Heat pump system

Abstract

Some embodiments of the present application provide a heat pump system, comprising: a compressor, used for compressing a refrigerant; a refrigerant-air heat exchanger, comprising a heat exchanger body and a subcooling section pipe in fluid connection with the heat exchanger body; a refrigerant-refrigerant heat exchanger, comprising a first heat exchange portion in fluid connection with a suction side of the compressor, and a second heat exchange portion in fluid connection with the subcooling section pipe, wherein the refrigerant exchanges heat between the first heat exchange portion and the second heat exchange portion; a refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; a first valve element, arranged between the second heat exchange portion and the refrigerant-water heat exchanger; and a second valve element, arranged between the heat exchanger body and the subcooling section pipe, wherein in a heating mode, the first valve element throttles the refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the refrigerant flowing out of the subcooling section pipe.

Description

heat pump system

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese patent application No. 2025102137365, filed on February 25, 2025; and to Chinese patent application No. 2025203111368, filed on February 25, 2025; the entire contents of all the aforementioned Chinese patent applications are incorporated herein by reference. Technical Field

[0003] Some embodiments of this application relate to the field of heat pump equipment technology, and in particular to a heat pump system. Background Technology

[0004] Heat pump systems using R290 refrigerant are becoming the main trend in future heat pump development due to their excellent environmental characteristics. The most common type of household heat pump is the air-source heat pump. Air-source heat pump systems using R290 or similar refrigerants have the following problems: low heat pump efficiency, especially at low ambient temperatures, resulting in poor heating capacity; and no advantage compared to heating using fossil fuels. The refrigerant has low saturation pressure, low isentropic adiabatic index, and low suction and exhaust superheat during operation; at low ambient temperatures, the oil viscosity in the oil sump is too low, compromising reliability. Under low ambient temperature conditions, after defrosting, water accumulates at the bottom of the heat exchanger, causing ice formation and affecting heating capacity. Summary of the Invention

[0005] Some embodiments of this application provide a heat pump system, including: a compressor for compressing a refrigerant; a refrigerant-air heat exchanger including: a heat exchanger body in which the refrigerant exchanges heat with air; and a subcooling section pipe fluidly connected to the heat exchanger body; a refrigerant-refrigerant heat exchanger including: a first heat exchange section fluidly connected to the suction side of the compressor; a second heat exchange section fluidly connected to the subcooling section pipe; the refrigerant exchanging heat between the first heat exchange section and the second heat exchange section; a refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; a first valve element disposed between the second heat exchange section and the refrigerant-water heat exchanger; and a second valve element disposed between the heat exchanger body and the subcooling section pipe; in a heating mode, the first valve element throttles the refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the refrigerant flowing out of the subcooling section pipe.

[0006] Some embodiments of this application provide a heat pump system, including: a compressor for compressing a refrigerant; a refrigerant-air heat exchanger including: a heat exchanger body in which the refrigerant exchanges heat with air; a subcooling section pipeline fluidly connected to the heat exchanger body; a refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; a first refrigerant-refrigerant heat exchanger including: a first heat exchange section fluidly connected to the suction side of the compressor; a second heat exchange section fluidly connected to the subcooling section pipeline; and refrigerant exchanging heat between the first heat exchange section and the second heat exchange section; a second refrigerant-refrigerant heat exchanger including: a first heat exchange section fluidly connected to the suction side of the compressor and the first heat exchange section; and a second heat exchange section fluidly connected to the suction side of the compressor. The system includes: a heat exchange section fluidly connected to the second heat exchange section; refrigerant exchanges heat between the first heat exchange section and the second heat exchange section; and further includes: a first valve element disposed between the second heat exchange section and the refrigerant-water heat exchanger; a second valve element disposed between the heat exchanger body and the subcooling section pipeline; a fourth valve element disposed between the first heat exchange section and the suction side of the compressor; and a fifth valve element disposed between the first heat exchange section and the suction side of the compressor. In heating mode, the first valve element throttles the refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the refrigerant flowing out of the subcooling section pipeline; one of the fourth and fifth valve elements is open, and the other is closed. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in some embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 is a schematic diagram of the structure of a heat pump system provided in some embodiments of this application;

[0009] Figure 2 is a schematic diagram of the refrigeration cycle of a heat pump system provided in some embodiments of this application;

[0010] Figure 3 is a schematic diagram of the refrigeration cycle of a heat pump system in the relevant technology;

[0011] Figure 4 is a comparison example of the pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under cooling mode provided in some embodiments of this application;

[0012] Figure 5 is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of this application;

[0013] Figure 6 is a schematic diagram of the heating cycle of a heat pump system in a related technology.

[0014] Figure 7 is a comparison example of the pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this application;

[0015] Figure 8 is a comparison example of the pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this application;

[0016] Figure 9 is a schematic diagram of the temperature change of R290 refrigerant along the path;

[0017] Figures 10 and 11 are flowcharts of the processing device of the heat pump system provided in some embodiments of this application under the cooling mode;

[0018] Figure 12 is an example of the initial compressor target frequency variation curve of a heat pump system provided in some embodiments of this application;

[0019] Figures 13 and 14 are flowcharts of the heat pump system processing device in heating mode provided in some embodiments of this application;

[0020] Figure 15 is an example of the initial compressor target frequency variation curve of a heat pump system provided in some embodiments of this application;

[0021] Figure 16 is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of this application;

[0022] Figure 17 is a comparison example of the pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this application;

[0023] Figure 18 is a schematic diagram of the temperature change of R290 refrigerant along the path;

[0024] Figure 19 is a flowchart of the heat pump system processing device in heating mode provided in some embodiments of this application;

[0025] Figure 20 is a schematic diagram of the structure of a heat pump system provided in some embodiments of this application;

[0026] Figure 21 is a flowchart of the heat pump system processing device in heating mode provided in some embodiments of this application;

[0027] Figure 22 is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of this application;

[0028] Figure 23 is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of this application;

[0029] In the diagram: 10. Heat pump system; 100. Compressor; 102. Refrigerant-air heat exchanger; 104. Heat exchanger body; 106. Subcooling section piping; 108. Fan; 110. Refrigerant-refrigerant heat exchanger; 112. First heat exchange section; 114. Second heat exchange section; 116. Refrigerant-water heat exchanger; 118. Water pump; 120. Water flow meter; 122. First valve element; 124. Second valve element; 126. Switching valve; 128. Liquid receiver; 130. Third valve element;

[0030] 132. First refrigerant-refrigerant heat exchanger; 134. First heat exchange section; 136. Second heat exchange section; 138. Fourth valve element; 140. Fifth valve element; 142. Second refrigerant-refrigerant heat exchanger; 144. First heat exchange section; 146. Second heat exchange section;

[0031] 201. Compressor; 202. Four-way reversing valve; 203. Refrigerant-air heat exchanger; 204. Refrigerant-water heat exchanger; 205. Throttling element; 206. Electric heater. Detailed Implementation

[0032] The technical solutions of some embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Heat pump systems are highly efficient heat transfer devices capable of providing heating or cooling under varying environmental conditions. They are primarily used for residential heating and cooling, heating domestic hot water, heat recovery in industrial processes, and temperature control. In the civilian sector, the most common type of heat pump system is the air-source heat pump system. This system extracts heat from the air for heating or cooling, representing a highly efficient and environmentally friendly energy utilization method. Heat pump systems can use various refrigerants. In recent years, low-GWP refrigerants such as R290 (propane) have gained increasing attention in the heat pump field. R290 is a natural refrigerant with extremely low global warming potential; using it can significantly reduce environmental impact and align with sustainable development requirements. However, at lower ambient temperatures, the energy efficiency of air-source heat pump systems using low-GWP refrigerants like R290 is significantly lower. Specifically, taking R290 as an example, under the same temperature conditions, R290 has a lower critical temperature and a lower critical pressure. Therefore, when operating at low temperatures and pressures, R290 refrigerant easily enters a higher compression range and reaches saturation under high pressure. Furthermore, its usable gas and liquid phase ranges are relatively small, requiring a larger compressor power to achieve the same cooling (heating) effect. Additionally, R290 refrigerant has a low saturation pressure and a low isentropic adiabatic index during operation. A lower isentropic adiabatic index indicates significant energy loss during compression, making it less likely to be converted into compression work. At low ambient temperatures, the oil viscosity in the oil sump is too low, compromising reliability.

[0034] This application provides a heat pump system in some embodiments. From a thermodynamic perspective, the refrigeration cycle of the heat pump system includes an evaporator, a compressor, a condenser, and a throttling device connected in sequence. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat an indoor space, or to heat domestic water. From a thermodynamic perspective, a low-temperature, low-pressure refrigerant enters the compressor, which compresses it into a high-temperature, high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process. The throttling device causes the high-temperature, high-pressure liquid refrigerant formed in the condenser to expand into a low-pressure gas-liquid two-phase refrigerant. The evaporator evaporates the refrigerant that has expanded in the throttling device and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves a cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material to be cooled.

[0035] From a hardware architecture perspective, referring to the accompanying drawings, this application describes a heat pump system provided in some embodiments. Figure 1 is a schematic diagram of the refrigeration cycle of a heat pump system 10 provided in some embodiments of this application, wherein the compressor 100 is the core component. The compressor 100 is used to compress the refrigerant, compressing the refrigerant from a low-pressure state to a high-pressure state, so that the refrigerant can effectively transfer heat in the refrigeration cycle.

[0036] In some embodiments, a refrigerant-air heat exchanger 102 is used for heat exchange between a refrigerant and air. The refrigerant-air heat exchanger 102 includes a heat exchanger body 104 and a subcooled section pipe 106. The refrigerant exchanges heat with air within the heat exchanger body 104. Heat exchanger pipes are disposed within the heat exchanger body 104, through which the refrigerant flows, and air flows on the surface of the heat exchanger body 104 via a fan 108 or natural convection. The subcooled section pipe 106 is fluidly connected to the heat exchanger body 104 and is primarily used to improve the efficiency of the heat pump system 10. The specific operating principle of the subcooled section pipe 106 will be described in detail below. In some embodiments, a refrigerant-refrigerant heat exchanger 110 is used for heat exchange between refrigerants in different states. The refrigerant-to-refrigerant heat exchanger 110 includes a first heat exchange section 112 and a second heat exchange section 114. The first heat exchange section 112 is fluidly connected to the suction side of the compressor 100, and the second heat exchange section 114 is fluidly connected to the subcooling section pipeline 106. Heat exchange occurs between the first heat exchange section 112 and the second heat exchange section 114. The suction side of the compressor 100 is the side closest to the inlet of the compressor 100, where the refrigerant returns from the evaporator and enters the compressor 100. On the suction side, the refrigerant is typically at low pressure and low temperature. In some embodiments of this application, the refrigerant-to-refrigerant heat exchanger 110 can be a plate heat exchanger, a shell-and-tube heat exchanger, a coaxial heat exchanger, a spiral plate heat exchanger, or other optional heat exchanger forms. In some embodiments, the refrigerant-to-water heat exchanger 116 is used to exchange heat between the refrigerant and water, transferring heat from the refrigerant to the water, causing the water temperature to rise or fall. Water heated to a higher temperature can be used in heating systems such as underfloor heating and radiators to provide hot water circulation, or in domestic hot water supply systems to provide hot water; water cooled to a lower temperature can be used to provide cooling water circulation for indoor cooling. The water circuit is equipped with components such as a flow meter 120 and a water pump 118 to maintain normal operation; no further limitations are imposed on the water circuit design here.

[0037] In some embodiments, the heat pump system 10 further includes a first valve element 122 and a second valve element 124. The first valve element 122 is disposed between the second heat exchange section 114 and the refrigerant-water heat exchanger 116, and the second valve element 124 is disposed between the heat exchanger body 104 and the subcooled section pipeline 106. In some embodiments of this application, the first valve element 122 is an electronic expansion valve. In some embodiments of this application, the second valve element 124 is an electronic expansion valve. In heating mode, the first valve element 122 throttles the refrigerant flowing out of the refrigerant-water heat exchanger 116, and the second valve element 124 throttles the refrigerant flowing out of the subcooled section pipeline 106. In some embodiments, the heat pump system 10 further includes a switching valve 126. The switching valve 126 is used to switch the operating mode of the heat pump system 10, enabling it to switch between a cooling mode and a heating mode. More specifically, the switching of the operating mode is achieved by switching the flow direction of the refrigerant. In some embodiments of this application, the switching valve 126 is a four-way valve. The four-way valve has four ports D, S, C, and E, which are respectively connected to the discharge port, suction port, condenser, and evaporator of the compressor 100. By changing the flow path inside the four-way valve, the flow direction of the refrigerant can be changed. In some embodiments, the heat pump system 10 also includes a liquid receiver 128, which is disposed between the first valve element 122 and the refrigerant-water heat exchanger 116. The liquid receiver 128 is used to store and regulate the flow and pressure of the refrigerant, and plays a buffering and stabilizing role.

[0038] In some embodiments, taking the use of R290 refrigerant as an example, the cooling mode of the heat pump system 10 is described with reference to FIG2. Low-temperature, low-pressure R290 refrigerant is compressed into high-temperature, high-pressure refrigerant by compressor 100, and enters refrigerant-air heat exchanger 102 through switching valve 126 (DC). Refrigerant-air heat exchanger 102 acts as a condenser. R290 refrigerant condenses into a liquid phase in the heat exchanger body 104 of refrigerant-air heat exchanger 102, and is throttled by second valve element 124 to become medium-temperature, medium-pressure R290 refrigerant. After passing through subcooling section pipe 106, it enters the second heat exchange section 114 of refrigerant-refrigerant heat exchanger 110, where it exchanges heat with the low-temperature, low-pressure R290 refrigerant in the first heat exchange section 112 before entering compressor 100. The refrigerant after heat exchange flows out from the second heat exchange section 114 and is throttled by first valve element 122 to become low-temperature, low-pressure R290 refrigerant. The low-temperature, low-pressure R290 refrigerant further enters the refrigerant-water heat exchanger 116. The refrigerant-water heat exchanger 116 acts as an evaporator. The R290 refrigerant entering the refrigerant-water heat exchanger 116 exchanges heat with the water to become a gas phase. After passing through the switching valve 126 (SE) and the first heat exchange section 112 of the refrigerant-water heat exchanger 110, it enters the compressor 100, completing the refrigeration cycle. In Figure 2, the solid line represents the high-pressure R290 refrigerant region, the dashed line represents the medium-pressure R290 refrigerant region, the dotted-dashed line represents the low-pressure R290 refrigerant region, and the double-dotted-dashed line represents the water flow path.

[0039] Figure 3 shows the refrigeration cycle of the heat pump system 10 in the refrigeration mode of the related technology. The solid line represents the high-pressure refrigerant region, the dashed line represents the low-pressure refrigerant region, and the double-dotted line represents the water flow path. The low-temperature, low-pressure refrigerant is compressed into a high-temperature, high-pressure refrigerant by the compressor 201, then enters the refrigerant-air heat exchanger 203 through the four-way reversing valve 202, where it exchanges heat with air and condenses into a liquid refrigerant. After passing through the throttling element 205, it becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant, which enters the refrigerant-water heat exchanger 204 and exchanges heat with water to become a gaseous refrigerant. Finally, it enters the compressor 201 through the four-way reversing valve 202, completing the refrigeration cycle. Figure 4 compares the pressure-enthalpy diagrams of the heat pump system 10 provided by the related technology scheme and some embodiments of this application. The refrigeration cycle of the related technology scheme is shown in Figures 1-2-3-4-1, and the refrigeration capacity per unit mass of R290 refrigerant is h1-h4. The refrigeration cycle of the heat pump system 10 provided in some embodiments of this application is shown in Figures 1′-2′-3′-4′-5′-6′-7′-8′-1′, and the refrigeration capacity per unit mass of R290 refrigerant is h1′-h8′. Compared with the refrigeration mode of the heat pump system 10 of related technologies, under the condition of using R290 refrigerant, when achieving the same capacity, the compressor 100 of the heat pump system 10 provided in some embodiments of this application has a lower frequency, lower condensing pressure, and improved energy efficiency.

[0040] In some embodiments, taking R290 refrigerant as an example, the heating mode of the heat pump system 10 is described with reference to FIG5. Low-temperature, low-pressure R290 refrigerant is compressed by compressor 100 into high-temperature, high-pressure R290 refrigerant, and enters refrigerant-water heat exchanger 116 through switching valve 126(DE). Refrigerant-water heat exchanger 116 acts as a condenser, where R290 refrigerant condenses into a liquid phase through heat exchange, and then passes through first valve element 122 to become medium-temperature, medium-pressure R290 refrigerant. The medium-temperature, medium-pressure R290 refrigerant further enters the second heat exchange section 114 of refrigerant-refrigerant heat exchanger 110, exchanging heat with the low-temperature, low-pressure R290 refrigerant in the first heat exchange section 112 before entering compressor 100; the R290 refrigerant after heat exchange flows out from the second heat exchange section 114 and enters the subcooled section pipe 106 to exchange heat with air. The R290 refrigerant entering the subcooling section pipe 106 prevents frost from forming at the bottom of the heat exchanger. The R290 refrigerant flowing out of the subcooling section pipe 106 is further throttled by the second valve element 124 to become a low-temperature, low-pressure R290 refrigerant, entering the heat exchanger body 104 of the refrigerant-air heat exchanger 102. After exchanging heat with the air, it passes through the switching valve 126 (CS) and enters the first heat exchange section 112 of the refrigerant-refrigerant heat exchanger 110. After exchanging heat with the medium-temperature, medium-pressure R290 refrigerant in the second heat exchange section 114, its temperature rises, and it enters the compressor 100. The increased temperature of the R290 refrigerant improves the suction temperature and oil sump temperature of the compressor 100, completing the heating cycle. In Figure 5, the solid line represents the high-pressure R290 refrigerant area, the dashed line represents the medium-pressure R290 refrigerant area, the dotted line represents the low-pressure R290 refrigerant area, and the double-dotted line represents the water flow path.

[0041] Figure 6 illustrates the heating cycle of a heat pump system in the heating mode of the related technology. The solid line represents the high-pressure refrigerant region, the dashed line represents the low-pressure refrigerant region, and the double-dotted line represents the water flow path. The low-temperature, low-pressure refrigerant is compressed into a high-temperature, high-pressure refrigerant by compressor 201, then enters the refrigerant-water heat exchanger 204 through a four-way reversing valve 202. There, it exchanges heat with water and condenses into a liquid refrigerant. After passing through a throttling element 205, it becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant, which enters the refrigerant-air heat exchanger 203. After exchanging heat with air, it enters the compressor 201 through the four-way reversing valve 202, completing the heating cycle. An electric heater 206 prevents frost buildup at the bottom of the heat exchanger. Figure 7 compares the pressure-enthalpy diagrams of the heat pump system provided by the related technology and some embodiments of this application. The heating cycle of the related technology is shown in Figure 7 (1-2-3-4-1). The R290 refrigerant at the outlet of the refrigerant-air heat exchanger 203 is in a gas-liquid two-phase state, and the oil sump temperature is low. When compressed by compressor 201, the compressor is wet-compressing, resulting in poor reliability. The heating capacity per unit mass of refrigerant is h2-h3, leading to low energy efficiency. An electric heater 206 needs to be added to the bottom of the refrigerant-air heat exchanger 203 to prevent frost buildup, increasing energy consumption. If the refrigerant-air heat exchanger 203 in related technologies also adopts the design of a heat exchanger body and subcooled section piping, the refrigeration cycle is as shown in Figure 7 (1-2-3-5-6-1). In the subcooled section piping, the refrigerant travels from 3 to 5, resulting in excessive heat dissipation.

[0042] The heating cycle of the heat pump system 10 provided in some embodiments of this application is shown in Figure 7 (1′-2′-3′-4′-5′-6′-7′-1′). In the refrigerant-refrigerant heat exchanger 110, the high-pressure R290 refrigerant changes from state 4′ to state 5′, and the low-pressure R290 refrigerant changes from state 1′ to state 2′, causing the compressor 100 to overheat during suction, increasing the oil sump temperature, and improving reliability. The heating capacity per unit mass of R290 refrigerant is h3′-h4′. Compared with the heating mode of related technology heat pump systems, under the condition of using R290 refrigerant, when achieving the same capacity, the compressor 100 of the heat pump system 10 provided in some embodiments of this application has a lower frequency and improved energy efficiency; in the subcooled section pipe 106, the R290 refrigerant changes from state 5′ to state 6′, satisfying the requirement of no frost while reducing heat loss.

[0043] Figure 8 compares the pressure-enthalpy diagrams of the heat pump system provided by the related technology solutions and some embodiments of this application. Under low ambient temperature conditions, the exhaust temperature is prone to over-increase (exceeding the normal or design temperature range). Taking the refrigerant-air heat exchanger in the related technology solution, which also uses a heat exchanger body and subcooled section piping, and adopts a refrigerant-to-refrigerant heat exchanger design as an example, the heating cycle is 1-2-3-4-5-6-7-1. In the refrigerant-to-refrigerant heat exchanger, the high-pressure refrigerant changes from state 4 to state 5, and the low-pressure refrigerant changes from state 1 to state 2. Due to the exhaust temperature limitation, the heat exchange of the refrigerant-to-refrigerant heat exchanger is relatively small, and the heat exchange in the refrigerant-to-refrigerant heat exchanger cannot be controlled; in the subcooled section piping, the refrigerant changes from state 5 to state 6, resulting in significant heat loss. The heat pump system provided in some embodiments of this application, under low ambient temperature conditions, exhibits a heating cycle as shown in Figures 1′-2′-3′-4′-5′-6′-7′-8′-1′. The heat exchange capacity of the R290 refrigerant in the refrigerant-to-refrigerant heat exchanger 110 and the subcooling section pipe 106 is controlled collaboratively by the first valve element 122 and the second valve element 124. In the refrigerant-to-refrigerant heat exchanger 110, the high-pressure R290 refrigerant changes from state 5′ to state 6′, and the low-pressure R290 refrigerant changes from state 1′ to state 2′, increasing the heat exchange capacity. In the subcooling section pipe 106, the refrigerant changes from state 6′ to state 7′, ensuring no frost forms at the bottom of the refrigerant-air heat exchanger 102 while reducing heat loss. In related heat pump systems, even with the addition of a subcooling section, the refrigerant after passing through the refrigerant-water heat exchanger remains a high-temperature, high-pressure refrigerant. High-temperature, high-pressure refrigerant directly enters the subcooled section pipeline. The refrigerant has a high enthalpy and a large temperature difference with the refrigerant inside the heat exchanger, further leading to a higher refrigerant temperature in the refrigerant-air heat exchanger and deteriorating its heat exchange performance. Although a refrigerant-to-refrigerant heat exchanger is designed, the compressor suction temperature is difficult to control at the optimal suction temperature, resulting in low energy efficiency and poor reliability. The heat pump system 10 provided in some embodiments of this application, in heating mode, controls the heat entering the refrigerant-to-refrigerant heat exchanger 110 and the subcooled section pipeline 106 through a first valve element 122. Part of the heat is consumed in the refrigerant-to-refrigerant heat exchanger 110, with only the remaining heat ensuring that the bottom of the refrigerant-air section does not frost, thus not significantly affecting the heat exchange performance of the refrigerant-air heat exchanger 102. This ensures that the compressor 100 suction temperature reaches the target suction temperature while reducing the inlet and outlet temperatures of the subcooled section pipeline 106. The temperature variation of R290 refrigerant along the pipeline is shown in Figure 9.

[0044] In some embodiments of this application, the refrigeration cycle of the heat pump system described above is also applicable to other refrigerants with similar physical properties. The opening control of the first valve element 122 and the second valve element 124 will be further described below. In the following description, both the first valve element 122 and the second valve element 124 are electronic expansion valves.

[0045] In some embodiments of this application, as shown in FIG1, the heat pump system 10 further includes a processing device 190. The processing device 190 is configured to monitor and regulate the operating status of the heat pump system 10 to ensure its efficient, stable, and safe operation. The processing device 190 includes components such as a processor, volatile memory, non-volatile memory, a display device, an operating device, a communication interface, and a drive device, which are interconnected via a bus. The processor can be a dedicated processor, a central processing unit (CPU), etc. The processor can access instructions or application programs stored in the volatile and non-volatile memory to implement related functions, such as sending control commands to actuators (e.g., compressor 100) via relays, MOSFETs, PWM outputs, etc. The display device is used to display various information, the operating device is used to receive various operations, and the drive device is a hardware terminal that interacts with the storage medium. The storage medium includes media that record information in optical, electrical, or magnetic ways, such as CD-ROMs, floppy disks, and optical disks. The storage medium can also be semiconductor memories that record information electrically, such as ROMs and flash memory. The processing device 190 can be the controller of the heat pump system 10 itself, such as an on-board system built on a microprocessor. The processing device 190 can also be a host computer, a cloud server, or other mobile terminals. The processing device 190 communicates with various sensors installed in the heat pump system 10. The processing device and the various sensors in the heat pump system 10 can communicate via networks such as LAN (Local Area Network), signal lines (e.g., Ethernet cable, coaxial cable, fiber optic cable, power line, serial cable, etc.), wireless signals, LTE, and 5G.

[0046] In some embodiments of this application, in a cooling mode, the processing device 190 is configured to perform multiple steps as shown in FIG10 to adjust the opening of the first valve element 122.

[0047] Step S101: Obtain the refrigerant-water heat exchanger outlet superheat at the outlet of refrigerant-water heat exchanger 116;

[0048] Step S102: Obtain the preset target superheat at the outlet of the refrigerant-water heat exchanger;

[0049] Step S103: Based on the rate of change of superheat at the outlet of the refrigerant-water heat exchanger, and the difference between the target superheat at the outlet of the refrigerant-water heat exchanger and the superheat at the outlet of the refrigerant-water heat exchanger, the opening of the first valve element 122 is adjusted through incremental feedback control to compensate for the deviation of the superheat at the outlet of the refrigerant-water heat exchanger from the target superheat at the outlet of the refrigerant-water heat exchanger, so as to ensure that the refrigerant-water heat exchanger 116 is in the optimal state of heat exchange performance.

[0050] In some embodiments, the processing device 190 adjusts the opening degree of the first valve element 122 using incremental control based on the feedback control principle. Incremental control involves calculating the incremental control quantity that needs to be adjusted in each control cycle and adding it to the control quantity of the previous cycle to obtain the control quantity of the current cycle.

[0051] In cooling mode, the incremental control of the first valve element 122 is represented as: EV EEV1_Cooling (n) = EV EEV1_Cooling (n-1)+ΔEV EEV1_Cooling

[0052] That is, the opening degree EV of the first valve element 122 in the current cycle EEV1_Cooling (n) is equal to the opening degree EV of the first valve element 122 in the previous cycle. EEV1_Cooling (n-1) and increment ΔEV EEV1_Cooling The sum, where ΔEV EEV1_Cooling It is calculated based on the rate of change of superheat at the outlet of the refrigerant-water heat exchanger and the difference between the superheat at the outlet of the refrigerant-water heat exchanger and the target superheat at the outlet of the refrigerant-water heat exchanger.

[0053] The following is about the incremental ΔEV EEV1_Cooling The calculation process will be introduced as follows:

[0054] In some embodiments of this application:

[0055] in:

[0056] This represents the rate of change of superheat at the outlet of the refrigerant-water heat exchanger with respect to the increment ΔEV. EEV1_Cooling The calculated impact (proportion); if the superheat is changing rapidly, the incremental ΔEV can be adjusted using the first refrigeration regulation coefficient m1. EEV1_Cooling Adjustments are made, and in some embodiments, the larger the change in superheat (e.g., in absolute value), the larger m1 (in absolute value); wherein, SH r-w,out (n) represents the refrigerant-water heat exchanger outlet superheat for the current cycle, SH r-w,out(n-1) represents the refrigerant-water heat exchanger outlet superheat in the previous cycle, Δt is the time interval of the set cycle, and m1 is the first refrigeration regulation coefficient; n1[SHo r-w,out -SH r-w,out (n)]

[0057] This represents the deviation between the refrigerant-water heat exchanger outlet superheat and the target refrigerant-water heat exchanger outlet superheat as expressed in increments ΔEV. EEV1_Cooling The impact of the calculation; if the superheat at the outlet of the refrigerant-water heat exchanger deviates significantly from the target superheat of the refrigerant-water heat exchanger 116, the incremental ΔEV can be adjusted using the second refrigeration regulation coefficient n1. EEV1_Cooling Adjustments are made, and in some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger n1 (expressed in absolute value); SHo r-w,out n1 is the target superheat at the outlet of the refrigerant-water heat exchanger, and n1 is the second refrigeration regulation coefficient.

[0058] Incremental ΔEV EEV1_Cooling The calculation combines the refrigerant-water heat exchanger outlet superheat change rate and the deviation of the refrigerant-water heat exchanger outlet superheat from the target superheat of refrigerant-water heat exchanger 116. It comprehensively considers the dynamic response and steady-state error of the heat pump system 10. Through the first refrigeration adjustment coefficient m1 and the second refrigeration adjustment coefficient n1, the influence of the refrigerant-water heat exchanger outlet superheat change rate and the deviation of the refrigerant-water heat exchanger outlet superheat from the target superheat of refrigerant-water heat exchanger 116 on the adjustment process of the first valve element 122 can be flexibly controlled, thereby achieving more accurate control. The above control process of the processing device is particularly suitable for scenarios involving dynamic adjustment of R290 refrigerant flow, flexibly responding to load changes, allowing the heat pump system 10 to respond quickly and maintain a stable operating state.

[0059] The outlet superheat of a refrigerant-water heat exchanger is the degree to which the actual temperature of the refrigerant exceeds its saturation temperature. The refrigerant temperature T at the outlet of refrigerant heat exchanger 116 is detected using a temperature sensor. g and refrigerant pressure P g The saturation temperature T(P) is determined based on the pressure-temperature relationship of the refrigerant. g The superheat at the outlet of the refrigerant-water heat exchanger is the difference between the actual temperature and the saturation temperature: SH r-w,out =T g -T(P g )

[0060] In some embodiments of this application, in cooling mode, the processing device 190 is configured to perform multiple steps as shown in FIG11 to adjust the opening of the second valve element 124.

[0061] Step S201: Obtain the superheat of the refrigerant-refrigerant heat exchanger 110 outlet at the outlet of the first heat exchange section 112.

[0062] Step S202: Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger 110.

[0063] Step S203: Based on the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger 110, and the difference between the target superheat at the outlet of the refrigerant-refrigerant heat exchanger 110 and the superheat at the outlet of the refrigerant-refrigerant heat exchanger 110, the opening of the second valve element 124 is adjusted by incremental control to compensate for the deviation of the superheat at the outlet of the refrigerant-refrigerant heat exchanger 110 from the target superheat at the outlet of the refrigerant-refrigerant heat exchanger 110.

[0064] The processing device 190 is based on the feedback control principle and uses incremental control to adjust the opening degree of the second valve element 124.

[0065] The incremental control of the second valve element 124 in cooling mode is represented as: EV EEV2_Cooling (n) = EV EEV2_Cooling (n-1)+ΔEV EEV2_Cooling

[0066] That is, the opening degree EV of the second valve element 124 in the current cycle EEV2_Cooling (n) equals the opening degree EV of the second valve element 124 in the previous cycle. EEV2_Cooling (n-1) and increment ΔEV EEV2_Cooling The sum; where ΔEV EEV2_Cooling It is calculated based on the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger 110, and the difference between the superheat at the outlet of the refrigerant-refrigerant heat exchanger 110 and the target superheat at the outlet of the refrigerant-refrigerant heat exchanger 110.

[0067] The following is about the incremental ΔEV EEV2_Cooling The calculation process will be introduced as follows:

[0068] In some embodiments of this application:

[0069] in:

[0070] This represents the rate of change of superheat at the outlet of refrigerant-refrigerant heat exchanger 110 with respect to the increment ΔEV. EEV2_Cooling The impact of calculations; if the superheat is changing rapidly, the incremental ΔEV can be adjusted using the third refrigeration regulation coefficient m2. EEV2_Cooling Adjustments are made, and in some embodiments, the larger the change in superheat (e.g., in absolute value), the larger m2 (in absolute value); wherein, SH r-r,out(n) represents the current cycle refrigerant-refrigerant heat exchanger 110 outlet superheat, SH r-r,out (n-1) represents the refrigerant-refrigerant heat exchanger outlet superheat of the previous cycle, Δt is the time interval of the set cycle, and m2 is the third refrigeration regulation coefficient; n2[SHo r-r,out -SH r-r,out (n)]

[0071] The deviation between the outlet superheat of refrigerant-refrigerant heat exchanger 110 and the target outlet superheat of refrigerant-refrigerant heat exchanger 110 is expressed as an increment ΔEV. EEV2_Cooling The impact of calculations; if the superheat at the outlet of the refrigerant-refrigerant heat exchanger 110 deviates significantly from the target superheat, the increment can be adjusted using the fourth refrigeration regulation coefficient n2. In some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger n2 (expressed in absolute value); SHo r-r,out n1 represents the target superheat at the outlet of refrigerant-refrigerant heat exchanger 110, and n2 is the fourth refrigeration regulation coefficient.

[0072] Incremental ΔEV EEV2_Cooling The calculation combines the rate of change of superheat at the outlet of the refrigerant-to-refrigerant heat exchanger 110 and the deviation of the superheat at the outlet of the refrigerant-to-refrigerant heat exchanger 110 from the target superheat of the refrigerant-to-refrigerant heat exchanger 110. It comprehensively considers the dynamic response and steady-state error of the heat pump system 10. Through the third refrigeration adjustment coefficient m2 and the fourth refrigeration adjustment coefficient n2, the influence of the rate of change of superheat at the outlet of the refrigerant-to-refrigerant heat exchanger 110 and the deviation of the superheat at the outlet of the refrigerant-to-refrigerant heat exchanger 110 from the target superheat of the refrigerant-to-refrigerant heat exchanger 110 on the adjustment process of the second valve element 124 can be flexibly controlled, thereby achieving more accurate control.

[0073] In cooling mode, the opening degree of the second valve element 124 is greater than that of the first valve element 122. The first valve element 122 plays a major throttling role, resulting in a higher temperature of the R290 refrigerant entering the refrigerant-refrigerant heat exchanger 110 and a larger heat exchange, thereby achieving high energy efficiency as shown in the pressure-enthalpy diagram.

[0074] The superheat at the outlet of refrigerant heat exchanger 110 is the degree to which the actual temperature of R290 refrigerant exceeds its saturation temperature. The temperature T of the R290 refrigerant at the outlet of the first heat exchange section 112 is detected using a temperature sensor. reg,o and R290 refrigerant pressure P reg,o The saturation temperature T(P) is determined based on the pressure-temperature relationship of R290 refrigerant. reg,o The superheat at the outlet of refrigerant-to-refrigerant heat exchanger 110 is the difference between the actual temperature and the saturation temperature: SH r-r,out =Treg,o -T(P reg,o )

[0075] In cooling mode, the compressor operates at a frequency of 100 Hz. O The following control methods are preferred:

[0076] Set the initial compressor target frequency Ho(0) to 100. The initial compressor target frequency Ho(0) satisfies: H o (0)=f(q,T w,i ,T w,o )=a1[q(T w,i -T w,o )]

[0077] Where q is the water flow rate and a1 is the frequency adjustment coefficient.

[0078] The frequency adjustment coefficient a1 can be set based on the ambient temperature and / or the outlet water temperature to achieve the same capability. As the ambient temperature increases, the initial compressor 100 target frequency Ho(0) increases; as the target outlet water temperature increases, the initial compressor 100 target frequency Ho(0) decreases.

[0079] For the same target outlet water temperature, the frequency adjustment coefficient a1 can be expressed as: a1=f(T a )=b1×T a +c1

[0080] Where b1 and c1 are constants, b1>0, c1>0.

[0081] An exemplary variation curve of the initial compressor 100 target frequency Ho(0) is shown in Figure 12. The heat pump has a cooling capacity of 14kW, an ambient temperature of 35°C, an outlet water temperature of 18°C, and the initial compressor 100 target frequency Ho(0) is 45Hz.

[0082] Based on feedback from the outlet water temperature, the treatment device 190 uses incremental control to adjust the operating frequency Ho(n) of the compressor 100.

[0083] The incremental control method for the compressor 100 operating frequency Ho(n) is expressed as: Ho(n) = Ho(n-1) + ΔHo

[0084] That is, the operating frequency Ho(n) of the compressor 100 in the current cycle is equal to the sum of the operating frequency Ho(n-1) of the compressor 100 in the previous cycle and the increment ΔHo; wherein, the increment ΔHo is calculated based on the rate of change of the outlet water temperature and the difference between the real-time outlet water temperature and the set target outlet water temperature.

[0085] The following describes the calculation process for the increment ΔHo:

[0086] In some embodiments of this application:

[0087] in:

[0088] This indicates the impact of the rate of change in outlet water temperature on the calculation of the increment ΔHo. If the outlet water temperature is changing rapidly, the increment ΔHo can be adjusted using the first frequency modulation coefficient x1. In some embodiments, the larger the change in outlet water temperature (e.g., expressed in absolute value), the larger x1 (expressed in absolute value) becomes. Wherein, T... w,o (n) represents the real-time outlet water temperature during the current temperature sampling period, T w,o (n-1) represents the real-time outlet water temperature of the previous temperature sampling period, Δt1 represents the time interval of the set temperature sampling period, and x1 represents the first frequency modulation coefficient; y1[To-T w,o (n)]

[0089] This indicates the impact of the deviation between the real-time outlet water temperature and the target outlet water temperature on the calculation of the increment ΔHo. If the deviation between the real-time outlet water temperature and the target outlet water temperature is large, the increment can be adjusted by the second frequency modulation coefficient y1. In some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger y1 (expressed in absolute value); To is the target outlet water temperature, and y1 is the second frequency modulation coefficient.

[0090] In some embodiments of this application, in heating mode, the processing device 190 is configured to perform multiple steps as shown in FIG13 to adjust the opening of the first valve element 122.

[0091] Step S301: Obtain the refrigerant-refrigerant heat exchanger outlet superheat at the outlet of the first heat exchange section 112.

[0092] Step S302: Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger.

[0093] Step S303: Based on the refrigerant-to-refrigerant heat exchanger outlet superheat change rate and the difference between the refrigerant-to-refrigerant heat exchanger outlet target superheat and the refrigerant-to-refrigerant heat exchanger outlet superheat, adjust the opening of the first valve element 122 through incremental feedback control to compensate for the deviation of the refrigerant-to-refrigerant heat exchanger outlet superheat relative to the refrigerant-to-refrigerant heat exchanger outlet target superheat.

[0094] The processing device 190 adjusts the opening degree of the first valve element 122 using an incremental control method based on the feedback control principle.

[0095] The incremental control of the first valve element 122 in heating mode is represented as: EV EEV1_Heating (n) = EV EEV1_Heating (n-1)+ΔEV EEV1_Heating

[0096] That is, the opening degree EV of the first valve element 122 in the current cycle EEV1_Heating (n) is equal to the opening degree EV of the first valve element 122 in the previous cycle. EEV1_Heating (n-1) and increment ΔEV EEV1_Heating The sum, where ΔEV EEV1_Heating It is calculated based on the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger and the difference between the superheat at the outlet of the refrigerant-refrigerant heat exchanger and the target superheat.

[0097] The following is about the incremental ΔEV EEV1_Heating The calculation process will be introduced as follows:

[0098] In some embodiments of this application:

[0099] in:

[0100] This represents the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger with respect to the increment ΔEV. EEV1_Heating The impact of calculations; if the superheat is changing rapidly, the incremental ΔEV can be adjusted using the first heating regulation coefficient m3. EEV1_Heating Adjustments are made, and in some embodiments, the larger the change in superheat (e.g., in absolute value), the larger the m3 (in absolute value); wherein, SH r-r,out (n) represents the refrigerant-refrigerant heat exchanger outlet superheat for the current cycle, SH r-r,out (n-1) represents the refrigerant-refrigerant heat exchanger outlet superheat in the previous cycle, Δt is the time interval of the set cycle, and m3 is the first heating regulation coefficient. n3[SHo r-r,out -SH r-r,out (n)]

[0101] This represents the deviation between the refrigerant-to-refrigerant heat exchanger outlet superheat and the refrigerant-to-refrigerant outlet target superheat in terms of increment ΔEV. EEV1_Heating The impact of the calculation; if the superheat at the outlet of the refrigerant-refrigerant heat exchanger deviates significantly from the target superheat of the refrigerant-refrigerant heat exchanger 110, the incremental ΔEV can be adjusted using the second heating regulation coefficient n3. EEV1_Heating Adjustments are made, and in some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger n3 (expressed in absolute value); SHo r-r,out n is the target superheat at the outlet of the refrigerant-refrigerant heat exchanger, and n3 is the second heating regulation coefficient.

[0102] Incremental ΔEV EEV1_HeatingThe calculation combines the refrigerant-to-refrigerant heat exchanger outlet superheat change rate and the deviation of the refrigerant-to-refrigerant heat exchanger outlet superheat from the target superheat of the refrigerant-to-refrigerant heat exchanger 110. It comprehensively considers the dynamic response and steady-state error of the heat pump system 10. Through the first heating regulation coefficient m3 and the second heating regulation coefficient n3, the influence of the refrigerant-to-refrigerant heat exchanger outlet superheat change rate and the deviation of the refrigerant-to-refrigerant heat exchanger outlet superheat from the target superheat of the refrigerant-to-refrigerant heat exchanger 110 on the adjustment process of the first valve element 122 can be flexibly controlled, thereby achieving more accurate control. In particular, the control process of the first valve element 122 can ensure that the temperature of the R290 refrigerant before entering the compressor 100 is at the optimal energy-efficiency temperature, meeting the oil sump temperature requirements while ensuring that the bottom of the refrigerant-air heat exchanger 102 does not frost.

[0103] The refrigerant-refrigerant heat exchanger outlet superheat is the degree to which the actual temperature of R290 refrigerant exceeds its saturation temperature. The R290 refrigerant temperature T at the outlet of the first heat exchange section 112 is detected using a temperature sensor. reg,o and R290 refrigerant pressure P reg,o The saturation temperature T(P) is determined based on the pressure-temperature relationship of R290 refrigerant. reg,o The superheat at the outlet of the refrigerant-refrigerant heat exchanger is the difference between the actual temperature and the saturation temperature: SH r-r,out =T reg,o -T(P reg,o )

[0104] In some embodiments of this application, for the same amount of change, the first heating regulation coefficient m3 is less than the first cooling regulation coefficient m1. Optionally, the second heating regulation coefficient n3 is equal to the second cooling regulation coefficient n1. In some embodiments of this application, the cooling regulation coefficient and the heating regulation coefficient can also be selected according to actual needs.

[0105] In some embodiments of this application, in heating mode, the processing device 190 is configured to perform multiple steps as shown in FIG14 to adjust the opening of the second valve element 124.

[0106] Step S401: Obtain the refrigerant-air heat exchanger outlet superheat at the outlet of the heat exchanger body 104.

[0107] Step S402: Obtain the preset target superheat at the outlet of the refrigerant-air heat exchanger.

[0108] Step S403: Based on the refrigerant-air outlet superheat change rate and the difference between the refrigerant-air heat exchanger outlet superheat and the refrigerant-air heat exchanger outlet target superheat, the opening of the second valve element 124 is adjusted through incremental feedback control to compensate for the deviation of the refrigerant-air outlet superheat relative to the refrigerant-air heat exchanger outlet target superheat, so as to ensure that the refrigerant-air heat exchanger 102 is in the optimal state of heat exchange performance.

[0109] The processing device 190 adjusts the opening of the second valve element 124 using incremental control based on the feedback control principle.

[0110] The incremental control of the second valve element 124 in heating mode is represented as: EV EEV2_Heating (n) = EV EEV2_Heating (n-1)+ΔEV EEV2_Heating

[0111] That is, the opening degree EV of the second valve element 124 in the current cycle EEV2_Heating (n) equals the opening degree EV of the second valve element 124 in the previous cycle. EEV2_Heating (n-1) and increment ΔEV EEV2_Heating The sum; where ΔEV EEV2_Heating It is calculated based on the refrigerant-air outlet superheat change rate and the difference between the refrigerant-air heat exchanger outlet superheat and the refrigerant-air heat exchanger outlet target superheat.

[0112] The following is about the incremental ΔEV EEV2_Heating The calculation process will be introduced as follows:

[0113] In some embodiments of this application:

[0114] in:

[0115] This represents the rate of change of superheat at the outlet of the refrigerant-air heat exchanger with respect to the increment ΔEV. EEV2_Heating The impact of calculations; if the superheat is changing rapidly, the incremental ΔEV can be adjusted using the third heating regulation coefficient m4. EEV2_Heating Adjustments are made, and in some embodiments, the larger the change in superheat (e.g., in absolute value), the larger m4 (in absolute value); wherein, SH r-a,out (n) represents the refrigerant-air heat exchanger outlet superheat for the current cycle, SH r-a,out (n-1) represents the refrigerant-air heat exchanger outlet superheat in the previous cycle, Δt is the time interval of the set cycle, and m4 is the third heating regulation coefficient; n4[SHo r-a,out -SH r-a,out (n)]

[0116] This represents the deviation between the refrigerant-air heat exchanger outlet superheat and the target refrigerant-air heat exchanger outlet superheat as expressed in increments ΔEV. EEV2_Heating The impact of calculations; if the superheat at the outlet of the refrigerant-air heat exchanger deviates significantly from the target superheat of the refrigerant-air heat exchanger 102, the increment can be adjusted using the fourth heating regulation coefficient n4. In some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger n4 (expressed in absolute value); SHo r-a,out n is the target superheat at the outlet of the refrigerant-air heat exchanger, and n4 is the fourth heating regulation coefficient.

[0117] Incremental ΔEV EEV2_Heating The calculation combines the refrigerant-air heat exchanger outlet superheat change rate and the deviation of the refrigerant-air outlet superheat from the target superheat of the refrigerant-air heat exchanger. It comprehensively considers the dynamic response and steady-state error of the heat pump system 10. Through the third heating adjustment coefficient m4 and the fourth heating adjustment coefficient n4, the influence of the refrigerant-air heat exchanger outlet superheat change rate and the deviation of the refrigerant-air heat exchanger outlet superheat from the target superheat of the refrigerant-air heat exchanger 102 on the adjustment process of the second valve element 124 can be flexibly controlled, thereby achieving more accurate control.

[0118] The refrigerant-air heat exchanger outlet superheat is the degree to which the actual temperature of R290 refrigerant exceeds its saturation temperature. The R290 refrigerant temperature T at the outlet of heat exchanger body 104 is detected using a temperature sensor. hex,o and R290 refrigerant pressure P hex,o The saturation temperature T(P) is determined based on the pressure-temperature relationship of R290 refrigerant. hex,o The superheat at the outlet of the refrigerant-air heat exchanger is the difference between the actual temperature and the saturation temperature: SH r-a,out =T hex,o -T(P hex,o )

[0119] In heating mode, the frequency control method of compressor 100 is similar to that in cooling mode. The frequency adjustment coefficient can be generated based on different constants, as shown in Figure 15. In some embodiments, for a heat pump with a heating capacity of 16kW, an ambient temperature of 7°C, a target outlet water temperature of 55°C, the initial compressor 100 frequency is 60Hz.

[0120] In some embodiments of this application, as shown in FIG16, the heat pump system 10 further includes a third valve element 130. The third valve element 130 is disposed between the subcooling pipe and the second heat exchange section 114. The third valve element 130 is used to control the refrigerant flow rate into the subcooling section pipe 106 and to ensure that the temperature of the refrigerant entering the subcooling section pipe 106 reaches the target temperature of the subcooling section pipe 106, so that the heat is just enough to meet the condition of no frosting. In FIG16, the solid line is the high-pressure refrigerant area, the dashed line is the refrigerant area after the first throttling, the double dashed line is the refrigerant area after the second throttling, the dotted-dash line is the low-pressure refrigerant area, and the double dotted-dash line is the water flow path. During heating operation, the low-temperature and low-pressure refrigerant is compressed into a high-temperature and high-pressure refrigerant by the compressor 100, enters the refrigerant-water heat exchanger 116 through the switching valve 126, exchanges heat with water and condenses into a liquid phase, and is throttled into a medium-temperature and medium-pressure refrigerant by the first valve element 122. The medium-temperature, medium-pressure refrigerant further enters the second heat exchange section 114 of the refrigerant-refrigerant heat exchanger 110, where it exchanges heat with the low-temperature, low-pressure refrigerant in the first heat exchange section 112 before entering the compressor 100. After passing through the third valve element 130 for secondary throttling, the refrigerant flow rate into the subcooling section pipeline 106 is adjusted. Then, it passes through the second valve element 124 for further throttling to become low-temperature, low-pressure refrigerant, which enters the heat exchanger body 104 of the refrigerant-air heat exchanger 102. After exchanging heat with the air, it passes through the switching valve 126 and enters the first heat exchange section 112 of the refrigerant-refrigerant heat exchanger 110. After exchanging heat with the medium-temperature, medium-pressure refrigerant in the second heat exchange section 114, the temperature rises, and it enters the compressor 100, improving the suction temperature and oil sump temperature, thus completing the heating cycle.

[0121] In some embodiments of this application, the heating cycle of the heat pump system described above is also applicable to other refrigerants with similar physical properties. Taking R290 refrigerant as an example, Figure 17 compares the pressure-enthalpy diagrams of the heat pump system 10 provided by related technologies and some embodiments of this application. The heating cycle of some embodiments of this application is shown as 1′-2′-3′-4′-5′-6′-7′-8′-9′-1′ in Figure 17. The first valve element 122 controls the heat exchange of R290 refrigerant entering the refrigerant-refrigerant heat exchanger 110 from state 5′ to state 6′, and the third valve element 130 controls the heat exchange of R290 refrigerant entering the subcooled section pipe 106 from state 7′ to state 8′, so that the heat exchange of the refrigerant-refrigerant heat exchanger 110 just meets the requirements of the compressor 100 suction temperature and oil sump temperature, and the heat exchange of the subcooled section pipe 106 just ensures that the bottom of the refrigerant-air heat exchanger 102 does not frost. The temperature variation along the path of R290 refrigerant is shown in Figure 18.

[0122] In some embodiments of this application, in heating mode, the processing device 190 is configured to perform multiple steps as shown in FIG19 to adjust the opening of the third valve element 130.

[0123] Step S501: Obtain the inlet temperature of the subcooled section pipe 106.

[0124] Step S502: Obtain the preset target temperature of the subcooled section pipeline inlet.

[0125] Step S503: Based on the rate of change of the inlet temperature of the subcooled section pipe and the difference between the inlet temperature of the subcooled section pipe and the target inlet temperature of the subcooled section pipe, the opening of the third valve element 130 is adjusted by incremental feedback control to compensate for the deviation of the inlet temperature of the subcooled section pipe relative to the target inlet temperature of the subcooled section pipe.

[0126] In some embodiments of this application, the third valve element 130 is an electronic expansion valve. The processing device 190 adjusts the opening degree of the third valve element 130 using an incremental control method based on the feedback control principle.

[0127] The incremental control of the third valve element 130 in heating mode is represented as: EV EEV3_Heating (n) = EV EEV3_Heating (n-1)+ΔEV EEV3_Heating

[0128] That is, the opening degree EV of the third valve element 130 in the current cycle EEV3_Heating (n) equals the opening degree EV of the third valve element 130 in the previous cycle. EEV3_Heating (n-1) and increment ΔEV EEV3_Heating The sum, where ΔEV EEV3_Heating It is calculated based on the rate of change of the inlet temperature of the subcooled section pipe and the difference between the inlet temperature of the subcooled section pipe and the target inlet temperature of the subcooled section pipe.

[0129] The following is about the incremental ΔEV EEV3_Heating The calculation process will be introduced as follows:

[0130] In some embodiments of this application:

[0131] in:

[0132] This indicates the rate of change of the inlet temperature of the subcooled section pipe with respect to the increment ΔEV. EEV3_Heating The impact of the calculation; if the inlet temperature of the subcooled section pipe changes rapidly, the incremental ΔEV can be adjusted using the first subcooled section adjustment coefficient m5. EEV3_Heating Adjustments are made, and in some embodiments, the larger the change in the inlet temperature of the subcooled section pipe (e.g., expressed in absolute value), the larger the adjustment amount (expressed in absolute value) of the first subcooled section adjustment coefficient m5; wherein, T sc (n) represents the inlet temperature of the subcooled section piping in the current cycle, T. sc(n-1) represents the inlet temperature of the subcooled section pipe in the previous cycle, Δt is the time interval of the set cycle, and m5 is the adjustment coefficient of the first subcooled section; n5[T sc,o -T sc (n)]

[0133] This represents the difference between the inlet temperature of the subcooled section pipe and the target inlet temperature of the subcooled section pipe as expressed in increment ΔEV. EEV3_Heating The impact of the calculation; if the inlet temperature of the subcooled section pipe deviates significantly from the target inlet temperature of the subcooled section pipe, the incremental ΔEV can be adjusted using the second subcooled section adjustment coefficient n5. EEV3_Heating Adjustments are made, and in some embodiments, the larger the deviation (e.g., expressed in absolute value), the larger the adjustment amount (expressed in absolute value) of the second subcooling section adjustment coefficient n5; T sc,o n is the target temperature at the inlet of the subcooled section pipe, and n5 is the adjustment coefficient for the second subcooled section. Increment ΔEV EEV3_Heating The calculation combines the rate of change of the subcooled section pipe inlet temperature and the deviation of the subcooled section pipe inlet temperature from the target temperature of the subcooled section pipe inlet. It comprehensively considers the dynamic response and steady-state error of the heat pump system 10. Through the first subcooled section adjustment coefficient m5 and the second subcooled section adjustment coefficient n5, the influence of the rate of change of the subcooled section pipe inlet temperature and the deviation of the subcooled section pipe inlet temperature from the target temperature of the subcooled section pipe inlet on the adjustment process of the third valve element 130 can be flexibly controlled, thereby achieving more accurate control and ensuring that the opening degree of the third valve element 130 can guarantee that the subcooled section pipe 106 is in the optimal state of critical non-frost.

[0134] In some embodiments of this application, the target temperature T at the inlet of the subcooled section pipe is... sc,o Generated based on ambient temperature. In some embodiments of this application, the target temperature T at the inlet of the subcooled section pipe is... sc,o It rises as the ambient temperature decreases.

[0135] Some embodiments of this application provide a heat pump system 10, which further optimizes the refrigerant-refrigerant heat exchanger based on the above embodiments. As shown in FIG20, the heat pump system 10 includes a first refrigerant-refrigerant heat exchanger 132 and a second refrigerant-refrigerant heat exchanger 142. The first refrigerant-refrigerant heat exchanger 132 and the second refrigerant-refrigerant heat exchanger 142 are used for heat exchange between refrigerants in different states. In some embodiments of this application, the first refrigerant-refrigerant heat exchanger 132 and the second refrigerant-refrigerant heat exchanger 142 can be a plate heat exchanger, a shell-and-tube heat exchanger, a coaxial heat exchanger, a spiral plate heat exchanger, or other optional heat exchanger forms. The first refrigerant-refrigerant heat exchanger 132 includes a first heat exchange section 134 and a second heat exchange section 136. The first heat exchange section 134 is fluidly connected to the suction side of the compressor 100, and the second heat exchange section 136 is fluidly connected to the subcooling section pipeline 106. R290 refrigerant exchanges heat between the first heat exchange section 134 and the second heat exchange section 136. The second refrigerant-refrigerant heat exchanger 142 includes a first heat exchange section 144 and a second heat exchange section 146. The first heat exchange section 144 is fluidly connected to the suction side of the compressor 100, and the second heat exchange section 146 is fluidly connected to the second heat exchange section 136. R290 refrigerant exchanges heat between the first heat exchange section 144 and the second heat exchange section 146. Corresponding to the first refrigerant-refrigerant heat exchanger 132 and the second refrigerant-refrigerant heat exchanger 142, there are also a fourth valve element 138 and a fifth valve element 140. The fifth valve element 140 is disposed between the first heat exchange section 134 and the suction side of the compressor 100, and the fourth valve element 138 is disposed between the first heat exchange section 144 and the suction side of the compressor 100.

[0136] In some embodiments of this application, a third valve element 130 can also be provided in the heat pump system 10, which is located between the subcooled section pipe 106 and the second heat exchange section 136. Through the first refrigerant-refrigerant heat exchanger 132, the second refrigerant-refrigerant heat exchanger 142, the fourth valve element 138, and the fifth valve element 140, the different requirements for the refrigerant-refrigerant heat exchanger area under different ambient temperatures and target outlet water temperatures can be addressed, solving the problem of excessive suction-side pressure loss at low ambient temperatures, and further improving low-temperature operating capabilities and energy efficiency. In some embodiments of this application, the refrigeration cycle of the above-described heat pump system is also applicable to other refrigerants with similar physical properties.

[0137] In some embodiments of this application, the processing device 190 is configured to perform a plurality of steps as shown in FIG21:

[0138] Step S601: Determine whether the ambient temperature meets the preset low-temperature operating conditions;

[0139] Step S602: If the low temperature operating conditions are met, the fourth valve element 138 is closed and the fifth valve element 140 is opened;

[0140] Step S603: If the low temperature operating conditions are not met, the fourth valve element 138 is opened and the fifth valve element 140 is closed.

[0141] At low ambient temperatures and high target outlet water temperatures, the heat exchange requirement for refrigerant-to-refrigerant heat exchangers is relatively small. In this case, only one refrigerant-to-refrigerant heat exchanger is needed to meet the heat exchange requirement. The processing device 190 is configured to close the fourth valve element 138 and open the fifth valve element 140, so that the heat exchange requirement can be met by using only the first refrigerant-to-refrigerant heat exchanger 132. Taking R290 refrigerant as an example, Figure 22 shows the heating cycle under low-temperature operating conditions. In Figure 22, the solid line represents the high-pressure R290 refrigerant region, the dashed line represents the R290 refrigerant region after the first throttling, the double dashed line represents the R290 refrigerant region after the second throttling, the dotted-dashed line represents the low-pressure R290 refrigerant region, the dotted line represents the non-flowing region, and the double dotted-dashed line represents the water flow path. Low-temperature, low-pressure R290 refrigerant is compressed into high-temperature, high-pressure refrigerant by compressor 100, and enters refrigerant-water heat exchanger 116 through switching valve 126, where it exchanges heat with water and condenses into liquid phase; after being throttled by first valve element 122, it becomes medium-temperature, medium-pressure gas-liquid two-phase refrigerant, and passes through second refrigerant-refrigerant heat exchanger 142. At this time, fourth valve element 138 is closed, first heat exchange section 144 is cut off, and second refrigerant-refrigerant heat exchanger 142 does not participate in heat exchange. After passing through the second refrigerant-refrigerant heat exchanger 142, the R290 refrigerant enters the second heat exchange section 136 of the first refrigerant-refrigerant heat exchanger 132, where it exchanges heat with the low-temperature, low-pressure R290 refrigerant in the first heat exchange section 134 before entering the compressor 100. After being throttled a second time by the third valve element 130, it enters the subcooling section pipeline 106 to exchange heat with the air, preventing frost from forming at the bottom of the refrigerant-air heat exchanger. After flowing out of the subcooling section pipeline 106, it is throttled a third time by the second valve element 124 to become a low-temperature, low-pressure refrigerant, which then enters the heat exchanger body 104 to exchange heat with the air. After exchanging heat with the air, it passes through the switching valve 126 into the first heat exchange section 134 of the first refrigerant-refrigerant heat exchanger 132, where it exchanges heat with the medium-temperature, medium-pressure R290 refrigerant in the second heat exchange section 136, raising its temperature. The fifth valve element 140 opens, and the heat-exchanged R290 refrigerant passes through the fifth valve element 140 and directly enters the compressor 100. The second refrigerant-to-refrigerant heat exchanger 142 is bypassed, reducing the pressure loss on the low-pressure side, improving the suction temperature and oil sump temperature, increasing energy efficiency, and completing the heating cycle. When the ambient temperature rises, the heat exchange demand of the refrigerant-to-refrigerant heat exchanger increases. At this time, using only one refrigerant-to-refrigerant heat exchanger cannot meet the heat exchange demand; the handling device is configured to open the fourth valve element 138 and close the fifth valve element 140.

[0142] Figure 23 shows the heating cycle under conditions that do not meet low-temperature operating requirements. In Figure 23, the solid line represents the high-pressure R290 refrigerant region, the dashed line represents the R290 refrigerant region after the first throttling, the double dashed line represents the R290 refrigerant region after the second throttling, the dotted-dash line represents the low-pressure R290 refrigerant region, the dotted line represents the non-flowing region, and the double dotted-dash line represents the water flow path. Low-temperature, low-pressure R290 refrigerant is compressed into high-temperature, high-pressure R290 refrigerant by compressor 100. It then enters refrigerant-water heat exchanger 116 via switching valve 126, where it exchanges heat with water and condenses into a liquid phase. After being throttled by first valve element 122, it becomes a medium-temperature, medium-pressure gas-liquid two-phase refrigerant. It then passes through the second heat exchange section 146 of the second refrigerant-refrigerant heat exchanger 142 and the second heat exchange section 136 of the first refrigerant-refrigerant heat exchanger 132, exchanging heat with the low-temperature, low-pressure R290 refrigerant before it enters compressor 100 in the first heat exchange sections 144 and 134. Finally, after a second throttling by third valve element 130... The refrigerant enters the subcooling section pipe 106, exchanges heat with the air to prevent frost from forming at the bottom of the heat exchanger, and then passes through the second valve element 124 for a third throttling to become low-temperature, low-pressure R290 refrigerant. It then enters the main body of the refrigerant-air heat exchanger, exchanges heat with the air, and then passes through the first heat exchange section 134 of the first refrigerant-refrigerant heat exchanger 132 and the first heat exchange section 144 of the second refrigerant-refrigerant heat exchanger 142 via the switching valve 126. After exchanging heat with the aforementioned medium-temperature, medium-pressure R290 refrigerant, its temperature rises. It then passes through the fourth valve element 138 and enters the compressor 100, improving the suction temperature and oil sump temperature, completing the heating cycle. In some embodiments of this application, the low-temperature operating condition is defined as an ambient temperature lower than a set ambient temperature threshold and an outlet water temperature higher than a set outlet water temperature threshold. When the ambient temperature is no longer lower than the set ambient temperature threshold, the low-temperature operating condition is considered no longer met. In some embodiments of this application, the first valve element 122, the second valve element 124, and the third valve element 130 can all employ the control methods provided in the aforementioned specification. In some embodiments of this application, the above-described heat pump system is also applicable to other refrigerants to improve the energy efficiency of the heat pump system under low-temperature conditions.

[0143] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. Heat pump system, including: A compressor is used to compress refrigerant; Refrigerant-air heat exchangers, including: The heat exchanger body, within which the refrigerant exchanges heat with the air; and The subcooling section piping is fluidly connected to the main body of the heat exchanger; Refrigerant-refrigerant heat exchanger, including: The first heat exchange section is fluidly connected to the suction side of the compressor; The second heat exchange section is fluidly connected to the subcooled section pipeline; In this process, the refrigerant exchanges heat between the first heat exchange section and the second heat exchange section; A refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; A first valve element is disposed between the second heat exchange section and the refrigerant-water heat exchanger; The second valve element is disposed between the heat exchanger body and the subcooled section pipeline; In heating mode, the first valve element throttles the refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the refrigerant flowing out of the subcooled section pipeline.

2. The heat pump system according to claim 1, further comprising: A switching valve, fluidly connected to the compressor, is used to switch the direction of refrigerant flow so that the heat pump system operates in cooling mode; The processing device is configured as follows: In cooling mode, the refrigerant-water heat exchanger outlet superheat is obtained. Obtain the preset target superheat at the outlet of the refrigerant-water heat exchanger; Based on the rate of change of superheat at the outlet of the refrigerant-water heat exchanger, and the difference between the target superheat at the outlet of the refrigerant-water heat exchanger and the superheat at the outlet of the refrigerant-water heat exchanger, the opening of the first valve element is adjusted through incremental feedback control to compensate for the deviation of the superheat at the outlet of the refrigerant-water heat exchanger from the target superheat at the outlet of the refrigerant-water heat exchanger.

3. The heat pump system according to claim 1, A switching valve, fluidly connected to the compressor, is used to switch the direction of refrigerant flow so that the heat pump system operates in cooling mode; The processing device is configured as follows: In cooling mode, the refrigerant-refrigerant heat exchanger outlet superheat at the outlet of the first heat exchange section is obtained; Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger; Based on the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger, and the difference between the target superheat at the outlet of the refrigerant-refrigerant heat exchanger and the superheat at the outlet of the refrigerant-refrigerant heat exchanger, the opening of the second valve element is adjusted by incremental feedback control to compensate for the deviation of the superheat at the outlet of the refrigerant-refrigerant heat exchanger from the target superheat at the outlet of the refrigerant-refrigerant heat exchanger. in, The opening degree of the second valve element is greater than that of the first valve element.

4. The heat pump system according to claim 1, further comprising: The processing device is configured as follows: In heating mode, the refrigerant-refrigerant heat exchanger outlet superheat at the outlet of the first heat exchange section is obtained; Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger; Based on the rate of change of superheat at the outlet of the refrigerant-refrigerant heat exchanger, and the difference between the target superheat at the outlet of the refrigerant-refrigerant heat exchanger and the superheat at the outlet of the refrigerant-refrigerant heat exchanger, the opening of the first valve element is adjusted through incremental feedback control to compensate for the deviation of the superheat at the outlet of the refrigerant-refrigerant heat exchanger from the target superheat at the outlet of the refrigerant-refrigerant heat exchanger.

5. The heat pump system according to claim 1, further comprising: The processing device is configured as follows: In heating mode, the refrigerant-air heat exchanger outlet superheat is obtained at the outlet of the heat exchanger body. Obtain the preset target superheat at the outlet of the refrigerant-air heat exchanger; Based on the rate of change of superheat at the outlet of the refrigerant-air heat exchanger, and the difference between the superheat at the outlet of the refrigerant-air heat exchanger and the target superheat at the outlet of the refrigerant-air heat exchanger, the opening of the second valve element is adjusted through incremental feedback control to compensate for the deviation of the superheat at the outlet of the refrigerant-air heat exchanger from the target superheat at the outlet of the refrigerant-air heat exchanger.

6. The heat pump system according to any one of claims 1 to 5, further comprising: The third valve element is disposed between the subcooled section pipeline and the second heat exchange section; The processing device is configured as follows: Obtain the inlet temperature of the subcooled section pipe at the inlet; Obtain the preset target temperature at the inlet of the subcooled section pipeline; Based on the rate of change of the subcooled section pipe inlet temperature and the difference between the subcooled section pipe inlet temperature and the target subcooled section pipe inlet temperature, the opening of the third valve element is adjusted through incremental feedback control to compensate for the deviation of the subcooled section pipe inlet temperature from the target subcooled section pipe inlet temperature.

7. The heat pump system according to claim 6, wherein, The target temperature at the inlet of the subcooled section pipeline is generated based on the ambient temperature.

8. Heat pump systems, including: A compressor is used to compress refrigerant; Refrigerant-air heat exchangers, including: The heat exchanger body is in which the refrigerant exchanges heat with the air; The subcooling section piping is fluidly connected to the main body of the heat exchanger; A refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; The first refrigerant-refrigerant heat exchanger includes: The first heat exchange section is fluidly connected to the suction side of the compressor; The second heat exchange section is fluidly connected to the subcooling section piping; The refrigerant exchanges heat between the first heat exchange section and the second heat exchange section. The second refrigerant-refrigerant heat exchanger includes: The first heat exchange section is fluidly connected to the suction side of the compressor and the first heat exchange section; The second heat exchange section is fluidly connected to the second heat exchange section; The refrigerant exchanges heat between the first heat exchange section and the second heat exchange section. A first valve element is disposed between the second heat exchange section and the refrigerant-water heat exchanger; The second valve element is disposed between the heat exchanger body and the subcooled section pipeline; The fourth valve element is disposed between the first heat exchange section and the suction side of the compressor; The fifth valve element is disposed between the first heat exchange section and the suction side of the compressor; In heating mode, the first valve element throttles the refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the refrigerant flowing out of the subcooled section pipeline; one of the fourth valve element and the fifth valve element is open, and the other is closed.

9. The heat pump system according to claim 8, further comprising: A third valve element is disposed between the subcooled section pipeline and the second heat exchange section to regulate the temperature of the refrigerant entering the subcooled section pipeline in heating mode.

10. The heat pump system according to claim 8 or 9, wherein, When the ambient temperature meets the preset low-temperature operating conditions, the fourth valve element is closed and the fifth valve element is open; when the ambient temperature does not meet the preset low-temperature operating conditions, the fourth valve element is open and the fifth valve element is closed.

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