Heat pump water heater unit and control method thereof

Abstract

The present invention discloses a heat pump water heater unit and a control method thereof. The unit includes a compressor, an evaporator, a condenser and a water tank, and also includes a four-way valve. The air inlet of the compressor is connected to the S port of the four-way valve to form a return air passage. One of the exhaust ports of the compressor is connected to the D port of the four-way valve, and the other is connected to the refrigerant inlet of the evaporator through a high-pressure pressure regulating valve to form a pressure relief passage. A heat exchanger is arranged between the return air passage and the pressure relief passage to exchange heat with the refrigerant between the two passages. When the water temperature of the unit continues to rise, the condensing pressure remains unchanged, and the exhaust temperature also remains basically unchanged, thereby improving the reliability of the heat pump operation. At the same time, the refrigerant liquid hammer problem caused by the increase in the opening of the electronic expansion valve is avoided, thereby ensuring the normal operation of the compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and in particular to a heat pump water heater unit and a control method thereof. Background Art

[0002] At present, when the air source heat pump heats hot water, as the water temperature rises, the condensing pressure and evaporation pressure of the heat pump system also rise. When the water temperature is close to the maximum production temperature, the condensing temperature corresponding to the condensing pressure is more than ten degrees higher than the water temperature at this time, far exceeding the condensing temperature of ordinary air conditioning heating. In order to improve the reliability of heat pump water heaters, compressors are all used for heat pumps. The adaptability range is greatly increased, but the challenges of heat pump water heaters are far from over. Its high water temperature, wide temperature range, and long-term heating have put forward high requirements for its reliability. In particular, high temperature and high pressure at high water temperature have a great impact on the life of the compressor. At this time, if the temperature or pressure is 10% higher than normal, it may cause a 50% decrease in the life of the compressor. Therefore, the temperature and pressure of the heat pump water heater should be controlled not to exceed the limit, or the reliability of the heat pump should be improved through load reduction design in actual operation. Summary of the invention

[0003] In order to solve the technical problem that when the existing air source heat pump heats hot water, the system reliability decreases as the water temperature rises, the present invention proposes a heat pump water heater unit and a control method thereof, which can solve the above problem.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A heat pump water heater unit includes a compressor, an evaporator, a condenser and a water tank, and also includes a four-way valve. The refrigerant inlet of the condenser is connected to the C port of the four-way valve, the refrigerant outlet of the condenser is connected to the electronic expansion valve and then connected to the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator is connected to the E port of the four-way valve, the air inlet of the compressor is connected to the S port of the four-way valve to form a return air passage, one of the exhaust ports of the compressor is connected to the D port of the four-way valve, and the other is connected to the refrigerant inlet of the evaporator through a high-pressure pressure regulating valve to form a pressure relief passage, and a heat exchanger is provided between the return air passage and the pressure relief passage for exchanging heat between the refrigerant in the two passages.

[0006] Furthermore, the heat exchanger is an economizer, one of the inlets of the economizer is connected to the high-pressure pressure regulating valve, the outlet corresponding to the inlet is connected to the refrigerant inlet of the evaporator, and the other inlet of the economizer is connected to the S port of the four-way valve, and the outlet corresponding to the inlet is connected to the air inlet of the compressor.

[0007] Furthermore, the pressure relief passage is connected to the front end of the electronic expansion valve, and is connected to the refrigerant inlet of the evaporator through the electronic expansion valve.

[0008] Furthermore, the high-pressure pressure regulating valve is a pressure valve.

[0009] Furthermore, an electric heating pipe is arranged in the water tank.

[0010] The present invention also proposes a heat pump water heater unit control method, including the heat pump water heater unit described in any one of the above items, and the unit control method includes the following steps:

[0011] (1) Start the compressor, and the exhaust port of the compressor discharges high-temperature and high-pressure gaseous refrigerant. When the exhaust pressure of the compressor is lower than the set threshold, the high-pressure pressure regulating valve is closed, and the refrigerant enters the condenser through the DC port of the four-way valve for heat exchange, becoming a low-temperature and high-pressure liquid refrigerant. It is throttled by the electronic expansion valve to become a low-temperature and low-pressure two-phase refrigerant, and then enters the evaporator to absorb heat, becoming a high-temperature gaseous refrigerant and then flows through the ES port of the four-way valve into the air inlet of the compressor;

[0012] (2) When the exhaust pressure of the compressor is not less than the set threshold, the high-pressure pressure regulating valve opens, and the exhaust port of the compressor discharges high-temperature and high-pressure gaseous refrigerant, one of which passes through the DC port of the four-way valve to enter the condenser for heat exchange, and the other passes through the high-pressure pressure regulating valve to enter the evaporator, forming a pressure relief passage. A return air passage is formed between the air inlet of the compressor and the S port of the four-way valve. The return air passage exchanges heat with the refrigerant in the pressure relief passage when passing through the heat exchanger. The refrigerant in the pressure relief passage releases heat and cools, and then enters the evaporator to absorb heat. The refrigerant in the return air passage absorbs heat when passing through the heat exchanger to form a high-temperature gaseous refrigerant. The suction temperature of the compressor increases, and the opening of the electronic expansion valve is controlled to increase.

[0013] Furthermore, the high-pressure pressure regulating valve is a pressure valve, and when the exhaust pressure of the compressor is not less than a set threshold, the pressure valve automatically opens.

[0014] Furthermore, the high-pressure pressure regulating valve is a solenoid valve, and also includes a step of detecting the exhaust pressure of the compressor. When the detected exhaust pressure of the compressor is not less than a set threshold, the solenoid valve is controlled to open.

[0015] Furthermore, after the refrigerant in the pressure relief passage undergoes heat exchange in the heat exchanger, it enters the electronic expansion valve to be throttled into a low-temperature and low-pressure two-phase mixed refrigerant, and then enters the evaporator to absorb heat.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: for the heat pump water heater unit of the present invention, after the water temperature in the water tank continues to rise, when the pressure of the refrigerant system reaches a limit value, the high-pressure pressure regulating valve opens, and part of the refrigerant flows through the high-pressure pressure regulating valve into the heat exchanger to exchange heat with the refrigerant at the outlet of the evaporator. After being cooled, the part of the refrigerant enters the evaporator to absorb heat, and then exchanges heat with the refrigerant coming out of the pressure relief valve from the outlet of the evaporator. At this time, due to the heat exchange, the refrigerant temperature at the suction port of the compressor rises, the opening of the electronic expansion valve increases, the evaporation temperature rises, the condensation pressure decreases, and the exhaust temperature decreases at the same time; when the water temperature continues to rise, the condensation pressure remains unchanged, and the exhaust temperature also remains basically unchanged, thereby improving the reliability of the heat pump operation. At the same time, the refrigerant liquid hammer problem caused by the increase in the opening of the electronic expansion valve is avoided, and the normal operation of the compressor is guaranteed.

[0017] Other features and advantages of the present invention will become more apparent after reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a system principle diagram of an embodiment of the heat pump water heater unit proposed by the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1: This embodiment proposes a heat pump water heater unit, such as Figure 1As shown, it includes a compressor 11, an evaporator 12, a condenser and a water tank 14, and also includes a four-way valve 15. The refrigerant inlet of the condenser is connected to the C port of the four-way valve 15, the refrigerant outlet of the condenser is connected to the electronic expansion valve 16 and then connected to the refrigerant inlet of the evaporator 12, the refrigerant outlet of the evaporator 12 is connected to the E port of the four-way valve 15, the air inlet of the compressor 11 is connected to the S port of the four-way valve to form a return air passage, one of the exhaust ports of the compressor 11 is connected to the D port of the four-way valve, and the other is connected to the refrigerant inlet of the evaporator 12 through a high-pressure pressure regulating valve 17 to form a pressure relief passage, and a heat exchanger 18 is arranged between the return air passage and the pressure relief passage for heat exchange of the refrigerant between the two passages. The heat pump water heater unit of this embodiment is provided with a high-pressure pressure regulating valve 17, which is connected to the exhaust port of the compressor 11 to form a pressure relief passage, and is used to release the pressure by heat when the exhaust pressure of the compressor 11 is too large, thereby reducing the damage to the compressor caused by excessive exhaust pressure and ensuring the life of the compressor. Moreover, while releasing the pressure, the heat of the refrigerant in the pressure relief passage is released to the refrigerant in the compressor return passage, and the temperature of the refrigerant gas entering the compressor is increased. The refrigerant temperature at the compressor suction port rises, and the opening of the electronic expansion valve is affected by the suction superheat. The compressor suction temperature increases, and the corresponding suction superheat increases. The opening of the electronic expansion valve also increases. When the opening of the electronic expansion valve increases, the pressure relief valve is opened, the evaporation temperature rises, and the condensation pressure decreases, but the condensation temperature corresponding to the condensation pressure is sufficient to heat the water to the set temperature, and the exhaust temperature decreases at the same time; when the water temperature continues to rise, the condensation pressure remains unchanged, and the exhaust temperature also remains basically unchanged, which improves the reliability of the heat pump operation. At the same time, when the exhaust temperature or evaporation temperature is high, the original machine adopts the method of increasing the opening of the electronic expansion valve and starting and stopping the fan to reduce the exhaust and evaporation temperatures, but the side effect is the generation of liquid return. The return liquid is heated by the action of the economizer, avoiding the refrigerant liquid shock problem caused by the increase in the opening of the electronic expansion valve, and ensuring the normal operation of the compressor.

[0022] As a preferred embodiment, the heat exchanger 18 can be implemented by an economizer, one of the inlets of the economizer is connected to the high-pressure pressure regulating valve 17, and the outlet corresponding to the inlet is connected to the refrigerant inlet of the evaporator 12, that is, the exhaust port of the compressor is connected to the heat exchanger 18 through this passage, and the other inlet of the economizer is connected to the S port of the four-way valve 15, and the outlet corresponding to the inlet is connected to the air inlet of the compressor 11, that is, the return air passage of the compressor is connected to the economizer through the passage, so that the two passages can exchange heat in the economizer.

[0023] The pressure relief passage is preferably not directly connected to the refrigerant inlet of the evaporator, but is connected to the front end of the electronic expansion valve, and is connected to the refrigerant inlet of the evaporator through the electronic expansion valve. After the refrigerant in the pressure relief passage is cooled by the heat exchanger, it first enters the front end of the electronic expansion valve, merges with the refrigerant coming out of the condenser after heat exchange, and is throttled by the electronic expansion valve into a low-temperature and low-pressure two-phase mixed refrigerant, and then enters the evaporator to absorb heat. This can further improve system safety and prevent the refrigerant pressure entering the evaporator from being too high.

[0024] Among them, the high-pressure pressure regulating valve can be implemented by a pressure valve. When the exhaust pressure of the compressor is not less than the set threshold of the pressure valve, the pressure valve automatically opens, that is, the pressure relief circuit is automatically connected to relieve pressure. When the exhaust pressure of the compressor is less than the set threshold of the pressure valve, it means that the exhaust pressure of the compressor has no effect or a small effect on the life of the compressor, and there is no need to relieve pressure. At this time, the pressure valve automatically remains closed and the pressure relief circuit is not connected.

[0025] In addition, the high-pressure pressure regulating valve can also be implemented by a solenoid valve. If a solenoid valve is used, a pressure sensor needs to be set at the exhaust port or exhaust pipe of the compressor to detect the exhaust pressure of the compressor. When the detected exhaust pressure of the compressor is not less than the set threshold, the solenoid valve is controlled to open, that is, the pressure relief circuit is automatically turned on to relieve pressure. When the detected exhaust pressure of the compressor is less than the set threshold, the solenoid valve is controlled to close and no pressure relief is performed.

[0026] The heat pump unit in this embodiment is mainly used in a heat pump water heater. The condenser is arranged in the water tank of the water heater to release heat to heat the water in the water tank. In order to prevent the heating capacity from decreasing due to the low ambient temperature and the large demand for hot water, when the heat pump heating cannot meet the hot water demand, it is preferred to provide an electric heating tube in the water tank for auxiliary electric heating.

[0027] Embodiment 2, the present invention also proposes a heat pump water heater unit control method, including the heat pump water heater unit recorded in embodiment 1, such as Figure 1 As shown, it includes a compressor 11, an evaporator 12, a condenser and a water tank 14, and also includes a four-way valve 15. The refrigerant inlet of the condenser is connected to the C port of the four-way valve 15, and the refrigerant outlet of the condenser is connected to the electronic expansion valve 16 and then connected to the refrigerant inlet of the evaporator 12. The refrigerant outlet of the evaporator 12 is connected to the E port of the four-way valve 15. The air inlet of the compressor 11 is connected to the S port of the four-way valve to form a return air passage. One of the exhaust ports of the compressor 11 is connected to the D port of the four-way valve, and the other is connected to the refrigerant inlet of the evaporator 12 through a high-pressure pressure regulating valve 17 to form a pressure relief passage. A heat exchanger 18 is provided between the return air passage and the pressure relief passage for heat exchange of the refrigerant between the two passages. The unit control method includes the following steps:

[0028] S1. Start the compressor, and the exhaust port of the compressor discharges high-temperature and high-pressure gaseous refrigerant. When the exhaust pressure of the compressor is less than the set threshold, the high-pressure pressure regulating valve is closed, and the refrigerant enters the condenser through the DC port of the four-way valve for heat exchange, becoming a low-temperature and high-pressure liquid refrigerant, and is throttled by the electronic expansion valve to become a low-temperature and low-pressure two-phase refrigerant, and then enters the evaporator to absorb heat, becoming a high-temperature gaseous refrigerant, and then flows through the ES port of the four-way valve into the air inlet of the compressor;

[0029] In this step, when the exhaust pressure of the compressor 11 is within the normal safety limit, the heat pump water heater can be operated to provide heating. Although the refrigerant in the return air passage also passes through the heat exchanger, no heat exchange is performed.

[0030] S2. When the exhaust pressure of the compressor is not less than the set threshold, the high-pressure pressure regulating valve opens, and the high-temperature and high-pressure gaseous refrigerant is discharged from the exhaust port of the compressor. One of the paths passes through the DC port of the four-way valve to enter the condenser for heat exchange, and the other path passes through the high-pressure pressure regulating valve to enter the evaporator, forming a pressure relief passage. A return air passage is formed between the air inlet of the compressor and the S port of the four-way valve. The return air passage exchanges heat with the refrigerant in the pressure relief passage when passing through the heat exchanger. The refrigerant in the pressure relief passage releases heat and cools, and then enters the evaporator to absorb heat. The refrigerant in the return air passage absorbs heat when passing through the heat exchanger to form a high-temperature gaseous refrigerant. The suction temperature of the compressor is increased, and the opening of the electronic expansion valve is controlled to increase. In the control method of this embodiment, a high-pressure pressure regulating valve 17 is set to connect with the exhaust port of the compressor 11 to form a pressure relief passage, which is used to release heat when the exhaust pressure of the compressor 11 is too high, thereby reducing the damage to the compressor caused by excessive exhaust pressure and ensuring the life of the compressor. Moreover, while releasing the pressure, the heat of the refrigerant in the pressure relief passage is released to the refrigerant in the compressor return passage, and the temperature of the refrigerant gas entering the compressor is increased. The refrigerant temperature at the compressor suction port rises, the opening of the electronic expansion valve increases, the evaporation temperature rises, the condensation pressure decreases, and the exhaust temperature decreases at the same time; when the water temperature continues to rise, the condensation pressure remains unchanged, and the exhaust temperature also remains basically unchanged, which improves the reliability of the heat pump operation. At the same time, it avoids the refrigerant liquid hammer problem caused by the increase in the opening of the electronic expansion valve, and ensures the normal operation of the compressor.

[0031] Among them, the heat exchanger 18 can be implemented by an economizer, one of the inlets of the economizer is connected to the high-pressure pressure regulating valve 15, and the outlet corresponding to the inlet is connected to the refrigerant inlet of the evaporator 12, that is, the exhaust port of the compressor is connected to the heat exchanger 18 through this passage, and the other inlet of the economizer is connected to the S port of the four-way valve 15, and the outlet corresponding to the inlet is connected to the air inlet of the compressor 11, that is, the return air passage of the compressor is connected to the economizer through the passage, so that the two passages can exchange heat in the economizer.

[0032] Among them, the high-pressure pressure regulating valve can be implemented by a pressure valve. When the exhaust pressure of the compressor is not less than the set threshold of the pressure valve, the pressure valve automatically opens, that is, the pressure relief circuit is automatically connected to relieve pressure. When the exhaust pressure of the compressor is less than the set threshold of the pressure valve, it means that the exhaust pressure of the compressor has no effect or a small effect on the life of the compressor, and there is no need to relieve pressure. At this time, the pressure valve automatically remains closed and the pressure relief circuit is not connected.

[0033] The high-pressure pressure regulating valve can also be implemented by a solenoid valve. If a solenoid valve is used, a pressure sensor needs to be installed at the exhaust port or exhaust pipe of the compressor to detect the exhaust pressure of the compressor. When the detected exhaust pressure of the compressor is not less than the set threshold, the solenoid valve is controlled to open, that is, the pressure relief circuit is automatically turned on to relieve pressure. When the detected exhaust pressure of the compressor is less than the set threshold, the solenoid valve is controlled to close and no pressure relief is performed.

[0034] The pressure relief passage is preferably not directly connected to the refrigerant inlet of the evaporator, but is connected to the front end of the electronic expansion valve, and is connected to the refrigerant inlet of the evaporator through the electronic expansion valve. After the refrigerant in the pressure relief passage passes through the heat exchanger, it first enters the front end of the electronic expansion valve, merges with the refrigerant coming out of the condenser after heat exchange, and is throttled by the electronic expansion valve into a low-temperature and low-pressure two-phase mixed refrigerant, and then enters the evaporator to absorb heat. This can further improve system safety and prevent the refrigerant pressure entering the evaporator from being too high.

[0035] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A heat pump water heater unit, comprising a compressor, an evaporator, a condenser and a water tank, characterized in that: It also includes a four-way valve, the refrigerant inlet of the condenser is connected to the C port of the four-way valve, the refrigerant outlet of the condenser is connected to the electronic expansion valve and then connected to the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator is connected to the E port of the four-way valve, the air inlet of the compressor is connected to the S port of the four-way valve to form a return air passage, one of the exhaust ports of the compressor is connected to the D port of the four-way valve, and the other is connected to the refrigerant inlet of the evaporator through a high-pressure pressure regulating valve to form a pressure relief passage, a heat exchanger is provided between the return air passage and the pressure relief passage for heat exchange of the refrigerant between the two passages, and when the exhaust pressure of the compressor is not less than a set threshold, the high-pressure pressure regulating valve automatically opens to relieve pressure; The heat exchanger is an economizer, one of the inlets of the economizer is connected to the high-pressure pressure regulating valve, and the outlet corresponding to the inlet is connected to the refrigerant inlet of the evaporator, and the other inlet of the economizer is connected to the S port of the four-way valve, and the outlet corresponding to the inlet is connected to the air inlet of the compressor.

2. The heat pump water heater unit according to claim 1, characterized in that: The pressure relief passage is connected to the front end of the electronic expansion valve, and is connected to the refrigerant inlet of the evaporator through the electronic expansion valve.

3. The heat pump water heater unit according to claim 1 or 2, characterized in that: An electric heating pipe is arranged in the water tank.

4. A heat pump water heater unit control method, characterized in that: The heat pump water heater unit comprises the heat pump water heater unit according to any one of claims 1 to 3, wherein the unit control method comprises the following steps: (1) Start the compressor, and the exhaust port of the compressor discharges high-temperature and high-pressure gaseous refrigerant. When the exhaust pressure of the compressor is lower than the set threshold, the high-pressure pressure regulating valve is closed, and the refrigerant enters the condenser through the DC port of the four-way valve for heat exchange, becoming a low-temperature and high-pressure liquid refrigerant. It is throttled by the electronic expansion valve to become a low-temperature and low-pressure two-phase refrigerant, and then enters the evaporator to absorb heat, becoming a high-temperature gaseous refrigerant and then flows through the ES port of the four-way valve into the air inlet of the compressor; (2) When the exhaust pressure of the compressor is not less than the set threshold, the high-pressure pressure regulating valve opens, and the exhaust port of the compressor discharges high-temperature and high-pressure gaseous refrigerant, one of which passes through the DC port of the four-way valve to enter the condenser for heat exchange, and the other passes through the high-pressure pressure regulating valve to enter the evaporator, forming a pressure relief passage. A return air passage is formed between the air inlet of the compressor and the S port of the four-way valve. The return air passage exchanges heat with the refrigerant in the pressure relief passage when passing through the heat exchanger. The refrigerant in the pressure relief passage releases heat and cools, and then enters the evaporator to absorb heat. The refrigerant in the return air passage absorbs heat when passing through the heat exchanger to form a high-temperature gaseous refrigerant. The suction temperature of the compressor increases, and the opening of the electronic expansion valve is controlled to increase.

5. The heat pump water heater unit control method according to claim 4, characterized in that: The high-pressure pressure regulating valve is a solenoid valve, and also includes a step of detecting the exhaust pressure of the compressor. When the detected exhaust pressure of the compressor is not less than a set threshold, the solenoid valve is controlled to open.

6. The heat pump water heater unit control method according to claim 4 or 5, characterized in that: After passing through the heat exchanger, the refrigerant in the pressure relief passage enters the electronic expansion valve to be throttled into a low-temperature and low-pressure two-phase mixed refrigerant, and then enters the evaporator to absorb heat.

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