Title:
REFRIGERATION SYSTEM INCLUDING A DESICCANT
Kind Code:
A1


Abstract:
A refrigeration system for providing conditioned air to a space includes a compressor operable to compress a refrigerant, a condenser configured to receive the refrigerant from the compressor, an expansion device configured to receive the refrigerant from the condenser, a desiccant operable to adsorb moisture from an airflow flowing through the desiccant such that the airflow is substantially dehumidified, and an evaporator assembly configured to receive the refrigerant from the expansion device and the airflow from the desiccant. The evaporator assembly is operable to condition the airflow prior to discharge from the evaporator assembly. The refrigeration system also includes a heat exchanger configured to selectively receive the refrigerant from at least one of the compressor and the condenser. The heat exchanger is in communication with the desiccant such that the refrigerant in the heat exchanger desorbs moisture from the desiccant.



Inventors:
Viegas, Herman H. (Bloomington, MN, US)
Mohs, William F. (Minneapolis, MN, US)
Application Number:
12/117905
Publication Date:
11/12/2009
Filing Date:
05/09/2008
Assignee:
THERMO KING CORPORATION (Minneapolis, MN, US)
Primary Class:
Other Classes:
62/196.4, 62/271
International Classes:
F25B1/00; F25B41/00; F25D23/00
View Patent Images:
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Primary Examiner:
RAYMOND, KEITH MICHAEL
Attorney, Agent or Firm:
MICHAEL BEST & FRIEDRICH LLP (Mke) (100 E WISCONSIN AVENUE Suite 3300, MILWAUKEE, WI, 53202, US)
Claims:
What is claimed is:

1. A refrigeration system for providing conditioned air to a space, the refrigeration system comprising: a compressor operable to compress a refrigerant; a condenser configured to receive the refrigerant from the compressor; an expansion device configured to receive the refrigerant from the condenser; a desiccant operable to adsorb moisture from an airflow flowing through the desiccant such that the airflow is substantially dehumidified; an evaporator assembly configured to receive the refrigerant from the expansion device and the airflow from the desiccant, the evaporator assembly operable to condition the airflow prior to discharge from the evaporator assembly; and a heat exchanger configured to selectively receive the refrigerant from at least one of the compressor and the condenser, the heat exchanger in communication with the desiccant such that the refrigerant in the heat exchanger desorbs moisture from the desiccant.

2. The refrigeration system of claim 1, wherein the refrigerant is heated when the compressor compresses the refrigerant, and wherein the heated refrigerant in the heat exchanger desorbs moisture from the desiccant.

3. The refrigeration system of claim 1, wherein the refrigerant is at least one of cooled prior to entering the heat exchanger and cooled while in the heat exchanger, and wherein the cooled refrigerant in the heat exchanger cools the desiccant.

4. The refrigeration system of claim 1, wherein the heat exchanger includes a coil configured to receive the refrigerant and a fan operable to propel a second airflow over the coil and through at least a portion of the desiccant to desorb moisture from the desiccant.

5. The refrigeration system of claim 1, wherein the heat exchanger includes a coil configured to receive the refrigerant, and wherein at least a portion of the coil is embedded in the desiccant to desorb moisture from the desiccant.

6. The refrigeration system of claim 1, wherein the heat exchanger selectively receives the refrigerant from the compressor, and further comprising at least one valve positioned between the compressor, the condenser, and the heat exchanger to selectively direct the refrigerant from the compressor to one of the condenser and the heat exchanger.

7. The refrigeration system of claim 6, further comprising a bypass extending from a point between the condenser, the heat exchanger, and the expansion device to a point between the evaporator assembly and the compressor, and wherein the bypass is configured to selectively direct the refrigerant from the heat exchanger to the compressor.

8. The refrigeration system of claim 7, further comprising a second bypass extending from a point between the condenser and the expansion device to a point between the at least one valve and the heat exchanger, wherein the second bypass includes a second expansion device, and wherein the second bypass is configured to selectively direct the refrigerant from the condenser through the second expansion device to the heat exchanger.

9. The refrigeration system of claim 1, wherein the heat exchanger selectively receives the refrigerant from the condenser, and further comprising: a bypass extending from a point between the condenser and the heat exchanger to a point between the heat exchanger and the expansion device, the bypass configured to direct the refrigerant from the condenser around the heat exchanger, and at least one valve positioned between the condenser and the heat exchanger, the at least one valve configured to selectively direct the refrigerant from the condenser to at least one of the bypass and the heat exchanger.

10. The refrigeration system of claim 9, further comprising a second bypass extending from a point between the heat exchanger and the expansion device to a point between the evaporator assembly and the compressor, and wherein the second bypass is configured to selectively direct the refrigerant from the heat exchanger to the compressor.

11. The refrigeration system of claim 10, further comprising a third bypass extending from a point between the condenser and the at least one valve to a point between the at least one valve and the heat exchanger, wherein the third bypass includes a second expansion device, and wherein the third bypass is configured to selectively direct the refrigerant from the condenser through the second expansion device to the heat exchanger.

12. The refrigeration system of claim 1, wherein the desiccant is a first desiccant and further comprising a second desiccant, and wherein when one of the first desiccant and the second desiccant adsorbs moisture from the airflow, the refrigerant in the heat exchanger desorbs moisture from the other of the first desiccant and the second desiccant.

13. The refrigeration system of claim 12, wherein the first desiccant and the second desiccant are reversible such that the other of the first desiccant and the second desiccant adsorbs moisture from the airflow and the refrigerant in the heat exchanger desorbs moisture from the one of the first desiccant and the second desiccant.

14. A method of providing conditioned air to a space with a refrigeration system, the refrigeration system including a compressor operable to compress a refrigerant, a condenser configured to receive the refrigerant from the compressor, an expansion device configured to receive the refrigerant from the condenser, a desiccant configured to receive an airflow, and an evaporator assembly configured to receive the refrigerant from the expansion valve and the airflow from the desiccant, the method comprising: providing a heat exchanger configured to selectively receive the refrigerant from at least one of the compressor and the condenser, the heat exchanger in communication with the desiccant; adsorbing moisture from the airflow flowing through the desiccant such that the airflow is substantially dehumidified; directing the airflow from the desiccant through the evaporator assembly; conditioning the airflow with the evaporator assembly prior to discharge from the evaporator assembly; and desorbing moisture from the desiccant with the refrigerant in the heat exchanger.

15. The method of claim 14, wherein the refrigerant is heated when the compressor compresses the refrigerant, and wherein desorbing moisture from the desiccant includes desorbing moisture from the desiccant with the heated refrigerant in the heat exchanger.

16. The method of claim 14, wherein the refrigerant is at least one of cooled prior to entering the heat exchanger and cooled while in the heat exchanger, and further comprising cooling the desiccant with the cooled refrigerant in the heat exchanger.

17. The method of claim 14, wherein the heat exchanger includes a coil configured to receive the refrigerant and a fan, and further comprising propelling a second airflow over the coil and through at least a portion of the desiccant with the fan to desorb moisture from the desiccant.

18. The method of claim 14, wherein the heat exchanger includes a coil configured to receive the refrigerant, wherein at least a portion of the coil is embedded in the desiccant, and wherein desorbing moisture from the desiccant includes desorbing moisture from the desiccant with the refrigerant in the embedded coil.

19. The method of claim 14, wherein the heat exchanger selectively receives the refrigerant from the compressor, and further comprising: positioning at least one valve between the compressor, the condenser, and the heat exchanger, and selectively directing the refrigerant from the compressor to one of the condenser and the heat exchanger.

20. The method of claim 19, further comprising: providing a bypass extending from a point between the condenser, the heat exchanger, and the expansion device to a point between the evaporator assembly and the compressor, and selectively directing the refrigerant from the heat exchanger through the bypass to the compressor.

21. The method of claim 20, further comprising: providing a second bypass extending from a point between the compressor and the expansion device to a point between the at least one valve and the heat exchanger, the second bypass including a second expansion device, and selectively directing the refrigerant from the condenser through the second expansion device to the heat exchanger.

22. The method of claim 14, wherein the heat exchanger selectively receives the refrigerant from the condenser, and further comprising: providing a bypass extending from a point between the condenser and the heat exchanger to a point between the heat exchanger and the expansion device, the bypass configured to direct the refrigerant from the condenser around the heat exchanger, providing at least one valve between the condenser and the heat exchanger, and selectively directing the refrigerant from the condenser to at least one of the bypass and the heat exchanger.

23. The method of claim 22, further comprising: providing a second bypass extending from a point between the heat exchanger and the expansion device to a point between the evaporator assembly and the compressor, and selectively directing the refrigerant from the heat exchanger through the second bypass to the compressor.

24. The method of claim 23, further comprising: providing a third bypass extending from a point between the condenser and the at least one valve to a point between the at least one valve and the heat exchanger, the third bypass including a second expansion device, and selectively directing the refrigerant from the condenser through the second expansion device to the heat exchanger.

25. The method of claim 14, wherein the desiccant is a first desiccant and the refrigeration system includes a second desiccant, wherein adsorbing moisture from the airflow includes adsorbing moisture from the airflow flowing through one of the first desiccant and the second desiccant such that the airflow is substantially dehumidified, and wherein desorbing moisture from the desiccant includes desorbing moisture from the other of the first desiccant and the second desiccant with the refrigerant in the heat exchanger.

26. The method of claim 25, further comprising reversing the first desiccant and the second desiccant such that the other of the first desiccant and the second desiccant adsorbs moisture from the airflow and the refrigerant in the heat exchanger desorbs moisture from the one of the first desiccant and the second desiccant.

Description:

BACKGROUND

The present invention relates to refrigeration systems and, more particularly, to refrigeration systems including desiccants.

Large tractors or trucks (e.g., semi-tractors) are commonly used to transport cargo within a trailer or container. Existing tractors in a tractor-trailer combination typically include cabins that are conditioned by multiple mechanically driven vapor compression air conditioning systems. In some constructions, the air conditioning systems include a desiccant to adsorb moisture from an airflow prior to the airflow passing over a cooling coil. Typically, waste heat from an engine (e.g., from a coolant fluid of the engine) is circulated through passages in the desiccant to drive out moisture from the desiccant.

SUMMARY

In one embodiment, the invention provides a refrigeration system for providing conditioned air to a space. The refrigeration system includes a compressor operable to compress a refrigerant, a condenser configured to receive the refrigerant from the compressor, an expansion device configured to receive the refrigerant from the condenser, a desiccant operable to adsorb moisture from an airflow flowing through the desiccant such that the airflow is substantially dehumidified, and an evaporator assembly configured to receive the refrigerant from the expansion device and the airflow from the desiccant. The evaporator assembly is operable to condition the airflow prior to discharge from the evaporator assembly. The refrigeration system also includes a heat exchanger configured to selectively receive the refrigerant from at least one of the compressor and the condenser. The heat exchanger is in communication with the desiccant such that the refrigerant in the heat exchanger desorbs moisture from the desiccant.

In another embodiment, the invention provides a method of providing conditioned air to a space with a refrigeration system. The refrigeration system includes a compressor operable to compress a refrigerant, a condenser configured to receive the refrigerant from the compressor, an expansion device configured to receive the refrigerant from the condenser, a desiccant configured to receive an airflow, and an evaporator assembly configured to receive the refrigerant from the expansion valve and the airflow from the desiccant. The method includes providing a heat exchanger configured to selectively receive the refrigerant from at least one of the compressor and the condenser. The heat exchanger is in communication with the desiccant. The method also includes adsorbing moisture from the airflow flowing through the desiccant such that the airflow is substantially dehumidified, directing the airflow from the desiccant through the evaporator assembly, conditioning the airflow with the evaporator assembly prior to discharge from the evaporator assembly, and desorbing moisture from the desiccant with the refrigerant in the heat exchanger.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a vehicle including a heating, ventilation, and air conditioning (HVAC) system.

FIG. 2 is a schematic of the HVAC system of FIG. 1.

FIG. 3 is a schematic of a first cooling circuit for use in the HVAC system of FIG. 2.

FIG. 4 is a schematic of a second cooling circuit for use in the HVAC system of FIG. 2.

FIG. 5 is a schematic of a third cooling circuit for use in the HVAC system of FIG. 2.

FIG. 6 is a schematic of a fourth cooling circuit for use in the HVAC system of FIG. 2.

FIG. 7 is a schematic of a fifth cooling circuit for use in the HVAC system of FIG. 2.

FIG. 8 is a schematic of a sixth cooling circuit for use in the HVAC system of FIG. 2.

FIG. 9 is a schematic of a seventh cooling circuit for use in the HVAC system of FIG. 2.

FIG. 10 is a schematic of a two-stage sorption system for use with the HVAC system of FIG. 2.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

FIG. 1 illustrates a vehicle 10 according to an embodiment of the invention. The illustrated vehicle 10 is a semi-tractor or other similar vehicle (e.g., a straight truck, a van, a bus, a car, etc.) that is used to transport cargo stored in a cargo compartment (e.g., a container, a trailer, etc.) or people to one or more destinations. Hereinafter, the term “vehicle” shall be used to represent all such vehicles, and shall not be construed to limit the invention's application solely to a tractor in a tractor-trailer combination. In addition, it should be readily apparent to one skilled in the art that aspects of the invention may also be applied to stationary refrigeration systems (e.g., refrigerated display cases, home or commercial air conditioning systems, or the like) that are not part of a vehicle.

In the illustrated construction, the vehicle 10 includes a frame 14, wheels 18, an alternator 22 or direct current (“DC”) generator, a prime mover 26, and a fuel reservoir 30. The wheels 18 are rotatably coupled to the frame 14 to permit movement of the vehicle 10. The alternator 22 is coupled to the prime mover 26 so that mechanical energy produced by the prime mover 26 can be converted into electrical energy, or electricity.

The prime mover 26 is coupled to the frame 14 and is disposed in a compartment 34 that is located adjacent to a forward end of the vehicle 10. The prime mover 26 is operable in a first mode and a second mode, and includes an “On” state and an “Off” state. The first mode corresponds to the prime mover 26 being engaged so that the vehicle 10 can be driven. The first mode further corresponds to when the prime mover 26 is idling, but is not engaged so that the operator can drive the vehicle 10. In other words, the prime mover 26 is operable in the first mode when the prime mover 26 is in the “On” state.

The prime mover 26 is in the second mode during standby operation of the vehicle 10 (e.g., when the vehicle 10 is parked, etc.). Generally, standby operation of the vehicle 10 corresponds to the prime mover 26 being disengaged. In other words, the prime mover 26 is operating in the second mode when the prime mover is in the “Off” state.

The illustrated fuel reservoir 30 is in fluid communication with the prime mover 26 to deliver fuel (e.g., diesel fuel, gasoline, etc.) to the prime mover 26 when the prime mover 26 is in the “On” state. As shown in FIG. 1, the fuel reservoir 30 is attached to the frame 14, although the fuel reservoir 30 may be attached to the vehicle 10 in other locations.

The prime mover 26 is in communication with one or more of the wheels 18 to power the wheels 18 when the vehicle 10 is in the first mode. The prime mover 26 can be an internal combustion engine (e.g., a diesel engine, etc.), or alternatively, a hybrid engine that includes an electrical power system coupled to the internal combustion engine. In other constructions, the prime mover 26 can be a fully electrical power system without a corresponding internal combustion engine. Hereinafter, the term “prime mover” shall be used to represent all such propulsion systems, and shall not be construed to limit the scope of the invention solely to internal combustion engines.

As shown in FIG. 2, the vehicle 10 also includes a coolant system 38. The prime mover 26 is in fluid communication with the coolant system 38 via a bypass 42, or inline feed, to maintain the prime mover 26 at an operable temperature when the prime mover 26 is in the “On” state, and to selectively heat the prime mover 26 when the prime mover 26 is in the “Off” state (e.g., approximately one hour before the prime mover 26 is started, etc.). The illustrated coolant system 38 includes a pump 46 to circulate a coolant (e.g., glycol, etc.), an expansion tank 50 that can receive some of the coolant when the coolant system 38 is operating at relatively high temperatures, and a valve 54 to control the flow of coolant.

Referring to FIG. 1, the vehicle 10 also includes a cabin 58, a power source 62, and a heating, ventilation, and air conditioning (“HVAC”) system 66. The cabin 58 is supported on the frame 14 rearward of the compartment 34 and includes walls 70 that define a space 74. In some constructions, the space 74 may be divided into a driving portion and a sleeping portion. Additionally or alternatively, the walls 70 may include insulation (e.g., mineral powder, mineral fiber, fiberglass, silica, polyurethane foam, polystyrene foam, etc.) to help insulate the space 74.

The HVAC system 66 is coupled to the vehicle 10 and is in communication with the cabin 58 to condition the space 74. The illustrated vehicle 10 includes a single HVAC system 66 that is located adjacent to and in communication with the space 74. In other constructions, one HVAC system can be positioned in the vehicle 10 to condition the driving portion and another HVAC system can be positioned to condition the sleeping portion. Generally, the number of HVAC systems in the vehicle 10 depends at least in part on the size and number of zones to be conditioned within the cabin 58.

Referring to FIG. 2, the HVAC system 66 includes a sorption system 78, a cooling circuit 82, and a heating circuit 86. In some constructions, the HVAC system 66 may also include a defrost system (not shown). Generally, the components of the HVAC system 66 can be located anywhere on the vehicle 10. In some constructions, the components of the HVAC system 66 can be in a single, unitary package. In other constructions, each component of the HVAC system 66 can be separate from the other components of the HVAC system 66.

The illustrated sorption system 78 includes a first inlet 90, a second inlet 94, a first outlet 98, a second outlet 102, and a desiccant 106 that is disposed between the inlets 90, 94 and the outlets 98, 102. In some constructions (see FIG. 3), the sorption system 78 may not include the second inlet 94 or the second outlet 102. Airflow 110 through the sorption system 78 is composed of air from the cabin 58 (e.g., recycled air) and air from the atmosphere (e.g., make-up fresh air) outside the vehicle 10. The sorption system 78 is in communication with the cabin 58 and with the atmosphere via ducting (not shown) so that air from the cabin 58 and/or the atmosphere can be directed through the desiccant 106. In other constructions, the sorption system 78 can receive air from only one of the cabin 58 or the atmosphere.

The desiccant 106 is operable to adsorb moisture from the airflow 110 so that a substantially dehumidified airflow 112 is discharged through the first outlet 98. Generally, the sorption system 78 is in communication with a heat source so that moisture adsorbed from the airflow 110 by the desiccant 106 can be desorbed from the desiccant 106 and vented into the atmosphere via the second outlet 102. The sorption system 78 is also in communication with a cooling source (e.g., ambient air) so that the desorbed, or regenerated, desiccant 106 can be cooled prior to the desiccant 106 continuing to adsorb moisture from the airflow 110.

FIG. 2 shows that the HVAC system 66 also includes a bypass 113 disposed adjacent the sorption system 78. The bypass 113 selectively directs the airflow 110 around the sorption system 78 without directing the airflow 110 through the sorption system 78 so that the airflow 110 is non-dehumidified prior to conditioning of the airflow 110 by the cooling circuit 82 and the heating circuit 86. The non-dehumidified airflow 110 in the bypass 113 is formed from air that is received from the cabin 58 (e.g., recycled air), and/or the air that is received from the atmosphere (e.g., make-up fresh air) outside the vehicle 10. In some constructions, one or more flow control devices (e.g., check valves, etc.) can be located adjacent the inlet 90 and located in the bypass 113 to inhibit flow of the airflow 110 into one or both of the sorption system 78 and the bypass 113. Generally, the flow control devices adjacent the inlet 90 and in the bypass 113 regulate the airflow 110 within the HVAC system 66 so that the airflow 110 can be directed through one of the sorption system 78 and the bypass 113 during operation of the HVAC system 66. In some constructions, the flow control devices can be partially open so that a portion of the airflow 152 can flow through the inlet 90 and a portion of the airflow 110 can flow through the bypass 113.

The illustrated cooling circuit 82, or refrigeration system, includes a condenser assembly 114, an expansion device 118, a heat exchanger or evaporator assembly 122, and a refrigerant that flows through the condenser assembly 114, the expansion device 118, and the evaporator assembly 122. The illustrated condenser assembly 114 includes a compressor 126, a condenser coil 130, and a condenser fan 134. In other constructions, the cooling circuit 82 may also include other components (e.g., flow control valves, multiple or multi-stage compressors, etc.).

The compressor 126 and the condenser coil 130 can be located anywhere on the vehicle 10. In some constructions, the condenser coil 130 can be mounted to an exterior surface of one of the walls 70. The condenser fan 134 is positioned adjacent to the condenser coil 130 to assist with transferring heat from the refrigerant in the condenser coil 130 to the atmosphere by directing air over the condenser coil 130.

The evaporator assembly 122 is located adjacent to and in communication with the sorption system 78 and the bypass 113 to selectively receive the dehumidified airflow 112 exiting the sorption system 78 through the outlet 98, and the non-dehumidified airflow 110 from the bypass 113. In some constructions, the evaporator assembly 122 is attached to the vehicle 10 adjacent a rear of the cabin 58. In other constructions, the evaporator assembly 122 can be positioned in the compartment 34. In still other constructions, the evaporator assembly 122 may have a compact design and be installed in a sleeping portion, or other convenient location, of the cabin 58.

As shown in FIG. 2, the evaporator assembly 122 includes a housing 138, a cooling coil 142 disposed in the housing 138, and an evaporator fan 146 disposed in the housing 138 and in communication with the cooling coil 142. The sorption system 78, the bypass 113, and the evaporator assembly 122 are substantially aligned so that the evaporator fan 146 can generate the airflow 110 through the sorption system 78, through the bypass 113, and over the cooling coil 142. In other constructions, the airflow 110 into the sorption system 78 and/or through the bypass 113 can be generated by other air moving devices (e.g., a blower, or the like).

The heating circuit 86 includes a heater 150, a fuel reservoir 154, and a heating coil 158. In some constructions, the fuel reservoir 154 can be the same as the fuel reservoir 30 of the vehicle 10. The heater 150 is a direct-fired diesel heater that is positioned in communication with the coolant in the coolant system 38 and that includes heating elements (e.g., a glow pin, a heat exchanger, etc.) that help heat the coolant. In the illustrated construction, the heating coil 158 is disposed in the housing 138 of the evaporator assembly 122 and is in communication with the sorption system 78 and the bypass 113 to receive one of the airflows 110, 112 and to heat the respective airflow 110, 112. The airflows 110, 112 can be heated by the heat source that is used to desorb the desiccant 106, or alternatively, by another heat source. In other constructions, the heating coil 158 can be located elsewhere in the vehicle 10. The cooling coil 142 and the heating coil 158 are separated from each other so that the heating circuit 86 and the cooling circuit 82 are not mixed.

During operation of the heating circuit 86 it may not be necessary for air that is directed over the heating coil 158 to be dehumidified by the sorption system 78. For example, the airflow 110 can bypass the sorption system 78 via the bypass 113 prior to heating the airflow 110 via heat exchange with heated coolant in the heating coil 158. Alternatively, the airflow 110 can be dehumidified by the sorption system 78, and the dehumidified airflow 112 can then be directed into the housing 138 to be heated by the heating coil 158. A heated airflow is then discharged into the space 74.

In operation, the HVAC system 66 selectively conditions the space 74 using the sorption system 78, the cooling circuit 82, and/or the heating circuit 86. When the space 74 is cooled, the evaporator fan 146 draws the airflow 110 through the first inlet 90 of the sorption system 78, over the desiccant 106, and through the first outlet 98. As the airflow 110 passes through the desiccant 106, the airflow 110 is substantially dehumidified via adsorption of moisture by the desiccant 106 as is known in the art. The dehumidified airflow 112 is then directed through the evaporator assembly 122, where the airflow 112 is conditioned so that a conditioned airflow 166 can be discharged into the space 74. In some constructions, at least a portion of the airflow 110 can be directed through the bypass 113 during operation of the cooling circuit 82 to bypass the sorption system 78 (e.g., when previously conditioned air from the cabin 58 is recirculated through the HVAC system 66).

Eventually, the desiccant 106 that has been adsorbing moisture from the airflow 110 becomes saturated and can no longer dehumidify the airflow 110. Once the desiccant 110 is saturated, a regeneration process of the sorption system 78 is begun to desorb the moisture from the desiccant 106. During the regeneration process, the HVAC system 66 conditions the space 74 with the non-dehumidified airflow 110 via the bypass 113. The flow control devices redirect the airflow 110 through the bypass 113 toward the evaporator assembly 122, and inhibit or prevent the airflow 110 from entering the sorption system 78. In some constructions, one or more of the components of the HVAC system 66 can be shutdown during the regeneration process.

For example, during operation of the sorption system 78, moisture in the airflow 110 is adsorbed by the desiccant 106 for approximately ninety percent of the operation time. In this example, regeneration (e.g., desorption and cooling) of the desiccant 106 lasts for approximately ten percent of the operation time. The time duration for adsorption by and regeneration of the desiccant 106 can be different from time frames discussed herein. During the regeneration process, the HVAC system 66 may operate under a relatively large load due to the non-dehumidified nature of the airflow 110 from the bypass 113. However, the duration of the regeneration process is relatively short and does not substantially affect the efficiency of the HVAC system 66. Furthermore, air from the cabin 74 that is recirculated through the HVAC system 66 can have a relatively low humidity due to adsorption of moisture from the air during a previous adsorption cycle, and may limit the impact of the airflow 110 on the load of the HVAC system 66.

The cooling circuit 82 conditions the dehumidified airflow 112 by heat transfer with the cooling coil 142. The conditioned airflow 166 is then directed from the evaporator assembly 122 into the space 74 via the evaporator fan 146. During operation of the cooling circuit 82 (i.e., a typical cooling mode), refrigerant is circulated through the cooling circuit 82 to cool the dehumidified airflow 112 via heat transfer with the cooling coil 142. Relatively warm refrigerant is compressed by the compressor 126, and the compressed refrigerant is then cooled within the condenser coil 130 by heat transfer with air that is adjacent to or directed over (e.g., with the condenser fan 134) the condenser coil 130. The cooled refrigerant is then directed through the expansion device 118 and into the evaporator assembly 122 through the cooling coil 142. The previously cooled refrigerant is heated and the dehumidified airflow 112 is cooled. The evaporator fan 146 directs the cooled, dehumidified airflow 166 into the cabin 58 to condition the space 74.

During operation of the heating circuit 86, the space 74 is conditioned using the non-dehumidified airflow 110 from the bypass 113. Generally, the airflow 110 bypasses the sorption system 78 during operation of the heating circuit 86 and is conditioned by the heating coil 158. In some constructions, some or all of the airflow 110 can be dehumidified by the sorption system 78, and the dehumidified airflow 112 can then be conditioned by the heating coil 158. Coolant is circulated to heat the non-dehumidified airflow 110 via heat transfer with the heating coil 158. A heated airflow (instead of the cooled, dehumidified airflow 166) is then propelled by the evaporator fan 146 into the cabin 58 to condition the space 74. When the prime mover 26 is in the first mode, heat from the prime mover 26 heats the coolant in the coolant circuit, which in turn can selectively provide heat to the space 74. When the prime mover 26 is in the second mode, the heater 150 can be selectively engaged to heat the coolant in the coolant system 38 to provide heat to the space 74. In addition, the coolant heated by the heater 150 can keep the prime mover 26 relatively warm as needed when the prime mover 26 is in the “Off” state.

As discussed above, in some scenarios, it is desired to regenerate the desiccant 106 of the sorption system 78 after or between operations of the HVAC system 66. In the illustrated construction, the desiccant 106 can be desorbed using waste heat from the cooling circuit 82. FIGS. 3-9 illustrate a variety of cooling circuits that are substantially similar to the cooling circuit 82 shown in FIG. 2, and like parts have been given the same reference numbers. The illustrated cooling circuits are substantially similar to one another such that the overall operation of each cooling circuit is generally the same. Each cooling circuit discussed below includes a secondary heat exchanger 186 operable to regenerate the desiccant 106 by heating the desiccant 106 using warm refrigerant in the cooling circuit. FIGS. 3-5 illustrate the secondary heat exchanger 186 arranged in parallel with the condenser coil 130, and FIGS. 6-9 illustrate the secondary heat exchanger 186 arranged in series with the condenser coil 130. The secondary heat exchangers 186 are also operable to pre-cool the desiccant 106 after regeneration.

In some constructions (see, for example, FIG. 3), the secondary heat exchanger 186 includes a secondary coil 190 embedded in the desiccant 106 to directly heat the desiccant 106. In other constructions (see, for example, FIG. 6), the secondary heat exchanger 186 includes a secondary fan 194 operable to propel purge air over the secondary coil 190 when the coil 190 is positioned adjacent to the desiccant 106. The warm purge air flows through the desiccant 106 to indirectly heat the desiccant 106. In such constructions, the secondary fan 194 may be powered by the primer mover 26, a battery, and/or an alternative power source. However, the embedded secondary coil 190 of FIG. 3 and the secondary fan 194 of FIG. 6 are shown for illustrative purposes only. It should be readily apparent to one skilled in the art that any one of the cooling circuits of FIGS. 3-9 may include the secondary coil 190 embedded in the desiccant 106 or a secondary fan 194 to propel purge air over the coil 190 and through the desiccant 106. Furthermore, the secondary heat exchangers 186 may include other means to transfer heat from the cooling circuit to the desiccant 106 to regenerate the desiccant 106.

FIG. 3 illustrates a first construction of a cooling circuit 200, or refrigeration system, for use with the sorption system 78. The cooling circuit 200 is operable to condition an airflow, regenerate the desiccant 106, and pre-cool the desiccant 106. The illustrated cooling circuit 200 includes a first valve 204 positioned between the compressor 126 and the condenser coil 130 and a second valve 208 positioned between the compressor 126 and the secondary coil 190. The valves 204, 208 are actuated (e.g., opened and closed) to selectively direct refrigerant from the compressor 126 through either the condenser coil 130 or the secondary coil 190. The illustrated valves 204, 208 may be actuated automatically (e.g., via a solenoid, pneumatic actuator, hydraulic actuator, or the like) or manually. In some constructions, the valves 204, 208 may be combined into a single three-way valve to direct the refrigerant to either the condenser coil 130 or the secondary coil 190.

In the typical cooling mode, the first valve 204 is opened and the second valve 208 is closed such that warm refrigerant from the compressor 126 is directed toward the condenser coil 130. In addition, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan (if present) is turned “Off”. The refrigerant flows through the condenser coil 130, through the expansion device 118, and through the evaporator coil 142 back to the compressor 126. Wet air from the environment is pulled through the first inlet 90 of the sorption system 78 and passes through the desiccant 106 such that dehumidified air exits the sorption system 78 through the first outlet 98. The dehumidified air enters the evaporator assembly 122 and passes over the evaporator coil 142 where it is conditioned (e.g., cooled) by refrigerant in the coil 142. Conditioned air then exits the evaporator assembly 122 and enters the surrounding environment (e.g., the cabin 58 of the vehicle 10 shown in FIG. 1).

To regenerate the desiccant 106, the first valve 204 is closed and the second valve 208 is opened such that warm refrigerant from the compressor 126 is directed toward the secondary coil 190. The condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. The warm refrigerant flows through the secondary coil 190, desorbing moisture from the desiccant 106 directly (e.g., when the secondary coil 190 is embedded in the desiccant 106) or indirectly (e.g., when the secondary fan 194 is provided to propel an airflow over the secondary coil 190 and through the desiccant 106). The refrigerant then flows through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To cool (i.e., pre-cool) the desiccant 106 after regeneration, the first valve 204 is opened, the second valve 208 is closed, and the condenser fan 135 is turned “On”. If the secondary fan 194 is present, it is also turned “On”. Warm refrigerant flows from the compressor 126 and through the condenser coil 130 such that the refrigerant is cooled and reduced in pressure. Since the refrigerant from the condenser coil 130 has a relatively lower pressure, refrigerant in the secondary coil 190 is drawn from the secondary coil 190 toward the expansion device 118. As the refrigerant is drawn out of the secondary coil 190, the temperature of the refrigerant drops, thereby cooling the desiccant 106 directly or indirectly.

FIG. 4 illustrates a second construction of a cooling circuit 200′ for use with the sorption system 78. The sorption system 78 is omitted from FIG. 4 for the sake of clarity. The illustrated cooling circuit 200′ is similar to the cooling circuit 200 shown in FIG. 3, but includes a third valve 212 positioned between the secondary coil 190 and the expansion device 118. The third valve 212 is actuated to selectively direct refrigerant from the secondary coil 190 to the expansion device 118. The cooling circuit 200′ also includes a bypass 216 extending from a point between the secondary coil 190 and the third valve 212 to a point between the evaporator coil 142 and the compressor 126. The bypass 216 also includes a fourth valve 220 that is actuated to selectively direct refrigerant from the secondary coil 190 through the bypass 316 to the compressor 126. The illustrated valves 212, 220 may be actuated automatically or manually. In some constructions, the third and fourth valves 212, 220 may be combined into a single three-way valve.

In the typical cooling mode, the first valve 204 is opened and the second, third, and fourth valves 208, 212, 220 are closed such that warm refrigerant from the compressor 126 is directed toward the condenser coil 130. In addition, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan (if present) is turned “Off”. The refrigerant flows through the condenser coil 130, through the expansion device 118, and through the evaporator coil 142 back to the compressor 126 such that the cooling circuit 200′ operates in a similar manner to the cooling circuit 200 discussed above.

To regenerate the desiccant 106, the first and fourth valves 204, 220 are closed and the second and third valves 208, 212 are opened such that warm refrigerant from the compressor 126 is directed toward the secondary coil 190. The condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. The warm refrigerant flows through the secondary coil 190, desorbing moisture from the desiccant 106 directly or indirectly. The refrigerant then flows through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the first and fourth valves 204, 220 are opened, the second and third valves 208, 212 are closed, and the condenser fan 134 is turned “On”. If the secondary fan 194 is present, it is also turned “On”. Warm refrigerant flows from the compressor 126 and through the condenser coil 130 such that the refrigerant is cooled. The cooled refrigerant then flows through the expansion device 118 and the evaporator coil 142 such that the refrigerant is further cooled and reduced in pressure. Since the refrigerant exiting the evaporator coil 142 has a relatively lower pressure than the refrigerant in the secondary coil 190, the refrigerant in the secondary coil 190 is drawn through the bypass 216 toward the compressor 126. As the refrigerant is drawn out of the secondary coil 190, the temperature of the refrigerant drops, thereby cooling the desiccant 106 directly or indirectly.

FIG. 5 illustrates a third construction of a cooling circuit 200″ for use with the sorption system 78. The sorption system 78 is omitted from FIG. 5 for the sake of clarity. The illustrated cooling circuit 200″ is similar to the cooling circuit 200′ shown in FIG. 4, but includes a second bypass 224 extending from a point between the condenser coil 130 and the third valve 212 to a point between the second valve 208 and the secondary coil 190. The second bypass 224 includes a fifth valve 228 and a second expansion device 232. The fifth valve 228 is actuated to selectively direct refrigerant from the condenser coil 130 through the second expansion device 232 and the secondary coil 190. The illustrated valve 228 may be actuated automatically or manually. In some constructions, the fifth valve 228 and the second expansion device 232 may be combined into a single device.

In the typical cooling mode, the first valve 204 is opened and the second, third, fourth, and fifth valves 208, 212, 220, 228 are closed such that warm refrigerant from the compressor 126 is directed toward the condenser coil 130. In addition, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan (if present) is turned “Off”. The refrigerant flows through the condenser coil 130, through the expansion device 118, and through the evaporator coil 142 back to the compressor 126 such that the cooling circuit 200″ operates in a similar manner to the cooling circuit 200 discussed above.

To regenerate the desiccant 106, the first, fourth, and fifth valves 204, 220, 228 are closed and the second and third valves 208, 212 are opened such that warm refrigerant from the compressor 126 is directed toward the secondary coil 190. The condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. The warm refrigerant flows through the secondary coil 190, desorbing moisture from the desiccant 106 directly or indirectly. The refrigerant then flows through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the first, fourth, and fifth valves 204, 220, 228 are opened, the second and third valves 208, 212 are closed, and the condenser fan 134 is turned “On”. If the secondary fan is present, it is also turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 such that the refrigerant is cooled. The cooled refrigerant flows into the second bypass 224 and through the fifth valve 228 and the second expansion device 232, further cooling the refrigerant. The cooled refrigerant then flows into the secondary coil 190 and directly or indirectly cools the desiccant 106. The refrigerant exits the secondary coil 190 and flows through the bypass 216 back to the compressor 126.

FIG. 6 illustrates a fourth construction of a cooling circuit 300 for use with the sorption system 78. To operate the illustrated cooling circuit 300 in the typical cooling mode, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan 194 is turned “Off”. Warm refrigerant flows from the compressor 126, through the condenser coil 130, the secondary coil 190, the expansion device 118, and the evaporator coil 142, and back to the compressor 126. Wet air from the environment is pulled through the first inlet 90 of the sorption system 78 and passes through the desiccant 106 such that dehumidified air exits the sorption system 78 through the first outlet 98. The dehumidified air enters the evaporator assembly 122 and passes over the evaporator coil 142 where it is conditioned (e.g., cooled) by the cooled refrigerant in the coil 142. Conditioned air then exits the evaporator assembly 122 and enters the surrounding environment (e.g., the cabin 58 of the vehicle 10 shown in FIG. 1).

To regenerate the desiccant 106, the condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan 194 is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 substantially unchanged (e.g., the temperature of the refrigerant remains generally the same) and flows into the secondary coil 190. The secondary fan 194 propels purge air over the secondary coil 190, warming the purge air with the refrigerant in the secondary coil 190. The warm purge air enters the sorption system 78 through the second inlet 94, passes through the desiccant 106 to desorb moisture from the desiccant 106, and exits the sorption system 78 through the second outlet 102. Moisture is thereby carried by the purge air out of the desiccant 106. In some constructions, the purge air can be formed from air returning from the cabin 58, air from the environment, and/or air from other sources. Additionally or alternatively, the purge air may enter the sorption system 78 through a common inlet with the wet air (e.g., the first inlet 90). In other constructions, the secondary fan 194 may be omitted and the secondary coil 190 may be embedded in the desiccant 106 to heat the desiccant 106 directly.

Meanwhile, the warm refrigerant is cooled at the secondary coil 190 by the purge air and directed through the expansion device 118 for further cooling. The cooled refrigerant passes through the evaporator coil 142, where the evaporator fan 146 may or may not be running to propel an airflow over the coil 142. The refrigerant continues through the cooling circuit 300 and is circulated back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the condenser and secondary fans 134, 194 are turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 where the refrigerant is cooled by air propelled over the coil 130 with the condenser fan 134. The cooled refrigerant flows from the condenser coil 130 to the secondary coil 190. The secondary fan 194 propels purge air over the secondary coil 190, cooling the purge air with the cooled refrigerant in the coil 190. The cooled purge air flows through the desiccant 106 to cool the desiccant 106 indirectly. In constructions where the secondary fan 194 is omitted, the secondary coil 190 may be embedded in the desiccant 106 to cool the desiccant 106 directly. The constructions using the fan 194 are referred to herein as cooling (or conversely heating) “indirectly”, while the constructions not using the fan 194 and having an embedded coil 190 are referred to herein as cooling (or conversely heating) “directly”. Meanwhile, the refrigerant exits the secondary coil 190 and flows through the expansion device 118 and the evaporator coil 142 back to the compressor 126.

FIG. 7 illustrates a fifth construction of a cooling circuit 300′ for use with the sorption system 78. The sorption system 78 is omitted from FIG. 7 for the sake of clarity. The illustrated cooling circuit 300′ is similar to the cooling circuit 300 shown in FIG. 6, but includes a first valve 304 positioned between the condenser coil 130 and the secondary coil 190. The cooling circuit 300′ also includes a bypass 308 extending from a point between the condenser coil 130 and the first valve 304 to a point between the secondary coil 190 and the expansion device 118. The bypass 308 includes a second valve 312. The valves 304, 312 are actuated to selectively direct refrigerant from the condenser coil 130 through or around the secondary coil 190. The illustrated valves 304, 312 may be actuated automatically or manually. In some constructions, the valves 304, 312 may be combined into a single three-way valve to direct the refrigerant through or around the secondary coil 190.

In the typical cooling mode, the first valve 304 is closed and the second valve 213 is opened such that refrigerant from the condenser coil 130 is directed around the secondary coil 190. In addition, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan 194 (if present) is turned “Off”. Warm refrigerant flows from the compressor 126, through the condenser coil 130, the bypass 308, the expansion device 118, and the evaporator coil 142, and back to the compressor 126 such that the cooling circuit 300′ operates in a similar manner to the cooling circuit 300 discussed above.

To regenerate the desiccant 106, the first valve is opened 304 and the second valve 312 is closed such that refrigerant from the condenser coil 130 is directed through the secondary coil 190. The condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan 194 (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. Warm refrigerant flows from the compressor 126 and through the condenser coil 130 substantially unchanged. The warm refrigerant then flows into the secondary coil 190, desorbing moisture from the desiccant 106 directly or indirectly. The refrigerant flows from the secondary coil 190 through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the first valve 304 is closed, the second valve 312 is opened, and the condenser fan 134 is turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 where the refrigerant is cooled by air propelled over the coil 130 with the condenser fan 134. The cooled refrigerant flows through the bypass 308 toward the expansion device 118 at a reduced pressure. Since the refrigerant in the bypass 308 is at a relatively lower pressure than refrigerant in the secondary coil 190, the refrigerant in the secondary coil 190 is drawn from the coil 190 toward the expansion device 118. As the refrigerant is drawn out of the secondary coil 190, the temperature of the refrigerant drops, thereby cooling the desiccant 106 directly or indirectly.

FIG. 8 illustrates a sixth construction of a cooling circuit 300″ for use with the sorption system 78. The sorption system 78 is omitted from FIG. 8 for the sake of clarity. The illustrated cooling circuit 300″ is similar to the cooling circuit 300′ shown in FIG. 7, but includes a second bypass 316 extending from a point between the secondary coil 190 and the first bypass 108 and a point between the evaporator coil 142 and the compressor 126. The second bypass 316 includes a third valve 320 that is actuated to selectively direct refrigerant from the secondary coil 190 through the second bypass 316 to the compressor 126. The illustrated valve 320 may be actuated automatically or manually. The cooling circuit 300″ also includes a check valve 324 positioned between the first and second bypasses 308, 316 to prevent refrigerant from the first bypass 308 from flowing into the secondary coil 190 or the second bypass 316.

In the typical cooling mode, the first and third valves 304, 320 are closed and the second valve 312 is opened such that refrigerant from the condenser coil 130 is directed around the secondary coil 190. In addition, the condenser and the evaporator fans 134, 146 are turned “On”, while the secondary fan 194 (if present) is turned “Off”. Warm refrigerant flows from the compressor 126, through the condenser coil 130, the bypass 308, the expansion device 118, and the evaporator coil 142, and back to the compressor 126 such that the cooling circuit 300″ operates in a similar manner to the cooling circuit 300 discussed above.

To regenerate the desiccant 106, the first valve 304 is opened and the second and third valves 312, 320 are closed such that the refrigerant from the condenser coil 130 flows through the secondary coil 190. The condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan 194 (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. Warm refrigerant flows from the compressor 126 and through the condenser coil 130 substantially unchanged. The warm refrigerant then flows into the secondary coil 190, desorbing moisture from the desiccant 106 directly or indirectly. The refrigerant flows from the secondary coil 190 through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the first valve 304 is closed, the second and third valves 312, 320 are opened, and the condenser fan 134 is turned “On”. If the secondary fan 194 is present, it is also turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 where the refrigerant is cooled by air propelled over the coil 130 with the condenser fan 134. The cooled refrigerant continues through the first bypass 308, the expansion device 118, and the evaporator coil 142 toward the compressor 126. Since the refrigerant exiting the evaporator coil 142 has a relatively lower pressure than refrigerant in the secondary coil 190, the refrigerant in the secondary coil 190 is drawn through the bypass 316 toward the compressor 126. As the refrigerant is drawn out of the secondary coil 190, the temperature of the refrigerant drops, thereby cooling the desiccant 106 directly or indirectly.

FIG. 9 illustrates a seventh construction of a cooling circuit 300′″ for use with the sorption system 78. The sorption system 78 is omitted from FIG. 9 for the sake of clarity. The illustrated cooling circuit 300′″ is similar to the cooling circuit 300″ shown in FIG. 8, but includes a third bypass 328 extending from a point between the condenser coil 130 and the first bypass 308 to a point between the first valve 304 and the secondary coil 190. The third bypass 328 includes a fourth valve 332 and a second expansion device 336. The fourth valve 332 is actuated to selectively direct refrigerant from the condenser coil 130 through the second expansion device 336 and the secondary coil 190. The illustrated valve 332 may be actuated automatically or manually. In some constructions, the fourth valve 332 and the second expansion device 336 may be combined into a single device.

In the typical cooling mode, the first, third, and fourth valves 304, 320, 332 are closed and the second valve 312 is opened such that the refrigerant from the condenser coil 130 is directed around the secondary coil 190. In addition, the condenser and evaporator fans 134, 146 are turned “On”, while the secondary fan 194 (if present) is turned “Off”. Warm refrigerant flows from the compressor 126, through the condenser coil 130, the bypass 308, the expansion device 118, and the evaporator coil 142, and back to the compressor 126 such that the cooling circuit 300′″ operates in a similar manner to the cooling circuit 300 discussed above.

To regenerate the desiccant, 106, the first valve 304 is opened and the second, third, and fourth valves 312, 320, 332 are closed. In addition, the condenser and evaporator fans 134, 146 are turned “Off”, while the secondary fan 194 (if present) is turned “On”. In some constructions, the evaporator fan 146 may also be turned “On”. Warm refrigerant flows from the compressor 126 and through the condenser coil 130 substantially unchanged. The warm refrigerant then flows into the secondary coil 190, desorbing moisture from the desiccant 106 directly or indirectly. The refrigerant flows from the secondary coil 190 through the expansion device 118 and the evaporator coil 142 back to the compressor 126. This process, or cycle, is continued until the desiccant 106 is sufficiently desorbed.

To pre-cool the desiccant 106 after regeneration, the first valve 304 is closed, the third and fourth valves 320, 332 are opened, and the condenser fan 134 is turned “On”. The second valve 312 may be either opened or closed. If the secondary fan 194 is present, it is also turned “On”. Warm refrigerant from the compressor 126 flows through the condenser coil 130 where the refrigerant is cooled by air propelled over the coil 130 with the condenser fan 134. The cooled refrigerant flows through the third bypass 328 and the second expansion device 336 and into the secondary coil 190. As the refrigerant flows through the second expansion device 336, the refrigerant is further reduced in temperature. The cooled refrigerant in the secondary coil 190 thereby cools the desiccant 106 directly or indirectly and flows out of the second coil 190 through the second bypass 316 toward the compressor 126. If the second valve 312 is opened, a portion of the refrigerant from the condenser coil 130 may flow through the first bypass 308 and the expansion device 118 toward the evaporator coil 142 such that the evaporator assembly 122 may begin or continue to operate while the desiccant 106 is pre-cooled.

In some constructions, such as the construction shown in FIG. 10, a sorption system 478 is divided into a two-stage system that provides continuous cooling capability. As shown in FIG. 10, the two-stage sorption system 478 includes a first desiccant 482 and a second desiccant 486. The illustrated two-stage sorption system 478 is usable with any of the cooling circuits 82, 200, 200′, 200″, 300, 300′, 300″, 300′″ described above with reference to FIGS. 2 to 9 in place of the sorption system 78 illustrated therein.

Providing a two-stage sorption system 478 allows one of the first and second desiccants 482, 486 to be desorbed or regenerated while the other desiccant 482, 486 adsorbs moisture from an airflow. For example, in the illustrated construction, the first desiccant 482 is regenerated while the second desiccant 486 adsorbs moisture from the airflow. Once the second desiccant 486 becomes saturated with moisture or the first desiccant 482 is substantially desorbed, the first and second desiccants 482, 486 may be reversed (e.g., flipped or switched) such that the second desiccant 486 is regenerated while the first desiccant 482 adsorbs moisture from the airflow. In some constructions, the sorption system 478 may include one or more sensors to determine when to reverse the desiccants 482, 486. In other constructions, the sorption system may include a timer to automatically reverse the desiccants 482, 486 after a predetermined period of time.

Sorption systems increase the efficiency of HVAC systems by reducing the load required to condition an airflow. For example, in some constructions, a sorption system may decrease the load of an HVAC system by up to about fifty percent. Using a secondary heat exchanger to transfer heat from a refrigerant to help desorb moisture from a desiccant also reduces energy and fuel consumption by decreasing the power normally required cool the refrigerant with a condenser. Furthermore, when using a secondary heat exchanger in vehicle applications, a diesel fired heater is not required to heat engine coolant to help desorb moisture from a desiccant.

Various features and advantages of the invention are set forth in the following claims.