An air source heat pump system

Abstract

The application relates to an air source heat pump system, a defrosting opening degree adjustment method of an electromagnetic expansion valve in defrosting operation is obtained based on monitoring of condensing side pressure, evaporating side pressure and water inlet temperature, the defrosting opening degree of the electromagnetic expansion valve can be automatically tracked and adjusted according to condensing side-evaporating side pressure transformation, the flow variation in the defrosting process can be effectively inhibited, the liquid return risk of the system is reduced, the operation safety of the system is ensured, and the failure rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of heat pumps, and more particularly to an air source heat pump system. Background Technology

[0002] An air source heat pump is a device that transfers heat energy from a lower-grade heat source to a higher-grade heat source. It typically consists of a compressor, an air-side heat exchanger, a water-side heat exchanger, and a throttling valve. When the heat pump is operating for heating in winter, its air-side heat exchanger remains at a low temperature, with its surface temperature 5°C to 10°C lower than the surrounding air temperature. When the surface temperature of the air-side heat exchanger is lower than the dew point of the surrounding air but higher than the freezing point of water, water vapor in the air will condense into water droplets and dew on the surface of the air-side heat exchanger. When the surface temperature of the air-side heat exchanger is lower than the freezing point of water, water vapor in the air will condense into frost on the surface of the heat exchanger. In these cases, defrosting of the air-side heat exchanger is necessary to prevent frost from affecting the system's heating capacity.

[0003] Currently, air source heat pump units all employ reverse circulation defrosting, which uses a four-way valve to redirect the high-temperature, high-pressure refrigerant through the air-side heat exchanger to achieve defrosting. In existing air source heat pump systems with electromagnetic expansion valves, during reverse defrosting, the opening of the electromagnetic expansion valve is generally adjusted to its maximum to achieve the fastest defrosting effect.

[0004] While this defrosting method achieves rapid defrosting, during the defrosting process, the temperature and condensing pressure of the air-side heat exchanger continuously rise, while the water temperature and evaporating pressure of the water-side heat exchanger decrease. This leads to an increase in the pressure difference between the condensing and evaporating sides, and an increase in the system refrigerant flow rate. Because the opening of the electromagnetic expansion valve is fixed and does not adjust for pressure changes, the increased refrigerant flow under increased pressure difference may cause refrigerant backflow, threatening system operational safety, reducing the lifespan of the air source heat pump system, or causing other malfunctions. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide an air source heat pump system that can adjust the electromagnetic expansion valve in real time according to the system pressure change during the defrosting process, so as to avoid the problem of system liquid return.

[0006] An air-source heat pump system includes a compressor, a four-way valve, a water-side heat exchanger, an electromagnetic expansion valve, an air-side heat exchanger, a pressure monitoring module, a temperature monitoring module, and a controller electrically and / or communicatively connected to the four-way valve, the electromagnetic expansion valve, the temperature monitoring module, and the pressure monitoring module, all connected via refrigerant piping. The controller controls the electromagnetic expansion valve and the four-way valve using the following method:

[0007] S10 receives the system's defrosting command, sends a valve switching command to the four-way valve to initiate defrosting operation, and controls the solenoid expansion valve to its maximum opening degree K. MAX The valve remains unchanged during the first time period t1.

[0008] S20 obtains the current condensing pressure P. t H Evaporation pressure P t D and inlet water temperature T t W-in Calculate the current opening degree K of the electromagnetic expansion valve. t ;

[0009] S30 controls the opening degree K of the electromagnetic expansion valve at the current moment. t After maintaining the valve unchanged for the second time period t2, the heat exchange tube temperature T is acquired in real time. t H And determine the heat exchange tube temperature T. t H Is it greater than or equal to the preset limit of heat exchange tube temperature?

[0010] If not, proceed to step S20;

[0011] If yes, proceed to step S40;

[0012] S40 sends a valve switching command to the four-way valve to exit defrosting operation and restore the system's heating mode control.

[0013] Compared with existing technologies, this invention effectively suppresses drastic flow changes during defrosting by monitoring the condenser-side pressure and evaporator-side pressure in real time and using these parameters to adjust the defrost opening of the electromagnetic expansion valve, thereby reducing the risk of liquid return to the system. Simultaneously, by monitoring the evaporator-side inlet water temperature in real time and using this temperature to correct the defrost opening of the electromagnetic expansion valve, the defrost opening adjustment of the electromagnetic expansion valve is more closely aligned with the pressure changes between the condenser-side and evaporator-side, resulting in a faster response and ensuring safe system operation while reducing the failure rate.

[0014] Furthermore, the current opening degree K of the electromagnetic expansion valve t satisfy:

[0015] K t =K MAX -α(P t H -P t D )+βT t W-in (1)

[0016] Where: KMAX P represents the maximum opening degree of the electromagnetic expansion valve. t H P represents the condensation pressure at the current moment. t D T represents the evaporation pressure at the current moment. t W-in The current inlet water temperature is represented by α, the pressure reference operating coefficient is represented by β, and the water temperature reference operating parameter is represented by β. Attached Figure Description

[0017] To better understand and implement the invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the controller control process of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention.

[0021] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a” and “the” used in the embodiments of this application and the appended claims are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; “and / or” means and includes any or all possible combinations of one or more associated listed items; “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance.

[0022] To address the issue of refrigerant return caused by the fixed opening of the electromagnetic expansion valve controlling refrigerant flow during defrosting in air source heat pump systems, which cannot be adjusted according to the pressure changes between the condenser and evaporator sides, this application provides an air source heat pump system that improves the control method for the defrosting opening of the electromagnetic expansion valve. By monitoring the refrigerant high pressure, refrigerant low pressure, and inlet water temperature during defrosting, a defrosting opening control method is formed by coupling the above monitoring parameters through a functional relationship, enabling the defrosting opening of the electromagnetic expansion valve to automatically track and adjust according to the pressure changes between condenser and evaporator sides.

[0023] For specific implementation details, please refer to [link / reference]. Figure 1The air source heat pump system proposed in this invention includes a compressor 10, a four-way valve 20, a water-side heat exchanger 30, a liquid receiver 40, an electromagnetic expansion valve 50, an air-side heat exchanger 60, a pressure monitoring module 70, a temperature monitoring module 80, a fan 90 located next to the air-side heat exchanger 60, a controller (not shown), and other auxiliary pipe fittings, all connected via refrigerant piping. The controller is electrically and / or communicatively connected to the four-way valve 20, the electromagnetic expansion valve 50, the pressure monitoring module 70, and the temperature monitoring module 80.

[0024] An electromagnetic expansion valve 50 is installed on the refrigerant pipeline between the liquid receiver 40 and the air-side heat exchanger 60 to control the refrigerant flow rate into the air-side heat exchanger 60. Furthermore, the electromagnetic expansion valve 50 is also equipped with a filter.

[0025] The pressure monitoring module 70 includes a first pressure sensor 71 and a second pressure sensor 72. The first pressure sensor 71 is located at the discharge end of the compressor 10 and is used to collect the pressure signal of the high-temperature, high-pressure liquid refrigerant discharged from the compressor 10, and to transmit the condensation pressure P of the refrigerant. H The pressure is transmitted to the controller. The second pressure sensor 72 is located at the inlet of the compressor 10 and is used to collect the pressure signal of the low-temperature gaseous refrigerant drawn into the compressor 10, and to transmit the evaporation pressure P. D Transmitted to the controller.

[0026] The temperature monitoring module 80 includes a first temperature sensor 81 and a second temperature sensor 82. The first temperature sensor 81 is located at the inlet of the water-side heat exchanger 30 and is used to collect the inlet water temperature signal of the water-side heat exchanger 30 and convert the inlet water temperature T... W -in The data is transmitted to the controller. The second temperature sensor 82 is installed on the outermost heat exchange tube of the air-side heat exchanger 60, used to collect the temperature signal of the heat exchange tube in the air-side heat exchanger 60, and transmit the heat exchange tube temperature signal T... H Transmitted to the controller.

[0027] The controller includes a storage unit and a processing unit.

[0028] The storage unit stores the condensing pressure P collected by the pressure monitoring module 70 at various time points of the air source heat pump system. H and evaporation pressure P D The temperature monitoring module 80 collects the inlet water temperature T. W-in ; and the preset limit temperature of the heat exchange tubes.

[0029] The processing unit is used for calculations, including based on the condensation pressure P. H Evaporation pressure P D and inlet water temperature T W-in Calculate the opening degree K of the electromagnetic expansion valve at the current moment.t Secondly, it is used to output an opening adjustment signal to the electromagnetic expansion valve 50 based on the calculation results, control the opening of the electromagnetic expansion valve 50, and control the flow rate of the high-temperature and high-pressure refrigerant entering the air-side heat exchanger 60.

[0030] Please see Figure 1 The controller adjusts the opening of the electromagnetic expansion valve 50 of the air source heat pump system through the following steps.

[0031] After receiving the defrosting command from the system, the S10 controller sends a valve switching command to the four-way valve and controls the electromagnetic expansion valve to its maximum opening degree K. MAX The valve remains unchanged during the first time period t1.

[0032] The maximum opening degree K of the electromagnetic expansion valve MAX The value range is 450 to 500P.

[0033] The first time period t1 is a programmable parameter that can be adjusted according to the operating conditions. The recommended value range is 30s to 60s.

[0034] S20 initiates defrosting operation, and the controller obtains the current condensing pressure P. t H Evaporation pressure P t D and inlet water temperature T t W-in Calculate the current opening degree K of the electromagnetic expansion valve. t .

[0035] Specifically, the current opening degree K of the electromagnetic expansion valve is calculated using the following method. t .

[0036] Current opening degree K t satisfy:

[0037] K t =K MAX -α(P t H -P t D )+βT t W-in (1)

[0038] Where: K MAX Indicates the maximum opening degree of the electromagnetic expansion valve; P t H P represents the condensation pressure at the current moment. t D T represents the evaporation pressure at the current moment. t W-inThis indicates the current inlet water temperature; α represents the pressure reference operating coefficient, which ranges from 1 to 1.5. To ensure system oil return, α(P) is used. t H -P t D The value of ) must be greater than 2; β represents the water temperature reference operating parameter, which is an empirical value and ranges from 0.2 to 0.5.

[0039] S30 controls the opening degree K of the electromagnetic expansion valve at the current moment. t After maintaining the valve unchanged for the second time period t2, the controller acquires the heat exchange tube temperature T in real time. t H And determine the heat exchange tube temperature T. t H Is it greater than or equal to the preset limit of heat exchange tube temperature?

[0040] If yes, proceed to step S40;

[0041] If not, proceed to step S20.

[0042] The second time period t2 is a programmable parameter that can be adjusted according to the operating conditions. The recommended value range is 30s to 120s.

[0043] The S40 controller sends a valve switching command to the four-way valve to exit the defrosting operation and restore the system's heating mode control.

[0044] The present invention is based on the following analysis and design of the defrosting opening of the electromagnetic expansion valve.

[0045] When the system first enters defrosting, the pressure difference between the condenser and evaporator sides is small. To ensure the refrigerant flow rate during defrosting, the opening of the electromagnetic expansion valve should be as large as possible. During defrosting, the pressure on the condenser side rises and the pressure on the evaporator side falls, increasing the pressure difference between the condenser and evaporator sides and thus increasing the refrigerant flow rate. To suppress drastic changes in flow rate, reduce the risk of liquid return, and ensure stable system operation, it is necessary to monitor the pressure difference between the condenser and evaporator sides in real time and use it to adjust the opening of the electromagnetic expansion valve during defrosting.

[0046] On the other hand, the evaporation capacity of the evaporator side is directly proportional to the water temperature on the evaporator side. When the water temperature rises, the evaporation capacity increases and the superheat of evaporation is large; when the water temperature falls, the evaporation capacity decreases and the superheat of evaporation is low. Based on this characteristic, it is necessary to monitor the inlet water temperature on the evaporator side in real time and use it to correct the opening of the expansion valve during defrosting.

[0047] Through the above adjustments and corrections, the opening of the electromagnetic expansion valve is adjusted to better match the pressure changes on the condenser-evaporator side, effectively avoiding system backflow problems during system defrosting, ensuring system operational safety, and reducing the failure rate.

[0048] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An air-source heat pump system, comprising a compressor, a four-way valve, a water-side heat exchanger, an electromagnetic expansion valve, an air-side heat exchanger, a pressure monitoring module, a temperature monitoring module, and a controller electrically and / or communicatively connected to the four-way valve, the electromagnetic expansion valve, the temperature monitoring module, and the pressure monitoring module, characterized in that, The controller controls the electromagnetic expansion valve and the four-way valve using the following method: S10 receives the system's defrosting command, sends a valve switching command to the four-way valve to initiate defrosting operation, and controls the solenoid expansion valve to its maximum opening degree K. MAX The valve remains unchanged during the first time period t1. S20 obtains the current condensing pressure P. t H Evaporation pressure P t D and inlet water temperature T t W-in Calculate the current opening degree K of the electromagnetic expansion valve. t ; S30 controls the opening degree K of the electromagnetic expansion valve at the current moment. t After maintaining the valve unchanged for the second time period t2, the heat exchange tube temperature T is acquired in real time. t H And determine the heat exchange tube temperature T. t H Is it greater than or equal to the preset limit of heat exchange tube temperature? If not, proceed to step S20; If yes, proceed to step S40; S40 sends a valve switching command to the four-way valve to exit defrosting operation and restore the system's heating mode control.

2. The air source heat pump system according to claim 1, characterized in that, Current opening degree K of the electromagnetic expansion valve t satisfy: K t =K MAX -a(P t H -P t D )+βT t W-in (1) Where: K MAX P represents the maximum opening degree of the electromagnetic expansion valve. t H P represents the condensation pressure at the current moment. t D T represents the evaporation pressure at the current moment. t W-in The current inlet water temperature is represented by α, the pressure reference operating coefficient is represented by β, and the water temperature reference operating parameter is represented by β.

3. The air source heat pump system according to claim 2, characterized in that, The pressure reference operating coefficient α ranges from 1 to 1.5, and α(P) t H -P t D The value of ) must be greater than 2.

4. The air source heat pump system according to claim 2 or 3, characterized in that, The reference operating parameter β for water temperature has a range of 0.2 to 0.

5.

5. The air source heat pump system according to claim 4, characterized in that, The first time period t1 ranges from 30s to 60s.

6. The air source heat pump system according to claim 4, characterized in that, The value range of the second time period t2 is 30s to 120s.

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