Heat pump type commercial dishwasher and defrosting method thereof

Abstract

A heat pump type commercial dishwasher and a defrosting method thereof, the commercial dishwasher comprising a rolling channel and a heat pump heating system, a double exhaust compressor of the heat pump heating system having an air inlet, a high-pressure exhaust port and a medium-pressure exhaust port; the high-pressure exhaust port being sequentially connected with an oil separator, a high-temperature heat exchanger, a first refrigerant channel of a medium-temperature heat exchanger, a high-pressure electronic expansion valve and an air-cooled evaporator; the medium-pressure exhaust port being sequentially connected with a second refrigerant channel of the medium-temperature heat exchanger, a medium-pressure electronic expansion valve and the air-cooled evaporator; the medium-temperature heat exchanger and the high-temperature heat exchanger heating water to provide heating for a cleaning section and a rinsing section; the air-cooled evaporator being connected with the air inlet of the double exhaust compressor, the double exhaust compressor, the oil separator and the air-cooled evaporator being arranged outdoors; the defrosting method being performed by cooperation of a cold storage tank, a solenoid valve and a low-pressure electronic expansion valve and the like. The application solves the problems of excessive pressure ratio of the heat pump heating and frequent start and stop of defrosting of the commercial dishwasher in winter.

Description

Technical Field

[0001] This invention belongs to the field of cleaning equipment technology, specifically relating to a heat pump commercial dishwasher and its defrosting method. Background Technology

[0002] Existing commercial dishwashers typically use electric or gas heating to generate hot water exceeding 80°C, resulting in high power consumption and energy costs. Unlike household dishwashers, commercial dishwashers operate continuously, with the entire washing process—pre-wash, main wash, rinse, and dry—taking only a few minutes, far less than the several hours required for a household dishwasher. Therefore, commercial dishwashers require significantly higher heating power, necessitating either increased electric heating capacity or the use of gas to quickly obtain hot water. For example, a typical 200 baskets / hour conveyor-type commercial dishwasher has a main wash tank heating power of 12kW, a rinse tank heating power of 36kW, and a drying tank heating power of nearly 10kW, totaling over 60kW of electrical power and over 350L / h of water consumption. Consequently, the entire washing process consumes a substantial amount of electricity and water, necessitating the adoption of more energy-efficient and economical technologies to achieve energy conservation and emission reduction in the commercial cleaning equipment sector.

[0003] Household heat pump dishwashers require relatively low hot water temperatures, generally below 60 degrees Celsius, so they can be heated using a heat pump. Patent CN 104905745B uses a heat pump system's heating condenser to heat both the washing and rinsing water, saving energy compared to electric heaters. During drying, a ventilation system guides cooled air from the evaporator to the outside of the drying condenser, accelerating the condensation of the hot, humid air inside, thus speeding up the drying process, improving efficiency, and saving energy. However, this is a household heat pump dishwasher, and the heat pump system is a conventional single-stage vapor compression system with limited heating temperature. Furthermore, the dishwasher is placed indoors, and the system does not address the issue of frosting and defrosting during low-temperature heating.

[0004] To address the high energy consumption of commercial dishwashers, current equipment often employs waste heat recovery devices to utilize the high-temperature wastewater and exhaust gas discharged from the dishwasher, thereby reducing heating energy consumption. For example, existing technologies typically reduce rinsing heating power by exchanging heat between the wastewater discharged from the main wash tank and the clean water entering the rinsing tank. Alternatively, a waste heat recovery device is installed above the rinsing area to increase the inlet water temperature and reduce the system's heating power through heat exchange between the clean water and exhaust gas (e.g., patents CN214549318U and CN101543390B). However, these technical solutions only reduce heating power to a certain extent (e.g., CN107773187A reduces drying heating power by 50%), and the core heater still relies on high-power electric heating in the high-temperature areas such as the main wash and rinsing, resulting in relatively high power consumption. Patent CN 107960967A addresses the heating needs of the main wash area by introducing heat pump heating into a commercial tunnel dishwasher, but the higher-temperature rinsing area can only be heated by an electric boiler. Moreover, its heat pump system is integrated inside the dishwasher. The working environment of the air-cooled evaporator is harsh, with issues such as grease buildup. In winter, when the indoor temperature is low, it cannot provide enough heat, and there will be cold air inside the kitchen. In addition, the kitchen has high humidity, and the system also faces the risk of not working due to frost in winter.

[0005] The reasons for heat exchanger frosting in commercial dishwashers during winter use and the defrosting process are as follows: When outdoor temperatures are low and humidity is high, such as in the middle and lower reaches of the Yangtze River in winter when the temperature is close to 0°C and the humidity is very high, the surface of the outdoor heat exchanger of the air source heat pump is prone to frosting, causing the unit to need frequent defrosting, thus affecting heating efficiency. The traditional defrosting method is reverse cycle defrosting. When the unit detects the need for defrosting, it stops the compressor and switches from heating mode to cooling mode via a four-way reversing valve. At this time, the outdoor evaporator becomes the condenser, and then the compressor restarts, using high-temperature, high-pressure hot airflow to defrost. After defrosting is complete, it stops again and switches back to heating mode. Therefore, the traditional defrosting method involves frequent mode switching, causing the hot water side heat exchanger to become an evaporator, resulting in drastic water temperature fluctuations. Summary of the Invention

[0006] The purpose of this invention is to provide a heat pump commercial dishwasher and its defrosting method. By using a mixed working fluid dual exhaust heat pump system, the problem of excessively high heating pressure ratio of heat pumps in winter is solved, the system temperature matching is improved, and the power consumption of the compressor is reduced. By setting up a cold storage tank, the problem of frequent shutdowns of the heat pump unit during the heating process in winter is solved, so that the dishwashing operation can be carried out without stopping, thus meeting the commercial needs of the equipment.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a heat pump commercial dishwasher, comprising a heat pump heating system for heating washing water and a rolling channel for continuously washing dishes. The rolling channel includes several functional sections arranged sequentially from the inlet to the outlet and a conveying device. The heat pump heating system includes a dual exhaust compressor, which has one air inlet and two exhaust ports with different pressures, namely a high-pressure exhaust port and a medium-pressure exhaust port. An oil separator, the inlet of which is connected to the high-pressure exhaust port, and the outlet of which is connected to the high-temperature heat exchanger; High-temperature heat exchanger and medium-temperature heat exchanger; the high-temperature heat exchanger is equipped with a refrigerant channel and a high-temperature water channel; the medium-temperature heat exchanger is equipped with a first refrigerant channel, a second refrigerant channel and a medium-temperature water channel. The refrigerant channel and the first refrigerant channel are connected in series. The refrigerant channel is connected to the oil separator. The first refrigerant channel is connected to the air-cooled evaporator via a high-pressure electronic expansion valve. The inlet of the second refrigerant channel is connected to the medium-pressure exhaust port, and the outlet is connected to the air-cooled evaporator via a medium-pressure electronic expansion valve. The high-temperature water channel and the medium-temperature water channel are connected in series. The outlet of the high-temperature water channel is connected to the rinsing section in the rolling channel to provide high-temperature hot water to the rinsing section. One outlet of the medium-temperature water channel is connected to the high-temperature water channel, and the other outlet is connected to the cleaning section upstream of the rinsing section to provide medium-temperature hot water to the cleaning section. The inlet of the medium-temperature water channel is connected to the cleaning water used for cleaning. The outlet of the air-cooled evaporator is connected to the inlet of the dual-exhaust compressor; the dual-exhaust compressor, oil separator, and air-cooled evaporator are located outdoors.

[0008] Furthermore, the outlet of the air-cooled evaporator is connected to the air inlet of the dual-exhaust compressor via two parallel pipes. One of the two parallel pipes is equipped with a solenoid valve, and the other pipe is equipped with a series-connected low-pressure electronic expansion valve and a cold storage tank. The solenoid valve, the low-pressure electronic expansion valve, and the cold storage tank are located outdoors.

[0009] The cold storage tank is equipped with a heat exchanger, and the cold storage medium inside the cold storage tank is a phase change material.

[0010] Furthermore, the cold storage tank is also equipped with a heater and a temperature sensor.

[0011] The dual-exhaust compressor uses a mixed refrigerant, the components of which are selected based on the critical boiling point and the atmospheric boiling point.

[0012] The heat pump heating system includes a waste heat recovery device and a drying heating device. The drying heating device uses the heat recovered by the waste heat recovery device to heat the air entering the drying section.

[0013] Alternatively, the waste heat recovery device and the drying heating device are respectively the evaporator and condenser of the same heat pump system. The evaporator is equipped with an exhaust fan for extracting waste gas from the dishwasher, and the condenser is equipped with a blower for supplying air to the drying section of the dishwasher. The clean air supplied by the blower is heated by exchanging heat with the medium in the condenser that has already absorbed the heat from the waste gas.

[0014] Alternatively, the heat pump heating system further includes a waste gas heat recovery device and a waste water heat recovery device. The waste gas heat recovery device includes an exhaust fan capable of extracting waste gas from the dishwasher and a waste gas heat exchanger for recovering heat from the waste gas. The waste gas heat exchanger has a room-temperature clean water channel for exchanging heat with the waste gas, and room-temperature clean water is introduced into the room-temperature clean water channel. The waste water heat recovery device includes a waste water heat exchanger. The waste water channel in the waste water heat exchanger connects the dishwasher and an external waste water collection pipe. The preheated clean water channel in the waste water heat exchanger connects the outlet of the room-temperature clean water channel and the inlet of the medium-temperature water channel of the medium-temperature heat exchanger.

[0015] The functional section includes a pre-cleaning section, a cleaning section, and a rinsing section that are connected to each other. A water tank is installed below the conveyor belts of each of the pre-cleaning section, the cleaning section, and the rinsing section to store hot water at the corresponding temperature.

[0016] This invention also proposes a defrosting method for the aforementioned heat pump commercial dishwasher. During defrosting, the frequency of the dual exhaust compressor is reduced to the defrosting frequency, the fan of the air-cooled evaporator is turned off, the medium-pressure electronic expansion valve and the high-pressure electronic expansion valve are adjusted to the defrosting opening, the solenoid valve is closed, and the low-pressure electronic expansion valve is opened. The high-temperature, high-pressure liquid refrigerant directly enters the air-cooled evaporator for defrosting, while the throttled low-temperature two-phase refrigerant enters the cold storage tank for heat exchange.

[0017] The beneficial effects of the present invention are: 1. By adopting a heat pump system, the present invention significantly reduces the heating power and electrical capacity of commercial dishwashers, thereby reducing operating costs.

[0018] 2. By using a mixed working fluid dual exhaust heat pump system, the problem of excessively high heating pressure ratio of heat pumps in winter is solved. At the same time, by using dual exhaust parallel compression and mixed working fluid, it is closer to the Lorentz cycle, which further improves the system temperature matching and reduces compressor power consumption.

[0019] 3. By setting up a cold storage tank, the problem of frequent start-stop defrosting of the heat pump unit during winter heating is solved, and the washing operation can be carried out without stopping.

[0020] 4. By setting up a waste heat recovery device, the system's heat can be utilized efficiently, resulting in economic and energy-saving benefits. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention in Embodiment 1; Figure 2 This is a schematic diagram of the structure of the present invention in Embodiment 2; Figure 3 This is a flowchart of the defrosting process of the dishwasher of the present invention; The markings in the diagram are: 1. Dual-exhaust compressor, 2. Oil separator, 3. High-temperature heat exchanger, 4. Medium-temperature heat exchanger, 5. Medium-pressure electronic expansion valve, 6. High-pressure electronic expansion valve, 7. Air-cooled evaporator, 8. Solenoid valve, 9. Low-pressure electronic expansion valve, 10. Cold storage tank, 11. Wastewater waste heat recovery device, 12. Waste gas waste heat recovery device, 13. Drying and heating device, 14. Compressor, 15. Throttling valve; 100, Inlet; 200, Pre-cleaning section; 300, Cleaning section; 400, Rinsing section; 500, Drying section; 600, Outlet. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the invention in any way.

[0023] Example 1: Refer to Appendix Figure 1 As shown, a heat pump commercial dishwasher includes a heat pump heating system for heating the washing water and a rolling channel for continuously washing dishes, cups and other utensils.

[0024] The rolling conveyor includes an inlet 100, a pre-washing section 200, a washing section 300, a rinsing section 400, a drying section 500, and an outlet 600. A conveyor system runs through all functional sections from the inlet to the outlet. Soiled tableware in the washing basket passes through each functional section sequentially on the conveyor belt, ultimately becoming dried and clean tableware at the outlet. A water tank is installed below the conveyor belts of the pre-washing section 200, washing section 300, and rinsing section 400 to store hot water at the corresponding temperatures. Spray devices are located above and below the conveyor belts of the pre-washing section 200, washing section 300, and rinsing section 400, enabling different stages of tableware cleaning through high-speed spraying.

[0025] The heat pump heating system includes a dual-exhaust compressor 1, an oil separator 2, a high-temperature heat exchanger 3, a medium-temperature heat exchanger 4, a medium-pressure electronic expansion valve 5, a high-pressure electronic expansion valve 6, an air-cooled evaporator 7, a solenoid valve 8, a low-pressure electronic expansion valve 9, and a cold storage tank 10, etc. Specific connections are as follows: Figure 1As shown, the dual exhaust compressor 1, oil separator 2, evaporator 7, solenoid valve 8, low-pressure electronic expansion valve 9, and cold storage tank 10 are installed outdoors. The dual-exhaust compressor 1 has one air inlet and two exhaust ports with different pressures, namely a high-pressure exhaust port and a medium-pressure exhaust port. The high-pressure exhaust port is connected to the oil separator 2, which is connected to the refrigerant channel inlet of the high-temperature heat exchanger 3. The refrigerant channel outlet of the high-temperature heat exchanger 3 is connected to the inlet of the first refrigerant channel of the medium-temperature heat exchanger 4, and the outlet of the first refrigerant channel is connected to the high-pressure electronic expansion valve 6. The medium-pressure exhaust port of the dual-exhaust compressor 1 is connected to the inlet of the second refrigerant channel of the medium-temperature heat exchanger 4, and the outlet of the second refrigerant channel is connected to the medium-pressure electronic expansion valve 5. The pipes containing the high-pressure electronic expansion valve 6 and the medium-pressure electronic expansion valve 5 converge and are connected to the inlet of the air-cooled evaporator 7. The outlet of the air-cooled evaporator 7 is connected to the air inlet of the dual-exhaust compressor 1 through two parallel pipes. One of the two parallel pipes is equipped with a solenoid valve 8, and the other pipe is equipped with a series-connected low-pressure electronic expansion valve 9 and a cold storage tank 10.

[0026] The high-temperature heat exchanger 3 provides high-temperature hot water (82-90°C) to the rinsing section 400, and the medium-temperature heat exchanger 4 provides medium-temperature hot water (around 60°C, e.g., 60-65°C) to the cleaning section 300. Simultaneously, a portion of the generated medium-temperature hot water enters the high-temperature heat exchanger 3 and is heated to high-temperature hot water. Therefore, the outlet of the medium-temperature water channel in the medium-temperature heat exchanger 4 is connected to the water tank of the cleaning section 300 on one hand, and to the inlet of the high-temperature water channel of the high-temperature heat exchanger 3 on the other. The outlet of the high-temperature water channel of the high-temperature heat exchanger 3 is connected to the water tank of the rinsing section 400.

[0027] The principle of this invention is as follows: During dishwasher operation, the heat pump provides heating. The high-pressure exhaust from the dual-exhaust compressor 1 enters the high-temperature heat exchanger 3 after passing through the oil separator 2. The resulting 90°C hot water enters the water tank and spray nozzle of the rinsing section 400. The refrigerant after heat exchange in the high-temperature heat exchanger 3 enters the medium-temperature heat exchanger 4, where it is cooled together with the medium-pressure exhaust from the dual-exhaust compressor 1. The resulting 60°C hot water enters the water tank and spray nozzle of the washing section 300. The two streams of refrigerant after heat exchange in the medium-temperature heat exchanger 4 are throttled by the high-pressure electronic expansion valve 6 and the medium-pressure electronic expansion valve 5, respectively, and then converge into the outdoor air-cooled evaporator 7. After absorbing heat from the air, the refrigerant becomes low-pressure vapor and returns to the dual-exhaust compressor 1. During the heat pump heating stage, the solenoid valve 8 is fully open, the electronic expansion valve 9 is closed, and the refrigerant does not pass through the cold storage tank 10.

[0028] To further improve the energy efficiency of this commercial dishwasher, it is necessary to recover the heat from the dishwasher's exhaust gas.

[0029] This embodiment includes a device for recovering heat from exhaust gas. A small heat pump system is installed in the indoor section of the dishwasher. The evaporator in this heat pump system is positioned above the pre-cleaning section 200, serving as the exhaust gas waste heat recovery device 12. The condenser in the heat pump system is arranged above the drying section 500, acting as the drying heating device 13. A compressor 14 and a throttling valve 15 are installed between the evaporator and the condenser. At the evaporator, an exhaust fan draws in the exhaust gas from the dishwasher and exchanges heat with the medium inside the evaporator. The heat-exchanged medium then enters the condenser and exchanges heat with the clean air supplied by the blower. The heated clean air then enters the drying section for drying, thereby reducing the drying power and ensuring that the exhaust gas is fully cooled, improving the working environment in the kitchen.

[0030] This invention addresses the drawbacks of traditional defrosting methods by incorporating a cold storage tank 10. When defrosting is required, the frequency of the dual-exhaust compressor 1 decreases, the medium-pressure electronic expansion valve 5 and the high-pressure electronic expansion valve 6 are adjusted to their maximum opening, the solenoid valve 8 is closed, and the low-pressure electronic expansion valve 9 is opened. At this time, the high-temperature, high-pressure liquid refrigerant directly enters the outdoor air-cooled evaporator 7 for defrosting, while the throttled low-temperature two-phase refrigerant enters the cold storage tank 10 for heat exchange. This ensures that the refrigerant entering the dual-exhaust compressor 1 is in the gas phase, preventing liquid slugging. The cold storage tank 10 is equipped with a heat exchanger to ensure sufficient heat exchange between the cold storage medium and the refrigerant. The cold storage medium can be water, paraffin wax, or hydrated salts, etc., as phase change materials. To ensure reuse after cold storage, the cold storage tank 10 is also equipped with a low-power electric heater. This allows the cold storage medium to be heated to the set temperature during normal heating cycles. Therefore, the cold storage tank 10 is also equipped with a temperature sensor.

[0031] It should be noted that in areas where defrosting is not required, the cold storage tank 10, the solenoid valve 8, and the low-pressure electronic expansion valve 9 can be omitted in this invention.

[0032] In summer, the temperature of the clean water intake is relatively high (generally around 20℃), while the outdoor air temperature is relatively high (generally around 30℃). At this time, even if conventional refrigerants (such as R134a and R1234yf) are used to produce 90℃ hot water, the overall system's operating pressure ratio will not be too high. However, in winter, the outdoor air temperature drops to 0℃. If conventional refrigerants are still used to produce 90℃ hot water, the system's pressure ratio will far exceed the compressor's operating range. Therefore, to achieve high-temperature-range heating in winter, this invention uses a mixed refrigerant. Its components are selected based on their critical boiling point and atmospheric boiling point, and must include components with a critical boiling point exceeding 100℃ and an atmospheric boiling point below -15℃ to ensure the system can operate normally in environments above -15℃. The low-boiling-point component can be one or more of R134a, CO2, R32, R1270, R290, R1234yf, R227ea, and R161a, and the high-boiling-point component can be one or more of R152a, R717, R1234ze(E), R1234ze(Z), R600a, R600, R245fa, n-Hexane, R1233zd(E), R1224yd(Z), R1336mzz(E), and R1336mzz(Z).

[0033] Example 2: This example is based on Example 1, and recovers heat from both the waste heat of the exhaust gas and the wastewater from the dishwasher. For example... Figure 2 As shown, the specific solution is as follows: the drying heating device 13 of the drying section 500 no longer uses the condenser of Example 1, but uses an electric heating device. The outside air introduced by the blower is heated by the electric heating device to dry the tableware in the drying section. Outside ambient temperature clean water is introduced into the ambient temperature clean water channel of the waste gas heat exchanger, which serves as the waste gas waste heat recovery device 12. During the flow of the ambient temperature clean water channel, it exchanges heat with the waste gas extracted by the blower, thereby absorbing the waste heat in the waste gas and becoming preheated clean water. A wastewater heat exchanger is used as the wastewater waste heat recovery device 11. The wastewater heat exchanger is equipped with a wastewater channel for heat exchange and a preheated clean water channel. One end of the wastewater channel is connected to the water tank of the pre-washing section of the dishwasher, and the other end is connected to an external wastewater collection pipe. One end of the preheated clean water channel is connected to the outlet of the ambient temperature clean water channel, and the other end is connected to the inlet of the medium temperature water channel of the medium temperature heat exchanger.

[0034] The ambient temperature cleaning water is preheated by the exhaust gas in the exhaust gas heat exchanger, then enters the wastewater heat exchanger. After exchanging heat with the wastewater discharged from the dishwasher, it is heated again, and then sequentially enters the medium-temperature heat exchanger 4 and the high-temperature heat exchanger 3 to be heated to the corresponding temperatures. In this way, the low-temperature cleaning water undergoes continuous series heating, which can reduce the subsequent heating power.

[0035] This embodiment can make full use of the residual heat from the wastewater and exhaust gas during the dishwasher's operation to heat the cleaning water, thereby reducing the subsequent heating power.

[0036] The other structural settings in this embodiment are the same as in Embodiment 1, so they will not be described again.

[0037] Example 3: Based on Example 1, combined with Figure 3 The defrosting process of the commercial dishwasher proposed in this invention is described in detail below: (1) After the dishwasher starts working, the heat pump heats up and monitors the outdoor temperature, the coil temperature of the air-cooled evaporator 7 and the medium temperature of the cold storage tank 10 in real time. (2) Determine whether the equipment has entered the frosting risk zone based on the temperature of the air-cooled evaporator coil 7 and the equipment running time. If it has entered the frosting risk zone, proceed to the next step. If it has not entered the frosting risk zone, return to the previous step. The judgment conditions can be set according to the actual situation. For example, if the evaporator coil temperature is less than 0℃ and the equipment running time is greater than 25 minutes, it can be determined that the equipment has entered the frosting risk zone. (3) Turn on the electric heater of the cold storage tank 10; (4) Determine whether defrosting is required based on the difference between the outdoor temperature and the temperature of the air-cooled evaporator 7 coil. If the defrosting conditions are met, proceed to the next step. If the defrosting conditions are not met, return to the previous step. The defrosting conditions can be set according to the actual situation. For example, if the temperature difference between the outdoor temperature and the temperature of the air-cooled evaporator 7 coil is greater than 3℃, then defrosting is required. (5) During defrosting, the frequency of the dual exhaust compressor 1 is reduced to the defrosting frequency, the fan of the air-cooled evaporator 7 stops, the medium-pressure electronic expansion valve 5 and the high-pressure electronic expansion valve 6 are adjusted to the maximum opening, i.e. the defrosting opening, the solenoid valve 8 is closed, and the low-pressure electronic expansion valve 9 is opened. (6) Monitor the refrigerant temperature at the outlet of the air-cooled evaporator 7; (7) Determine whether defrosting needs to be ended based on the temperature value monitored in the previous step. If defrosting can be ended, proceed to the next step; otherwise, return to the previous step. The conditions for ending defrosting can be set according to the actual situation. For example, if the refrigerant temperature at the outlet of the air-cooled evaporator 7 is greater than 18°C, it indicates that defrosting can be ended. (8) To end the defrosting process, the frequency of the dual exhaust compressor 1 is adjusted to the heating frequency, the air-cooled evaporator 7 is restarted, the medium-pressure electronic expansion valve 5 and the high-pressure electronic expansion valve 6 are adjusted to the heating opening, the solenoid valve 8 is opened, and the low-pressure electronic expansion valve 9 is closed. The defrosting process ends here.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the specific implementation of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the pending claims.

Claims

1. A heat pump commercial dishwasher, comprising a heat pump heating system for heating washing water and a rolling conveyor for continuously washing dishes, the rolling conveyor comprising a plurality of functional sections arranged sequentially from inlet to outlet and a conveying device, characterized in that: The heat pump heating system includes a dual exhaust compressor, which has one air inlet and two exhaust ports with different pressures, namely a high-pressure exhaust port and a medium-pressure exhaust port. An oil separator, the inlet of which is connected to the high-pressure exhaust port, and the outlet of which is connected to the high-temperature heat exchanger; High-temperature heat exchanger and medium-temperature heat exchanger; the high-temperature heat exchanger is equipped with a refrigerant channel and a high-temperature water channel; the medium-temperature heat exchanger is equipped with a first refrigerant channel, a second refrigerant channel and a medium-temperature water channel. The refrigerant channel and the first refrigerant channel are connected in series. The refrigerant channel is connected to the oil separator. The first refrigerant channel is connected to the air-cooled evaporator via a high-pressure electronic expansion valve. The inlet of the second refrigerant channel is connected to the medium-pressure exhaust port, and the outlet is connected to the air-cooled evaporator via a medium-pressure electronic expansion valve. The high-temperature water channel and the medium-temperature water channel are connected in series. The outlet of the high-temperature water channel is connected to the rinsing section in the rolling channel to provide high-temperature hot water to the rinsing section. One outlet of the medium-temperature water channel is connected to the high-temperature water channel, and the other outlet is connected to the cleaning section upstream of the rinsing section to provide medium-temperature hot water to the cleaning section. The inlet of the medium-temperature water channel is connected to the cleaning water used for cleaning. The outlet of the air-cooled evaporator is connected to the air inlet of the dual exhaust compressor through two parallel pipes. One of the two parallel pipes is equipped with a solenoid valve, and the other pipe is equipped with a series low-pressure electronic expansion valve and a cold storage tank. The cold storage tank is equipped with a heat exchanger, and the cold storage medium in the cold storage tank is a phase change material. The dual-exhaust compressor, oil separator, air-cooled evaporator, solenoid valve, low-pressure electronic expansion valve, and cold storage tank are located outdoors.

2. A heat pump commercial dishwasher according to claim 1, characterized in that: The cold storage tank is also equipped with a heater and a temperature sensor.

3. A heat pump commercial dishwasher according to claim 1, characterized in that: The dual-exhaust compressor uses a mixed refrigerant, the components of which are selected based on the critical boiling point and the atmospheric boiling point.

4. A heat pump commercial dishwasher according to claim 1, characterized in that: The heat pump heating system includes a waste heat recovery device and a drying heating device. The drying heating device uses the heat recovered by the waste heat recovery device to heat the air entering the drying section.

5. A heat pump commercial dishwasher according to claim 4, characterized in that: The waste heat recovery device and the drying heating device are respectively the evaporator and condenser in the same heat pump system. An exhaust fan is installed at the evaporator to extract waste gas from the dishwasher, and a blower is installed at the condenser to supply air to the drying section of the dishwasher. The clean air supplied by the blower is heated by exchanging heat with the medium in the condenser that has already absorbed the heat of the waste gas.

6. A heat pump commercial dishwasher according to claim 1, characterized in that: The heat pump heating system further includes a waste gas heat recovery device and a waste water heat recovery device. The waste gas heat recovery device includes an exhaust fan capable of extracting waste gas from the dishwasher and a waste gas heat exchanger for recovering heat from the waste gas. The waste gas heat exchanger has a room temperature clean water channel for exchanging heat with the waste gas, and room temperature clean water is introduced into the room temperature clean water channel. The waste water heat recovery device includes a waste water heat exchanger. The waste water channel in the waste water heat exchanger connects the dishwasher and an external waste water collection pipe. The preheated clean water channel in the waste water heat exchanger connects the outlet of the room temperature clean water channel and the inlet of the medium temperature water channel of the medium temperature heat exchanger.

7. A heat pump commercial dishwasher according to claim 1, characterized in that: The functional section includes a pre-cleaning section, a cleaning section, and a rinsing section that are connected to each other. A water tank is installed below the conveyor belts of each of the pre-cleaning section, the cleaning section, and the rinsing section to store hot water at the corresponding temperature.

8. A defrosting method for a heat pump commercial dishwasher as described in claim 1, characterized in that: During defrosting, the frequency of the dual exhaust compressor is reduced to the defrosting frequency, the fan of the air-cooled evaporator is turned off, the medium-pressure electronic expansion valve and the high-pressure electronic expansion valve are adjusted to the defrosting opening, the solenoid valve is closed, and the low-pressure electronic expansion valve is opened. The high-temperature and high-pressure liquid refrigerant directly enters the air-cooled evaporator for defrosting, while the low-temperature two-phase refrigerant after throttling enters the cold storage tank for heat exchange.

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