Dry ice jet cooling and cold and heat supply combined system of electric vehicle driving mechanism

Abstract

The invention provides a dry ice jet cooling and cold and heat supply combined system for an electric vehicle driving mechanism. The dry ice jet cooling and cold and heat supply combined system comprises a compressor unit, a heat exchanger outside a compartment, a heat exchanger inside the compartment, a heat regenerator and a gas-liquid separator. An outlet of the compressor unit is simultaneously connected with the heat exchanger outside the compartment and the heat exchanger inside the compartment, the other connectors of the heat exchanger outside the compartment and the heat exchanger inside the compartment are respectively and simultaneously connected with an in-pipe inlet and a shell side outlet of the heat regenerator, and an in-pipe outlet of the heat regenerator is connected with a gas-liquid two-phase fluid inlet of the gas-liquid separator through an expansion valve. A gas outlet of the gas-liquid separator is connected with the compressor unit, a liquid outlet of the gas-liquid separator is connected with the nozzle, and the nozzle extends into the electric automobile driving mechanism. According to the technical scheme, the driving mechanism of the electric automobile is cooled through sublimation heat absorption of the dry ice, meanwhile, air conditioner cooling in the automobile in summer is achieved through residual cold generated by sublimation of the dry ice, and heat generated by high-temperature exhaust of the compressor is recycled for heating in the automobile in winter.

Description

Technical Field

[0001] The present invention belongs to the field of refrigeration and cryogenic technology, and in particular relates to a dry ice jet cooling and hot and cold supply combined system for an electric vehicle drive mechanism. Background Art

[0002] With the development of today's society and the need for energy conservation and environmental protection, the demand for electric vehicles is gradually increasing. However, as key components of the electric vehicle's drive mechanism, the battery and drive motor of the electric vehicle have high heat flux density and small size. The heat load generated during operation directly affects the efficiency, lifespan, and operational reliability of the electric vehicle. Existing air cooling and liquid cooling methods are unable to meet the cooling requirements.

[0003] Known Technology: Carbon dioxide (CO2), as a natural working fluid, possesses excellent thermal properties. Its solid form, commonly known as dry ice, undergoes a sublimation phase transition at -78.5°C at standard atmospheric pressure, with a latent heat of 573 kJ / kg. Dry ice releases a significant amount of cold energy during its sublimation process.

[0004] Therefore, how to rationally utilize the thermal properties of CO2 to cool the drive mechanism, as well as to cool electric vehicles in hot weather and heat them in winter, is an urgent problem that needs to be solved. Summary of the Invention

[0005] In view of this, the present invention aims to propose a combined dry ice jet cooling and heating and cooling system for the electric vehicle drive mechanism, so as to utilize dry ice to cool the equipment of the electric vehicle drive mechanism, while utilizing the residual cold from the sublimation of dry ice to realize air conditioning and cooling in the vehicle in summer, and recover the heat from the high-temperature exhaust gas of the compressor to heat the vehicle in winter, thereby effectively improving energy efficiency and economic benefits, saving energy and protecting the environment.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] Electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system, the circulating working fluid of this system is carbon dioxide, and the system includes a compressor unit, an external heat exchanger, an internal heat exchanger, a regenerator and a gas-liquid separator;

[0008] The compressor unit outlet is divided into two paths, one path is connected to the inlet of the second solenoid valve, and the other path is connected to the inlet of the third solenoid valve;

[0009] The first interface of the heat exchanger in the vehicle compartment is divided into two paths, one path is connected to the outlet of the third solenoid valve, and the other path is connected to the inlet of the compressor unit through the fourth solenoid valve;

[0010] The second interface of the heat exchanger in the carriage is divided into two routes, one route is connected to the shell side outlet of the regenerator through the sixth solenoid valve, and the other route is connected to the pipe inlet of the regenerator through the eighth solenoid valve;

[0011] The first interface of the external heat exchanger is divided into two paths, one path is connected to the outlet of the second solenoid valve, and the other path is connected to the inlet of the compressor unit through the first solenoid valve;

[0012] The second interface of the external heat exchanger is divided into two routes, one of which is connected to the shell-side outlet of the regenerator through the fifth solenoid valve, and the other is connected to the pipe inlet of the regenerator through the seventh solenoid valve;

[0013] The inner tube outlet of the regenerator is connected to the gas-liquid two-phase fluid inlet of the gas-liquid separator through an expansion valve. The gas outlet of the gas-liquid separator is connected to the compressor unit to deliver the separated gaseous working fluid to the compressor unit. The liquid outlet of the gas-liquid separator is connected to the nozzle. The nozzle extends into the driving mechanism of the electric vehicle to output the low-temperature working fluid to the driving mechanism to cool the driving mechanism. The driving mechanism is provided with a working fluid outlet, which is connected to the shell side inlet of the regenerator.

[0014] Furthermore, the compressor unit includes a low-pressure stage compressor and a high-pressure stage compressor, the inlet of the low-pressure stage compressor is the inlet of the compressor unit, and the outlet of the high-pressure stage compressor is the outlet of the compressor unit;

[0015] The gas outlet of the gas-liquid separator and the outlet of the low-pressure compressor are connected in parallel and then connected to the inlet of the high-pressure compressor.

[0016] Furthermore, the driving mechanism includes a driving motor and a battery pack. The liquid outlet of the gas-liquid separator is divided into two paths, one of which is connected to a first nozzle and the other is connected to a second nozzle. The first nozzle extends into the battery pack and the second nozzle extends into the driving motor. The working fluid outlet of the battery pack and the working fluid outlet of the driving motor are connected in parallel and then connected to the shell side inlet of the regenerator.

[0017] Furthermore, the battery pack and the drive motor are respectively provided with sealed shells, and spaces are respectively left between the battery pack and the corresponding shells, and between the drive motor and the corresponding shells, and the first nozzle and the second nozzle are respectively provided in the corresponding shells.

[0018] Furthermore, the exterior heat exchanger is installed at the front of the vehicle facing the wind.

[0019] Furthermore, the in-car heat exchanger is installed in an air supply duct at the chassis of the electric vehicle at the co-pilot position; an air inlet door is provided at the inlet of the air supply duct, and an air supply door is provided at the air supply outlet of the air supply duct;

[0020] An air supply fan is provided in the air supply duct at the windward side of the heat exchanger in the vehicle compartment;

[0021] An exhaust port is provided on the side wall of the air supply duct at the air outlet side of the heat exchanger in the vehicle compartment. The exhaust port is provided with an exhaust door. The exhaust port is connected to the exhaust duct inlet of the electric vehicle, and the exhaust duct outlet blows toward the compressor unit.

[0022] The side wall of the air supply duct is provided with a return air port on the windward side of the heat exchanger in the vehicle compartment, and the return air port is arranged on the side of the air supply fan away from the heat exchanger in the vehicle compartment, and the return air port is provided with a return air door.

[0023] Compared with the prior art, the electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system of the present invention has the following advantages:

[0024] (1) The technical solution of the present invention utilizes the heat absorption of dry ice sublimation to cool the electric vehicle drive mechanism, and at the same time utilizes the residual cold of dry ice sublimation to realize air conditioning cooling in the vehicle in summer, and recovers the heat of the high-temperature exhaust gas of the compressor to heat the vehicle in winter.

[0025] (2) The present invention comprehensively and efficiently utilizes cold and heat energy, effectively improving the energy efficiency of the combined system. The system is simple, safe, reliable, energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 Schematic diagram of a combined dry ice blasting cooling and heating and cooling system for an electric vehicle drive mechanism according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the air supply duct provided with an in-car heat exchanger in the present invention;

[0029] Figure 3 This is a working medium CO2 cycle state diagram when the present invention is operated in winter;

[0030] Figure 4 This is a working fluid CO2 cycle state diagram during summer operation of the present invention.

[0031] Description of reference numerals:

[0032] 1- low-pressure compressor, 2- high-pressure compressor, 3- first solenoid valve, 4- second solenoid valve, 5- third solenoid valve, 6- fourth solenoid valve, 7- heat exchanger outside the vehicle compartment, 8- fifth solenoid valve, 9- sixth solenoid valve, 10- seventh solenoid valve, 11- eighth solenoid valve, 12- regenerator, 13- expansion valve, 14- gas-liquid separator, 15- first nozzle, 16- second nozzle, 17- drive motor, 18- battery pack, 19- heat exchanger inside the vehicle compartment, 20- air supply fan, 21- air inlet door, 22- air supply duct, 23- return air door, 24- exhaust door, 25- air supply door. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0034] like Figure 1 As shown, a combined dry ice blasting cooling and heating and cooling system for an electric vehicle drive mechanism, wherein the circulating working fluid of the combined system is CO2, comprises a low-pressure compressor 1, a high-pressure compressor 2, a first solenoid valve 3, a second solenoid valve 4, a third solenoid valve 5, a fourth solenoid valve 6, an external heat exchanger 7, a fifth solenoid valve 8, a sixth solenoid valve 9, a seventh solenoid valve 10, an eighth solenoid valve 11, a regenerator 12, an expansion valve 13, a gas-liquid separator 14, a first nozzle 15, a second nozzle 16, a drive motor 17, a battery pack 18, and an internal heat exchanger 19, wherein the exhaust interface of the low-pressure compressor 1 is connected in parallel with the gas outlet of the gas-liquid separator and then connected to the inlet of the high-pressure compressor 2, the outlet of the high-pressure compressor 2 is divided into two paths, one path is connected to the inlet of the second solenoid valve 4, and the other path is connected to the inlet of the third solenoid valve 5, the outlet pipe of the second solenoid valve 4 is connected in parallel with the inlet pipe of the first solenoid valve 3 and then connected to the first interface of the external heat exchanger 7. The outlet pipe of the third solenoid valve 5 is connected in parallel with the inlet pipe of the fourth solenoid valve 6 and is connected to the first interface of the heat exchanger 19 in the vehicle compartment; the outlet pipe of the first solenoid valve 3 is connected to the inlet pipe of the low-pressure stage compressor 1, and the outlet pipe of the fourth solenoid valve 6 is connected to the inlet pipe of the low-pressure stage compressor 1.

[0035] The second interface of the in-car heat exchanger 19 is connected to the outlet pipe of the sixth solenoid valve 9 and the inlet of the eighth solenoid valve 11, respectively. The second interface of the out-car heat exchanger 7 is connected to the outlet pipe of the fifth solenoid valve 8 and the inlet pipe of the seventh solenoid valve 10, respectively. The outlets of the seventh and eighth solenoid valves 10 and 11 are connected to the inlet of the regenerator 12. The shell-side outlet of the regenerator 12 is connected to the inlet of the fifth and sixth solenoid valves 8 and 9, respectively. The in-car outlet of the regenerator 12 is connected to the gas-liquid two-phase fluid inlet of the gas-liquid separator 14 via the expansion valve 13. The gas outlet of the gas-liquid separator 14 is connected in parallel with the exhaust outlet of the low-pressure stage compressor 1 and then to the inlet of the high-pressure stage compressor 2. The liquid outlet of the gas-liquid separator 14 is divided into two paths, connected to the inlet pipes of the first and second nozzles 15 and 16, respectively. The fluid outlets of the drive motor 17 and battery pack 18 are connected in parallel and then to the shell-side inlet of the regenerator 12.

[0036] The drive motor 17 and the battery pack 18 are respectively provided with a casing, and a gap is left between the drive motor 17 and the corresponding casing, and between the battery pack 18 and the corresponding casing. The first nozzle 15 and the second nozzle 16 are respectively provided in the sealed casing of the drive motor 17 and the battery pack 18. The casing of the drive motor 17 and the casing of the battery pack 18 are respectively provided with an inlet and a fluid outlet.

[0037] The number of first nozzles 15 and second nozzles 16 can be set as needed. In the present invention, both the first nozzle 15 and the second nozzle 16 are of a reduced diameter nozzle structure, that is, the nozzle outlet size is smaller than the size of the medium flow channel within the nozzle. For example, the diameter of the medium flow channel within the nozzle is gradually reduced from the nozzle inlet end to the outlet end, so that the first nozzle 15 and the second nozzle 16 can throttle and cool the working medium CO2 flowing through.

[0038] In the present invention, the first solenoid valve 3, the second solenoid valve 4, the third solenoid valve 5, the fourth solenoid valve 6, the fifth solenoid valve 8, the sixth solenoid valve 9, the seventh solenoid valve 10, and the eighth solenoid valve 11 can be automatically controlled to open and close through temperature sensors to meet the cooling and heating needs in different seasons.

[0039] The exterior heat exchanger 7 is installed at the front of the car facing the wind, and the interior heat exchanger 19 is installed in the air supply duct 22 at the chassis of the passenger seat. Figure 2As shown, the air supply duct 22 is provided with an insulation layer, and an air inlet door 21 is provided at the inlet of the air supply duct 22. The air supply outlet of the air supply duct 22 is connected to the air duct in the car, and the air supply outlet is provided with an air supply door 25. An air supply fan 20 is provided at the windward position of the heat exchanger 19 in the car in the air supply duct 22. The air supply duct 22 is provided with an exhaust outlet on the side of the air outlet position of the heat exchanger 19 in the car, and a return air outlet is provided on the side of the windward position of the heat exchanger 19 in the car, and the air supply fan 21 is spatially located between the return air outlet and the heat exchanger 19 in the car, the exhaust outlet is provided with an exhaust door 24, and the return air outlet is provided with a return air door 23. The exhaust outlet is connected to the exhaust duct inlet of the electric car (not shown in the figure), and the exhaust duct outlet blows toward the high-pressure stage compressor 2.

[0040] The specific operation mode of the present invention is:

[0041] During winter operation, the second solenoid valve 4, the fourth solenoid valve 6, the sixth solenoid valve 9, and the seventh solenoid valve 10 are closed, and the first solenoid valve 3, the third solenoid valve 5, the fifth solenoid valve 8, and the eighth solenoid valve 11 are opened. The working medium CO2 circulates as follows: Figure 3 As shown, at this time, the air supply fan 20 in the air supply duct 22 is started, the return air door 23 is opened, the air supply door 25 is opened, and the exhaust door 24 is closed. The air inlet door 21 is opened and controlled according to the air demand in the vehicle compartment to adjust the amount of fresh air entering from the outside.

[0042] The high-temperature CO2 gas discharged from the high-pressure stage compressor 2 enters the vehicle cabin heat exchanger 19 through the third solenoid valve 5 to exchange heat with the vehicle cabin air to provide heat for the vehicle cabin. The CO2 gas after releasing heat enters the pipe of the regenerator 12 through the eighth solenoid valve 11. After throttling and reducing the pressure through the expansion valve 13, the gas-liquid two-phase fluid enters the gas-liquid separator 14. The separated gas is mixed with the exhaust gas of the low-pressure stage compressor 1 and then enters the high-pressure stage compressor 2. The separated liquid is throttled and reduced in pressure through the first nozzle 15 and the second nozzle 16 respectively to form a mixed fluid of dry ice and gas, which enters the sealed housing of the drive motor 17 and the battery pack 18 to absorb heat. After cooling the drive motor 17 and the battery pack 18 respectively, the dry ice sublimates into gas. The low-temperature gas in parallel enters the shell side of the regenerator 12 to exchange heat with the fluid in the pipe, then enters the heat exchanger 7 outside the vehicle cabin through the fifth solenoid valve 8 to absorb heat, and then enters the low-pressure stage compressor 1 through the first solenoid valve 3.

[0043] When the combined system is running in summer, the second solenoid valve 4, the fourth solenoid valve 6, the sixth solenoid valve 9, and the seventh solenoid valve 10 are opened, and the first solenoid valve 3, the third solenoid valve 5, the fifth solenoid valve 8, and the eighth solenoid valve 11 are closed. The working medium CO2 circulates as follows: Figure 4 As shown, the air supply fan 20 is started, the return air door 23 is opened, the air supply door 25 is opened, and the exhaust air door 24 is closed. The air inlet door 21 is opened and controlled according to the air demand in the vehicle compartment to adjust the amount of fresh air entering from the outside.

[0044] The high-temperature CO2 gas discharged from the high-pressure stage compressor 2 enters the exterior heat exchanger 7 through the second solenoid valve 4 for heat exchange with the exterior air. The CO2 gas, after releasing heat, enters the pipe of the regenerator 12 through the seventh solenoid valve 10. After throttling and reducing the pressure through the expansion valve 13, the gas-liquid two-phase fluid enters the gas-liquid separator 14. The separated gas mixes with the exhaust gas from the low-pressure stage compressor 1 and enters the high-pressure stage compressor 2. The separated liquid is throttled and reduced in pressure through the first nozzle 15 and the second nozzle 16, respectively, to form a mixed fluid of dry ice and gas. The mixed fluid enters the sealed housing of the drive motor 17 and the battery pack 18 to absorb heat, cooling the drive motor 17 and the battery pack 18 respectively. The dry ice sublimates into gas. The low-temperature gas, after being connected in parallel, enters the shell side of the regenerator 12 for heat exchange with the fluid in the pipe. It then enters the interior heat exchanger 19 through the sixth solenoid valve 9 to absorb heat from the interior of the vehicle. The residual cold of the low-temperature CO2 gas is used to cool the interior of the vehicle, and then enters the low-pressure stage compressor 1 through the fourth solenoid valve 6.

[0045] In addition, this combined system can also be used in spring and autumn. In spring and autumn, if the temperature in the car is higher than the comfortable temperature and cooling is required, the system can be operated in the same way as the piping and valve components in summer. The start, stop, and speed of the air supply fan 20 of the heat exchanger 19 in the car are controlled by the temperature in the car, thereby adjusting the amount of cold air supplied to the car: the air supply fan 20 at the windward position of the heat exchanger 19 in the car is started, and the speed of the air supply fan 20 is adjusted according to the temperature in the car, thereby adjusting the amount of cold air supplied to the car. When the temperature in the car reaches the comfortable temperature, the air supply fan 20 is turned off, and the supply of cold air to the car is stopped.

[0046] In spring and autumn, if the cabin temperature falls below the comfortable level and heating is required, the system uses the same piping and valve control methods used during winter operation. The cabin temperature is used to control the start / stop and speed of the supply fan 20 for the cabin heat exchanger 19, thereby adjusting the volume of heated air delivered to the cabin. The fan supplying air to the cabin heat exchanger 19 is started, and its speed is adjusted according to the temperature. When the cabin temperature reaches the comfortable level, the supply fan 20 is shut down, stopping the delivery of heated air to the cabin.

[0047] When there is no need for cooling or heating in the cabin, but the car is moving, the battery and motor are still working and need temperature control and cooling. The system operates in the control mode of the pipelines and valves during summer operation. The air supply fan 20 is started, the return air door 23 is closed, the air supply door 25 is closed, the exhaust door 24 is opened, and the air inlet door 21 is opened. The outside air enters the air duct through the air inlet door 21, flows through the heat exchanger 19 in the starting cabin, and the cooled cold air is blown to the high-pressure stage compressor 2 through the exhaust door 24 to cool the high-pressure stage compressor 2.

[0048] The innovation of the present invention lies in the circulation system designed for the corresponding working fluid CO2. The automatic control of the start and stop of the solenoid valve, as well as the start and stop of the air supply fan and other electrical components involved in this system, activates different operating modes of the system according to the temperature inside the car. This is a commonly used temperature control method for automobiles and is common knowledge among those skilled in the art. Therefore, the connection and control principles of the electrical components are not described in detail in the embodiments of the present invention.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system, characterized by: The circulating working fluid of the system is carbon dioxide, and the system comprises a compressor unit, an external heat exchanger (7), an internal heat exchanger (19), a regenerator (12), and a gas-liquid separator (14); The compressor unit outlet is divided into two paths, one path is connected to the inlet of the second solenoid valve (4), and the other path is connected to the inlet of the third solenoid valve (5); The first interface of the heat exchanger (19) in the vehicle compartment is divided into two paths, one path is connected to the outlet of the third solenoid valve (5), and the other path is connected to the inlet of the compressor unit through the fourth solenoid valve (6); The second interface of the interior heat exchanger (19) is divided into two paths, one path is connected to the shell side outlet of the regenerator (12) through the sixth solenoid valve (9), and the other path is connected to the pipe inlet of the regenerator (12) through the eighth solenoid valve (11); The first interface of the external heat exchanger (7) is divided into two paths, one path is connected to the outlet of the second solenoid valve (4), and the other path is connected to the inlet of the compressor unit through the first solenoid valve (3); The second interface of the external heat exchanger (7) is divided into two paths, one path is connected to the shell side outlet of the regenerator (12) through the fifth solenoid valve (8), and the other path is connected to the pipe inlet of the regenerator (12) through the seventh solenoid valve (10); The outlet of the regenerator (12) in the pipe is connected to the gas-liquid two-phase fluid inlet of the gas-liquid separator (14) through the expansion valve (13); the gas outlet of the gas-liquid separator (14) is connected to the compressor unit to deliver the separated gaseous working medium to the compressor unit; the liquid outlet of the gas-liquid separator (14) is connected to the nozzle, which extends into the driving mechanism of the electric vehicle and outputs the low-temperature working medium to the driving mechanism to cool the driving mechanism; the driving mechanism is provided with a working medium outlet, and the working medium outlet is connected to the shell side inlet of the regenerator (12).

2. The electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system according to claim 1, characterized in that: The compressor unit comprises a low-pressure stage compressor (1) and a high-pressure stage compressor (2), wherein the inlet of the low-pressure stage compressor (1) is the inlet of the compressor unit, and the outlet of the high-pressure stage compressor (2) is the outlet of the compressor unit; The gas outlet of the gas-liquid separator (14) and the outlet of the low-pressure compressor (1) are connected in parallel and then connected to the inlet of the high-pressure compressor (2).

3. The electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system according to claim 1, characterized in that: The driving mechanism includes a driving motor (17) and a battery pack (18). The liquid outlet of the gas-liquid separator (14) is divided into two paths, one of which is connected to a first nozzle (15) and the other is connected to a second nozzle (16). The first nozzle (15) extends into the battery pack (18), and the second nozzle (16) extends into the driving motor (17). The working medium outlet of the battery pack (18) and the working medium outlet of the driving motor (17) are connected in parallel and then connected to the shell side inlet of the regenerator (12).

4. The electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system according to claim 3, characterized in that: The battery pack (18) and the drive motor (17) are respectively provided with sealed housings, and spaces are respectively left between the battery pack (18) and the corresponding housings, and between the drive motor (17) and the corresponding housings. The first nozzle (15) and the second nozzle (16) are respectively provided in the corresponding housings.

5. The electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system according to claim 1, characterized in that: The exterior heat exchanger (7) is installed at the front of the vehicle in a windward position.

6. The electric vehicle drive mechanism dry ice blasting cooling and heating and cooling combined system according to claim 1, characterized in that: The in-car heat exchanger (19) is installed in an air supply duct (22) at the vehicle chassis at the co-pilot position of the electric vehicle; the inlet of the air supply duct (22) is provided with an air inlet door (21), and the air supply outlet of the air supply duct (22) is provided with an air supply door (25); An air supply fan (20) is provided in the air supply duct (22) at a position on the windward side of the heat exchanger (19) in the vehicle compartment; An exhaust port is provided on the side wall of the air supply duct (22) at the air outlet side of the heat exchanger (19) in the vehicle compartment. The exhaust port is provided with an exhaust door (24). The exhaust port is connected to the exhaust duct inlet of the electric vehicle, and the exhaust duct outlet blows toward the compressor unit. The side wall of the air supply duct (22) is provided with a return air port on the windward side of the heat exchanger (19) in the vehicle compartment, and the return air port is arranged on the side of the air supply fan (20) facing away from the heat exchanger (19) in the vehicle compartment, and the return air port is provided with a return air door (23).

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