Quaternary heat recovery type air conditioning unit and working method

Abstract

The invention relates to the technical field of dehumidification air conditioning units, and particularly discloses a quaternary heat recovery type air conditioning unit and a working method.The heat recovery air conditioning unit comprises an air conditioning filter, a front heat recovery heat exchanger, a main heat exchanger, a rear heat recovery heat exchanger, a reheating heat exchanger and an air feeder; the heat recovery exhaust unit comprises an exhaust filter, an exhaust heat recovery heat exchanger and an exhaust fan; the heat pump device comprises a compressor, a three-way valve and a four-way reversing valve; the heat pump system is arranged between the air conditioning unit and the exhaust unit, cold of exhausted air is recycled in summer and used for precooling, deep dehumidification and reheating of inlet air of the air conditioning unit, the evaporation temperature of the rear heat recycling heat exchanger of the heat pump is low, deep dehumidification can be achieved, the cold source temperature of the main heat exchanger can be increased, and the heat pump system can be used for heat exchange of the air conditioning unit. The energy efficiency of the cold source is improved; and in winter, heat of exhaust air can be recycled and used for preheating and reheating inlet air of the air conditioning unit, the air supply temperature can be stabilized through reheating, and constant temperature and humidity are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of dehumidification air conditioning units, and in particular to a four-element heat recovery air conditioning unit and a working method thereof. Background Art

[0002] Heat recovery units are mostly used for heat recovery between new exhaust air in industrial and civil buildings. Heat recovery units are widely used in most areas, especially in hospitals, office buildings, libraries, hotels, laboratories, public transportation buildings, production plants and other environments with large exhaust air and large temperature or enthalpy differences between new exhaust air.

[0003] Common forms of heat recovery include plate heat recovery, rotary heat recovery, solution heat recovery, heat pipe heat recovery and other forms. However, the above devices can only recover heat through heat transfer, and the recovered energy is subject to the enthalpy difference between the recovered air and the recycled air. The heat recovery system constructed by the heat pump can achieve higher heat recovery through the phase change of the refrigerant. Even if the enthalpy difference between the recovered air and the recycled air is very small, the refrigerant used for energy transfer has a greater temperature difference between the refrigerant and the air due to the change in phase. In addition, by switching the pipeline and adjusting the expansion valve, not only can the exhaust energy be recovered, but the low-temperature refrigerant can also achieve deep dehumidification of the air. The high-temperature refrigerant can be used for air reheating to meet the temperature and humidity control requirements of the air handling unit, achieving three goals at one stroke.

[0004] Therefore, there is an urgent need to design a four-element heat recovery air-conditioning unit and a working method to solve the problem that the current air-conditioning unit is restricted by large temperature difference or large enthalpy difference. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a quaternary heat recovery air conditioning unit and a working method, which realizes the recovery of the coldness of the exhaust air in the summer cooling condition, precooling the air intake of the air conditioning unit, and deep dehumidification and reheating of the air in the summer heating condition by arranging a heat pump device between the air conditioning unit and the exhaust unit, and recovers the heat of the exhaust air in the summer heating condition, preheats the air intake of the air conditioning unit, prevents the unit from freezing, and reheats the humidified air, achieving four goals at one stroke. The heat recovery efficiency is as high as 75% or more.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a quaternary heat recovery air conditioning unit, including a heat recovery air conditioning unit, a heat recovery exhaust unit and a heat pump device, the heat recovery air conditioning unit includes an air conditioning filter, a front heat recovery heat exchanger, a main heat exchanger, a rear heat recovery heat exchanger, a reheat heat exchanger, and a blower, the heat recovery exhaust unit includes an exhaust filter, an exhaust heat recovery heat exchanger, and an exhaust fan, and the heat pump device includes a compressor, a three-way valve, and a four-way reversing valve;

[0007] The exhaust port of the compressor is connected to the inlet of the three-way valve, one outlet of the three-way valve is connected to the inlet of the reheat heat exchanger, the other outlet of the three-way valve is connected in parallel with the outlet of the reheat heat exchanger and then connected to the inlet of the four-way reversing valve, and a one-way valve 1 is arranged on the outlet of the reheat heat exchanger; one reversing outlet of the four-way reversing valve is connected to the inlet of the exhaust heat recovery heat exchanger, the other reversing outlet of the four-way reversing valve is connected to the pipeline in parallel with the outlets of the front heat recovery heat exchanger and the rear heat recovery heat exchanger, and a one-way valve 2 is arranged on the outlet pipeline of the rear heat recovery heat exchanger; the outlet of the four-way reversing valve is connected to the suction port of the compressor.

[0008] Specifically, the outlet of the exhaust heat recovery heat exchanger is divided into two paths, one of the outlets of the exhaust heat recovery heat exchanger is connected to the inlet of the rear heat recovery heat exchanger through the heating electronic expansion valve and the main electronic expansion valve, and the other outlet of the exhaust heat recovery heat exchanger is connected to the inlet of the front heat recovery heat exchanger through the auxiliary electronic expansion valve.

[0009] Specifically, the heating electronic expansion valve is connected in parallel with the check valve four, and the auxiliary electronic expansion valve is connected in parallel with the check valve three.

[0010] Specifically, the heat pump device is provided with four sets of pipelines, which are respectively connected to the front heat recovery heat exchanger, the rear heat recovery heat exchanger, the reheat heat exchanger in the heat recovery air conditioning unit and the exhaust heat recovery heat exchanger in the heat recovery exhaust unit.

[0011] Specifically, the main heat exchanger is connected to an external cold and heat source device through a pipeline, and the external cold and heat source device adopts one of an air-cooled heat pump, a cold water main unit, an air-cooled direct expansion machine, and a water-cooled direct expansion machine.

[0012] Specifically, the front heat recovery heat exchanger, the main heat exchanger, the rear heat recovery heat exchanger, the reheat heat exchanger, and the exhaust heat recovery heat exchanger are all finned heat exchangers.

[0013] Specifically, an air conditioning filter is installed at the air inlet of the heat recovery air conditioning unit, a blower is installed at the air outlet of the heat recovery air conditioning unit, an exhaust filter is installed at the return air outlet of the heat recovery exhaust unit, and an exhaust fan is installed at the exhaust outlet of the heat recovery exhaust unit.

[0014] Specifically, the air supply fan and the exhaust fan both adopt an AC motor or a brushless DC EC motor.

[0015] Specifically, the air inlet of the heat recovery air conditioning unit takes in outdoor fresh air or indoor return air or a mixture of fresh and return air.

[0016] A working method of a quaternary heat recovery air conditioning unit comprises the following steps:

[0017] S1. When the heat recovery air conditioning unit is cooling, the heat pump device operates according to the cooling condition, the front heat recovery heat exchanger and the rear heat recovery heat exchanger become evaporators, the reheat heat exchanger becomes the first-stage condenser, and the exhaust heat recovery heat exchanger becomes the second-stage condenser;

[0018] S2. The air is first purified by the air conditioning filter, and then pre-cooled by the front heat recovery heat exchanger, dehumidified by the main heat exchanger, deeply dehumidified by the rear heat recovery heat exchanger, and reheated by the reheat heat exchanger. Whether the reheat heat exchanger is heating is controlled by the three-way valve of the heat pump device to control the flow direction of Freon. The compressor condensation heat that cannot be used by the reheat heat exchanger is dissipated to the exhaust fan through the exhaust heat recovery heat exchanger and discharged to the outside.

[0019] S3. When the heat recovery air conditioning unit is heating, the heat pump device operates according to the heating condition, the reheat heat exchanger is still the primary condenser, the front heat recovery heat exchanger becomes the secondary condenser, the rear heat recovery heat exchanger does not work, the four one-way valves and three electronic expansion valves cut off the refrigerant from entering, and the exhaust heat recovery heat exchanger becomes the evaporator;

[0020] S4. The air is first purified by the air conditioning filter, then preheated by the pre-heat recovery heat exchanger, secondary heated by the main heat exchanger, and reheated by the reheat heat exchanger. Whether the reheat heat exchanger generates heat is achieved by controlling the flow direction of Freon through the three-way valve of the heat pump device.

[0021] The present invention has the following beneficial effects:

[0022] The quaternary heat recovery air conditioning unit and working method designed by the present invention realizes the recovery of exhaust air coldness in summer by setting a heat pump system between the air conditioning unit and the exhaust unit, which is used for precooling, deep dehumidification and reheating the air intake of the air conditioning unit. Since the evaporation temperature of the heat recovery heat exchanger after the heat pump is low and can meet the deep dehumidification, the cold source temperature of the main heat exchanger can be increased to improve the energy efficiency of the cold source. At the same time, the condensation heat of the heat pump can be used for free to reheat the dehumidified air to achieve the purpose of constant temperature and humidity; in winter, the heat of the exhaust air can be recovered to preheat and reheat the air intake of the air conditioning unit. In particular, the system using isenthalpic humidification has a lower temperature after the humidifier, and the air supply temperature can be stabilized by reheating to achieve constant temperature and humidity. The heat recovery efficiency is as high as 75% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a four-element heat recovery air-conditioning unit.

[0024] In the figure: 1. Heat recovery air conditioning unit box; 2. Heat recovery exhaust unit box; 3. Heat pump device; 4. External cold and heat source device; 1-1. Air conditioning filter; 1-2. Pre-heat recovery heat exchanger; 1-3. Main heat exchanger; 1-4. Post-heat recovery heat exchanger; 1-5. Reheat heat exchanger; 1-6. Supply air fan; 2-1. Exhaust filter; 2-2. Exhaust heat recovery heat exchanger; 2-3. Exhaust fan; 3-1. Compressor; 3-2. Three-way valve; 3-3. One-way valve one; 3-4. Four-way reversing valve; 3-5. Main electronic expansion valve; 3-6. Auxiliary electronic expansion valve; 3-7. One-way valve two; 3-8. One-way valve three; 3-9. One-way valve four; 3-10. Heating electronic expansion valve. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely further describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, a four-element heat recovery air conditioning unit includes a heat recovery air conditioning unit 1, a heat recovery exhaust unit 2, a heat pump device 3 and a heat recovery pipeline.

[0027] It should be noted that the heat recovery exhaust fan unit 2 includes: an exhaust filter 2-1, an exhaust heat recovery heat exchanger 2-2, and an exhaust fan 2-3.

[0028] It should be noted that the heat recovery air conditioning unit 1 includes: an air conditioning filter 1-1, a pre-heat recovery heat exchanger 1-2, a main heat exchanger 1-3, a post-heat recovery heat exchanger 1-4, a reheat heat exchanger 1-5, and a blower 1-6.

[0029] It should be noted that the heat pump device 3 includes: a compressor 3-1, a three-way valve 3-2, a four-way reversing valve 3-4, a one-way valve 1 3-3, a one-way valve 2 3-7, a one-way valve 3 3-8 and a one-way valve 4 3-9, a main electronic expansion valve 3-5, an auxiliary electronic expansion valve 3-6, a heating expansion valve 3-10 and pipelines.

[0030] It should be noted that the heat pump device 3 has four sets of pipelines (one inlet and one outlet as a set), among which e-1 and e-2 are respectively connected to the inlet and outlet of the front heat recovery heat exchanger 1-2 in the heat recovery air-conditioning unit, d-1 and d-2 are respectively connected to the inlet and outlet of the rear heat recovery heat exchanger 1-4, c-1 and c-2 are respectively connected to the inlet and outlet of the reheat heat exchanger 1-5, and o-1 and o-2 are respectively connected to the inlet and outlet of the exhaust heat recovery heat exchanger 2-2 in the heat recovery exhaust unit.

[0031] It should be noted that the exhaust port of the compressor 3-1 is connected to the inlet of the three-way valve 3-2, the outlet a of the three-way valve 3-2 is connected to the inlet c-1 of the reheat heat exchanger 1-5, the outlet c-2 of the reheat heat exchanger 1-5 is connected to the inlet f-1 of the one-way valve 3-3, the outlet b of the three-way valve 3-2 is connected to the outlet f-2 of the one-way valve 3-3, and then connected to the inlet i of the four-way reversing valve 3-4 in parallel; the outlet m of the four-way reversing valve 3-4 is connected to the inlet o-1 of the exhaust heat recovery heat exchanger 2-2, the outlet j is connected in parallel to the outlet e-2 of the front heat recovery heat exchanger 1-2 and the outlet g-2 of the one-way valve 3-7, respectively, and the outlet d-2 of the rear heat recovery heat exchanger 1-4 is connected to the inlet g-1 of the one-way valve 3-7. The outlet k of the four-way reversing valve 3-4 is connected to the suction port of the compressor 3-1; the outlet o-2 of the exhaust heat recovery heat exchanger 2-2 is divided into two paths, and the outlet o-2 is connected to the one-way valve three 3-9 and the heating expansion valve 3-10 in parallel. The outlet of the exhaust heat recovery heat exchanger 2-2 is divided into two paths, one of which is connected to the h-2 port of the main electronic expansion valve 3-5, and the other is connected to the p-2 port of the auxiliary electronic expansion valve 3-6. The h-1 port of the main electronic expansion valve 3-5 is connected to the inlet d-1 of the rear heat recovery heat exchanger 1-4, and the p-1 port of the auxiliary electronic expansion valve 3-6 is connected to the inlet e-1 of the front heat recovery heat exchanger. The heating electronic expansion valve 3-10 is connected in parallel with the one-way valve four 3-9, and the auxiliary electronic expansion valve 3-6 is connected in parallel with the one-way valve three 3-8.

[0032] It should be noted that when the heat recovery air conditioning unit 1 is cooling, the heat pump device 3 operates according to the cooling condition, the front heat recovery heat exchanger 1-2 and the rear heat recovery heat exchanger 1-4 become evaporators, the reheat heat exchanger 1-5 becomes a primary condenser, and the exhaust heat recovery heat exchanger 2-2 becomes a secondary condenser. The air is first purified by the filter 1-1, and then pre-cooled by the front heat recovery heat exchanger 1-2, the main heat exchanger 1-3 is cooled and dehumidified for the second time, and then deeply dehumidified by the rear heat recovery heat exchanger 1-4, and finally reheated by the reheat heat exchanger 1-5. The refrigerant flow direction of the heat pump device 3 is the high-temperature and high-pressure refrigerant discharged from the compressor 3-1 through the three-way valve 3-2. When the condensation heat needs to be used for reheating, the a port of the three-way valve 3-2 is opened and the b port is closed, and the high-temperature and high-pressure refrigerant flows into the reheat heat exchanger 1-5, which can reheat the air flowing through the reheat heat exchanger 1-5. When reheating is not required, port b of the three-way valve 3-2 is opened and port a is closed, and the high-temperature and high-pressure refrigerant flow is blocked by the one-way valve 3-3 and cannot enter the reheat heat exchanger 1-5. The high-temperature refrigerant flowing out of the reheat heat exchanger 1-5 or directly flowing out of port b of the three-way valve 3-2 flows in through port i of the four-way reversing valve 3-4, flows out through port m, and enters the exhaust heat recovery heat exchanger 2-2 through port o-1. The high-temperature and high-pressure refrigerant entering the heat recovery heat exchanger 2-2 exchanges heat with the exhaust air, dissipates heat into the exhaust air, becomes a high-pressure liquid, and then flows out through port o-2. The liquid refrigerant flowing out through the o-2 port flows out through the one-way valve four 3-9. At this time, the heating expansion valve 3-10 is closed. After coming out of the one-way valve four 3-9, it is divided into two paths. One path passes through the auxiliary electronic expansion valve 3-6 and then enters the front heat recovery heat exchanger 1-2 after throttling. The other path passes through the main electronic expansion valve 3-5 and then enters the rear heat recovery heat exchanger 1-4. The liquid refrigerant evaporated in the evaporator becomes a gas state, and respectively merges through the d-2 and e-2 ports to enter the j port of the four-way reversing valve 3-4, and then returns to the compressor 3-1 through the k port to complete the cycle.

[0033] It should be noted that when the heat recovery air conditioning unit 2 is heating, the heat pump device 3 operates according to the heating condition, the reheat heat exchanger 1-5 is still a primary condenser, the front heat recovery heat exchanger 1-2 becomes a secondary condenser, the rear heat recovery heat exchanger 1-4 does not work (the refrigerant is cut off by the one-way valve 3-3 and the main electronic expansion valve 3-5), and the exhaust heat recovery heat exchanger 2-2 becomes an evaporator. The refrigerant flow direction of the heat pump device 3 is the high-temperature and high-pressure refrigerant discharged from the compressor 3-1 through the three-way valve 3-2. When it is necessary to use the condensation heat for reheating, the port a of the three-way valve 3-2 is opened and the port b is closed, and the high-temperature and high-pressure refrigerant flows into the reheat heat exchanger 1-5, which can reheat the air flowing through the reheat heat exchanger 1-5. When reheating is not required, the port b of the three-way valve 3-2 is opened and the port a is closed, and the high-temperature and high-pressure refrigerant flow is blocked by the one-way valve 3-3 and cannot enter the reheat heat exchanger 1-5. The high-temperature refrigerant flowing out of the reheat heat exchanger 1-5 or directly flowing out of the port b of the three-way valve 3-2 flows in through the port i of the four-way reversing valve 3-4, flows out from the port j and enters the pre-heat recovery heat exchanger 1-2 through the port e-2. The high-temperature and high-pressure refrigerant entering the pre-heat recovery heat exchanger 1-2 exchanges heat with the air in the heat recovery air conditioning unit 1, dissipates heat to the air, becomes a high-pressure liquid, and then flows out from the port e-1. The liquid refrigerant flowing out of the port e-1 flows out through the check valve three 3-8. At this time, the auxiliary electronic expansion valve 3-6 is closed, and the check valve three 3-8 comes out and enters the exhaust heat recovery heat exchanger 2-2 after being throttled by the heating electronic expansion valve 3-10. The liquid refrigerant evaporated in the evaporator becomes a gas state, and enters the port m of the four-way reversing valve 3-4 through the port o-1, and returns to the compressor 3-1 through the port k to complete the cycle. During heating, the main electronic expansion valve 3-5 is closed, and the high-temperature and high-pressure refrigerant flow is blocked by the one-way valve 3-7 and cannot enter the post-heat recovery heat exchanger 1-4, so the post-heat recovery heat exchanger does not work.

[0034] In this embodiment, the main heat exchanger 1-3 in the heat recovery air conditioning unit 1 and the external cold and heat source device 4 are one of an air-cooled heat pump, a chiller, an air-cooled direct expansion machine, and a water-cooled direct expansion machine.

[0035] In this embodiment, the pre-heat recovery heat exchanger 1-2, the main heat exchanger 1-3, the post-heat recovery heat exchanger 1-4, and the reheat heat exchanger 1-5 in the heat recovery air conditioning unit 1 are finned heat exchangers.

[0036] In this embodiment, the exhaust fan 2-3 in the heat recovery exhaust fan unit 2 is an AC motor or a brushless DC EC motor.

[0037] In this embodiment, the blower 1-6 in the heat recovery air conditioning unit 1 is an AC motor or a brushless DC EC motor.

[0038] In this embodiment, the air intake of the air conditioner in the heat recovery air conditioner 1 is outdoor fresh air or indoor return air or a mixture of fresh and return air.

[0039] In this embodiment, the heat recovery air conditioning unit 1 is provided with primary, medium and high efficiency filters or purifiers (in any form) as required, and a humidifier (in any type) and other functional components may also be provided.

[0040] In this embodiment, the heat pump device 3 system can be equipped with refrigeration components such as filters, oil separators, liquid storage tanks, and gas-liquid separators as required.

[0041] The present invention is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention, and all those having the same or similar technical solutions as the present invention fall within the protection scope of the present invention.

[0042] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A four-element heat recovery air conditioning unit, characterized in that: It includes a heat recovery air conditioning unit, a heat recovery exhaust unit and a heat pump device. The heat recovery air conditioning unit includes an air conditioning filter, a front heat recovery heat exchanger, a main heat exchanger, a rear heat recovery heat exchanger, a reheat heat exchanger, and a blower. The heat recovery exhaust unit includes an exhaust filter, an exhaust heat recovery heat exchanger, and an exhaust fan. The heat pump device includes a compressor, a three-way valve, and a four-way reversing valve. The exhaust port of the compressor is connected to the inlet of the three-way valve, one outlet of the three-way valve is connected to the inlet of the reheat heat exchanger, the other outlet of the three-way valve is connected in parallel with the outlet of the reheat heat exchanger and then connected to the inlet of the four-way reversing valve, and a one-way valve 1 is arranged on the outlet of the reheat heat exchanger; one reversing outlet of the four-way reversing valve is connected to the inlet of the exhaust heat recovery heat exchanger, the other reversing outlet of the four-way reversing valve is connected to the pipeline in parallel with the outlets of the front heat recovery heat exchanger and the rear heat recovery heat exchanger, and a one-way valve 2 is arranged on the outlet pipeline of the rear heat recovery heat exchanger; the outlet of the four-way reversing valve is connected to the suction port of the compressor.

2. The quaternary heat recovery air conditioning unit according to claim 1, characterized in that: The outlet of the exhaust heat recovery heat exchanger is divided into two paths. One path of the outlet of the exhaust heat recovery heat exchanger is connected to the inlet of the rear heat recovery heat exchanger through the heating electronic expansion valve and the main electronic expansion valve, and the other path of the outlet of the exhaust heat recovery heat exchanger is connected to the inlet of the front heat recovery heat exchanger through the auxiliary electronic expansion valve.

3. The quaternary heat recovery air conditioning unit according to claim 2, characterized in that: The heating electronic expansion valve is connected in parallel with the check valve four, and the auxiliary electronic expansion valve is connected in parallel with the check valve three.

4. The quaternary heat recovery air conditioning unit according to claim 1, characterized in that: The heat pump device is provided with four sets of pipelines, which are respectively connected to the front heat recovery heat exchanger, the rear heat recovery heat exchanger, the reheat heat exchanger in the heat recovery air conditioning unit and the exhaust heat recovery heat exchanger in the heat recovery exhaust unit.

5. The quaternary heat recovery air conditioning unit according to claim 1, characterized in that: The main heat exchanger is connected to an external cold and heat source device through a pipeline, and the external cold and heat source device is one of an air-cooled heat pump, a cold water main unit, an air-cooled direct expansion machine, and a water-cooled direct expansion machine.

6. The quaternary heat recovery air conditioning unit according to claim 1, characterized in that: The front heat recovery heat exchanger, main heat exchanger, rear heat recovery heat exchanger, reheat heat exchanger, and exhaust heat recovery heat exchanger are all finned heat exchangers.

7. The quaternary heat recovery air conditioning unit according to claim 1, characterized in that: An air conditioning filter is installed at the air inlet of the heat recovery air conditioning unit, a blower is installed at the air outlet of the heat recovery air conditioning unit, an exhaust filter is installed at the return air outlet of the heat recovery exhaust unit, and an exhaust fan is installed at the exhaust outlet of the heat recovery exhaust unit.

8. The quaternary heat recovery air conditioning unit according to claim 7, characterized in that: The air supply fan and the exhaust fan both adopt an AC motor or a brushless DC EC motor.

9. The quaternary heat recovery air conditioning unit according to claim 7, characterized in that: The air inlet of the heat recovery air conditioning unit takes in outdoor fresh air or indoor return air or a mixture of fresh and return air.

10. The operating method of the quaternary heat recovery air conditioning unit according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. When the heat recovery air conditioning unit is cooling, the heat pump device operates according to the cooling condition, the front heat recovery heat exchanger and the rear heat recovery heat exchanger become evaporators, the reheat heat exchanger becomes the first-stage condenser, and the exhaust heat recovery heat exchanger becomes the second-stage condenser; S2. The air is first purified by the air conditioning filter, and then pre-cooled by the front heat recovery heat exchanger, dehumidified by the main heat exchanger, deeply dehumidified by the rear heat recovery heat exchanger, and reheated by the reheat heat exchanger. Whether the reheat heat exchanger is heating is controlled by the three-way valve of the heat pump device to control the flow direction of Freon. The compressor condensation heat that cannot be used by the reheat heat exchanger is dissipated to the exhaust fan through the exhaust heat recovery heat exchanger and discharged to the outside. S3. When the heat recovery air conditioning unit is heating, the heat pump device operates according to the heating condition, the reheat heat exchanger is still the primary condenser, the front heat recovery heat exchanger becomes the secondary condenser, the rear heat recovery heat exchanger does not work, the four one-way valves and three electronic expansion valves cut off the refrigerant from entering, and the exhaust heat recovery heat exchanger becomes the evaporator; S4. The air is first purified by the air conditioning filter, then preheated by the pre-heat recovery heat exchanger, secondary heated by the main heat exchanger, and reheated by the reheat heat exchanger. Whether the reheat heat exchanger generates heat is achieved by controlling the flow direction of Freon through the three-way valve of the heat pump device.

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