the refrigerant discharged from the second non-inverter compressor 31c pass through the respective discharge pipes 48b, 48c and merge with each other in the high-pressure pipe 45. The refrigerant after merging passes through the first four-way switching valve 35 and the first gas pipe 50 and is sent to the outdoor heat exchanger 32. In the outdoor heat exchanger 32, the refrigerant dissipates heat to the outdoor air, thereby being condensed. The refrigerant condensed in the outdoor heat exchanger 32 passes through the receiver 33 and flows through the first liquid side connection piping 21 and then flows into the second liquid side connection pipe 23.

On the other hand, part of the refrigerant discharged from the first non-inverter compressor 31b and the second non-inverter compressor 31c flows through the high stage side hot gas passage 46, the first low-pressure gas pipe 42, and the first gas side connection piping 22 and then is distributed to the chiller side branch gas pipe 22a and the freezer side branch gas pipe 22b.

The refrigerant flowing through the chiller side branch gas pipe 22a flows into the chiller heat exchanger 72. In the chiller heat exchanger 72, the refrigerant dissipates heat to the air in the chiller showcase 13, thereby being condensed. At that time, frost adhering to the chiller heat exchanger 72 is melted. The refrigerant condensed in the chiller heat exchanger 72 passes through the chiller expansion valve 71 and flows through the chiller side branch liquid pipe 21a and then flows into the second liquid side connection piping 23 and there merges with the refrigerant from the outdoor unit 11.

The refrigerant flowing through the freezer side branch gas pipe 22b passes through the low stage side hot gas passage 89 and flows into the freezer heat exchanger 84 where the refrigerant dissipates heat to the air in the freezer showcase 14, thereby being condensed. At that time, frost adhering to the freezer heat exchanger 84 is defrosted. The refrigerant condensed in the freezer heat exchanger 84 passes through the freezer expansion valve 83, the drain pan heater 82, the refrigerant heat exchanger 81, and flows through the freezer side branch liquid pipe 21b and then flows into the second liquid side connection piping 23 and there merges with the refrigerant from the outdoor unit 11.

The refrigerant after merging in the second liquid side connection piping 23 is supplied to the air-conditioning circuit 60. The refrigerant flowing into the air-conditioning circuit 60 has its pressure reduced when the refrigerant passes through the air-conditioning expansion valve 61. Then, the refrigerant is introduced into the air-conditioning heat exchanger 62. In the air-conditioning heat exchanger 62, the refrigerant absorbs heat from the indoor air, thereby being evaporated. In the air-conditioning unit 12, the indoor air cooled by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant evaporated in the air-conditioning heat exchanger 62 passes through the second gas side connection piping 24 and flows into the outdoor circuit 30 and then passes through the second gas pipe 51, the first four-way switching valve 35, and the second four-way switching valve 36 in sequence, and then passes through the second low-pressure gas pipe 44, the second suction pipe 41b, and the third suction pipe 41c, and then is sucked by the first non-inverter compressor 31b and the second non-inverter compressor 31c. The first non-inverter compressor 31b and the second non-inverter compressor 31c compress the sucked refrigerant and discharge the refrigerant into the second discharge pipe 48b and the third discharge pipe 48c, respectively.

As described above, in the defrosting operation shown in FIG. 3, the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted at the same time by the use of heat absorbed by the indoor heat exchanger 62 and heat produced by compressing the refrigerant by the first and second non-inverter compressors 31b, 31c.

Here, FIG. 3 shows the operation using two compressors of the first non-inverter compressor 31b and the second non-inverter compressor 31c, but only any one of the compressors may be operated.

Moreover, in the case of defrosting only the freezer heat exchanger 84, it suffices to perform an operation in which the chiller expansion valve 71 is closed to prevent the refrigerant from flowing through the chiller showcase 13 in the operation state shown in FIG. 3.

Next, the defrosting operation shown in FIG. 4 will be described.

As shown in FIG. 4, in the refrigerant circuit 20, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the chiller expansion valve 71 is fully opened, whereas the freezer expansion valve 83 and the air-conditioning expansion valve 61 have their degrees of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 is opened and the second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant discharged from the first non-inverter compressor 31b and the refrigerant discharged from the second non-inverter compressor 31c pass through the respective discharge pipes 48b, 48c and merge with each other in the high-pressure pipe 45. The refrigerant after merging passes through the first four-way switching valve 35 and the first gas pipe 50 and is sent to the outdoor heat exchanger 32. In the outdoor heat exchanger 32, the refrigerant dissipates heat to the outdoor air, thereby being condensed. The refrigerant condensed in the outdoor heat exchanger 32 passes through the receiver 33 and flows through the first liquid side connection piping 21 and then is distributed to the second liquid side connection piping 23 and the freezer side branch liquid pipe 21b.

The refrigerant flowing into the freezer heat circuit 80 from the freezer side branch gas pipe 21b passes through the refrigerant heat exchanger 81 and the drain pan heater 82. Then, when the refrigerant passes through the freezer expansion valve 83, the refrigerant has its pressure reduced and then is introduced into the freezer heat exchanger 84. In the freezer heat exchanger 84, the refrigerant absorbs heat from the air in the freezer showcase 14 and evaporates. At that time, in the freezer heat exchanger 84, the evaporation temperature of the refrigerant is set to about −30° C., for example. In the freezer showcase 14, the air in the freezer showcase 14 cooled by the freezer heat exchanger 84 is supplied, whereby the temperature in the freezer showcase 14 is kept at about −20° C., for example.

The refrigerant evaporated by the freezer heat exchanger 84 passes through the suction pipe 88 and then is sucked by the booster compressor 85. The refrigerant compressed by the booster compressor 85 passes through the discharge pipe 98 and the freezer side branch gas pipe 22b and then flows into the first gas side connection piping 22. At this time, the electronic expansion valve 87 disposed in the branch pipe 86 has the degree of opening controlled and performs the function of an economizer. For this reason, the discharge pressure of the booster compressor 85 is increased to a level nearly equal to the discharge pressure of the first non-inverter compressor 31b and the second non-inverter compressor 31c.

On the other hand, part of the refrigerant discharged from the first non-inverter compressor 31b and the second non-inverter compressor 31c flows through the high stage side hot gas passage 46, the first low-pressure gas pipe 42, and the first gas side connection piping 22 and then merges with the refrigerant from the freezer unit 14 and then flows through the chiller side branch gas pipe 22a.

The refrigerant flowing through the chiller side branch gas pipe 22a flows into the chiller heat exchanger 72. In the chiller heat exchanger 72, the refrigerant dissipates heat to the air in the chiller showcase 13, thereby being condensed. At that time, frost adhering to the chiller heat exchanger 72 is melted. The refrigerant condensed in the chiller heat exchanger 72 passes through the chiller expansion valve 71 and flows through the chiller side branch liquid pipe 21a. Then, the refrigerant is distributed, together with the refrigerant from the outdoor unit 11, to the second liquid side connection piping 23 and the freezer side branch liquid pipe 21b.

The refrigerant flowing through the second liquid side connection piping 23 is supplied to the air-conditioning circuit 60. When the refrigerant flowing into the air-conditioning circuit 60 passes through the air-conditioning expansion valve 61, the refrigerant has its pressure reduced and then is introduced into the air-conditioning heat exchanger 62. In the air-conditioning heat exchanger 62, the refrigerant absorbs heat from the indoor air, thereby being evaporated. In the air-conditioning unit 12, the indoor air cooled by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant evaporated in the air-conditioning heat exchanger 62 passes through the second gas side, connection piping 24 and flows into the outdoor heat exchanger 30 and then passes through the second gas pipe 51, the first four-way switching valve 35, and the second four-way switching valve 36 in sequence and then passes through the second low-pressure gas pipe 44, the second suction pipe 41b, and the third suction pipe 41c and then is sucked by the first non-inverter compressor 31b and the second non-inverter compressor 31c. The first non-inverter compressor 31b and the second non-inverter compressor 31c compress the sucked refrigerant and discharge the compressed refrigerant into the second discharge pipe 48b and the third discharge pipe 48c.

As described above, in the defrosting operation shown in FIG. 4, the chiller heat exchanger 72 can be defrosted by the use of heat absorbed by the indoor heat exchanger 62 and the freezer heat exchanger 84 and heat produced by compressing the refrigerant by the compressors 31b, 31c, and 85.

Here, FIG. 4 shows the operation using two compressors of the first non-inverter compressor 31b and the second non-inverter compressor 31c, but only any one of the compressors may be operated.

(Heating Operation)

A heating operation is the operation of refrigerating air in the chiller showcase 13 and the freezer showcase 14 and heating the indoor air by the air-conditioning unit 12 to heat the interior of the store.

As shown in FIG. 5, in the refrigerant circuit 20, the first four-way switching valve 35 is set to the second state and the second four-way switching valve 36 and the third four-way switching valve 37 are set to the first state, respectively. Moreover, the air-conditioning expansion valve 61 is fully opened, whereas the outdoor expansion valve 34, the chiller expansion valve 71, and the freezer expansion valve have their degrees of opening suitably adjusted, and the first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant discharged from the DC inverter compressor 31a, the first non-inverter compressor 31b, and the second non-inverter compressor 31c passes through the high-pressure gas pipe 45, the first four-way switching valve 35, the second gas pipe 51, and the second gas side connection piping 24 and then is introduced into the air-conditioning heat exchanger 62 of the air-conditioning circuit 60. In the air-conditioning circuit 60, the refrigerant dissipates heat to the indoor air, thereby being condensed. In the air-conditioning unit 12, the indoor air heated by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant condensed in the air-conditioning heat exchanger 62 flows through the second liquid side connection piping 23 and then is distributed to the chiller side branch liquid pipe 21a, the freezer side branch liquid pipe 21b, and the first liquid side connection piping 21.

The refrigerant flowing through the chiller side branch liquid pipe 21a flows into the chiller showcase 13 and the refrigerant flowing through the freezer side branch liquid pipe 21b flows into the freezer showcase 14. In the chiller showcase 13 and the freezer showcase 14, the airs in the showcases are cooled as is the case with the cooling operation. The refrigerant evaporated in the chiller heat exchanger 72 and the refrigerant evaporated in the freezer heat exchanger 84 and then compressed by the booster compressor 85 merge with each other in the first gas side connection piping 22. The refrigerant flowing through the first gas side connection piping 22 is distributed to the first suction pipe 41a and the second suction pipe 41b. Then, the distributed refrigerants are sucked and compressed by the first non-inverter compressor 31b and the second non-inverter compressor 31c, respectively.

The refrigerant flowing through the first liquid side connection piping 21 flows into the receiver 33 from the third liquid pipe 55 and flows through the fourth liquid pipe 56 and has its pressure reduced by the outdoor expansion valve 34. The refrigerant having the pressure reduced by the outdoor expansion valve 34 is introduced into the outdoor heat exchanger 32 and there absorbs heat from the outdoor air, thereby being evaporated. The refrigerant evaporated by the outdoor heat exchanger 32 passes through the first four-way switching valve 35 and the second four-way switching valve 36 and then passes through the second low-pressure gas pipe 44 and the third suction pipe 41c and then is sucked and compressed by the second non-inverter compressor 31c.

In this manner, at the time of the heating operation, the refrigerant absorbs heat in the chiller heat exchanger 72, the freezer heat exchanger 84, and the outdoor heat exchanger 32, and dissipates heat in the air-conditioning heat exchanger 62. The store is heated by the use of heat that the refrigerant absorbs from the air in the chiller showcase 13 and the freezer showcase 14 in the chiller heat exchanger 72 and the freezer heat exchanger 84 and heat that the refrigerant absorbs from the outside air at the outdoor heat exchanger 32.

In this regard, when a heating capacity becomes excessive in the heating operation of using the outdoor heat exchanger 32 as an evaporator, it is recommended to stop the second non-inverter compressor 31c and to close the outdoor expansion valve 34 in the state shown in FIG. 5 and to perform the heating operation in a state where the refrigerant absorbs heat in the chiller heat exchanger 72 and in the freezer heat exchanger 84 and dissipates heat in the air-conditioning heat exchanger 62.

Moreover, when the heating capacity still becomes excessive, it is recommended to perform the heating operation of using the outdoor heat exchanger 32 as an evaporator and dissipating excessive heat to the outside of the room by switching the second four-way switching valve 36 to the second state and by switching the outdoor expansion valve 34 to a fully opened state (at this time, by stopping the second non-inverter compressor 31c).

(Defrosting Operation at the Time of the Heating Operation)

As for a defrosting operation at the time of the heating operation, a defrosting operation shown in FIG. 6 in which the chiller heat exchanger 72 and the freezer heat exchanger 84 are defrosted at the same time and a defrosting operation shown in FIG. 7 in which the chiller heat exchanger 72 is defrosted while the freezer heat exchanger 84 performs a freezing operation can be performed.

First, the defrosting operation shown in FIG. 6 will be described. As shown in FIG. 6, in the refrigerant circuit 20, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the air-conditioning expansion valve 61, the chiller expansion valve 71, and the freezer expansion valve 83 are fully opened, whereas the outdoor expansion valve 34 has its degree of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant discharged from the first non-inverter compressor 31b and the refrigerant discharged from the second non-inverter compressor 31c pass through the respective discharge pipes 48b, 48c and merge with each other in the high-pressure pipe 45. The refrigerant after merging passes through the first four-way switching valve 35, the second gas pipe 51, and the second gas side connection piping 24 and is introduced into the outdoor heat exchanger 32 of the air-conditioning circuit 60 where the refrigerant dissipates heat to the indoor air, thereby being condensed. In the air-conditioning unit 12, the indoor air heated by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant condensed in the air-conditioning heat exchanger 62 flows through the second liquid side connection piping 23 and then flows into the first liquid side connection piping 21.

On the other hand, part of the refrigerant discharged from the first non-inverter compressor 31b and the second non-inverter compressor 31c flows through the high stage side hot gas passage 46, the first low-pressure gas pipe 42, and the first gas side connection piping 22 and then are distributed to the chiller side branch gas pipe 22a and the freezer side branch gas pipe 22b.

The refrigerant flowing through the chiller side branch gas pipe 22a flows into the chiller heat exchanger 72. In chiller heat exchanger 72, the refrigerant dissipates heat to the air in the chiller showcase 13, thereby being condensed. At that time, frost adhering to the chiller heat exchanger 72 is melted. The refrigerant condensed in the chiller heat exchanger 72 passes through the chiller expansion valve 71 and flows through the chiller side branch liquid pipe 21a and then flows into the first liquid side connection piping 21 and then merges with the refrigerant from the air-conditioning unit 12.

The refrigerant flowing through the freezer side branch gas pipe 22b passes through the low stage side hot gas passage 89 and flows into the freezer heat exchanger 84. In the freezer heat exchanger 84, the refrigerant dissipates heat to the air in the freezer showcase 14, thereby being condensed. At that time, frost adhering to the freezer heat exchanger 84 is melted. The refrigerant condensed in the freezer heat exchanger 84 passes through the freezer expansion valve 83, the drain pan heater 82, the refrigerant heat exchanger 81, and flows through the freezer side branch liquid pipe 21b and then flows into the first liquid side connection piping 21 and then merges with the refrigerant from the air-conditioning unit 12.

The refrigerant flowing through the first liquid side connection piping 21 flows into the receiver 33 from the third liquid pipe 55 and flows through the fourth liquid pipe 56 and has its pressure reduced by the outdoor expansion valve 34. The refrigerant having the pressure reduced by the outdoor expansion valve 34 is introduced into the outdoor heat exchanger 32 and there absorbs heat from the outdoor air, thereby being evaporated. The refrigerant evaporated in the outdoor heat exchanger 32 passes through the first four-way switching valve 35, the second four-way switching valve 36, the second low-pressure gas pipe 44, the second suction pipe 41b, and the third suction pipe 41c, and then is sucked and compressed by the first non-inverter compressor 31b and the second non-inverter compressor 31c.

As described above, in the defrosting operation shown in FIG. 6, the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted at the same time by the use of heat absorbed by the outdoor heat exchanger 32 and heat produced by compressing the refrigerant by the first and second non-inverter compressors 31b, 31c.

Here, FIG. 6 shows the operation using two compressors of the first non-inverter compressor 31b and the second non-inverter compressor 31c, but only any one of the compressors may be operated.

Moreover, in the case of defrosting only the freezer heat exchanger 84, it suffices to perform an operation in which the chiller expansion valve 71 is closed to prevent the refrigerant from flowing through the chiller showcase 13 in the operation state shown in FIG. 3.

Next, the defrosting operation shown in FIG. 7 will be described.

As shown in FIG. 7, in the refrigerant circuit 20, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the air-conditioning expansion valve 61 and the chiller expansion valve 71 are fully opened, whereas the freezer expansion valve 83 and the outdoor expansion valve 34 have their degrees of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 is opened and the second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant discharged from the first non-inverter compressor 31b and the refrigerant discharged from the second non-inverter compressor 31c pass through the respective discharge pipes 48b, 48c and merge with each other in the high-pressure pipe 45. The refrigerant after merging passes through the first four-way switching valve 35, the second gas pipe 51, and the second gas side connection piping 24 and is introduced into the outdoor heat exchanger 32 where the refrigerant dissipates heat to the indoor air, thereby being condensed. In the air-conditioning unit 12, the indoor air heated by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant condensed in the air-conditioning heat exchanger 62 flows through the second liquid side connection piping 23 and then is distributed to the freezer side branch liquid pipe 21b and the first liquid side connection piping 21.

The refrigerant flowing into the freezer circuit 80 from the freezer side branch liquid pipe 21b passes through the refrigerant heat exchanger 81 and the drain pan heater 82. When the refrigerant passes through the freezer expansion valve 83, the refrigerant has its pressure reduced and then is introduced into the freezer heat exchanger 84. In the freezer heat exchanger 84, the refrigerant absorbs heat from the air in the freezer showcase 14, thereby being evaporated. At that time, in the freezer heat exchanger 84, the evaporation temperature of the refrigerant is set to about −30° C., for example. In the freezer showcase 14, the air in the freezer showcase 14 cooled by the freezer heat exchanger 84 is supplied into the freezer showcase 14, whereby the temperature in the freezer showcase 14 is kept at about −20° C., for example.

The refrigerant evaporated by the freezer heat exchanger 84 passes through the suction pipe 88 and then is sucked by the booster compressor 85. The refrigerant compressed by the booster compressor 85 passes through the discharge pipe 98 and the freezer side branch gas pipe 22b and then flows into the first gas side connection piping 22. At this time, the electronic expansion valve 87 disposed in the branch pipe 86 has the degree of opening controlled and performs the function of an economizer. For this reason, the discharge pressure of the booster compressor 85 is increased to a level nearly equal to the discharge pressure of the first non-inverter compressor 31b and the second non-inverter compressor 31c.

On the other hand, part of the refrigerant discharged from the first non-inverter compressor 31b and the second non-inverter compressor 31c flows through the high stage side hot gas passage 46, the first low-pressure gas pipe 42, and the first gas side connection piping 22 and then merges with the refrigerant from the freezer unit 14 and then flows through the chiller side branch gas pipe 22a.

The refrigerant flowing through the chiller side branch gas pipe 22a flows into the chiller heat exchanger 72. In the chiller heat exchanger 72, the refrigerant dissipates heat to the air in the chiller showcase 13, thereby being condensed. At that time, frost adhering to the chiller heat exchanger 72 is melted. The refrigerant condensed in the chiller heat exchanger 72 passes through the chiller expansion valve 71 and flows through the chiller side branch liquid pipe 21a. Then, the refrigerant and is distributed, together with the refrigerant from the air-conditioning unit 12, to the freezer side branch liquid pipe 21b and the first liquid side connection piping 21.

The refrigerant flowing through the first liquid side connection piping 21 flows into the receiver 33 from the third liquid pipe 55 and flows through the fourth liquid pipe 56 and has it pressure reduced by the outdoor expansion valve 34. The refrigerant having its pressure reduced by the outdoor expansion valve 34 is introduced into the outdoor heat exchanger 32. In the outdoor heat exchanger 32, the refrigerant absorbs heat from the outdoor air, thereby being evaporated. The refrigerant evaporated in the outdoor heat exchanger 32 passes through the first four-way switching valve 35, the second four-way switching valve 36, the second low-pressure gas pipe 44, the second suction pipe 41b, and the third suction pipe 41c, and then is sucked and compressed by the first non-inverter compressor 31b and the second non-inverter compressor 31c.

As described above, in the defrosting operation shown in FIG. 7, the chiller heat exchanger 72 can be defrosted by the use of heat absorbed by the outdoor heat exchanger 32 and the freezer heat exchanger 84 and heat produced by compressing the refrigerant by the compressors 31b, 31c.

Here, FIG. 7 shows the operation using two compressors of the first non-inverter compressor 31b and the second non-inverter compressor 31c, but only any one of the compressors may be operated.

—Effect of Embodiment 1—

According to the refrigeration system 10 of this embodiment, even if a defrosting mechanism such as an electric heater is not provided in addition to the refrigerant circuit, both of the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted, so it is possible to prevent the construction of the refrigeration system from becoming complex. Moreover, it is possible not only to defrost both of the chiller heat exchanger 72 and the freezer heat exchanger 84 at the same time but also to defrost only one of them. In this manner, the refrigeration system 10 of this embodiment can defrost the chiller heat exchanger 72 and the freezer heat exchanger 84 individually and hence can respond to a variety of patterns of the defrosting operations.

Further, in a refrigeration system of the related art in which a freezer heat exchanger is defrosted by using a chiller heat exchanger as a heat source, it is necessary to bring the chiller heat exchanger and the freezer heat exchanger into a good balance between heat absorption and heat dissipation at the time of the defrosting operation. This presents the problem of imposing a restriction on design. On the other hand, the refrigeration system 10 of this embodiment does not impose such a restriction on design.

Still further, the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted by the use of the heat absorbed by the air-conditioning heat exchanger 62, the heat absorbed by the outdoor heat exchanger 32, and the heat produced by compressing the refrigerant by the compression mechanism 31, so the defrosting operation can be performed efficiently.

Still further, when the frost adhering to the chiller heat exchanger 72 and the freezer heat exchanger 84 is melted from outside by the use of an electric heater, the temperature in the refrigerator is easily increased. However, in this embodiment, the frost adhering to the chiller heat exchanger 72 and the freezer heat exchanger 84 is melted from inside by the use of heat of the refrigerant, so an increase in the temperature in the refrigerator can be prevented.

Still further, in the construction in which only the operating pattern of defrosting the chiller heat exchanger 72 and the freezer heat exchanger 84 at the same time can be performed, when hot gas continues flowing through the heat exchanger defrosted earlier, the temperature in the refrigerator is increased. However, in this embodiment, the respective heat exchangers 72, 84 can be defrosted individually, so when one of the heat exchangers 72, 84 is defrosted earlier, by stopping flowing the hot gas through the heat exchanger, an increase in the temperature in the refrigerator can be prevented with reliability.

Still further, while only the chiller heat exchanger 72 is defrosted, the function of the economizer is performed in the freezer showcase 14 to increase the discharge pressure of the booster compressor 85. When the function of the economizer is not used, a comparatively large pressure difference is developed between the discharge pressure of the compression mechanism 31 of the outdoor unit 11 and the discharge pressure of the booster compressor 85, which raises a possibility that the booster compressor 85 might be damaged. However, the use of the function of the economizer can prevent such a problem.

In this embodiment, the description of the detailed flow of the refrigerant in the refrigerant circuit 20 has been omitted, but it is also possible to perform only the chilling/freezing operation without performing the air-conditioning operation and to perform only the air-conditioning operation without performing the chilling/freezing operation.

Embodiment 2 of the Invention

A refrigeration system 10 of an embodiment 2, as shown in FIG. 8, is an embodiment that is different from the embodiment 1 in the construction of a part of the outdoor unit 11. Specifically, the embodiment 2 is different from the embodiment ° in the construction relating to the high stage side hot gas passage 46. The hot gas introduction passage 46 of the embodiment 2 has its one end connected to the high-pressure gas pipe 45 and has the other end connected to the fourth port P4 of the third four-way switching valve 37. Moreover, the check valve CV1 disposed in the first connection pipe 43a in the embodiment 1 is not disposed in the embodiment 2.

The other construction of the embodiment 2 is the same as that of the embodiment 1.

—Operation—

In this embodiment 2, the cooling operation and the heating operation can be also performed in the same way as in the embodiment 1, and two or one of the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted at the time of the cooling operation or the heating operation.

At the time of the cooling operation, as shown in FIG. 9, the first four-way switching valve 35, the second four-way switching valve 36, and the third four-way switching valve 37 are set to the first state, respectively. Moreover, the outdoor expansion valve 34 is totally closed whereas the air-conditioning expansion valve 61, the chiller expansion valve 71, and the freezer expansion valve 83 have their degrees of opening suitably adjusted and the second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are actuated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 2. A refrigeration cycle is performed in which the outdoor heat exchanger 32 is used as a condenser and in which the air-conditioning heat exchanger 62, the chiller heat exchanger 72, and the freezer heat exchanger 84 are used as evaporators.

As for the defrosting operation at the time of the cooling operation, the defrosting operation shown in FIG. 10 in which the chiller heat exchanger 72 and the freezer heat exchanger 84 are defrosted at the same time and the defrosting operation shown in FIG. 11 in which the chiller heat exchanger 72 is defrosted while the freezer heat exchanger 84 performs the cooling operation can be performed.

At the time of the defrosting operation shown in FIG. 10, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the chiller expansion valve 71 and the freezer expansion valve 83 are fully opened, whereas the air-conditioning expansion valve 61 has its degree of opening suitably adjusted. The second solenoid valve SV2 of the low stage side hot gas passage 89 is opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 3 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46, the third four-way switching valve 37, and the first low-pressure gas pipe 42 to the chiller showcase 13 and the freezer showcase 14. A refrigeration cycle is performed in which the outdoor heat exchanger 32, the chiller heat exchanger 72, and the freezer heat exchanger 84 are used as condensers and in which the air-conditioning heat exchanger 62 is used as an evaporator.

At the time of the defrosting operation shown in FIG. 11, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the chiller expansion valve 71 is fully opened, whereas the freezer expansion valve 83 and the air-conditioning expansion valve 61 have their degrees of opening suitably adjusted. The second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 4 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46, the third four-way switching valve 37, and the first low-pressure gas pipe 42 to the chiller showcase 13. A refrigeration cycle is performed in which the outdoor heat exchanger 32 and the chiller heat exchanger 72 are used as condensers and in which the air-conditioning heat exchanger 62 and the freezer heat exchanger 84 are used as evaporators.

At the time of the heating operation, as shown in FIG. 12, the first four-way switching valve 35 is set to the second state and the second four-way switching valve 36 and the third four-way switching valve 37 are set to the first state, respectively. Moreover, the air-conditioning expansion valve 61 is fully opened whereas the outdoor expansion valve 34, the chiller expansion valve 71, and the freezer expansion valve 83 have their degrees of opening suitably adjusted. The second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 5. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62 is used as a condenser and in which the outdoor heat exchanger 32, the chiller heat exchanger 72, and the freezer heat exchanger 84 are used as evaporators.

In this regard, when a heating capacity becomes excessive in the heating operation of using the outdoor heat exchanger 32 as an evaporator, it is recommended to stop the second non-inverter compressor 31c and to close the outdoor expansion valve 34 in the state shown in FIG. 12 and to perform the heating operation in a state where the refrigerant absorbs heat in the chiller heat exchanger 72 and in the freezer heat exchanger 84 and dissipates heat in the air-conditioning heat exchanger 62.

Moreover, when the heating capacity still becomes excessive, it is recommended to perform the heating operation of using the outdoor heat exchanger 32 as an evaporator and dissipating excessive heat to the outside of the room by switching the second four-way switching valve 36 to the second state and by switching the outdoor expansion valve 34 to a fully opened state (at this time, by stopping the second non-inverter compressor 31c).

As for the defrosting operation at the time of the heating operation, the defrosting operation shown in FIG. 13 in which the chiller heat exchanger 72 and the freezer heat exchanger 84 are defrosted at the same time and the defrosting operation shown in FIG. 14 in which the chiller heat exchanger 72 is defrosted while the freezer heat exchanger 84 performs the cooling operation can be performed.

At the time of the defrosting operation shown in FIG. 13, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the air-conditioning expansion valve 61, the chiller expansion valve 71, and the freezer expansion valve 83 are fully opened, whereas the outdoor expansion valve 34 has its degree of opening suitably adjusted. The second solenoid valve SV2 of the low stage side hot gas passage 89 is opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 6 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46, the third four-way switching valve 37, and the first low-pressure gas pipe 42 to the chiller showcase 13 and the freezer showcase 14. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62, the chiller heat exchanger 72, and the freezer heat exchanger 84 are used as condensers and in which the outdoor heat exchanger 32 is used as an evaporator.

At the time of the defrosting operation shown in FIG. 14, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the air-conditioning expansion valve 61 and the chiller expansion valve 71 are fully opened, whereas the freezer expansion valve 83 and the outdoor expansion valve 34 have their degrees of opening suitably adjusted. The second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 7 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46, the third four-way switching valve 37, and the first low-pressure gas pipe 42 to the chiller showcase 13. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62 and the chiller heat exchanger 72 are used as condensers and in which the freezer heat exchanger 84 and the outdoor heat exchanger 32 are used as evaporators.

—Effect of Embodiment 2—

The refrigeration system 10 of this embodiment 2, just as with the embodiment 1, can respond to a variety of patterns of the defrosting operations while preventing the construction of the refrigeration system from becoming complex. Moreover, this embodiment 2 is the same as the embodiment 1 also in that unlike a refrigeration system of the related art in which a freezer heat exchanger is defrosted by using a chiller heat exchanger as a heat source, there is not a restriction in design such that it is necessary to bring the chiller heat exchanger and the freezer heat exchanger into a good balance between heat absorption and heat dissipation at the time of the defrosting operation.

Furthermore, this embodiment 2 is the same as the embodiment 1 also: in that the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted by the use of the heat absorbed by the air-conditioning heat exchanger 62 and the outdoor heat exchanger 32 and the heat produced by compressing the refrigerant by the compression mechanism 31, so the defrosting operation can be performed efficiently; and in that the frost adhering to the chiller heat exchanger 72 and the freezer heat exchanger 84 can be melted from inside by the heat of the refrigerant without using an electric heater, whereby an increase in the chiller showcase 13 and the freezer showcase 14 can be prevented.

Embodiment 3 of the Invention

A refrigeration system 10 of an embodiment 3 is an embodiment in which one air-conditioning unit 12 and two freezer units 14 are connected to the outdoor unit 11, as shown in FIG. 15, in place of connecting one air-conditioning unit 12, one chiller showcase 13, and one freezer showcase 14 to the outdoor unit 11. Two freezer showcases 14 are connected in parallel to the outdoor unit 11 via two freezer side branch liquid pipes 21b branched from the first liquid side connection piping 21 and via two freezer side branch gas pipes 22b branched from the first gas side connection piping 22. In other words, in this embodiment 3, two freezer circuits 80 each of which is provided with the freezer heat exchanger 84 and the booster compressor 85 are connected in parallel.

The other construction of the embodiment 3 is the same as that of the embodiment 1.

—Operation—

This embodiment 3, just as with the embodiments 1 and 2, can also perform the cooling operation and the heating operation and can defrost two or one of the freezer heat exchangers 84 at the time of the cooling operation and the heating operation.

At the time of the cooling operation, as shown in FIG. 16, the first four-way switching valve 35, the second four-way switching valve 36, and the third four-way switching valve 37 are set to the first state, respectively. Moreover, the outdoor expansion valve 34 is totally closed, whereas the air-conditioning expansion valve 61, and each freezer expansion valve 83 have their degrees of opening suitably adjusted and the second solenoid valve SV2 of the low stage side hot gas passage 89 is closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 are actuated.

The refrigerant circulates through the refrigerant circuit 10 in the nearly same state as shown in FIG. 2. A refrigeration cycle is performed in which the outdoor heat exchanger 32 is used as a condenser and in which the air-conditioning heat exchanger 62 and the respective freezer heat exchangers 84 are used as evaporators.

As for the defrosting operation at the time of the cooling operation, the defrosting operation shown in FIG. 17 in which two freezer heat exchangers 84 are defrosted at the same time and the defrosting operation shown in FIG. 18 in which one freezer heat exchanger 84 is defrosted while the other freezer heat exchanger 84 performs the refrigerating operation can be performed.

At the time of the defrosting operation shown in FIG. 17, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the respective freezer expansion valves 83 are fully opened, whereas the air-conditioning expansion valve 61 has its degree of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valves SV2 of the respective low stage side hot gas passages 89 are opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 3 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46 and the first low-pressure gas pipe 42 and then is branched to two freezer side branch gas pipes 22b and that the branched refrigerants then flow to the respective freezer showcases 14. A refrigeration cycle is performed in which the outdoor heat exchanger 32, the respective freezer heat exchangers 84 are used as condensers and in which the air-conditioning heat exchanger 62 is used as an evaporator.

The defrosting operation shown in FIG. 18 is an embodiment in which the freezer showcase 14 shown on the upper side in the drawing performs the defrosting operation. In the following description, this freezer showcase 14 is referred to as a defrosting side showcase and the freezer showcase 14 shown on the lower side in the drawing is referred to as a refrigerating side showcase.

In FIG. 18, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed, whereas the freezer expansion valve 83 of the refrigerating side showcase and the air-conditioning expansion valve 61 have their degrees of opening suitably adjusted and the freezer expansion valve 83 of the defrosting side showcase is fully opened. The first solenoid valve SV1 of the high stage side hot gas passage 46 is opened and the second solenoid valve SV2 of the low stage side hot gas passage 89 of the defrosting side showcase is opened and the second solenoid valve SV2 of the low stage side hot gas passage 89 of the refrigerating side showcase is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 of the refrigerating side showcase are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 4 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46 and the first low-pressure gas pipe 42 to freezer heat exchanger 84 of the defrosting side showcase. A refrigeration cycle is performed in which the outdoor heat exchanger 32 and the freezer heat exchanger 84 of the defrosting side showcase are used as condensers and in which the air-conditioning heat exchanger 62 and the freezer heat exchanger 84 of the refrigerating side showcase are used as evaporators.

At the time of the heating operation, as shown in FIG. 19, the first four-way switching valve 35 is set to the second state and the second four-way switching valve 36 and the third four-way switching valve 37 are set to the first state, respectively. Moreover, the air-conditioning expansion valve 61 is fully opened whereas the outdoor expansion valve 34 and the respective freezer expansion valves 83 have their degrees of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are closed. In this state, the DC inverter compressor 31a, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the respective booster compressors 85 are operated.

The refrigerant circulates through the refrigerant circuit 10 in the nearly same state as shown in FIG. 5. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62 is used as a condenser and in which the outdoor heat exchanger 32 and the respective freezer heat exchangers 84 are used as evaporators.

When a heating capacity becomes excessive in the operation of using the outdoor heat exchanger 32 as an evaporator, it is recommended to stop the second non-inverter compressor 31c and to close the outdoor expansion valve 34 in the state shown in FIG. 19 and to perform the heating operation in a state where the refrigerant absorbs heat in the respective freezer heat exchangers 84 and dissipates heat in the air-conditioning heat exchanger 62.

Moreover, when the heating capacity still becomes excessive, it is recommended to perform the operation of using the outdoor heat exchanger 32 as an evaporator and dissipating the excessive heat to the outside of the room by switching the second four-way switching valve 36 to the second state and by switching the outdoor expansion valve 34 to a fully opened state (at this time, by stopping the second non-inverter compressor 31c).

As for the defrosting operation at the time of the heating operation, the defrosting operation shown in FIG. 20 in which two freezer heat exchangers 84 are defrosted at the same time and the defrosting operation shown in FIG. 21 in which one freezer heat exchanger 84 is defrosted while the other freezer heat exchanger 84 performs the refrigerating operation can be performed.

At the time of the defrosting operation shown in FIG. 20, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the air-conditioning expansion valve 61 and the respective freezer expansion valves 83 are fully opened, whereas the outdoor expansion valve 34 has its degree of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valves SV2 of the respective low stage side hot gas passages 89 are opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 6 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46 and the first low-pressure gas pipe 42 and then is distributed to two freezer side branch gas pipes 22b and that the distributed refrigerants flow to the respective freezer showcases 14. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62 and the respective freezer heat exchangers 84 are used as condensers and in which the outdoor heat exchanger 32 is used as an evaporator.

The defrosting operation shown in FIG. 21 is an embodiment in which the freezer showcase 14 shown on the upper side in the drawing performs the defrosting operation. At the time of this defrosting operation, the first four-way switching valve 35 and the third four-way switching valve 37 are set to the second state and the second four-way switching valve 36 is set to the first state. Moreover, the freezer expansion valve 83 of the refrigerating side showcase and the outdoor expansion valve 34 have their degrees of opening suitably adjusted, whereas the air-conditioning expansion valve 61 and the freezer expansion valve 83 of the defrosting side showcase are fully opened. The first solenoid valve SV1 of the high stage side hot gas passage 46 is opened and the second solenoid valve SV2 of the low stage side hot gas passage 89 of the defrosting side showcase is opened, whereas the second solenoid valve SV2 of the low stage side hot gas passage 89 of the refrigerating side showcase is closed. In this state, the first non-inverter compressor 31b, the second non-inverter compressor 31c, and the booster compressor 85 of the cooling side showcase are operated.

The refrigerant circulates through the refrigerant circuit 10 in the same state as shown in FIG. 7 except that part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 10 flows through the high stage side hot gas passage 46 and the first low-pressure gas pipe 42 to the freezer heat exchanger 84 of the defrosting side showcase. A refrigeration cycle is performed in which the air-conditioning heat exchanger 62 and the freezer heat exchanger 84 of the defrosting side showcase are used as condensers and in which the freezer heat exchanger 84 of the refrigerating side showcase and the outdoor heat exchanger 32 are used as evaporators.

—Effect of Embodiment 3—

The refrigeration system 10 of this embodiment 3, just as with the embodiments 1 and 2, can respond to a variety of patterns of the defrosting operations while preventing the construction of the refrigeration system from becoming complex. In particular, even when any one of the two freezer heat exchangers 84 is defrosted, the other freezer heat exchangers 84 can perform the refrigerating operation. Moreover, this embodiment 3 is the same as the embodiments 1 and 2 also in that there is not a restriction in design such that it is necessary to bring heat absorption and heat dissipation in the chiller heat exchanger and the freezer heat exchanger into a good balance at the time of the defrosting operation.

Furthermore, this embodiment 3 is the same as the embodiments 1 and 2 also: in that the freezer heat exchangers 84 can be defrosted by the use of the heat absorbed by the air-conditioning heat exchanger 62 and the outdoor heat exchanger 32 and the heat produced by compressing the refrigerant by the compression mechanism 31, so the defrosting operation can be performed efficiently; and in that the frosts adhering to the freezer heat exchangers 84 can be melted from inside by the heat of the refrigerant without using an electric heater, which can prevent an increase of the temperature in the chiller showcase 13 and the freezer showcase 14.

Embodiment 4 of the Invention

A refrigeration system 10 of an embodiment 4 is basically equivalent to that of the embodiment 1 in the construction of the refrigerant circuit 20, but is different from that of the embodiment 1 in the defrosting operation.

In this embodiment, in the period during which the freezer heat exchanger 84 is defrosted, the refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 is further compressed by the booster compressor 85 and then the discharged refrigerant is supplied to the freezer heat exchanger 84. Specifically, part of the refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 passes through the low stage side hot gas passage 89 and is supplied to the freezer heat exchanger 84 and the other part of the refrigerant is compressed by the booster compressor 85 and then is merged with the refrigerant flowing through the low stage side hot gas passage 89 from the compression mechanism 31 and the refrigerant after merging is supplied to the freezer heat exchanger 84.

During this defrosting operation, part of the refrigerant condensed by the freezer heat exchanger 84 is supplied for the liquid injection into the booster compressor 85.

In this embodiment 4, it is assumed to think that the hot gas introduction passage 46, 89 is divided into a first introduction passage 96 for introducing the refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into the booster compressor 85 and a second introduction passage 97 for introducing the refrigerant discharged from the booster compressor 85 into the freezer heat exchanger 84. The second introduction passage 97 is connected to the compression mechanism 31 of the outdoor circuit 30 and the freezer heat exchanger 84 (the second introduction passage 97 is a passage including the low stage side hot gas passage 89). On the other hand, the first introduction passage 96 is branched from second introduction passage 97 and is connected to the booster compressor 85 so as to introduce part of the refrigerant discharged from the compression mechanism 31 of the outdoor circuit 30 into the booster compressor 85. Moreover, the discharge pipe 98 of the booster compressor 85 is connected to the compression mechanism 31 side of the outdoor circuit 30 in the second introduction passage 97.

In this embodiment 4, the branch pipe 86 connected to the low-pressure side passage 81b of the refrigerant heat exchanger 81 constructs a liquid injection passage 99 for introducing part of the liquid refrigerant flowing out of the freezer heat exchanger 84 to the booster compressor 85 in the period during which the freezer heat exchanger 84 is defrosted.

—Operation—

As for the operation of the embodiment 4, the defrosting operation of the freezer heat exchanger 84 at the time of the cooling operation will be described.

The refrigeration system 10 of the embodiment 4 switches between a defrosting operation (first defrosting operation) shown in FIG. 3 of the embodiment 1 and a defrosting operation (second defrosting operation) shown in FIG. 22, which will be described later. These two defrosting operations are switched according to the detection temperature of the heat exchanger temperature sensor 90 disposed in the freezer heat exchanger 84.

In this refrigeration system 10, usually, the first defrosting operation shown in FIG. 3 is performed. In the first defrosting operation, as described above, the first non-inverter compressor 31b and the second non-inverter compressor 31c of the outdoor circuit 30 are operated, whereas the DC inverter compressor 31a and the booster compressor 85 are bought into a stop state and both of the chiller heat exchanger 72 and the freezer heat exchanger 84 are defrosted.

On the other hand, when the defrosting capacity of the freezer heat exchanger 84 is not sufficient in the first defrosting operation and hence the time required to defrost the freezer heat exchanger 84 becomes long, the following second defrosting operation is performed.

Specifically, when it takes a lot of time for the detection temperature of the heat exchanger temperature sensor 90 to be raised to a specified temperature in the first defrosting operation, it is determined that the defrosting capacity of the freezer heat exchanger 84 is not sufficient. As a result, the first defrosting operation is shifted to the second defrosting operation.

In this second defrosting operation, just as with the first defrosting operation, in the refrigerant circuit 20, the first four-way switching valve 35 and the second four-way switching valve 36 are set to the first state and the third four-way switching valve 37 is set to the second state. Moreover, the outdoor expansion valve 34 is totally closed and the chiller expansion valve 71 and the freezer expansion valve 83 are fully opened, whereas the air-conditioning expansion valve 61 has its degree of opening suitably adjusted. The first solenoid valve SV1 of the high stage side hot gas passage 46 and the second solenoid valve SV2 of the low stage side hot gas passage 89 are opened. In this state, the first non-inverter compressor 31b and the second non-inverter compressor 31c are operated. Moreover, the electronic expansion valve 87 of the branch pipe 86 as the liquid injection passage 99 has the degree of opening suitably adjusted and the booster compressor 85 is actuated.

The refrigerant discharged in this state from the first non-inverter compressor 31b and the refrigerant discharged from the second non-inverter compressor 31c pass through the respective discharge pipes 48b, 48c and merge with each other in the high-pressure pipe 45. The refrigerant after merging passes through the first four-way switching valve 35 and the first gas pipe 50 and is sent to the outdoor heat exchanger 32. In the outdoor heat exchanger 32, the refrigerant dissipates heat to the outdoor air, thereby being condensed. The refrigerant condensed in the outdoor heat exchanger 32 passes through the receiver 33 and flows through the first liquid side connection piping 21 and then flows into the second liquid side connection piping 23.

On the other hand, part of the refrigerant discharged from the first non-inverter compressor 31b and the second non-inverter compressor 31c flows through the high stage side hot gas passage 46, the first low-pressure gas pipe 42, and the first gas side connection piping 22 and then is distributed to the chiller side branch gas pipe 22a and the freezer side branch gas pipe 22b.

The refrigerant flowing through the chiller side branch gas pipe 22a flows into the chiller heat exchanger 72 and there dissipates heat to the air in the chiller showcase 13, thereby being condensed. At that time, frost adhering to the chiller heat exchanger 72 is melted. The refrigerant condensed in the chiller heat exchanger 72 passes through the chiller expansion valve 71 and flows through the chiller side branch liquid pipe 21a and then flows into the second liquid side connection piping 23 and then merges with the refrigerant from the outdoor unit 11.

The refrigerant flowing through the freezer side branch gas pipe 22b passes through the second introduction passage 97 including the low stage side hot gas passage 89 and part of the refrigerant flows into the freezer heat exchanger 84 and the other part of the refrigerant passes through the first introduction passage 96 and is sucked by the booster compressor 85.

The refrigerant compressed by the booster compressor 85 flows through the discharge pipe 98 and is sent to the low stage side hot gas passage 89 and then is merged with the refrigerant discharged from the compressor 31 of the outdoor circuit 30. Then, the refrigerant merged in the low stage side hot gas passage 89 flows into the freezer heat exchanger 84. In other words, in the freezer circuit 80, part of the refrigerant is compressed and circulated by the booster compressor 85 and the input heat of the booster compressor 85 is given to the refrigerant.

In the freezer heat exchanger 84, the refrigerant dissipates heat to the air in the freezer showcase 14, thereby being condensed. At that time, frost adhering to the freezer heat exchanger 84 is melted. The refrigerant condensed in the freezer heat exchanger 84 passes through the freezer expansion valve 83, the drain pan heater 82, and the refrigerant heat exchanger 81 and then flows through the freezer side branch liquid pipe 21b and then flows into the second liquid side connection piping 23 and then merges with the refrigerant from the outdoor unit 11.

At the time of this second defrosting operation, part of the refrigerant compressed by the compression mechanism 31 of the outdoor circuit 30 is further compressed by the booster compressor 85, so when this operation is continued, there is a possibility that the temperature of the refrigerant discharged from the booster compressor 85 is remarkably increased to cause the failure of the booster compressor 85. For this reason, in the refrigeration system 10 of the embodiment 4, to prevent the failure of the booster compressor 85, the operation of injecting liquid is performed.

Specifically, at the time of the second defrosting operation, the degree of opening of the electronic expansion valve 87 is adjusted according to the temperature of the refrigerant discharged from the booster compressor 85. For example, when the temperature of the refrigerant discharged from the booster compressor 85 is higher than a specified temperature, the degree of opening of the electronic expansion valve 87 is made larger. As a result, part of the refrigerant condensed by the freezer heat exchanger 84 is passed through the branch pipe 86 of the liquid injection passage 99 and is sent to the booster compressor 85. For this reason, the refrigerant sucked into the booster compressor 85 is refrigerated. Thus, this can prevent the temperature of the refrigerant discharged from the booster compressor 85 from being abnormally increased.

On the other hand, the refrigerants merged with each other in the second liquid side connection piping 23 are supplied to the air-conditioning circuit 60. Subsequent operations are the same as in the embodiment shown in FIG. 3. In other words, when the refrigerant flowing into the air-conditioning circuit 60 passes through the air-conditioning expansion valve 61, the refrigerant has its pressure reduced and then is introduced into the air-conditioning heat exchanger 62. In the air-conditioning heat exchanger 62, the refrigerant absorbs heat from the indoor air, thereby being evaporated. In the air-conditioning unit 12, the indoor air refrigerated by the air-conditioning heat exchanger 62 is supplied into the store. The refrigerant evaporated in the air-conditioning heat exchanger 62 passes through the second gas side connection piping 24 and flows into the outdoor circuit 30 and then passes through the second gas pipe 51, the first four-way switching valve 35, and the second four-way switching valve 36 in sequence, and then passes through the second low-pressure gas pipe 44, the second suction pipe 41b, and the third suction pipe 41c, and then is sucked by the first non-inverter compressor 31b and the second non-inverter compressor 31c. The first non-inverter compressor 31b and the second non-inverter compressor 31c compress the sucked refrigerant and discharge the compressed refrigerant into the second discharge pipe 48b and the third discharge pipe 48c.

As described above, in the defrosting operation shown in FIG. 22, the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted at the same time by the use of heat absorbed by the indoor heat exchanger 62 and heat produced by compressing the refrigerant by the first and second non-inverter compressors 31b, 31c of the outdoor circuit 30 and the booster compressor 85 of the freezer circuit 80. Moreover, the same operation as shown in FIG. 4 can be also performed and the operation can be also performed in which only the freezer heat exchanger 84 is defrosted by closing the chiller expansion valve 71.

In this regard, the defrosting operation of the freezer heat exchanger 84 at the time of the heating operation will be omitted.

—Effect of Embodiment 4—

In this embodiment 4, in addition to the same effect as in the embodiment 1, the following effect can be produced.

That is, this embodiment 4 can switch the first defrosting operation and the second defrosting operation and when the defrosting capacity of the freezer heat exchanger 84 is not sufficient in the first defrosting operation, the second defrosting operation of operating also the booster compressor 85 is operated. For this reason, according to the embodiment 4, heat to be given to the refrigerant by the second defrosting operation can be increased and hence the defrosting capacity of the freezer heat exchanger 84 can be increased. Thus, the freezer heat exchanger 84 can be effectively defrosted by the second defrosting operation.

Moreover, in the embodiment 4, an abnormal increase in the temperature of the refrigerant discharged from the booster compressor 85 can be prevented by injecting liquid into the booster compressor 85 during the second defrosting operation, so the booster compressor 85 can be protected with reliability.

—Modification of Embodiment 4—

In the embodiment 4, the branch pipe 86 of the liquid injection passage 99 is connected to the intermediate-pressure position of the booster compressor 85, but this branch pipe 86 may be connected to the first introduction passage 96 of the suction pipe of the booster compressor 85.

Moreover, in the embodiment 4, an abnormal increase in the temperature of the refrigerant discharged from the booster compressor 85 can be prevented by injecting the liquid into the booster compressor 85, but the operating capacity of the booster compressor 85 may be controlled in place of injecting the liquid. This can also prevent an abnormal increase in the temperature of the refrigerant discharged from the booster compressor 85.

Embodiment 5 of the Invention

A refrigeration system 10 of an embodiment 5 is an embodiment that is different from the refrigeration system 10 of the embodiment 1 in a part of the construction of the refrigerant circuit 20 and also in the construction of the hot gas introduction passages 100, 102. The points in which this embodiment 5 is different from the embodiment 1 will be mainly described below. Here, in this embodiment 5, the sensors are omitted in the drawing.

In this embodiment 5, the high-pressure introduction pipe 47 shown in FIG. 1 is not shown in the outdoor unit 11, but the high-pressure introduction pipe 47 is provided, just as with the embodiment 1, to introduce the high pressure of the refrigerant circuit 20 into the fourth port P4 of the third four-way switching valve 37.

In the freezer showcase 14, the refrigerant heat exchanger 81 is not provided but the gas side piping 110 (88) of the freezer heat exchanger 84 is connected to the suction side of the booster compressor 85. An oil separator 120 is disposed in the discharge pipe 98 of the booster compressor 85 and an oil return pipe 122 having a capillary tube 121 is connected between the oil separator 120 and the suction pipe 111 of the booster compressor 85. Moreover, a bypass piping 125 bypassing the booster compressor 85 when the booster compressor 85 fails is connected to the suction pipe 111 and the discharge pipe 98 of the booster compressor 85. This bypass piping 125 has a check valve CV10 disposed therein.

As for a feature of this embodiment 5, unlike the embodiment 1, the hot gas introduction passage 100 is not disposed individually on the higher stage side and the lower stage side but is constructed of one piping connected to the discharge line (high-pressure gas pipe) 45 of the compression mechanism 31 of the outdoor unit 11 and to the gas side piping 110 of the freezer heat exchanger 84. This hot gas introduction passage 100 has an electronic expansion valve 101 disposed therein as a flow control mechanism.

Moreover, it is also recommended to connect the hot gas introduction passage 100 not only to the freezer heat exchanger 84 but also, as shown by a broken line in FIG. 23, to the gas side piping 112 of the chiller heat exchanger 72 by a branch pipe (hot gas introduction passage) 102 disposed in the hot gas introduction passage 100 and to provide a switching mechanism 103 such as a three-way valve capable of switching or selecting a hot gas flow to the freezer heat exchanger 84 and a hot gas flow to the chiller heat exchanger 72. With this, both of the chiller heat exchanger 72 and the freezer heat exchanger 84 can be defrosted at the same time or only one of them can be defrosted. Thus, just as with the respective embodiments, this embodiment 5 can defrost the respective heat exchangers 72, 84 individually and hence can respond to a variety of patterns of defrosting operations.

For example, when the freezer heat exchanger 84 is defrosted, part of the refrigerant discharged from the compression mechanism 31 of the outdoor unit 11 flows through the hot gas introduction passage 100 and is introduced into the freezer heat exchanger 84. In the freezer heat exchanger 84, the frost adhering to the freezer heat exchanger 84 is melted by the heat of the high-pressure refrigerant. The refrigerant is evaporated in the chiller heat exchanger 72, the air-conditioning heat exchanger 62, or the outdoor heat exchanger 32 and then is sucked by the compressor mechanism 31. At that time, when the electronic expansion valve 101 is fully opened, the flow of refrigerant is large, so it can be thought that the frost adhering to the freezer heat exchanger 84 is melted around a coil at a stretch, whereby the blocks of the frost not melted around the coil will be dropped from the coil on goods for sale. However, when the flow of the refrigerant is controlled by adjusting the degree of opening of the electronic expansion valve 101, it is possible to melt the frost slowly around the coil and hence to prevent the frost from dropping on the goods for sale.

The operation at the time of the cooling operation and the heating operation in this embodiment is nearly the same as those in the respective embodiments described above and hence the description of the operation will be omitted here.

Other Embodiments

The above-mentioned embodiments may be constructed in the following manner. For example, in the embodiments 1 and 2, an example has been described in which one air-conditioning unit 12, one chiller showcase 13, and one freezer showcase 14 are connected, but the numbers of the air-conditioning unit 12, the chiller showcase 13, and the freezer showcase 14 may be changed as appropriate.

Moreover, in the embodiment 3, an example has been described in which one air-conditioning unit 12 and two freezer showcases 14 are connected to the outdoor unit 11, but three or more freezer showcases 14 may be connected.

Moreover, in any one of the embodiments 1 to 3, when the store is air-conditioned by a dedicated air-conditioner, the refrigeration system 10 of each embodiment does not need to be provided with the air-conditioning unit 12.

Further, while the compression mechanism 31 of the outdoor unit 11 is constructed of three compressors 31a, 31b, and 31c in the respective embodiments, the number of compressors may be changed and when the air-conditioning unit 12 is not provided, the number of compressor may be one.

Still further, the embodiment 4 is an embodiment in which the effect of the defrosting operation is enhanced by utilizing the booster compressor 85 at the time of defrosting the freezer heat exchanger 84 in the embodiment 1. The same idea can be applied also to the embodiment 2 and the embodiment 3. Still further, in the embodiment 4, at the time of the second defrosting operation, the refrigerant discharged from the compressor mechanism 31 of the outdoor unit 11 is circulated while part of the refrigerant is supplied to the freezer heat exchanger 84 and while the other part of the refrigerant is supplied to the booster compressor 85. However, the entire refrigerant discharged from the compressor mechanism 31 may be supplied to and compressed by the booster compressor 85 and then be supplied to the freezer heat exchanger 84.

The above-mentioned embodiments have been described by way of essentially preferable examples and do not intend to limit the present invention, its applications, or the scope of its usage.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful for a refrigeration system having a refrigerant circuit of a vapor compression type refrigeration cycle of the construction in which plural lines of refrigeration circuits each having a refrigeration heat exchanger are connected to an outdoor circuit provided with an outdoor heat exchanger and a compression mechanism and in which an auxiliary compressor is connected in series to the refrigeration heat exchanger in at least one line of refrigeration circuit.