Heat pump system

Abstract

The utility model provides a heat pump system. The heat pump system comprises a compressor for compressing an R290 refrigerant; a refrigerant-air heat exchanger includes: a heat exchanger body; the supercooling section pipeline is in fluid connection with the heat exchanger main body; a refrigerant-refrigerant heat exchanger including: a first heat exchange portion fluidly connected to a suction side of the compressor; the second heat exchange part is in fluid connection with the supercooling section pipeline; a refrigerant exchanges heat between the first heat exchange part and the second heat exchange part; a refrigerant-water heat exchanger in which the refrigerant exchanges heat with water; the first valve element is arranged between the second heat exchange part and the refrigerant-water heat exchanger; and the second valve element is arranged between the heat exchanger main body and the supercooling section pipeline. The energy efficiency of the heat pump system under the R290 low-temperature working condition is improved, the oil temperature is increased, and frosting is avoided.

Description

Technical Field

[0001] This utility model relates to the field of heat pump equipment technology, and in particular to a heat pump system. Background Technology

[0002] The use of R290 refrigerant is becoming the main trend in the future development of heat pumps due to its excellent environmental protection characteristics.

[0003] The most common type of heat pump for residential use is the air source heat pump. Air source heat pump systems using R290 have the following problems:

[0004] First, heat pumps have low energy efficiency, especially when the ambient temperature is low, resulting in poor heating capacity; they do not have an advantage compared to traditional heating systems that use fossil fuels.

[0005] Secondly, R290 refrigerant has low saturation pressure, low isentropic adiabatic index, and low suction and discharge superheat under operating conditions; when operating at low ambient temperatures, the oil viscosity in the oil sump is too low, and reliability cannot be guaranteed.

[0006] Third, under low ambient temperature conditions, after defrosting, water accumulates at the bottom of the heat exchanger, causing ice to form at the bottom of the heat exchanger and affecting its heating capacity.

[0007] To address the first problem, existing technologies typically employ auxiliary electric heating or vapor injection enthalpy enhancement. Auxiliary electric heating increases the power consumption of the heat pump system, reduces energy efficiency, and fails to provide energy-saving advantages. Vapor injection enthalpy enhancement technology requires the use of a supplementary gas compressor. Furthermore, under low ambient temperature conditions, the compressor suction temperature and compressor oil sump temperature are both low, resulting in poor compressor lubrication and a shortened lifespan.

[0008] To address the second problem, existing technologies typically employ the addition of a regenerator or six-pulse electromagnetic heating. However, in operating conditions where regeneration is not required, the regenerator actually reduces the energy efficiency of the heat pump system; and six-pulse electromagnetic heating cannot solve the reliability problem of excessively low oil tank temperature under all operating conditions.

[0009] To address the third issue, existing technologies typically employ either chassis electric heating or subcooling section heating. Chassis electric heating, however, increases the power consumption of the heat pump system and reduces its energy efficiency. Subcooling section heating, on the other hand, requires strict control of the subcooling section's heat output, potentially leading to excessive heat exchange with the upper part of the heat exchanger, which negatively impacts the unit's capacity and energy efficiency.

[0010] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Utility Model Content

[0011] The first aspect of this application provides a heat pump system, comprising:

[0012] The compressor is used to compress R290 refrigerant;

[0013] Refrigerant-air heat exchangers, which include:

[0014] The heat exchanger body, within which R290 refrigerant exchanges heat with air; and

[0015] The subcooling section piping is fluidly connected to the main body of the heat exchanger;

[0016] Refrigerant-refrigerant heat exchanger, which includes:

[0017] The first heat exchange section is fluidly connected to the suction side of the compressor;

[0018] The second heat exchange section is fluidly connected to the subcooled section pipeline;

[0019] R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section;

[0020] A refrigerant-water heat exchanger in which R290 refrigerant exchanges heat with water;

[0021] Also includes:

[0022] A first valve element is disposed between the second heat exchange section and the refrigerant-water heat exchanger;

[0023] The second valve element is disposed between the heat exchanger body and the subcooled section pipeline.

[0024] In some embodiments of this application, in heating mode, the first valve element throttles the R290 refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the R290 refrigerant flowing out of the subcooled section pipeline.

[0025] In some embodiments of this application, the heat pump system further includes a switching valve, which is fluidly connected to the compressor, for switching the flow direction of R290 refrigerant so that the heat pump system operates in cooling mode.

[0026] In some embodiments of this application, the heat pump system further includes: a third valve element disposed between the subcooled section pipe and the second heat exchange section;

[0027] In another aspect of this application, a heat pump system is provided, comprising:

[0028] The compressor is used to compress R290 refrigerant;

[0029] Refrigerant-air heat exchangers, which include:

[0030] The heat exchanger body is in which R290 refrigerant exchanges heat with air.

[0031] The subcooling section piping is fluidly connected to the main body of the heat exchanger;

[0032] A refrigerant-water heat exchanger in which R290 refrigerant exchanges heat with water;

[0033] The first refrigerant-refrigerant heat exchanger includes:

[0034] The first heat exchange section is fluidly connected to the suction side of the compressor;

[0035] The second heat exchange section is fluidly connected to the subcooling section piping.

[0036] R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section;

[0037] The second refrigerant-refrigerant heat exchanger includes:

[0038] A first heat exchange section is fluidly connected to the suction side of the compressor and the first heat exchange section;

[0039] The second heat exchange section is fluidly connected to the second heat exchange section;

[0040] R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section;

[0041] Its characteristic is that it further includes:

[0042] A first valve element is disposed between the second heat exchange section and the refrigerant-water heat exchanger;

[0043] The second valve element is disposed between the heat exchanger body and the subcooled section pipeline.

[0044] In some embodiments, the heat pump system further includes a third valve element disposed between the subcooling section pipe and the second heat exchange section to regulate the temperature of the R290 refrigerant entering the subcooling section pipe in heating mode.

[0045] In some embodiments, the heat pump system further includes a fourth valve element disposed between the first heat exchange section and the suction side of the compressor;

[0046] The fifth valve element is located between the first heat exchange section and the suction side of the compressor.

[0047] In some embodiments, the heat pump system further includes: in heating mode, the first valve element throttles the R290 refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the R290 refrigerant flowing out of the subcooled section pipe; one of the fourth valve element and the fifth valve element is open, and the other is closed.

[0048] In some embodiments, the heat pump system further includes: when the ambient temperature meets a preset low-temperature operating condition, the fourth valve element is closed and the fifth valve element is opened; when the ambient temperature does not meet the preset low-temperature operating condition, the fourth valve element is opened and the fifth valve element is closed. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of a heat pump system provided in some embodiments of the present invention;

[0051] Figure 2 This is a schematic diagram of the refrigeration cycle of a heat pump system provided in some embodiments of the present invention;

[0052] Figure 3 A schematic diagram of the refrigeration cycle in a traditional heat pump system;

[0053] Figure 4 A comparative example of pressure-enthalpy diagrams under the control mode of a heat pump system provided in some embodiments of this utility model and a conventional heat pump system;

[0054] Figure 5 This is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of the present invention;

[0055] Figure 6 A schematic diagram of the refrigeration cycle in a traditional heat pump system;

[0056] Figure 7 A comparative example of pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this utility model;

[0057] Figure 8 A comparative example of pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this utility model;

[0058] Figure 9 This is a schematic diagram showing the temperature variation of R290 refrigerant along the path.

[0059] Figure 10 and Figure 11 A flowchart of the heat pump system processing device in cooling mode provided in some embodiments of this utility model;

[0060] Figure 12 This is an example of an initial compressor target frequency variation curve for a heat pump system provided in some embodiments of the present invention;

[0061] Figure 13 and Figure 14 A flowchart of the heat pump system processing device in heating mode provided in some embodiments of this utility model;

[0062] Figure 15 This is an example of an initial compressor target frequency variation curve for a heat pump system provided in some embodiments of the present invention;

[0063] Figure 16 This is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of the present invention;

[0064] Figure 17 A comparative example of pressure-enthalpy diagrams of a heat pump system and a conventional heat pump system under heating mode provided in some embodiments of this utility model;

[0065] Figure 18 This is a schematic diagram showing the temperature variation of R290 refrigerant along the path.

[0066] Figure 19 A flowchart of the heat pump system processing device in heating mode provided in some embodiments of this utility model;

[0067] Figure 20 This is a schematic diagram of the structure of a heat pump system provided in some embodiments of the present invention;

[0068] Figure 21 A flowchart of the heat pump system processing device in cooling mode provided in some embodiments of this utility model;

[0069] Figure 22 This is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of the present invention;

[0070] Figure 23 This is a schematic diagram of the heating cycle of a heat pump system provided in some embodiments of the present invention;

[0071] 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;

[0072] 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;

[0073] 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

[0074] The technical solutions of the 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.

[0075] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0076] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0077] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0078] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0079] The following disclosure provides many different embodiments or examples for implementing various structures of this invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0080] Heat pump systems are highly efficient heat transfer devices capable of providing heating or cooling under various 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 residential sector, the most common type of heat pump system is the air-source heat pump system. Air-source heat pump systems extract heat from the air for heating or cooling, representing a highly efficient and environmentally friendly energy utilization method.

[0081] Heat pump systems can use a variety of refrigerants. In recent years, R290 (propane) refrigerant has received increasing attention in the heat pump field. R290 is a natural refrigerant with extremely low global warming potential. Using R290 refrigerant can significantly reduce environmental impact and meet the requirements of sustainable development. However, at low ambient temperatures, the energy efficiency of air-source heat pump systems using R290 refrigerant is significantly lower. Specifically, under the same temperature conditions, R290 refrigerant has a lower critical temperature and lower critical pressure. Therefore, when operating at low temperatures and low pressures, R290 refrigerant easily enters a higher compression range and easily reaches saturation at high pressures. Furthermore, the usable gas and liquid phase ranges are relatively small, requiring a larger compressor power to achieve the same cooling (heating) effect. In addition, R290 refrigerant has a low saturation pressure and a low isentropic adiabatic index during operation. A lower isentropic adiabatic index indicates a significant energy loss during compression of the R290 refrigerant gas, 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.

[0082] To address the aforementioned problems, the first aspect of this application provides a heat pump system.

[0083] From a thermodynamic perspective, the refrigeration cycle of a heat pump system includes an evaporator, compressor, condenser, and throttling device connected in sequence. The refrigeration cycle involves a series of processes, including compression, condensation, expansion, and evaporation, to cool or heat indoor spaces or to heat domestic water.

[0084] 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 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.

[0085] The throttling device causes the high-temperature, high-pressure liquid refrigerant that condenses in the condenser to expand into a low-pressure liquid refrigerant. The evaporator evaporates the refrigerant that has expanded in the throttling device, returning the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves its cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled.

[0086] From a hardware architecture perspective, with reference to the accompanying drawings, some embodiments of the heat pump system provided in this application are described.

[0087] Figure 1This 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 R290 refrigerant, compressing the R290 refrigerant from a low-pressure state to a high-pressure state, so that the R290 refrigerant can effectively transfer heat in the refrigeration cycle.

[0088] The refrigerant-air heat exchanger 102 is used for heat exchange between R290 refrigerant and air. The refrigerant-air heat exchanger 102 includes a heat exchanger body 104 and a subcooling section pipe 106. R290 refrigerant exchanges heat with air within the heat exchanger body 104. Heat exchanger pipes are installed within the heat exchanger body 104, through which R290 refrigerant flows, and air flows on the surface of the heat exchanger body 104 via a fan 108 or natural convection. The subcooling section pipe 106 is fluidly connected to the heat exchanger body 104 and is mainly used to improve the efficiency of the heat pump system 10. The specific working principle of the subcooling section pipe 106 will be described in detail below.

[0089] The refrigerant-to-refrigerant heat exchanger 110 is used for heat exchange between R290 refrigerant 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 pipe 106. The R290 refrigerant exchanges heat 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 R290 refrigerant returns from the evaporator and enters the compressor 100. On the suction side, the R290 refrigerant is typically in a low-pressure and low-temperature state.

[0090] In some embodiments of this application, the refrigerant-refrigerant heat exchanger 110 may 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.

[0091] The refrigerant-water heat exchanger 116 facilitates heat exchange between R290 refrigerant and water, transferring heat from the R290 refrigerant to the water, thus raising or lowering the water temperature. The heated water can be used in underfloor heating, radiator heating, and other heating systems to provide hot water circulation, or in domestic hot water supply systems to provide hot water; the cooled water can be used to provide cooling water circulation for indoor cooling. The water circuit includes components such as a flow meter 120 and a water pump 118 to maintain normal operation; further limitations on the water circuit design are not provided here.

[0092] The heat pump system 10 also 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.

[0093] In some embodiments of this application, the first valve element 122 is an electronic expansion valve.

[0094] In some embodiments of this application, the second valve element 124 is an electronic expansion valve.

[0095] In heating mode, the first valve element 122 throttles the R290 refrigerant flowing out of the refrigerant-water heat exchanger 116, and the second valve element 124 throttles the R290 refrigerant flowing out of the subcooling section pipe 106.

[0096] The heat pump system 10 also 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 operating mode is switched by changing the flow direction of the R290 refrigerant.

[0097] 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 R290 refrigerant can be changed.

[0098] The heat pump system 10 also includes a liquid receiver 128, which is located 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 R290 refrigerant, and plays a buffering and stabilizing role.

[0099] Reference Figure 2 The cooling mode of the heat pump system 10 will be introduced.

[0100] Low-temperature, low-pressure R290 refrigerant is compressed into a high-temperature, high-pressure refrigerant by compressor 100, and then enters the refrigerant-air heat exchanger 102 through switching valve 126. The refrigerant-air heat exchanger 102 acts as a condenser, where the R290 refrigerant condenses into a liquid phase through heat exchange. After being throttled by the second valve element 124, it becomes medium-temperature, medium-pressure R290 refrigerant. After passing through the subcooling section pipe 106, it enters the second heat exchange section 114 of the refrigerant-refrigerant heat exchanger 110, where it exchanges heat with the low-temperature, low-pressure R290 refrigerant that entered the compressor 100 in the first heat exchange section 112. The heat-exchanged R290 refrigerant flows out from the second heat exchange section 114 and is throttled into a low-temperature, low-pressure R290 refrigerant by the first valve element 122. The low-temperature, low-pressure R290 refrigerant further enters the refrigerant-water heat exchanger 116. The refrigerant-water heat exchanger 116 is used as an evaporator. The R290 refrigerant entering the refrigerant-water heat exchanger 116 exchanges heat with the water to form a gas phase. After passing through the switching valve 126, the first heat exchange section 112 of the refrigerant-refrigerant heat exchanger 110 enters the compressor 100 to complete the refrigeration cycle.

[0101] Figure 2 In the diagram, 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.

[0102] Figure 3 This diagram illustrates the refrigeration cycle in a traditional heat pump system under refrigeration mode 10. Solid lines represent the high-pressure refrigerant region, dashed lines represent the low-pressure refrigerant region, and double-dotted lines represent the water flow path. The low-temperature, low-pressure refrigerant is compressed into a high-temperature, high-pressure refrigerant by compressor 201. It then passes through a four-way reversing valve 202 and enters the refrigerant-air heat exchanger 203, where it exchanges heat with air 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 then enters the refrigerant-water heat exchanger 204 and exchanges heat with water to become a gaseous refrigerant. Finally, it passes through the four-way reversing valve 202 and enters compressor 201, completing the refrigeration cycle.

[0103] Figure 4 A comparison of the pressure-enthalpy diagrams of the conventional scheme and the heat pump system 10 provided in this application is shown. The refrigeration cycle of the conventional scheme is shown in Figure 1-2-3-4-1, with a refrigeration capacity of h1-h4 per unit mass of R290 refrigerant. The refrigeration cycle of the heat pump system 10 provided in this application is shown in Figure 1′-2′-3′-4′-5′-6′-7′-8′-1′, with a refrigeration capacity of h1-h8 per unit mass of R290 refrigerant. Compared with the refrigeration mode of the conventional heat pump system 10, under the condition of using R290 refrigerant, to achieve the same capacity, the compressor 100 of the heat pump system 10 provided in this embodiment has a lower frequency, lower condensing pressure, and improved energy efficiency.

[0104] Reference Figure 5 The heating mode of the heat pump system 10 will be introduced.

[0105] Low-temperature, low-pressure R290 refrigerant is compressed by compressor 100 into high-temperature, high-pressure R290 refrigerant, which then enters refrigerant-water heat exchanger 116 via switching valve 126. Refrigerant-water heat exchanger 116 acts as a condenser, where R290 refrigerant condenses into a liquid phase through heat exchange. This liquid phase is then throttled by first valve element 122 to become medium-temperature, medium-pressure R290 refrigerant. This medium-temperature, medium-pressure R290 refrigerant further 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. After heat exchange, the R290 refrigerant flows out of the second heat exchange section 114 and enters subcooling section pipe 106 to exchange heat with air. The R290 refrigerant entering subcooling section pipe 106 prevents frost formation at the bottom of the heat exchanger. The R290 refrigerant flowing from the subcooling section pipe 106 is further throttled by the second valve element 124 to become a low-temperature, low-pressure R290 refrigerant. It then enters the heat exchanger body 104 of the refrigerant-air heat exchanger 102, where it exchanges heat with the air. After passing through the switching valve 126, it enters the first heat exchange section 112 of the refrigerant-refrigerant heat exchanger 110. There, it exchanges heat with the medium-temperature, medium-pressure R290 refrigerant in the second heat exchange section 114, resulting in a temperature increase before entering 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.

[0106] Figure 5 In the diagram, 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.

[0107] Figure 6 This is the refrigeration cycle in a traditional heat pump system's heating mode. Solid lines represent the high-pressure refrigerant region, dashed lines represent the low-pressure refrigerant region, and double-dotted lines represent the water flow path. The low-temperature, low-pressure refrigerant is compressed into a high-temperature, high-pressure refrigerant by compressor 201. It then passes through a four-way reversing valve 202 into the refrigerant-water heat exchanger 204, where it exchanges heat with water and condenses into a liquid refrigerant. This liquid refrigerant then passes through a throttling element 205, becoming a low-temperature, low-pressure gas-liquid two-phase refrigerant. It then enters the refrigerant-air heat exchanger 203, exchanges heat with air, and then passes through the four-way reversing valve 202 back into compressor 201, completing the heating cycle. An electric heater 206 prevents frost buildup at the bottom of the heat exchanger.

[0108] Figure 7 A comparison of the pressure-enthalpy diagrams of the conventional scheme and the heat pump system provided in this application is presented. The heating cycle of the conventional scheme is as follows: Figure 7As shown in Figure 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 with a low oil sump temperature. When compressed by compressor 201, the compressor performs wet compression, resulting in poor reliability. The heating capacity per unit mass of refrigerant is h2-h3, indicating 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 the traditional design also uses the heat exchanger body and subcooling section piping design, the refrigeration cycle would be as follows: Figure 7 In the circuit 1-2-3-5-6-1, the refrigerant level in the subcooled section of the piping changes from 3 to 5, resulting in excessive heat dissipation.

[0109] The heating cycle of the heat pump system 10 provided in this embodiment is as follows: Figure 7 As shown in Figures 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 traditional heat pump systems, under the condition of using R290 refrigerant, when achieving the same capacity, the compressor 100 frequency of the heat pump system 10 provided in this embodiment is reduced, and the energy efficiency is improved; in the subcooled section pipe 106, the R290 refrigerant changes from state 5′ to state 6′, and the heat dissipation meets the requirement of no frosting while reducing heat loss.

[0110] Figure 8 A comparison of the pressure-enthalpy diagrams of the traditional scheme and the heat pump system provided in this application is presented. Under low ambient temperature conditions, the exhaust temperature is prone to overheating (exceeding the normal or design temperature range). Taking the traditional scheme's refrigerant-air heat exchanger, which also uses a heat exchanger body and subcooled section piping, and employs 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 exhaust temperature limitations, the heat exchange capacity of the refrigerant-to-refrigerant heat exchanger is relatively small, and the heat exchange capacity 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.

[0111] The heat pump system provided in this embodiment operates under low ambient temperature conditions. The heating cycle is shown in Figure 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 subcooled 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 subcooled section pipe 106, the refrigerant changes from state 6′ to state 7′, ensuring that the bottom of the refrigerant-air heat exchanger 102 does not frost while reducing heat loss.

[0112] In traditional heat pump systems, even with the addition of a subcooling section, the refrigerant, after passing through the refrigerant-water heat exchanger, becomes a high-temperature, high-pressure refrigerant. This high-temperature, high-pressure refrigerant directly enters the subcooling section piping, resulting in a high enthalpy and a significant temperature difference between the refrigerant and the refrigerant within the heat exchanger body. This further leads to a higher refrigerant temperature in the refrigerant-air heat exchanger, degrading its heat exchange performance. Although a refrigerant-to-refrigerant heat exchanger is designed, it is difficult to control the compressor suction temperature at the optimal suction temperature, resulting in low energy efficiency and poor reliability.

[0113] The heat pump system 10 provided in this application, in heating mode, controls the heat entering the refrigerant-refrigerant heat exchanger 110 and the subcooled section pipe 106 through the first valve element 122. Part of the heat is consumed in the refrigerant-refrigerant heat exchanger 110, and only the remaining heat ensures 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 pipe 106. The temperature variation of R290 refrigerant along the pipe is as follows: Figure 9 As shown.

[0114] The opening control of the first valve element 122 and the second valve element 124 will be further explained below.

[0115] The first valve element 122 and the second valve element 124 mentioned below are both electronic expansion valves.

[0116] The heat pump system 10 also includes a processing unit (not shown).

[0117] The processing unit is used to monitor and regulate the operating status of the heat pump system 10, ensuring its efficient, stable, and safe operation. The processing unit includes components such as a processor, volatile memory, non-volatile memory, a display device, an operating device, a communication interface, and a drive device, all 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 optically, electrically, or magnetically, such as CD-ROMs, floppy disks, and optical disks. The storage medium can also be semiconductor memory that records information electrically, such as ROM or flash memory.

[0118] The processing device can be the controller of the heat pump system 10 itself, such as an on-board system based on a microprocessor.

[0119] The processing device can also be a host computer or a cloud server, or other smart mobile terminals.

[0120] The processing device is communicatively connected to 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, optical fiber, power line, serial cable, etc.), wireless signals, LTE, and 5G.

[0121] In some embodiments of this application, in cooling mode, the processing device is configured to perform, as Figure 10 The steps shown are for adjusting the opening of the first valve element 122.

[0122] Step S101: Obtain the refrigerant-water heat exchanger outlet superheat at the outlet of refrigerant-water heat exchanger 116;

[0123] Step S102: Obtain the preset target superheat at the outlet of the refrigerant-water heat exchanger;

[0124] 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, adjust the opening of the first valve element 122 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.

[0125] The processing device is based on the feedback control principle and uses incremental control to adjust the opening of the first valve element 122. Incremental control involves calculating the increment of the 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.

[0126] In the cooling mode, the incremental control of the first valve element 122 is expressed as follows:

[0127] EV EEV1_Cooling (n) = EV EEV1_Cooling (n-1)+ΔEV EEV1_Cooling

[0128] 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.

[0129] The following is about the incremental ΔEV EEV1_Cooling The calculation process will be introduced as follows:

[0130] In some embodiments of this application:

[0131]

[0132] in:

[0133]

[0134] 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 impact of calculations; if the superheat is changing rapidly, the incremental ΔEV can be adjusted using the first refrigeration regulation coefficient m1. EEV1_Cooling Adjustments are made, for example, the larger the change in superheat (e.g., expressed in absolute value), the larger m1 is; where 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 represents the time interval of the set cycle, and m1 represents the first refrigeration regulation coefficient.

[0135] n1[SHo r-w，out -SH r-w，out (n)]

[0136] 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; for example, the larger the deviation (e.g., expressed in absolute value), the larger n1 becomes; 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.

[0137] 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 precise 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.

[0138] The superheat at the outlet of the refrigerant-water heat exchanger is the degree to which the actual temperature of R290 refrigerant exceeds its saturation temperature. The temperature T of the R290 refrigerant at outlet 116 of the refrigerant-water heat exchanger is detected using a temperature sensor. g and R290 refrigerant pressure P g The saturation temperature T(P) is determined based on the pressure-temperature relationship of R290 refrigerant. g The superheat at the outlet of the refrigerant-water heat exchanger is the difference between the actual temperature and the saturation temperature.

[0139] SH r-w，out =T g -T(P g )

[0140] In some embodiments of this application, in cooling mode, the processing device is configured to perform, as Figure 11 The steps shown are for adjusting the opening of the second valve element 124.

[0141] Step S201: Obtain the superheat of the refrigerant-refrigerant heat exchanger 110 outlet at the outlet of the first heat exchange section 112.

[0142] Step S202: Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger 110.

[0143] 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, adjust the opening of the second valve element 124 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.

[0144] The processing device is based on the feedback control principle and uses incremental control to adjust the opening degree of the second valve element 124.

[0145] The incremental control of the second valve element 124 in refrigeration mode is represented as follows:

[0146] EV EEV2_Cooling (n) = EV EEV2_Cooling (n-1)+ΔEV EEV2_Cooling

[0147] 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.

[0148] The following is about the incremental ΔEV EEV2_Cooling The calculation process will be introduced as follows:

[0149] In some embodiments of this application:

[0150]

[0151] in:

[0152]

[0153] 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, for example, the larger the change in superheat (e.g., expressed in absolute value), the larger m2; where SH r-r，out (n) represents the current cycle refrigerant-refrigerant heat exchanger 110 outlet superheat, SH r-r，out(n-1) represents the superheat at the outlet of the refrigerant-refrigerant heat exchanger 110 in the previous cycle, Δt represents the time interval of the set cycle, and m2 represents the third refrigeration regulation coefficient.

[0154] n2[SHo r-r，out -SH r-r，out (n)]

[0155] 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 the calculation; 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. For example, the larger the deviation (e.g., expressed in absolute value), the larger n2. 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.

[0156] Incremental ΔEV EEV2_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 the refrigerant-water heat exchanger 116. 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 refrigerant-water heat exchanger outlet superheat change rate and the deviation of the refrigerant-water heat exchanger outlet superheat from the target superheat of the refrigerant-water heat exchanger 116 on the adjustment process of the second valve element 124 can be flexibly controlled, thereby achieving more precise control.

[0157] 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.

[0158] 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-refrigerant heat exchanger 110 is the difference between the actual temperature and the saturation temperature.

[0159] SH r-r，out =T reg,o -T(P reg，o)

[0160] In cooling mode, the compressor operates at a frequency of 100 Hz. O The following control methods are preferred:

[0161] Set the initial compressor target frequency Ho(0) to 100. The initial compressor target frequency Ho(0) satisfies:

[0162] H o (0)=f(q,T w，i T w，o )=a1[q(T w，i -T w，o )]

[0163] Where q is the water flow rate and a1 is the frequency adjustment coefficient.

[0164] 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 outlet water temperature increases, the initial compressor 100 target frequency Ho(0) decreases.

[0165] For the same outlet water temperature, the frequency adjustment coefficient a1 can be expressed as:

[0166] a1=f(T a )=b1×T a +c1

[0167] Where b1 and c1 are constants, b1>0, c1>0.

[0168] An exemplary variation curve of the initial compressor's target frequency Ho(0) is shown below. Figure 12 As shown, the heat pump has a cooling capacity of 14kW, an ambient temperature of 35℃, an outlet water temperature of 18℃, and an initial compressor target frequency Ho(0) of 45Hz.

[0169] Based on feedback from the outlet water temperature, the treatment device uses incremental control to adjust the operating frequency Ho(n) of the compressor 100.

[0170] The incremental control method for the operating frequency Ho(n) of compressor 100 is expressed as follows:

[0171] Ho(n)=Ho(n-1)+ΔHo

[0172] 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.

[0173] The following describes the calculation process for the increment ΔHo:

[0174] In some embodiments of this application:

[0175]

[0176] in:

[0177]

[0178] 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. For example, the larger the change in outlet water temperature (e.g., expressed in absolute value), the larger x1 becomes. Where T... w,o (n) represents the real-time outlet water temperature during the current temperature sampling period, T w，o (n-1) is the real-time outlet water temperature of the previous temperature sampling period, Δt1 is the time interval of the set temperature sampling period, and x1 is the first frequency modulation coefficient.

[0179] y1[To-T w，o (n)]

[0180] 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. For example, the larger the deviation (e.g., expressed in absolute value), the larger y1 is; To is the target outlet water temperature, and y1 is the second frequency modulation coefficient.

[0181] In some embodiments of this application, in heating mode, the processing device is configured to perform, as Figure 13 The steps shown are for adjusting the opening of the first valve element 122.

[0182] Step S301: Obtain the refrigerant-refrigerant heat exchanger outlet superheat at the outlet of the first heat exchange section 112.

[0183] Step S302: Obtain the preset target superheat at the outlet of the refrigerant-refrigerant heat exchanger.

[0184] Step S303: 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, adjust the opening of the first valve element 122 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.

[0185] The processing device is based on the feedback control principle and uses incremental control to adjust the opening degree of the first valve element 122.

[0186] Incremental control of the first valve element 122 in heating mode is represented as follows:

[0187] EV EEV1_Heating (n) = EV EEV1_Heating (n-1)+ΔEV EEV1_Heating

[0188] 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 target superheat at the outlet of the refrigerant-refrigerant heat exchanger.

[0189] The following is about the incremental ΔEV EEV1_Heating The calculation process will be introduced as follows:

[0190] In some embodiments of this application:

[0191]

[0192] in:

[0193]

[0194] 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, for example, the larger the change in superheat (e.g., expressed in absolute value), the larger the m3; where 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 represents the time interval of the set cycle, and m3 represents the first heating regulation coefficient.

[0195] n3[SHo r-r，out -SH r-r，out (n)]

[0196] 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_HeatingAdjustments are made; for example, the larger the deviation (e.g., expressed in absolute value), the larger n3 becomes; 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.

[0197] Incremental ΔEV EEV1_Heating The 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 precise 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.

[0198] 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 refrigerant-to-refrigerant heat exchanger outlet superheat is the difference between the actual temperature and the saturation temperature.

[0199] SH r-r，out =T reg，o -T(P reg，o )

[0200] 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.

[0201] In some other embodiments of this application, the cooling regulation coefficient and the heating regulation coefficient can also be selected according to actual needs.

[0202] In some embodiments of this application, in heating mode, the processing device is configured to perform, as Figure 14 The steps shown are for adjusting the opening of the second valve element 124.

[0203] Step S401: Obtain the refrigerant-air heat exchanger outlet superheat at the outlet of the heat exchanger body 104.

[0204] Step S402: Obtain the preset target superheat at the outlet of the refrigerant-air heat exchanger.

[0205] 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, adjust the opening of the second valve element 124 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.

[0206] The processing device is based on the feedback control principle and uses incremental control to adjust the opening of the second valve element 124.

[0207] The incremental control of the second valve element 124 in heating mode is represented as follows:

[0208] EV EEV2_Heating (n) = EV EEV2_Heating (n-1)+ΔEV EEV2_Heating

[0209] 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.

[0210] The following is about the incremental ΔEV EEV2_Heating The calculation process will be introduced as follows:

[0211] In some embodiments of this application:

[0212]

[0213] in:

[0214]

[0215] 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, for example, the larger the change in superheat (e.g., expressed in absolute value), the larger m4; where SH r-a，out (n) represents the refrigerant-air heat exchanger outlet superheat for the current cycle, SHr-a，out (n-1) is 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.

[0216] n4[SHo r-a，out -SH r-a，out (n)]

[0217] 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 the calculation; if the superheat at the outlet of the refrigerant-air heat exchanger deviates significantly from the target superheat of refrigerant-air heat exchanger 102, the increment can be adjusted using the fourth heating regulation coefficient n4. For example, the larger the deviation (e.g., expressed in absolute value), the larger n4 becomes; 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.

[0218] 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-water heat exchanger 116. 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 precise control.

[0219] 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.

[0220] SH r-a，out =T hex，o -T(P hex,o )

[0221] In heating mode, the compressor frequency control method is similar to that in cooling mode. The frequency adjustment coefficient can be generated based on different constants, such as... Figure 15 As shown, an exemplary heat pump with a heating capacity of 16kW, an ambient temperature of 7°C, an outlet water temperature of 55°C, and an initial compressor frequency of 60Hz.

[0222] In some embodiments of this application, such as Figure 16 As shown, the heat pump system 10 also includes a third valve element 130, which is disposed between the subcooling pipe and the second heat exchange section 114. The third valve element 130 is used to control the flow rate of R290 refrigerant flowing into the subcooling section pipe 106 and to ensure that the temperature of the R290 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 conditions for no frost formation. Figure 16 In the diagram, the solid line represents the high-pressure R290 refrigerant area, the dashed line represents the R290 refrigerant area after the first throttling, the double dashed line represents the R290 refrigerant area after the second throttling, the dotted-dash line represents the low-pressure R290 refrigerant area, and the double dotted-dash line represents the water flow path.

[0223] During heating operation, the low-temperature, low-pressure R290 refrigerant is compressed into a high-temperature, high-pressure refrigerant by the compressor 100, and then enters the refrigerant-water heat exchanger 116 through the switching valve 126. It exchanges heat with water and condenses into a liquid phase, and then passes through the first valve element 122 to throttle into a medium-temperature, medium-pressure R290 refrigerant. The medium-temperature, medium-pressure R290 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 R290 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 flow rate of R290 refrigerant entering 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 R290 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, its temperature rises, and it enters the compressor 100, improving the suction temperature and oil sump temperature, thus completing the heating cycle.

[0224] Figure 17 Comparing the pressure-enthalpy diagrams of the conventional scheme and the heat pump system 10 provided in this application, the heating cycle of this embodiment is as follows: Figure 17 As shown in Figures 1′-2′-3′-4′-5′-6′-7′-8′-9′-1′. The first valve element 122 controls the heat exchange of the R290 refrigerant entering the refrigerant-refrigerant heat exchanger 110 from state 5′ to state 6′. The third valve element 130 controls the heat exchange of the R290 refrigerant entering the subcooling section pipe 106 from state 7′ to state 8′, ensuring that the heat exchange of the refrigerant-refrigerant heat exchanger 110 just meets the suction temperature and oil sump temperature requirements of the compressor 100, and that the heat exchange of the subcooling section pipe 106 just prevents frost from forming at the bottom of the refrigerant-air heat exchanger 102. The temperature change of the R290 refrigerant along the pipe is as follows: Figure 18 As shown.

[0225] In some embodiments of this application, in heating mode, the processing device is configured to perform, as Figure 19 The steps shown are for adjusting the opening of the third valve element 130.

[0226] Step S501: Obtain the inlet temperature of the subcooled section pipe 106.

[0227] Step S502: Obtain the preset target temperature of the subcooled section pipeline inlet.

[0228] 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, adjust the opening of the third valve element 130 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.

[0229] In some embodiments of this application, the third valve element 130 is an electronic expansion valve.

[0230] The processing device is based on the feedback control principle and uses incremental control to adjust the opening degree of the third valve element 130.

[0231] The incremental control of the third valve element 130 in heating mode is represented as follows:

[0232] EV EEV3_Heating (n) = EV EEV3_Heating (n-1)+ΔEV EEV3_Heating

[0233] 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.

[0234] The following is about the incremental ΔEV EEV3_Heating The calculation process will be introduced as follows:

[0235] In some embodiments of this application:

[0236]

[0237] in:

[0238]

[0239] This indicates the rate of change of the inlet temperature of the subcooled section pipe with respect to the increment ΔEV. EEV3_HeatingThe 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, for example, the larger the change in superheat (e.g., expressed in absolute value), the larger the adjustment amount (expressed in absolute value) of the first subcooling section adjustment coefficient m5; where T sc (n) represents the inlet temperature of the subcooled section piping in the current cycle, SH r-w，out (n-1) is 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.

[0240] n5[T sc，o -T sc (n)]

[0241] This represents the deviation between the inlet temperature of the subcooled section pipe and the target inlet temperature of the subcooled section pipe in terms of the increment ΔEV. EEV3_Heating 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 subcooling section adjustment coefficient n5. EEV3_Heating Adjustments are made, for example, 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 pipeline, and n5 is the adjustment coefficient of the second subcooled section.

[0242] Incremental 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 precise control. This ensures 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.

[0243] In some embodiments of this application, the target temperature T at the inlet of the subcooled section pipe is... sc，o Generates based on ambient temperature or target effluent temperature.

[0244] In some embodiments of this application, the target temperature T at the inlet of the subcooled section pipe is... sc，o It is generated based on ambient temperature and target effluent temperature.

[0245] In some embodiments of this application, the target temperature T at the inlet of the subcooled section pipe is... sc，oThe target temperature T at the inlet of the subcooled section pipe increases with increasing ambient temperature; and corresponds to a lower target outlet water temperature. sc,o Relatively high.

[0246] Other aspects of this application provide a heat pump system 10, which further optimizes the refrigerant-refrigerant heat exchanger based on the above embodiments. For example... Figure 20 As shown, the heat pump system 10 includes a first refrigerant-to-refrigerant heat exchanger 132 and a second refrigerant-to-refrigerant heat exchanger 142. The first refrigerant-to-refrigerant heat exchanger 132 and the second refrigerant-to-refrigerant heat exchanger 142 are used for heat exchange between R290 refrigerants in different states.

[0247] In some embodiments of this application, the first refrigerant-refrigerant heat exchanger 132 and the second refrigerant-refrigerant heat exchanger 142 may be plate heat exchangers, shell-and-tube heat exchangers, coaxial heat exchangers, spiral plate heat exchangers, or other optional heat exchanger forms.

[0248] 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.

[0249] 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.

[0250] Corresponding to the first refrigerant-refrigerant heat exchanger 132 and the second refrigerant-refrigerant heat exchanger 142 are a fourth valve element 138 and a fifth valve element 140. The fourth valve element 138 is disposed between the first heat exchange section 134 and the suction side of the compressor 100, and the fifth valve element 140 is disposed between the first heat exchange section 144 and the suction side of the compressor 100.

[0251] In some embodiments of this application, a third valve element 130 may also be provided in the heat pump system 10, and the third valve element 130 is disposed between the subcooling section pipe 106 and the second heat exchange section 136.

[0252] 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 are used to meet the different requirements of refrigerant-refrigerant heat exchanger area under different ambient temperatures and different target outlet water temperatures, solve the problem of excessive pressure loss on the suction side under low ambient temperatures, and further improve the low-temperature operating capability and energy efficiency.

[0253] In some embodiments of this application, the processing device is configured to perform, such as Figure 21 The following steps are shown:

[0254] Step S601: Determine whether the ambient temperature meets the preset low-temperature operating conditions;

[0255] 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;

[0256] 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.

[0257] At low ambient temperatures and high target effluent 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 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.

[0258] like Figure 22 The diagram shows the heating cycle that meets low-temperature operating conditions. Figure 22In the diagram, 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. The low-temperature, low-pressure R290 refrigerant is compressed by compressor 100 into a high-temperature, high-pressure refrigerant, then enters the refrigerant-water heat exchanger 116 through switching valve 126, where it exchanges heat with water and condenses into a liquid phase. After being throttled by the first valve element 122, it becomes a medium-temperature, medium-pressure gas-liquid two-phase refrigerant, and then passes through the second refrigerant-refrigerant heat exchanger 142. At this point, the fourth valve element 138 is closed, the first heat exchange section 144 is cut off, and the 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 pipe 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 pipe 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 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. Second refrigerant - The refrigerant is bypassed, the pressure loss on the low-pressure side is reduced, the suction temperature and oil sump temperature are improved, the energy efficiency is increased, and the heating cycle is completed.

[0259] When the ambient temperature rises and the target outlet water temperature decreases, the heat exchange demand of the refrigerant-refrigerant heat exchanger increases. At this time, using only one refrigerant-refrigerant heat exchanger cannot meet the heat exchange demand. The processing device is configured to open the fourth valve element 138 and close the fifth valve element 140.

[0260] like Figure 23 The diagram shows a heating cycle that does not meet the low-temperature operating conditions. Figure 23 In the diagram, the solid line represents the high-pressure R290 refrigerant area, the dashed line represents the R290 refrigerant area after the first throttling, the double dashed line represents the R290 refrigerant area after the second throttling, the dotted-dash line represents the low-pressure R290 refrigerant area, the dotted line represents the non-flowing area, and the double dotted-dash line represents the water flow path.

[0261] 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 the 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, the temperature rises, and after passing through the fourth valve element 138, it enters the compressor 100 to improve the suction temperature and oil sump temperature, thus completing the heating cycle.

[0262] 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.

[0263] In this embodiment, the first valve element 122, the second valve element 124, and the third valve element 130 can all adopt the control method provided in the aforementioned specification.

[0264] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0265] The above are merely specific embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. Heat pump system, including: The compressor is used to compress R290 refrigerant; Refrigerant-air heat exchangers, which include: The heat exchanger body, within which R290 refrigerant exchanges heat with air; and The subcooled section piping is fluidly connected to the main body of the heat exchanger; Refrigerant-refrigerant heat exchanger, which 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 subcooled section pipeline; R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section; A refrigerant-water heat exchanger in which R290 refrigerant exchanges heat with water; Its characteristic is that it further includes: 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.

2. The heat pump system according to claim 1, characterized in that: In heating mode, the first valve element throttles the flow of R290 refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the flow of R290 refrigerant flowing out of the subcooled section pipeline.

3. The heat pump system according to claim 1, characterized in that: Also includes: A switching valve, which is fluidly connected to the compressor, is used to switch the flow direction of R290 refrigerant so that the heat pump system operates in cooling mode.

4. The heat pump system according to any one of claims 1 to 3, characterized in that: Also includes: The third valve element is disposed between the subcooled section pipeline and the second heat exchange section.

5. Heat pump system, including: The compressor is used to compress R290 refrigerant; Refrigerant-air heat exchangers, which include: The heat exchanger body is in which R290 refrigerant exchanges heat with air. The subcooling section piping is fluidly connected to the main body of the heat exchanger; A refrigerant-water heat exchanger in which R290 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. R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section; The second refrigerant-refrigerant heat exchanger includes: A 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; R290 refrigerant exchanges heat between the first heat exchange section and the second heat exchange section; Its characteristic is that it further includes: 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.

6. The heat pump system according to claim 5, characterized in that: It also includes a third valve element, which is disposed between the subcooled section pipeline and the second heat exchange section, to regulate the temperature of the R290 refrigerant entering the subcooled section pipeline in heating mode.

7. The heat pump system according to claim 5, characterized in that, include: A fourth valve element is disposed between the first heat exchange section and the suction side of the compressor; The fifth valve element is located between the first heat exchange section and the suction side of the compressor.

8. The heat pump system according to claim 7, characterized in that, include: In heating mode, the first valve element throttles the R290 refrigerant flowing out of the refrigerant-water heat exchanger, and the second valve element throttles the R290 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 7, characterized in that: 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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