Title:
HEAT EXCHANGE TUBE AND EVAPORATOR
Kind Code:
A1


Abstract:
An evaporator includes a plurality of flat heat exchange tubes extending in a vertical direction and arranged at intervals along a left-right direction with a width direction thereof coinciding with a front-rear direction. The heat exchange tube has a plurality of refrigerant channels arranged along the width direction. The evaporator satisfies a relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the refrigerant channels of the heat exchange tube by a width W of the heat exchange tube as measured in the front-rear direction. Also, the evaporator satisfies a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm of the heat exchange tube. This evaporator can reduce the temperature difference between air discharged into a compartment when a compressor is turned ON and that when the compressor is turned OFF.



Inventors:
Higashiyama, Naohisa (Oyama-shi, JP)
Mori, Daisuke (Oyama-shi, JP)
Watanabe, Sumitaka (Oyama-shi, JP)
Application Number:
11/755300
Publication Date:
12/06/2007
Filing Date:
05/30/2007
Assignee:
SHOWA DENKO K.K. (Tokyo, JP)
Primary Class:
Other Classes:
62/515, 165/176
International Classes:
F28D1/02; F25B39/02; F28D7/06
View Patent Images:
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Primary Examiner:
ROSATI, BRANDON MICHAEL
Attorney, Agent or Firm:
OBLON, MCCLELLAND, MAIER & NEUSTADT, L.L.P. (ALEXANDRIA, VA, US)
Claims:
What is claimed is:

1. A heat exchange tube assuming a flat form and having a plurality of channels arranged along a width direction of the heat exchange tube, the heat exchange tube satisfying a relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the channels by a tube width W and is expressed by A=N/W.

2. A heat exchange tube assuming a flat form and having a plurality of channels arranged along a width direction of the heat exchange tube, the heat exchange tube satisfying a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm.

3. A heat exchange tube according to claim 1 or 2, wherein each of all the channels excluding two channels located at widthwise opposite ends has an elongated protrusion formed on an inner peripheral surface of the channel and extending in a longitudinal direction of the channel.

4. A heat exchange tube according to claim 1 or 2, wherein each of all the channels excluding two channels located at widthwise opposite ends has a rectangular cross section, and a corner portion of the rectangular cross section has a radius R of 0.1 mm or less.

5. A heat exchange tube according to claim 1 or 2, comprising two flat walls in parallel with each other; first and second side walls extending between and over corresponding side ends of the two flat walls; and partition walls provided between the first and second side walls and extending between the two flat walls and in a longitudinal direction of the two flat walls for separating the adjacent channels from each other; wherein the heat exchange tube is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions on sides opposite the connection portion, and adapted to form the second side wall; and a plurality of partition-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side-wall-forming elongated projections butt against each other, and brazing the butting side-wall-forming elongated projections together; and the partition-wall-forming elongated projections of at least either flat-wall-forming portion form the partition walls.

6. An evaporator comprising a plurality of heat exchange tubes each assuming a flat form, the heat exchange tubes being arranged at intervals along a left-right direction with a width direction of the heat exchange tubes coinciding with a front-rear direction, the heat exchange tubes extending in a vertical direction, and each of the heat exchange tubes having a plurality of refrigerant channels arranged along the width direction, the evaporator satisfying a relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the refrigerant channels of the heat exchange tube by a width W of the heat exchange tube as measured in the front-rear direction and is expressed by A=N/W.

7. An evaporator comprising a plurality of heat exchange tubes each assuming a flat form, the heat exchange tubes being arranged at intervals along a left-right direction with a width direction of the heat exchange tubes coinciding with a front-rear direction, the heat exchange tubes extending in a vertical direction, and each of the heat exchange tubes having a plurality of refrigerant channels arranged along the width direction, the evaporator satisfying a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm of the heat exchange tube.

8. An evaporator according to claim 6 or 7, wherein each of all the refrigerant channels of the heat exchange tube excluding two refrigerant channels located at widthwise opposite ends has an elongated protrusion formed on an inner peripheral surface of the refrigerant channel and extending in a longitudinal direction of the refrigerant channel.

9. An evaporator according to claim 6 or 7, wherein each of all the refrigerant channels of the heat exchange tube excluding two refrigerant channels located at widthwise opposite ends has a rectangular cross section, and a corner portion of the rectangular cross section has a radius R of 0.1 mm or less.

10. An evaporator according to claim 6 or 7, wherein each of the heat exchange tubes comprises two flat walls in parallel with each other; first and second side walls extending between and over corresponding side ends of the two flat walls; and partition walls provided between the first and second side walls and extending between the two flat walls and in a longitudinal direction of the two flat walls for separating the adjacent refrigerant channels from each other; the heat exchange tube is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions on sides opposite the connection portion, and adapted to form the second side wall; and a plurality of partition-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side-wall-forming elongated projections butt against each other, and brazing the butting side-wall-forming elongated projections together; and the partition-wall-forming elongated projections of at least either flat-wall-forming portion form the partition walls.

11. An evaporator according to claim 6 or 7, further comprising: a refrigerant inlet/outlet header tank having a refrigerant inlet header section and a refrigerant outlet header section arranged in juxtaposition in the front-rear direction; a refrigerant turn header tank disposed below and apart from the refrigerant inlet/outlet header tank and having a first intermediate header section opposed to the refrigerant inlet header section, and a second intermediate header section opposed to the refrigerant outlet header section and communicating with the first intermediate header section; and a heat exchange core section formed between the refrigerant inlet/outlet header tank and the refrigerant turn header tank; wherein the heat exchange core section comprises a heat exchange tube group consisting of a plurality of heat exchange tubes arranged at intervals in a longitudinal direction of the refrigerant inlet/outlet and turn header tanks and connected, at opposite end portions, to the refrigerant inlet/outlet and turn header tanks, and fins each disposed between adjacent heat exchange tubes; two or more heat exchange tube groups are arranged between the refrigerant inlet/outlet and turn header tanks and in juxtaposition in an air flow direction; and the heat exchange tubes of at least one heat exchange tube group are connected between the refrigerant inlet header section and the first intermediate header section, and the heat exchange tubes of at least one heat exchange tube group are connected between the refrigerant outlet header section and the second intermediate header section.

Description:

BACKGROUND OF THE INVENTION

The present invention relates to a heat exchange tube and an evaporator, and more particularly to a heat exchange tube preferably used in, for example, an evaporator of a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, as well as to an evaporator.

Herein and in the appended claims, the downstream side (a direction represented by arrow X in FIG. 1) of an air flow through air-passing clearances between adjacent heat exchange tubes will be referred to as the “front,” and the opposite side as the “rear,” and the upper, lower, left-hand, and right-hand sides of FIG. 2 will be referred to as “upper,” “lower,” “left,” and “right,” respectively. Also, herein, the term “aluminum” encompasses aluminum alloys in addition to pure aluminum.

Conventionally, a so-called laminated evaporator has been widely employed as an evaporator for use in a car air conditioner. In the laminated evaporator, a plurality of flat, hollow members, each of which includes a pair of depressed plates facing each other and brazed to each other at their peripheral edge portions, are arranged in parallel, and corrugate fins are each disposed between and brazed to the adjacent flat, hollow members.

In recent years, evaporators have been demanded to have further reduction in size and weight and to exhibit higher performance. Herein, the expression “higher performance” refers to the cooling performance of a car air conditioner as observed when a compressor of the car air conditioner is ON. An evaporator which has been proposed to fulfill those requirements (refer to, for example, Japanese Patent Application Laid-Open (kokai) No. 2003-214794) includes a heat exchange core section in which heat exchange tube groups are arranged in two rows in a front-rear direction, each heat exchange tube group consisting of a plurality of heat exchange tubes arranged at intervals; a refrigerant inlet header section which is disposed on an upper-end side of the heat exchange tubes and to which the heat exchange tubes of a left half of a front heat exchange tube group are connected; a refrigerant outlet header section which is disposed on the upper-end side of the heat exchange tubes and rearward of the refrigerant inlet header section and to which the heat exchange tubes of a left half of a rear heat exchange tube group are connected; a first intermediate header section which is disposed on a lower-end side of the heat exchange tubes and to which the heat exchange tubes connected to the refrigerant inlet header section are connected; a second intermediate header section which is disposed rightward of the first intermediate header section and to which the remaining heat exchange tubes of the front heat exchange group are connected; a third intermediate header section which is disposed on the upper-end side of the heat exchange tubes and rightward of the refrigerant inlet header section and to which the heat exchange tubes connected to the second intermediate header section are connected; a fourth intermediate header section which is disposed on the upper-end side of the heat exchange tubes and rearward of the third intermediate header section and to which the remaining heat exchange tubes of the rear heat exchange group are connected; a fifth intermediate header section which is disposed on the lower-end side of the heat exchange tubes and rearward of the second intermediate header section and to which the heat exchange tubes connected to the fourth intermediate header section are connected; and a sixth intermediate header section which is disposed on the lower-end side of the heat exchange tubes and leftward of the fifth intermediate header section and to which the heat exchange tubes connected to the refrigerant outlet header section are connected. In the proposed evaporator, a refrigerant which has flown into the refrigerant inlet header section flows through the heat exchange tubes and through the first to sixth intermediate header sections; flows into the refrigerant outlet header section; and then flows out from the refrigerant outlet header section. The heat exchange tube used in the evaporator disclosed in the above publication is formed by bending an aluminum sheet into a flat form such that its width direction coincides with the air flow direction, and has an inner fin arranged therein, thereby forming a plurality of channels arranged along the width direction.

Generally, in the case where a fixed-capacity-type compressor is used in a car air conditioner which uses an evaporator, the temperature of air at an outlet of the evaporator (discharge air temperature) is detected by means of a thermistor, and on the basis of the detected discharge air temperature, the compressor is controlled so as to be cyclically turned ON and OFF. Specifically, the compressor is controlled as follows: as shown by the broken line in FIG. 12, when the discharge air temperature drops to a preset low temperature t1 while the compressor is ON, the compressor is turned OFF; subsequently, when the discharge air temperature rises to a preset high temperature t2, the compressor is turned ON. In association with the ON-OFF operation of the compressor, air of a relatively low temperature and air of a relatively high temperature are discharged into the compartment of an automobile in cycles of a constant period.

In recent years, in order to further improve comfort in the compartment of an automobile, reducing the temperature difference between air discharged into the compartment when the compressor is turned ON and that when the compressor is turned OFF has been contemplated. In the case of the evaporator disclosed in the above publication, a simple method of reducing the temperature difference between air discharged into the compartment when the compressor is turned ON and that when the compressor is turned OFF is to reduce the temperature difference between the preset low temperature t1 and the preset high temperature t2 by means of lowering the preset high temperature t2. However, in this case, the compressor is frequently turned ON and OFF. This may have adverse effect on the fuel economy of an automobile.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above problem and to provide a heat exchange tube which, when used in an evaporator, enables a reduction in the temperature difference between air discharged into the compartment of an automobile when a compressor is turned ON and that when the compressor is turned OFF, as well as an evaporator.

While conducting various studies, the inventors of the present invention have focused on heat exchange tubes and found that the temperature difference between air discharged into the compartment of an automobile when a compressor is turned ON and that when the compressor is turned OFF can be reduced through improvement of retainability of liquid within channels of heat exchange tubes used in an evaporator. Specifically, we have found the following: even after the compressor is turned OFF, while a liquid-phase refrigerant remains in the channels of heat exchange tubes of the evaporator, heat exchange continues between the remaining liquid-phase refrigerant and air which passes through the evaporator, so that an abrupt increase in discharge air temperature can be restrained.

The present invention has been accomplished based on the above findings and comprises the following modes.

1) A heat exchange tube assuming a flat form and having a plurality of channels arranged along a width direction of the heat exchange tube,

the heat exchange tube satisfying a relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the channels by a tube width W and is expressed by A=N/W.

In the heat exchange tube of par. 1), when A is less than 0.558, the capillary effect fails to provide sufficient retainability of liquid within the channels of the heat exchange tube. Accordingly, in a refrigeration cycle having an evaporator in which the heat exchange tubes are used with their longitudinal direction coinciding with the vertical direction, when a compressor is turned OFF, a refrigerant flows out from the channels of the heat exchange tubes in a short period of time. This causes an abrupt increase in discharge air temperature of the evaporator. When A is greater than 1.235, the capillary effect provides improved retainability of liquid within the channels of the heat exchange tube. Accordingly, in a refrigeration cycle having an evaporator in which the heat exchange tubes are used with their longitudinal direction coinciding with the vertical direction, when a compressor is turned OFF, there can be prevented outflow of refrigerant from the channels of the heat exchange tubes in a short period of time. However, cooling performance while the compressor is ON deteriorates.

2) A heat exchange tube assuming a flat form and having a plurality of channels arranged along a width direction of the heat exchange tube,

the heat exchange tube satisfying a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm.

As well known, the equivalent diameter appearing in the heat exchange tube of par. 2) has the following meaning. The heat exchange tube having a plurality of noncircular channels is considered as a circular tube having a single circular channel. The equivalent diameter means the diameter of the circular channel and is defined by


Dh=4Ac/Pi

where Ac is the total cross-sectional area of the plurality of channels, and Pi is the total cross-sectional, perimetric length of the plurality of channels.

In the heat exchange tube of par. 2), when Dh is less than 0.35, the capillary effect provides improved retainability of liquid within the channels of the heat exchange tubes. Accordingly, in a refrigeration cycle having an evaporator in which the heat exchange tubes are used with their longitudinal direction coinciding with the vertical direction, when a compressor is turned OFF, there can be prevented outflow of refrigerant from the channels of the heat exchange tubes in a short period of time. However, cooling performance while the compressor is ON deteriorates. When Dh is greater than 1.0, the capillary effect fails to provide sufficient retainability of liquid within the channels of the heat exchange tubes. Accordingly, in a refrigeration cycle having an evaporator in which the heat exchange tubes are used with their longitudinal direction coinciding with the vertical direction, when a compressor is turned OFF, a refrigerant flows out from the channels of the heat exchange tubes in a short period of time. This causes an abrupt increase in discharge air temperature of the evaporator as well as a drop in cooling performance while the compressor is ON.

3) A heat exchange tube according to par. 1) or 2), wherein each of all the channels excluding two channels located at widthwise opposite ends has an elongated protrusion formed on an inner peripheral surface of the channel and extending in a longitudinal direction of the channel.

4) A heat exchange tube according to par. 1) or 2), wherein each of all the channels excluding two channels located at widthwise opposite ends has a rectangular cross section, and a corner portion of the rectangular cross section has a radius R of 0.1 mm or less.

5) A heat exchange tube according to par. 1) or 2), comprising two flat walls in parallel with each other; first and second side walls extending between and over corresponding side ends of the two flat walls; and partition walls provided between the first and second side walls and extending between the two flat walls and in a longitudinal direction of the two flat walls for separating the adjacent channels from each other;

    • wherein the heat exchange tube is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions on sides opposite the connection portion, and adapted to form the second side wall; and a plurality of partition-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections;

the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side-wall-forming elongated projections butt against each other, and brazing the butting side-wall-forming elongated projections together; and

the partition-wall-forming elongated projections of at least either flat-wall-forming portion form the partition walls.

6) An evaporator comprising a plurality of heat exchange tubes each assuming a flat form, the heat exchange tubes being arranged at intervals along a left-right direction with a width direction of the heat exchange tubes coinciding with a front-rear direction, the heat exchange tubes extending in a vertical direction, and each of the heat exchange tubes having a plurality of refrigerant channels arranged along the width direction,

    • the evaporator satisfying a relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the refrigerant channels of the heat exchange tube by a width W of the heat exchange tube as measured in the front-rear direction and is expressed by A=N/W.

7) An evaporator comprising a plurality of heat exchange tubes each assuming a flat form, the heat exchange tubes being arranged at intervals along a left-right direction with a width direction of the heat exchange tubes coinciding with a front-rear direction, the heat exchange tubes extending in a vertical direction, and each of the heat exchange tubes having a plurality of refrigerant channels arranged along the width direction,

    • the evaporator satisfying a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm of the heat exchange tube.

8) An evaporator according to par. 6) or 7), wherein each of all the refrigerant channels of the heat exchange tube excluding two refrigerant channels located at widthwise opposite ends has an elongated protrusion formed on an inner peripheral surface of the refrigerant channel and extending in a longitudinal direction of the refrigerant channel.

9) An evaporator according to par. 6) or 7), wherein each of all the refrigerant channels of the heat exchange tube excluding two refrigerant channels located at widthwise opposite ends has a rectangular cross section, and a corner portion of the rectangular cross section has a radius R of 0.1 mm or less.

10) An evaporator according to par. 6) or 7), wherein each of the heat exchange tubes comprises two flat walls in parallel with each other; first and second side walls extending between and over corresponding side ends of the two flat walls; and partition walls provided between the first and second side walls and extending between the two flat walls and in a longitudinal direction of the two flat walls for separating the adjacent refrigerant channels from each other;

the heat exchange tube is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions on sides opposite the connection portion, and adapted to form the second side wall; and a plurality of partition-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections;

the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side-wall-forming elongated projections butt against each other, and brazing the butting side-wall-forming elongated projections together; and

the partition-wall-forming elongated projections of at least either flat-wall-forming portion form the partition walls.

11) An evaporator according to par. 6) or 7), further comprising:

a refrigerant inlet/outlet header tank having a refrigerant inlet header section and a refrigerant outlet header section arranged in juxtaposition in the front-rear direction;

a refrigerant turn header tank disposed below and apart from the refrigerant inlet/outlet header tank and having a first intermediate header section opposed to the refrigerant inlet header section, and a second intermediate header section opposed to the refrigerant outlet header section and communicating with the first intermediate header section; and

a heat exchange core section formed between the refrigerant inlet/outlet header tank and the refrigerant turn header tank;

wherein the heat exchange core section comprises a heat exchange tube group consisting of a plurality of heat exchange tubes arranged at intervals in a longitudinal direction of the refrigerant inlet/outlet and turn header tanks and connected, at opposite end portions, to the refrigerant inlet/outlet and turn header tanks, and fins each disposed between adjacent heat exchange tubes;

two or more heat exchange tube groups are arranged between the refrigerant inlet/outlet and turn header tanks and in juxtaposition in an air flow direction; and

the heat exchange tubes of at least one heat exchange tube group are connected between the refrigerant inlet header section and the first intermediate header section, and the heat exchange tubes of at least one heat exchange tube group are connected between the refrigerant outlet header section and the second intermediate header section.

According to the heat exchange tube of par. 1) or 2), the capillary effect provides improved retainability of liquid within the channels of the heat exchange tube. Accordingly, in a refrigeration cycle having an evaporator in which the heat exchange tubes are used with their longitudinal direction coinciding with the vertical direction, even when a compressor is turned OFF, a liquid-phase refrigerant is retained within the channels of the heat exchange tubes for a relatively long period of time by virtue of the capillary effect, thereby preventing outflow of the liquid-phase refrigerant from the channels of the heat exchange tubes in a short period of time. Additionally, even after the compressor is turned OFF, while the liquid-phase refrigerant remains within the channels of the heat exchange tubes of the evaporator, heat exchange continues between the remaining liquid-phase refrigerant and air passing through the evaporator, so that an abrupt increase in discharge air temperature can be restrained. As a result, in the case where the compressor is controlled on the basis of discharge air temperature of the evaporator, the preset high temperature can be set lower than in the case of the evaporator disclosed in the above publication. Therefore, the temperature difference between air discharged into a compartment of an automobile when the compressor is turned ON and that when the compressor is turned OFF can be reduced, thereby improving comfort in the compartment. Furthermore, an abrupt increase in discharge air temperature after the compressor is turned OFF can be restrained. Thus, in the case where the compressor is controlled on the basis of discharge air temperature of the evaporator, even when the preset high temperature is set lower than in the case of the evaporator disclosed in the above publication, the cycle of turning ON and OFF the compressor can have the same period as in the case where the compressor is used in combination with the evaporator disclosed in the above publication. Therefore, as opposed to the case where the evaporator disclosed in the above publication is used, the compressor does not frequently go ON and OFF, so that the fuel economy of an automobile is not adversely effected.

According to the heat exchange tube of par. 3) or 4), the capillary effect provides further improved retainability of liquid within the channels of the heat exchange tube.

According to the evaporator of par. 6) or 7), the capillary effect provides improved retainability of liquid within the channels of the heat exchange tubes. Accordingly, in a refrigeration cycle having this evaporator, even when a compressor is turned OFF, a liquid-phase refrigerant is retained within the channels of the heat exchange tubes for a relatively long period of time by virtue of the capillary effect, thereby preventing outflow of the liquid-phase refrigerant from the channels of the heat exchange tubes in a short period of time. Additionally, even after the compressor is turned OFF, while the liquid-phase refrigerant remains within the channels of the heat exchange tubes of the evaporator, heat exchange continues between the remaining liquid-phase refrigerant and air passing through the evaporator, so that an abrupt increase in discharge air temperature can be restrained. As a result, in the case where the compressor is controlled on the basis of discharge air temperature of the evaporator, the preset high temperature can be set lower than in the case of the evaporator disclosed in the above publication. Therefore, the temperature difference between air discharged into a compartment of an automobile when the compressor is turned ON and that when the compressor is turned OFF can be reduced, thereby improving comfort in the compartment. Furthermore, an abrupt increase in discharge air temperature after the compressor is turned OFF can be restrained. Thus, in the case where the compressor is controlled on the basis of discharge air temperature of the evaporator, even when the preset high temperature is set lower than in the case of the evaporator disclosed in the above publication, the cycle of turning ON and OFF the compressor can have the same period as in the case where the compressor is used in combination with the evaporator disclosed in the above publication. Therefore, as opposed to the case where the evaporator disclosed in the above publication is used, the compressor does not frequently go ON and OFF, so that the fuel economy of an automobile is not adversely effected.

According to the evaporator of par. 8) or 9), the capillary effect provides further improved retainability of liquid within the channels of the heat exchange tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut-away perspective view showing the overall configuration of an evaporator according to the present invention;

FIG. 2 is a fragmentary view in vertical section showing the evaporator of FIG. 1 with its intermediate portion omitted as it is seen from the rear;

FIG. 3 is an enlarged fragmentary view in section taken along line A-A of FIG. 2;

FIG. 4 is a cross-sectional view showing a heat exchange tube of the evaporator of FIG. 1;

FIG. 5 is an exploded perspective view of a refrigerant inlet/outlet header tank of the evaporator of FIG. 1;

FIG. 6 is a sectional view taken along line B-B of FIG. 2;

FIG. 7 is an enlarged sectional view taken along line C-C of FIG. 6;

FIG. 8 is a sectional view taken along line D-D of FIG. 7;

FIG. 9 is a partially cut-away perspective view showing a right-hand closing member and a joint plate for the refrigerant inlet/outlet header tank of the evaporator of FIG. 1;

FIG. 10 is an exploded perspective view of a refrigerant turn header tank of the evaporator of FIG. 1;

FIG. 11 is a sectional view taken along line E-E of FIG. 2;

FIG. 12 is a graph showing variation of discharge air temperature when a fixed-capacity-type compressor is turned ON and OFF in a car air conditioner which uses an evaporator;

FIGS. 13a to 13e are cross-sectional views showing heat exchange tubes used in evaporators of Examples 2 to 5 and Comparative Example;

FIG. 14 is a graph showing the relationship of equivalent diameter with cooling performance and the amount of remaining liquid-phase refrigerant;

FIG. 15 is a graph showing the relationship of the number of refrigerant channels with cooling performance and the amount of remaining liquid-phase refrigerant;

FIG. 16 is a cross-sectional view showing a modified heat exchange tube;

FIG. 17 is a fragmentary enlarged view of FIG. 16;

FIGS. 18a to 18c are views showing a method of manufacturing the heat exchange tube of FIGS. 16 and 17; and

FIG. 19 is a cross-sectional view showing another modified heat exchange tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will next be described in detail with reference to the drawings. The embodiment is implemented by applying a heat exchange tube according to the present invention to an evaporator of a car air conditioner using a chlorofluorocarbon-based refrigerant.

FIGS. 1 and 2 show the overall configuration of an evaporator, and FIGS. 3 to 11 show the configuration of essential portions of the evaporator.

As shown in FIGS. 1 to 3, an evaporator 20 is configured such that a heat exchange core section 21 is provided between a refrigerant inlet/outlet header tank 22 and a refrigerant turn header tank 23. The refrigerant inlet/outlet header tank 22 and the refrigerant turn header tank 23 are made of aluminum and are vertically spaced apart from each other.

The refrigerant inlet/outlet header tank 22 includes a refrigerant inlet header section 24 located on a side toward the front (downstream side with respect to the air flow direction), a refrigerant outlet header section 25 located on a side toward the rear (upstream side with respect to the air flow direction), and a connection section 26 which integrally connects the header sections 24 and 25. A refrigerant inlet pipe 27 made of aluminum is connected to the refrigerant inlet header section 24 of the refrigerant inlet/outlet header tank 22. A refrigerant outlet pipe 28 made of aluminum is connected to the refrigerant outlet header section 25.

The refrigerant turn header tank 23 includes a first intermediate header section 30 located on the side toward the front, a second intermediate header section 31 located on the side toward the rear, and a connection section 32 which integrally connects the header sections 30 and 31. The header sections 30 and 31 and the connection section 32 form a drain gutter 33.

The heat exchange core section 21 is configured as follows: heat exchange tube groups 35 are arranged in a plurality of; herein, two, rows in the front-rear direction, each heat exchange tube group 35 consisting of a plurality of heat exchange tubes 34 arranged in parallel at intervals in the left-right direction; corrugated fins 36 are disposed within corresponding air-passing clearances between the adjacent heat exchange tubes 34 of the heat exchange tube groups 35 and externally of the left-end and right-end heat exchange tubes 34 of the heat exchange tube groups 35 and are brazed to the corresponding heat exchange tubes 34; and side plates 37 made of aluminum are disposed externally of the left-end and right-end corrugated fins 36 and are brazed to the corresponding corrugated fins 36. Upper and lower ends of the heat exchange tubes 34 of the front heat exchange tube group 35 are connected to the refrigerant inlet header section 24 and the first intermediate header section 30, respectively, whereby the heat exchange tubes 34 form a forward refrigerant flow section. Upper and lower ends of the heat exchange tubes 34 of the rear heat exchange tube group 35 are connected to the refrigerant outlet header section 25 and the second intermediate header section 31, respectively, whereby the heat exchange tubes 34 form a return refrigerant flow section. The first intermediate header section 30, the second intermediate header section 31, and the heat exchange tubes 34 of the front and rear heat exchange tube groups 35 form a refrigerant circulation path for establishing communication between the refrigerant inlet header section 24 and the refrigerant outlet header section 25.

The heat exchange tube 34 is formed from a bare aluminum extrudate. As shown in FIG. 4, the heat exchange tube 34 assumes a flat form with its width direction coinciding with the front-rear direction and has a plurality of refrigerant channels 34a arranged along the width direction. The heat exchange tube 34 includes flat left and right walls 341 and 342 facing each other; front and rear side walls 343 and 344 extending between and over corresponding side ends of the left and right flat walls 341 and 342; and partition walls 345 provided between the front and rear side walls 343 and 344 and extending between the left and right walls 341 and 342 and in a longitudinal direction of the left and right walls 341 and 342 for separating the adjacent refrigerant channels 34a from each other. Each of all the refrigerant channels 34a of the heat exchange tube 34 excluding two refrigerant channels 34a located at widthwise opposite ends has two or more; in the present embodiment, four, elongated protrusions 346 formed on an inner peripheral surface of the refrigerant channel 34a and extending in a longitudinal direction of the refrigerant channel 34a. That is, in each of all the refrigerant channels 34a of the heat exchange tube 34 excluding two refrigerant channels 34a located at widthwise opposite ends, the two elongated protrusions 346 are formed on the inner surface of each of the left and right walls 341 and 342 in such a manner as to be spaced apart from each other in the front-rear direction. Also, each of all the refrigerant channels 34a excluding two refrigerant channels 34a located at widthwise opposite ends has a rectangular cross section, and corner portions 34b of the rectangular cross section each have a radius R of 0.1 mm or less. Each of the front and rear side walls 343 and 344 of the heat exchange tube 34 has such an arcuate cross section that a central portion projects outward. The front heat exchange tubes 34 and the rear heat exchange tubes 34 are arranged so as to be identical in position in the left-right direction. The front heat exchange tubes 34 communicate with the refrigerant inlet header section 24 and the first intermediate header section 30. The rear heat exchange tubes 34 communicate with the refrigerant outlet header section 25 and the second intermediate header section 31.

The heat exchange tube 34 satisfies a relation 0.558 ≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of the refrigerant channels 34a by a width W of the heat exchange tube 34 as measured in the front-rear direction and is expressed by A=N/W. Also, the heat exchange tube 34 satisfies a relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter in mm of the heat exchange tube 34. The heat exchange tube 34 satisfies one of or both of the above two requirements.

The corrugated fin 36 is made in a wavy form from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof. The corrugated fin 36 includes wave crest portions, wave trough portions, and flat horizontal connection portions each connecting together the wave crest portion and the wave trough portion. A plurality of louvers are formed at the connection portions in juxtaposition in the front-rear direction. The front and rear heat exchange tubes 34 which constitute the front and rear heat exchange tube groups 35 share the corresponding corrugated fins 36. The width of the corrugated fin 36 as measured in the front-rear direction is substantially equal to the span between the front end of the front heat exchange tube 34 and the rear end of the rear heat exchange tube 34. The wave crest portions and wave trough portions of the corrugated fin 36 are brazed to the front and rear heat exchange tubes. Notably, the front end of the corrugated fin 36 slightly projects frontward beyond the front end of the front heat exchange tube 34.

As shown in FIGS. 3, 5, and 6, the refrigerant inlet/outlet header tank 22 is formed from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof, and includes a first member 38 assuming a plate-like form and to which all the heat exchange tubes 34 are connected; a second member 39 formed from a bare aluminum extrudate and covering the upper side of the first member 38; and closing members 41 and 42 formed from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof, and joined to the opposite ends of the first and second members 38 and 39. A joint plate 43 made of aluminum and elongated in the front-rear direction is brazed to the outer surface of the right-hand closing member 42 while facing the ends of the refrigerant inlet header section 24 and the refrigerant outlet header section 25. The refrigerant inlet pipe 27 and the refrigerant outlet pipe 28 are connected to the joint plate 43.

The first member 38 includes a first header formation portion 44, which assumes a downward bulging form and forms a lower portion of the refrigerant inlet header section 24; a second header formation portion 45, which assumes a downward bulging form and forms a lower portion of the refrigerant outlet header section 25; and a connection wall 46, which connects a rear end portion of the first header formation portion 44 and a front end portion of the second header formation portion 45 and forms a lower portion of the connection section 26. A plurality of tube insertion holes 47 elongated in the front-rear direction are formed in the header formation portions 44 and 45 at intervals in the left-right direction. The tube insertion holes 47 of the header formation portion 44 and those of the header formation portion 45 are identical in position in the left-right direction. Upper end portions of the heat exchange tubes 34 of the front and rear heat exchange tube groups 35 of the heat exchange core section 21 are inserted into the respective tube insertion holes 47 of the first and second header formation portions 44 and 45 and are brazed to the first member 38 by utilization of the brazing material layers of the first member 38. Thus, the upper end portions of the heat exchange tubes 34 of the front heat exchange tube group 35 are connected to the refrigerant inlet header section 24 in a communicating condition, whereas the upper end portions of the heat exchange tubes 34 of the rear heat exchange tube group 35 are connected to the refrigerant outlet header section 25 in a communicating condition. A plurality of drain through-holes 48 elongated in the left-right direction are formed in the connection wall 46 at intervals in the left-right direction. Also, a plurality of fixation though-holes 49 are formed in the connection wall 46 at intervals in the left-right direction while being shifted from the drain through-holes 48.

The second member 39 includes a first header formation portion 51, which assumes an upward bulging form and forms an upper portion of the refrigerant inlet header section 24; a second header formation portion 52, which assumes an upward bulging form and forms an upper portion of the refrigerant outlet header section 25; and a connection wall 53, which connects a rear end portion of the first header formation portion 51 and a front end portion of the second header formation portion 52 and is brazed to the connection wall 46 of the first member 38 to form an upper portion of the connection section 26. The first header formation portion 51 has a horizontal intra-inlet-header-section flow-dividing control wall 51b, which integrally connects lower end portions of front and rear walls 51a of the first header formation portion 51 and vertically divides the interior of the refrigerant inlet header section 24 into two spaces 24A and 24B. The second header formation portion 52 has a horizontal intra-outlet-header-section flow-dividing control wall 52b, which is at the same level as that of the intra-inlet-header-section flow-dividing control wall 51b, integrally connects lower end portions of front and rear walls 52a of the second header formation portion 52, and vertically divides the interior of the refrigerant outlet header section 25 into two spaces 25A and 25B.

A cutout 50 is formed at the left end of the intra-inlet-header-section flow-dividing control wall 51b of the second member 39. The intra-inlet-header-section flow-dividing control wall 51b has flow-division-adjusting holes 60, which are formed in a through-hole form at a portion biased toward the cutout 50 and at a portion biased toward the right end. A plurality of oblong refrigerant passage holes 54A and 54B in a through-hole form and elongated in the left-right direction are formed in a rear region, excluding left and right end portions thereof, of the intra-outlet-header-section flow-dividing control wall 52b of the second member 39 at intervals in the left-right direction. The central oblong refrigerant passage hole 54A is shorter than the other oblong refrigerant passage holes 54B and is located between the adjacent heat exchange tubes 34.

A plurality of drain through-holes 55 elongated in the left-right direction are formed in the connection wall 53 of the second member 39 in alignment with the corresponding drain through-holes 48 of the first member 38. Also, a plurality of projections 56 are formed on the connection wall 53 in alignment with the corresponding fixation through-holes 49 of the first member 38 and are fitted into the corresponding fixation through-holes 49. The first member 38 and the second member 39 are assembled together as follows. The first and second members 38 and 39 are tentatively assembled together such that the projections 56 are tightly inserted into the corresponding fixation through-holes 49. In this tentatively assembled condition, by utilization of the brazing material layers of the first member 38, the first and second members 38 and 39 are assembled together such that front end portions of the first header formation portions 44 and 51, rear end portions of the second header formation portions 45 and 52, and the connection walls 46 and 53 are respectively brazed together.

The first header formation portion 44 of the first member 38 and the first header formation portion 51 of the second member 39 form a hollow inlet header section body 240 whose opposite ends are open. The second header formation portion 45 of the first member 38 and the second header formation portion 52 of the second member 39 form a hollow outlet header section body 250 whose opposite ends are open.

The left-hand closing member 41 is formed such that a front cap 41a for closing the left end opening of the inlet header section body 240 and a rear cap 41b for closing the left end opening of the outlet header section body 250 are integrated with each other via a connection portion 41c. The front cap 41a of the left-hand closing member 41 has an integrally formed rightward projecting portion 57 to be fitted into the inlet header section body 240. Similarly, the rear cap 41b has an integrally formed upper rightward-projecting portion 58 to be fitted into a space of the outlet header section body 250 located above the intra-outlet-header-section flow-dividing control wall 52b, and an integrally formed lower rightward-projecting portion 59 to be fitted into a space of the outlet header section body 250 located below the intra-outlet-header-section flow-dividing control wall 52b. The upper rightward-projecting portion 58 and the lower rightward-projecting portion 59 are vertically spaced apart from each other. Engagement fingers 61 projecting rightward are formed integrally with the left-hand closing member 41 at a connection portion between a front side edge and a top edge of the left-hand closing member 41, at a connection portion between the front side edge and a bottom edge, at a connection portion between a rear side edge and the top edge, and at a connection portion between the rear side edge and the bottom edge, respectively. The engagement fingers 61 are engaged with the first and second members 38 and 39. The left-hand closing member 41 is brazed to the first and second members 38 and 39 by utilization of its own brazing material layers. The front cap 41a of the left-hand closing member 41 closes the left end opening of the cutout 50 of the intra-inlet-header-section flow-dividing control wall 51b, thereby forming a communication hole 70 for establishing communication between the upper and lower spaces 24A and 24B of the inlet header section 24 at a left end portion of the inlet header section 24. In the present embodiment, the communication hole 70 is formed by means of closing the left end opening of the cutout 50 by the front cap 41a. However, instead of formation of a cutout, a through-hole may be formed at a left end portion of the intra-inlet-header-section flow-dividing control wall 51b so as to serve as a communication hole.

The right-hand closing member 42 is formed such that a front cap 42a for closing the right end opening of the inlet header section body 240 and a rear cap 42b for closing the right end opening of the outlet header section body 250 are integrated with each other via a connection portion 42c. The front cap 42a of the right-hand closing member 42 has an integrally formed upper leftward-projecting portion 62 to be fitted into a space of the inlet header section body 240 located above the intra-inlet-header-section flow-dividing control wall 51b, and an integrally formed lower leftward-projecting portion 80 to be fitted into a space of the inlet header section body 240 located below the intra-inlet-header-section flow-dividing control wall 51b. The upper leftward-projecting portion 62 and the lower leftward-projecting portion 80 are vertically spaced apart from each other. Similarly, the rear cap 42b has an integrally formed upper leftward-projecting portion 63 to be fitted into a space of the outlet header section body 250 located above the intra-outlet-header-section flow-dividing control wall 52b, and an integrally formed lower leftward-projecting portion 64 to be fitted into a space of the outlet header section body 250 located below the intra-outlet-header-section flow-dividing control wall 52b. The upper leftward-projecting portion 63 and the lower leftward-projecting portion 64 are vertically spaced apart from each other. A refrigerant inlet 66 is formed in a projecting end wall of the upper leftward-projecting portion 62 of the front cap 42a of the right-hand closing member 42. Similarly, a refrigerant outlet 67 is formed in a projecting end wall of the upper leftward-projecting portion 63 of the rear cap 42b. Engagement fingers 65 projecting leftward are formed integrally with the right-hand closing member 42 at a connection portion between a front side edge and a top edge of the right-hand closing member 42, at a connection portion between the front side edge and a bottom edge, at a connection portion between a rear side edge and the top edge, and at a connection portion between the rear side edge and the bottom edge, respectively. The engagement fingers 65 are engaged with the first and second members 38 and 39.

As shown in FIGS. 7 to 9, an upwardly projecting first engagement male portion 1 is formed integrally with the right-hand closing member 42 at a front-rear-direction central portion of the upper end of the connection portion 42c. Similarly, a downwardly projecting second engagement male portion 2 is formed integrally with the right-hand closing member 42 at a front-rear-direction central portion of the lower end of the connection portion 42c. In the course of manufacture of the evaporator 20, in a state before assembly of the right-hand closing member 42 and the joint plate 43, the second engagement male portion 2 projects rightward. The rightward-projecting second engagement male portion is denoted by reference numeral 2A in FIG. 9 (represented by the phantom line). Furthermore, cutouts 3 are formed in the right-hand closing member 42 at front and rear end portions of a bottom edge portion of the right-hand closing member 42. The right-hand closing member 42 is brazed to the first and second members 38 and 39 by utilization of its own brazing material layers.

The joint plate 43 has a short, cylindrical refrigerant inflow port 68 communicating with the refrigerant inlet 66 of the right-hand closing member 42, and a short, cylindrical refrigerant outflow port 69 communicating with the refrigerant outlet 67 of the right-hand closing member 42. Each of the refrigerant inflow port 68 and the refrigerant outflow port 69 includes a circular through-hole and a rightward-projecting short, cylindrical portion formed integrally around the circular through-hole.

A slit 4 extending in the vertical direction and adapted to prevent short circuit is formed in a portion of the joint plate 43 between the refrigerant inflow port 68 and the refrigerant outflow port 69. Also, generally trapezoidal through-holes 5 and 6 are formed in the portion of the joint plate 43 in such a manner as to be connected to the upper and lower ends, respectively, of the slit 4. Furthermore, a portion of the joint plate 43 located above the upper through-hole 5 and a portion of the joint plate 43 located below the lower through-hole 6 are bent in such a U-shaped fashion as to project leftward (toward the right-hand closing member 42), thereby forming first and second engagement female portions 7 and 8, respectively. The first engagement male portion 1 of the right-hand closing member 42 is inserted into the first engagement female portion 7 from underneath for engagement, and the second engagement male portion 2 of the right-hand closing member 42 is inserted into the second engagement female portion 8 from above for engagement, thereby preventing movement of the joint plate 43 in the left-right direction. The second engagement male portion 2 of the right-hand closing member 42 in a rightward projecting condition represented by the phantom line of FIG. 9 is inserted into the lower through-hole 6 and then bent downward; in other words, the second engagement male portion 2 is inserted into the second engagement female portion 8 from above. The first engagement female portion 7 is engaged with front and rear portions of the connection portion 42c of the right-hand closing member 42 which are located on front-rear-direction opposite sides of the first engagement male portion 1, thereby preventing downward movement of the joint plate 43. Furthermore, engagement fingers 9 projecting leftward are formed integrally with the joint plate 43 at front and rear end portions of a bottom edge of the joint plate 43. The engagement fingers 9 are engaged with the right-hand closing member 42 while being fitted into the respective cutouts 3 formed in the bottom edge of the right-hand closing member 42, thereby preventing movement of the joint plate 43 in the upward direction and in the front-rear direction. While the joint plate 43 is engaged with the right-hand closing member 42 in such a manner that movement thereof in the left-right direction, the vertical direction, and the front-rear direction is prevented, the joint plate 43 is brazed to the right-hand closing member 42 by utilization of the brazing material layers of the right-hand closing member 42.

A diameter-reduced portion formed at one end portion of the refrigerant inlet pipe 27 is inserted into and brazed to the refrigerant inflow port 68 of the joint plate 43. Similarly, a diameter-reduced portion formed at one end portion of the refrigerant outlet pipe 28 is inserted into and brazed to the refrigerant outflow port 69 of the joint plate 43. Although unillustrated, an expansion valve attachment member is joined to the other end portions of the refrigerant inlet and outlet pipes 27 and 28 in such a manner as to face the ends of the pipes 27 and 28.

As shown in FIGS. 2, 3, 10, and 11, the refrigerant turn header tank 23 is formed from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and includes a first member 73 which has a plate-like shape and to which all the heat exchange tubes 34 are connected; a second member 74 formed from a bare aluminum extrudate and covering the lower side of the first member 73; closing members 75 and 76 formed from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and brazed to the opposite ends of the first and second members 73 and 74; and a communication member 77 formed from an aluminum bare material, elongated in the front-rear direction, and brazed to the outer surface of the right-hand closing member 76 in such a manner as to face the ends of the first intermediate header section 30 and the second intermediate header section 31. The first intermediate header section 30 and the second intermediate header section 31 communicate with each other at their right end portions via the communication member 77.

The first member 73 includes a first header formation portion 78, which assumes an upward bulging form and forms an upper portion of the first intermediate header section 30; a second header formation portion 79, which assumes an upward bulging form and forms an upper portion of the second intermediate header section 31; and a connection wall 81, which connects a rear end portion of the first header formation portion 78 and a front end portion of the second header formation portion 79 and forms an upper portion of the connection section 32. Inclined walls 78a and 79a are provided at the front-rear-direction inside of the first and second header formation portions 78 and 79 and are inclined in such a manner as to fan out upward and in the front-rear direction. The inclined walls 78a and 79a and the connection wall 81 form a drain gutter 33 whose side surfaces are inclined in such a manner as to fan out upward and in the front-rear direction. A plurality of tube insertion holes 82 elongated in the front-rear direction are formed in the first and second header formation portions 78 and 79 at predetermined intervals in the left-right direction. The tube insertion holes 82 of the first header formation portion 78 and those of the second header formation portion 79 are identical in position in the left-right direction. End portions, located on a side toward the connection section 32, of the tube insertion holes 82; i.e., rear end portions of the tube insertion holes 82 of the first header formation portion 78 and front end portions of the tube insertion holes 82 of the second header formation portion 79, are located in the inclined walls 78a and 79a, respectively. Thus, the end portions, located on the side toward the connection section 32, of the tube insertion holes 82 are located in the side surfaces of the drain gutter 33. Drain grooves 83 are formed on the first and second header formation portions 78 and 79 on the front side of the corresponding tube insertion holes 82 of the first header formation portion 78 and on the rear side of the corresponding tube insertion holes 82 of the second header formation portion 79 in such a manner as to be connected to front end portions of the corresponding tube insertion holes 82 of the first header formation portion 78 and in such a manner as to be connected to rear end portions of the corresponding tube insertion holes 82 of the second header formation portion 79, as well as in such a manner that the bottom of each drain groove 83 extends gradually downward as the distance from the corresponding tube insertion hole 82 increases. Lower end portions of the heat exchange tubes 34 of the front and rear heat exchange tube groups 35 of the heat exchange core section 21 are inserted into the corresponding tube insertion holes 82 of the first and second header formation portions 78 and 79 and brazed to the first member 73 by utilization of the brazing material layers of the first member 73. Thus, the lower end portions of the heat exchange tubes 34 of the front heat exchange tube group 35 are connected to the first intermediate header section 30 in a communicating condition, whereas the lower end portions of the heat exchange tubes 34 of the rear heat exchange tube group 35 are connected to the second intermediate header section 31 in a communicating condition. A plurality of drain through-holes 84 elongated in the left-right direction are formed in the connection wall 81 of the first member 73 at intervals in the left-right direction. Also, a plurality of fixation though-holes 85 are formed in the connection wall 81 of the first member 73 at intervals in the left-right direction while being shifted from the drain through-holes 84. The first member 73 has the same shape as that of the first member 38 of the refrigerant inlet/outlet header tank 22. The first members 73 and 38 are disposed in a mirror image relation.

The second member 74 includes a first header formation portion 86, which assumes a downward bulging form and forms a lower portion of the first intermediate header section 30; a second header formation portion 87, which assumes a downward bulging form and forms a lower portion of the second intermediate header section 31; and a connection wall 88, which connects the first and second header formation portions 86 and 87 and is brazed to the connection wall 81 of the first member 73 to form the connection section 32. The second header formation portion 87 has a horizontal flow-dividing control wall 87b, which integrally connects upper end portions of front and rear walls 87a of the second header formation portion 87 and vertically divides the interior of the second intermediate header section 31 into two spaces 31A and 31B. A plurality of circular refrigerant passage holes 89 in a through-hole form are formed in a rear portion of the flow-dividing control wall 87b at intervals in the left-right direction. The distance between the adjacent circular refrigerant passage holes 89 increases gradually as the distance from the right end of the flow-dividing control wall 87b increases. Notably, the distance between the adjacent circular refrigerant passage holes 89 may be constant. A plurality of drain through-holes 91 elongated in the left-right direction are formed in the connection wall 88 of the second member 74 in alignment with the corresponding drain through-holes 84 of the first member 73. Also, a plurality of projections 92 projecting upward are formed on the connection wall 88 in alignment with the corresponding fixation through-holes 85 of the first member 73 and are fitted into the corresponding fixation through-holes 85. The first member 73 and the second member 74 are assembled together as follows. The first and second members 73 and 74 are tentatively assembled together such that the projections 92 are tightly inserted into the corresponding fixation through-holes 85. In this tentatively assembled condition, by utilization of the brazing material layers of the first member 73, the first and second members 73 and 74 are assembled together such that front end portions of the first header formation portions 78 and 86, rear end portions of the second header formation portions 79 and 87, and the connection walls 81 and 88 are respectively brazed together. The second member 74 has the same shape as that of the second member 39 of the refrigerant inlet/outlet header tank 22 except that the refrigerant passage holes 89 differ in shape and position from the refrigerant passage holes 54A and 54B and that the counterpart of the intra-inlet-header-section flow-dividing control wall 51b is absent. The second members 74 and 39 are disposed in a mirror image relation. The second members 74 and 39 are formed from the same extrudate.

The first header formation portion 78 of the first member 73 and the first header formation portion 86 of the second member 74 form a hollow, first intermediate header section body 300 whose opposite ends are open. The second header formation portion 79 of the first member 73 and the second header formation portion 87 of the second member 74 form a hollow, second intermediate header section body 310 whose opposite ends are open.

The left-hand closing member 75 is formed such that a front cap 75a for closing the left end opening of the first intermediate header section body 300 and a rear cap 75b for closing the left end opening of the second intermediate header section body 310 are integrated with each other. The front cap 75a has an integrally formed rightward projecting portion 93 to be fitted into the first intermediate header section body 300. Similarly, the rear cap 75b has an integrally formed upper rightward-projecting portion 94 to be fitted into a space of the second intermediate header section body 310 located above the flow-dividing control wall 87b, and an integrally formed lower rightward-projecting portion 95 to be fitted into a space of the second intermediate header section body 310 located below the flow-dividing control wall 87b. The upper rightward-projecting portion 94 and the lower rightward-projecting portion 95 are vertically spaced apart from each other. Engagement fingers 100 projecting rightward are formed integrally with the left-hand closing member 75 at a connection portion between a front side edge and a top edge of the left-hand closing member 75, at a connection portion between the front side edge and a bottom edge, at a connection portion between a rear side edge and the top edge, and at a connection portion between the rear side edge and the bottom edge, respectively. The engagement fingers 100 are engaged with the first and second members 73 and 74. The left-hand closing member 75 is brazed to the first and second members 73 and 74 by utilization of its own brazing material layers.

The right-hand closing member 76 is formed such that a front cap 76a for closing the right end opening of the first intermediate header section body 300 and a rear cap 76b for closing the right end opening of the second intermediate header section body 310 are integrated with each other. The front cap 76a has an integrally formed leftward projecting portion 96 to be fitted into the first intermediate header section body 300. Similarly, the rear cap 76b has an integrally formed upper leftward-projecting portion 97 to be fitted into a space of the second intermediate header section body 310 located above the flow-dividing control wall 87b, and an integrally formed lower leftward-projecting portion 98 to be fitted into a space of the second intermediate header section body 310 located below the flow-dividing control wall 87b. The upper leftward-projecting portion 97 and the lower leftward-projecting portion 98 are vertically spaced apart from each other. Engagement fingers 99 projecting leftward are formed integrally with the right-hand closing member 76 at a connection portion between a front side edge and a top edge of the right-hand closing member 76, at a connection portion between the front side edge and a bottom edge, at a connection portion between a rear side edge and the top edge, and at a connection portion between the rear side edge and the bottom edge, respectively. Also, engagement fingers 104 projecting rightward are formed integrally with the right-hand closing member 76 at front and rear end portions of the upper edge of the right-hand closing member 76. The rightward-projecting engagement fingers 104 are bent downward so as to be engaged with an upper edge portion of the communication member 77. The engagement finger 104 projecting rightward is formed integrally with the right-hand closing member 76 at a front-rear-direction central portion of the lower end of the right-hand closing member 76. The rightward-projecting engagement finger 104 is bent upward so as to be engaged with a lower edge portion of the communication member 77. A refrigerant outflow port 101 through which a refrigerant flows out from the first intermediate header section 30 is formed in a projecting end wall of the leftward projecting portion 96 of the front cap 76a of the right-hand closing member 76. Similarly, a refrigerant inflow port 102 through which the refrigerant flows into the lower space 31B of the second intermediate header section 31 located below the flow-dividing control wall 87b is formed in a projecting end wall of the lower leftward-projecting portion 98 of the rear cap 76b. Also, a guide portion 103 which is inclined or curved upward; in the present embodiment, curved upward, toward the interior of the second intermediate header section 31 is formed integrally with a lower portion of a circumferential portion of the refrigerant inflow port 102 of the lower leftward-projecting portion 98 of the rear cap 76b. The guide portion 103 guides upward (toward the flow-dividing control wall 87b) the refrigerant which flows into the lower space 31B of the second intermediate header section 31 located below the flow-dividing control wall 87b. The right-hand closing member 76 is brazed to the first and second members 73 and 74 by utilization of its own brazing material layers.

The communication member 77 is formed from an aluminum bear material by press work and assumes, as viewed from the right, a plate-like form identical with that of the right-hand closing member 76. A peripheral edge portion of the communication member 77 is brazed to the outer surface of the right-hand closing member 76 by utilization of the brazing material layers of the right-hand closing member 76. An outward bulging portion 105 is formed on the communication member 77 so as to establish communication between the refrigerant outflow port 101 and the refrigerant inflow port 102 of the right-hand closing member 76. The interior of the outward bulging portion 105 serves as a communication channel for establishing communication between the refrigerant outflow port 101 and the refrigerant inflow port 102 of the right-hand closing member 76. Cutouts 106 are formed in the communication member 77 at front and rear end portions of the upper edge of the communication member 77 and at a front-rear-direction central portion of the lower edge, respectively. The engagement fingers 104 of the right-hand closing member 76 are fitted into the corresponding cutouts 106.

In manufacture of the evaporator 20, component members thereof excluding the refrigerant inlet pipe 27 and the refrigerant outlet pipe 28 are provisionally assembled together, and the resultant assembly is subjected to batch brazing.

The evaporator 20, together with a fixed-capacity-type compressor and a condenser serving as a refrigerant cooler, constitutes a refrigeration cycle which uses a chlorofluorocarbon-based refrigerant. This refrigeration cycle is installed in a vehicle, such as an automobile, as a car air conditioner.

In the evaporator 20 described above, while the fixed-capacity-type compressor is ON, a two-phase refrigerant of vapor-liquid phase having passed through a compressor, a condenser, and an expansion valve enters the upper space 24A of the refrigerant inlet header section 24 of the refrigerant inlet/outlet header tank 22 from the refrigerant inlet pipe 27 through the refrigerant inflow port 68 of the joint plate 43 and the refrigerant inlet 66 of the front cap 42a of the right-hand closing member 42. The refrigerant having entered the upper space 24A of the refrigerant inlet header section 24 flows leftward and enters the lower space 24B through the communication hole 70 and through the flow-division-adjusting holes 60.

The refrigerant having entered the lower space 24B dividedly flows into the refrigerant channels 34a of the heat exchange tubes 34 of the front heat exchange tube group 35. The refrigerant having flown into the refrigerant channels 34a of the heat exchange tube 34 flows downward through the refrigerant channels 34a and enters the first intermediate header section 30 of the refrigerant turn header tank 23. The refrigerant having entered the first intermediate header section 30 flows rightward and then flows through the refrigerant outflow port 101 of the front cap 76a of the right-hand closing member 76, the communication channel in the outward bulging portion 105 of the communication member 77, and the refrigerant inflow port 102 of the rear cap 76b, thereby turning its flow direction and entering the lower space 31B of the second intermediate header section 31.

The refrigerant having entered the lower space 31B of the second intermediate header section 31 flows leftward; enters the upper space 31A through the circular refrigerant passage holes 89 of the flow-dividing control wall 87b; and dividedly flows into the refrigerant channels 34a of all the rear heat exchange tubes 34. At the time of entry of the refrigerant into the lower space 31B, while being guided by the guide portion 103, the refrigerant flows leftward in an obliquely upward direction; i.e., into the interior of the lower space 31B while being biased toward the flow-dividing control wall 87b. By virtue of this combined with the feature that the distance between the adjacent circular refrigerant passage holes 89 formed in the flow-dividing control wall 87b increases as the distance from the right end of the flow-dividing control wall 87b increases, the refrigerant which flows into the upper space 31A through the refrigerant passage holes 89 is distributed uniformly in the left-right direction as opposed to the case where the guide portion 103 is not provided. Accordingly, the refrigerant flows into the heat exchange tubes 34 connected to the second intermediate header section 31 easily in a uniformly divided condition; thus, nonuniform distribution of the refrigerant in the heat exchange core section 21 becomes unlikely to arise. Therefore, the temperature of air having passed through the heat exchange core section 21 is homogenized, thereby improving heat exchange performance.

The refrigerant having flown into the refrigerant channels 34a of the heat exchange tubes 34 flows upward, in opposition to the previous flow direction, through the refrigerant channels 34a; enters the lower space 25B of the refrigerant outlet header section 25; and then enters the upper space 25A through the oblong refrigerant passage holes 54A and 54B of the intra-outlet-header-section flow-dividing control wall 52b.

Next, the refrigerant having entered the upper space 25A of the refrigerant outlet header section 25 flows out into the refrigerant outlet pipe 28 through the refrigerant outlet 67 of the rear cap 42b of the right-hand closing member 42 and through the refrigerant outflow port 69 of the joint plate 43.

While flowing through the refrigerant channels 34a of the front heat exchange tubes 34 and through the refrigerant channels 34a of the rear heat exchange tubes 34, the refrigerant is subjected to heat exchange with air flowing through the air-passing clearances of the heat exchange core section 21. Then, the refrigerant flows out from the evaporator 20 in a vapor phase.

When the fixed-capacity-type compressor is turned OFF, the liquid-phase refrigerant remaining within the refrigerant channels 34a of the heat exchange tubes 34 is effectively retained within the refrigerant channels 34a by virtue of the capillary effect. This prevents outflow of the liquid-phase refrigerant from the refrigerant channels 34a of the heat exchange tubes 34 in a short period of time. Additionally, even after the compressor is turned OFF, while the liquid-phase refrigerant remains within the refrigerant channels 34a of the heat exchange tubes 34 of the evaporator 20, heat exchange continues between the remaining liquid-phase refrigerant and air passing through the evaporator 20, so that an abrupt increase in discharge air temperature can be restrained.

FIG. 12 shows, by the solid line, variation of discharge air temperature when the fixed-capacity-type compressor is turned ON and OFF in a car air conditioner which uses the evaporator 20. As is apparent from FIG. 12, use of the evaporator 20 shows a gentle increase in discharge air temperature after the compressor is turned OFF as opposed to variation in discharge air temperature when a fixed-capacity-type compressor is turned ON and OFF in a car air conditioner which uses the evaporator disclosed in the aforementioned publication, as represented by the broken line in FIG. 12. Accordingly, in the case where the compressor is controlled on the basis of discharge air temperature of the evaporator 20, even when the preset high temperature T2 is set lower than the preset high temperature t2 of the evaporator disclosed in the aforementioned publication, the cycle of turning ON and OFF the compressor can have the same period as in the case where the compressor is used in combination with the evaporator disclosed in the aforementioned publication. As a result, the temperature difference between air discharged into a compartment of an automobile when the compressor is turned ON and that when the compressor is turned OFF can be reduced, thereby improving comfort in the compartment. Furthermore, even when the temperature difference between the preset high temperature T2 and the preset low temperature T1 is reduced by means of lowering the preset high temperature T2, the cycle of turning ON and OFF the compressor can have the same period as in the case of the evaporator disclosed in the aforementioned publication. Therefore, as opposed to the case where the evaporator disclosed in the aforementioned publication is used, the compressor does not frequently go ON and OFF, so that the fuel economy of an automobile is not adversely effected.

Next, examples of an evaporator according to the present invention, together with a comparative example, will be described.

EXAMPLE 1

The evaporator 20 was prepared which employed the heat exchange tubes 34 each having the configuration shown in FIG. 4; i.e., the number of the refrigerant channels 34a is 11, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

EXAMPLE 2

An evaporator was prepared which employed heat exchange tubes 34A each having the configuration shown in FIG. 13a; i.e., the number of the refrigerant channels 34a is 14, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

EXAMPLE 3

An evaporator was prepared which employed heat exchange tubes 34B each having the configuration shown in FIG. 13b; i.e., the number of the refrigerant channels 34a is 16, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

EXAMPLE 4

An evaporator was prepared which employed heat exchange tubes 34C each having the configuration shown in FIG. 13c; i.e., the number of the refrigerant channels 34a is 18, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

EXAMPLE 5

An evaporator was prepared which employed heat exchange tubes 34D each having the configuration shown in FIG. 13d; i.e., the number of the refrigerant channels 34a is 20, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

COMPARATIVE EXAMPLE

An evaporator was prepared which employed heat exchange tubes 34E each having the configuration shown in FIG. 13e; i.e., the number of the refrigerant channels 34a is 7, and the number of the protrusions 346 on the inner peripheral surface of each of the refrigerant channels 34a excluding the opposite-end refrigerant channels 34a is 4.

The heat exchange tubes 34, 34A, 34B, 34C, 34D, and 34E used in the evaporators of Examples 1 to 5 and Comparative Example have a width W of 17 mm as measured in the front-rear direction and a tube height H, which is a thickness as measured in the left-right direction, of 1.4 mm. Table 1 shows the following characteristic values of the heat exchange tubes 34, 34A, 34B, 34C, 34D, and 34E: the total cross-sectional area of the plurality of refrigerant channels 34a; the total cross-sectional, perimetric length of the plurality of refrigerant channels 34a; the equivalent diameter Dh; and the value A in pieces/mm obtained by dividing the number N of the refrigerant channels 34a by the width W as measured in the front-rear direction (A=N/W).

Evaluation Test:

The evaporators of Examples 1 to 5 and Comparative Example were incorporated into a refrigeration cycle and were examined for cooling performance while a fixed-capacity-type compressor was ON. Also, the evaporators were examined for the amount of a liquid-phase refrigerant remaining within the refrigerant channels 34a of the heat exchange tubes 34, 34A, 34B, 34C, 34D, and 34E. Furthermore, the evaporators were examined for time which elapsed after the elapse of 5 seconds after the fixed-capacity-type compressor was turned OFF, until the liquid-phase refrigerant remaining within the refrigerant channels 34a of the heat exchange tubes 34, 34A, 34B, 34C, 34D, and 34E evaporated. Table 1 shows the results of the examinations, and FIGS. 14 and 15 show the relationship of the equivalent diameter Dh with cooling performance and the amount of remaining liquid-phase refrigerant and the relationship of the number of the refrigerant channels 34a with cooling performance and the amount of remaining liquid-phase refrigerant, respectively. In FIGS. 14 and 15, the solid line indicates cooling performance, and the broken line indicates the amount of remaining liquid-phase refrigerant. Cooling performance is represented in percentage based on the cooling performance of Example 2 which is taken as 100%. The amount of liquid-phase refrigerant remaining within the refrigerant channels 34a of the heat exchange tubes 34, 34A, 34B, 34C, 34D, and 34E as measured after the elapse of 5 seconds after the fixed-capacity-type compressor was turned OFF is represented in percentage based on the amount of Example 1 which is taken as 100%. If cooling performance falls within a range of 95% to 100% as indicated by the arrow Z in FIGS. 14 and 15, the evaporator can be said to have sufficient performance for use in a car air conditioner.

TABLE 1
Total cross-Total
sectional,cross-
perimetricsectional
length ofarea of allEquivalentAmount ofEvaporation
all channelschannelsdiameterNumber ofCoolingrefrigeranttime
mmmm2Dhchannels/width Aperformance Qafter 5 secSec
Example159.1211.9040.80540.647991004.40
266.9211.1840.66850.824100116.344.97
372.1210.7040.59370.94199123.375.36
477.3210.2240.52891.05998134.485.75
591.559.0900.39721.176961516.60
Comparative40.8813.5361.32542.4299273.933.04
Example

As is apparent from Table 1 and FIGS. 14 and 15, the evaporators of Examples 1 to 5—whose heat exchange tubes satisfy the relation 0.558≦A≦1.235, where A is a value in pieces/mm obtained by dividing the number N of refrigerant channels by the front-rear width W (A=N/W), and the relation 0.35≦Dh≦1.0, where Dh is an equivalent diameter—exhibits cooling performance better than that of the evaporator of Comparative Example and has sufficient performance for use in a car air conditioner. Also, the evaporators of Examples 1 to 5 is greater than the evaporator of Comparative Example in the amount of liquid-phase coolant remaining within the refrigerant channels of the heat exchange tubes when the compressor is turned OFF. This, as mentioned previously, can reduce the temperature difference between air discharged into a compartment of an automobile when the compressor is turned ON and that when the compressor is turned OFF, thereby improving comfort in the compartment.

FIGS. 16 to 18 show a modified heat exchange tube. In the following description of the modified heat exchange tube, the upper, lower, left-hand, and right-hand sides of FIGS. 16 to 19 will be referred to as “left,” “right,” “front,” and “rear,” respectively.

In FIGS. 16 and 17, a heat exchange tube 130 is oriented such that its width direction coincides with the front-rear direction; assumes a flat form; and has a plurality of refrigerant channels 130a arranged along its width direction and each having a rectangular cross section. The heat exchange tube 130 includes mutually opposed flat left and right walls 131 and 132 (a pair of flat walls); front and rear side walls 133 and 134 which extend between and over front and rear side ends, respectively, of the left and right walls 131 and 132; and a plurality of partition walls 135 which are provided between the front and rear side walls 133 and 134 and extend longitudinally and between the left and right walls 131 and 132 for separating adjacent refrigerant channels 130a from each other. Preferably, the refrigerant channel 130a has a rectangular cross section, and a corner portion of the rectangular cross section has a radius R of 0.1 mm or less.

The front side wall 133 has a dual structure and includes an outer side-wall-forming elongated projection 136 which is integrally formed with the front side end of the left wall 131 in a rightward raised condition and extends along the entire height of the heat exchange tube 130; an inner side-wall-forming elongated projection 137 which is located inside the outer side-wall-forming elongated projection 136 and is integrally formed with the left wall 131 in a rightward raised condition; and an inner side-wall-forming elongated projection 138 which is integrally formed with the front side end of the right wall 132 in a leftward raised condition. The front side wall 133 has flat inner and outer surfaces. The outer side-wall-forming elongated projection 136 is brazed to the inner side-wall-forming elongated projections 137 and 138 and to the right wall 132 while a right end portion thereof is engaged with a front side edge portion of the right surface of the right wall 132. The inner side-wall-forming elongated projections 137 and 138 are brazed together while butting against each other. The rear side wall 134 is integrally formed with the left and right walls 131 and 132. The rear side wall 134 has flat inner and outer surfaces. A projection 138a is integrally formed on the tip end face of the inner side-wall-forming elongated projection 138 of the right wall 132 and extends in the longitudinal direction of the inner side-wall-forming elongated projection 138 along the entire length of the inner side-wall-forming elongated projection 138. A groove 137a is formed on the tip end face of the inner side-wall-forming elongated projection 137 of the left wall 131 and extends in the longitudinal direction of the inner side-wall-forming elongated projection 137 along the entire length of the inner side-wall-forming elongated projection 137. The projection 138a is press-fitted into the groove 137a.

The partition walls 135 are formed such that partition-wall-forming elongated projections 140 and 141, which are integrally formed with the left wall 131 in a rightward raised condition, and partition-wall-forming elongated projections 142 and 143, which are integrally formed with the right wall 132 in a leftward raised condition, are brazed together while the partition-wall-forming elongate projections 140 and 141 butt against the partition-wall-forming elongated projections 143 and 142, respectively. The left wall 131 has the partition-wall-forming elongated projections 140 and 141, which are of different projecting heights and are arranged alternately in the front-rear direction. The right wall 132 has the partition-wall-forming elongated projections 142 and 143, which are of different projecting heights and are arranged alternately in the front-rear direction. The partition-wall-forming elongated projections 140 of a high projecting height of the left wall 131 and the respective partition-wall-forming elongated projections 143 of a low projecting height of the right wall 132 are brazed together. The partition-wall-forming elongated projections 141 of a low projecting height of the left wall 131 and the respective partition-wall-forming elongated projections 142 of a high projecting height of the right wall 132 are brazed together. Hereinafter, the partition-wall-forming elongated projections 140 and 142 of a high projecting height of the left and right walls 131 and 132 are called the first partition-wall-forming elongated projections. Similarly, the partition-wall-forming elongated projections 141 and 143 of a low projecting height of the left and right walls 131 and 132 are called the second partition-wall-forming elongated projections. A groove 144 (145) is formed on the tip end face of the second partition-wall-forming elongated projection 141 (143) of the left wall 131 (right wall 132) and extends in the longitudinal direction of the second partition-wall-forming elongated projection 141 (143) along the entire length of the second partition-wall-forming elongated projection 141 (143). A tip end portion of the first partition-wall-forming elongated projection 142 (140) of the right wall 132 (left wall 131) is fitted into the groove 144 (145) of the second partition-wall-forming elongated projection 141 (143) of the left wall 131 (right wall 132). While tip end portions of the first partition-wall-forming elongated projections 140 and 142 of the left and right walls 131 and 132 are fitted into the respective grooves 145 and 144, the partition-wall-forming elongated projections 140 and 143 are brazed together, and the partition-wall-forming elongated projections 141 and 142 are brazed together.

Also, in the heat exchange tube 130 shown in FIGS. 16 and 17, each of all the refrigerant channels 130a excluding two refrigerant channels 130a located at widthwise opposite ends, or each of all the refrigerant channels 130a may have two or more elongated protrusions formed on an inner peripheral surface of the refrigerant channel 130a and extending in a longitudinal direction of the refrigerant channel 130a.

The heat exchange tube 130 is manufactured by use of a tube-forming metal sheet 150 as shown in FIG. 18a. The tube-forming metal sheet 150 is formed, by rolling, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof. The tube-forming metal sheet 150 includes a flat left-wall-forming portion 151 (flat-wall-forming portion); a flat right-wall-forming portion 152 (flat-wall-forming portion); a connection portion 153 connecting the left-wall-forming portion 151 and the right-wall-forming portion 152 and adapted to form the rear side wall 134; the inner side-wall-forming elongated projections 137 and 138, which are integrally formed with the side ends of the left-wall-forming and right-wall-forming portions 151 and 152 opposite the connection portion 153 in a leftward raised condition and which are adapted to form an inner portion of the front side wall 133; an outer side-wall-forming-elongated-projection forming portion 154, which extends outward from the side end of the left-wall-forming portion 151 opposite the connection portion 153; and a plurality of partition-wall-forming elongated projections 140, 141, 142, and 143, which are integrally formed with the left-wall-forming and right-wall-forming portions 151 and 152 in a leftward raised condition and which are arranged at predetermined intervals in the width direction of the tube-forming metal sheet 150. The first partition-wall-forming elongated projections 140 of the left-wall-forming portion 151 and the second partition-wall-forming elongated projections 143 of the right-wall-forming portion 152 are located symmetrically with respect to the centerline of the width direction of the connection portion 153. Similarly, the second partition-wall-forming elongated projections 141 of the left-wall-forming portion 151 and the first partition-wall-forming elongated projections 142 of the right-wall-forming portion 152 are located symmetrically with respect to the centerline of the width direction of the connection portion 153. The projection 138a is formed on the tip end face of the inner side-wall-forming elongated projection 138 of the right-wall-forming portion 152, and the groove 137a is formed on the tip end face of the inner side-wall-forming elongated projection 137 of the left-wall-forming portion 151. The groove 144 (145), into which a tip end portion of the first partition-wall-forming elongated projection 142 (140) of the right-wall-forming portion 152 (left-wall-forming portion 151) is fitted, is formed on the tip end face of the second partition-wall-forming elongated projection 141 (143) of the left-wall-forming portion 151 (right-wall-forming portion 152).

The inner side-wall-forming elongated projections 137 and 138 and the partition-wall-forming elongated projections 140, 141, 142, and 143 are integrally formed, by rolling, on one side of the aluminum brazing sheet whose opposite sides are clad with respective brazing materials, whereby a brazing material layer (not shown) is formed on the opposite side surfaces and tip end faces of the inner side-wall-forming elongated projections 137 and 138 and the partition-wall-forming elongated projections 140, 141, 142, and 143; on the inner peripheral surfaces of the grooves 144 and 145 of the second partition-wall-forming elongated projections 141 and 143; and on the left and right surfaces of the left-wall-forming and right-wall-forming portions 151 and 152 and the outer side-wall-forming-elongated-projection forming portion 154.

The tube-forming metal sheet 150 is gradually folded at opposite side edges of the connection portion 153 by a roll forming process (see FIG. 18b) until a hairpin form is assumed. The inner side-wall-forming elongated projections 137 and 138 are caused to butt against each other; tip end portions of the first partition-wall-forming elongated projections 140 and 142 are fitted into the respective grooves 145 and 144 of the second partition-wall-forming elongated projections 143 and 141; and the projection 138a is press-fitted into the groove 137a.

Next, the outer side-wall-forming-elongated-projection forming portion 154 is folded along the outer surfaces of the inner side-wall-forming elongated projections 137 and 138, and a tip end portion thereof is deformed so as to be engaged with the right-wall-forming portion 152, thereby yielding a folded member 155 (see FIG. 18c).

Subsequently, the folded member 155 is heated at a predetermined temperature so as to braze together tip end portions of the inner side-wall-forming elongated projections 137 and 138; to braze together tip end portions of the first and second partition-wall-forming elongated projections 140 and 143; to braze together tip end portions of the first and second partition-wall-forming elongated projections 142 and 141; and to braze the outer side-wall-forming-elongated-projection forming portion 154 to the inner side-wall-forming elongated projections 137 and 138 and to the right-wall-forming portion 152. Thus is manufactured the heat exchange tube 130.

FIG. 19 shows another modified heat exchange tube.

In FIG. 19, a heat exchange tube 160 is oriented such that its width direction coincides with the front-rear direction; assumes a flat form; and has a plurality of refrigerant channels 160a arranged along its width direction. The heat exchange tube 160 includes mutually opposed flat left and right walls 161 and 162; front and rear side walls 163 and 164 which extend between and over front and rear side ends, respectively, of the left and right walls 161 and 162; and a plurality of partition walls 165 which are provided between the front and rear side walls 163 and 164 and extend longitudinally and between the left and right walls 161 and 162 for separating adjacent refrigerant channels 160a from each other.

The front side wall 163 has a dual structure and includes an outer side-wall-forming elongated projection 166 which is integrally formed with the front side end of the left wall 161 in a rightward raised condition and extends along the entire height of the heat exchange tube 160; and an inner side-wall-forming elongated projection 167 which is located inside the outer side-wall-forming elongated projection 166 and is integrally formed with the front side end of the right wall 162 in a leftward raised condition and extends along the entire height of the heat exchange tube 160. The rear side wall 164 has a dual structure and includes an outer side-wall-forming elongated projection 168 which is integrally formed with the rear side end of the right wall 162 in a leftward raised condition and extends along the entire height of the heat exchange tube 160; and an inner side-wall-forming elongated projection 169 which is located inside the outer side-wall-forming elongated projection 168 and is integrally formed with the right side end of the left wall 161 in a rightward raised condition and extends along the entire height of the heat exchange tube 160. Each of the front and rear side walls 163 and 164 has such an arcuate cross section that a central portion with respect to the left-right direction projects outward. The outer side-wall-forming elongated projections 166 and 168 of the front and rear side walls 163 and 164 are brazed to the inner side-wall-forming elongated projections 167 and 169.

A corrugated partition-wall-forming portion 170 is integrally formed between a tip end portion of the inner side-wall-forming elongated projection 167 of the front wall 163 and a tip end portion of the inner side-wall-forming elongated projection 169 of the rear wall 164. The partition-wall-forming portion 170 includes wave crest portions 171 brazed to the left wall 161, wave trough portions 172 brazed to the right wall 162, and connection portions 173 connecting together the wave crest portions 171 and the wave trough portions 172 and serving as the partition walls 165.

Although unillustrated, the heat exchange tube 160 is manufactured as follows: a tube-forming metal sheet formed from an aluminum brazing sheet having a brazing material layer on each of opposite sides is bent to yield a folded member, and the folded member is subjected to brazing so as to simultaneously braze together the outer side-wall-forming elongated projections 166 and 168 and the inner side-wall-forming elongated projections 167 and 169, respectively, of the front and rear side walls 163 and 164, the wave crest portions 171 of the partition-wall-forming portion 170 and the left wall 161, and the wave trough portions 172 of the partition-wall-forming portion 170 and the right wall 162.

In the above-described embodiment, the evaporator according to the present invention is applied to a car air conditioner which uses a chlorofluorocarbon-based refrigerant. However, the present invention is not limited thereto. The present invention may be applied to an evaporator of a car air conditioner which is used in a vehicle, for example, in an automobile and which includes a compressor, a gas cooler serving as a refrigerant cooler, an intermediate heat exchanger, an expansion valve, and an evaporator and uses a supercritical refrigerant such as CO2.