Heat pump system and control method of heat pump system

Abstract

The present disclosure provides a heat pump system and a control method for the heat pump system. The refrigerant circulation loop of the heat pump system includes a main refrigerant pipeline, an evaporator, a compression device, a condenser, and a throttling device, and has a cooling mode and a heating mode; the compression device includes a low-pressure compressor and a high-pressure compressor; the refrigerant circulation loop also includes a switching device, the switching device being configured to enable the refrigerant circulation loop to have a single compressor operating state in the cooling mode, in which the high-pressure compressor alone compresses the refrigerant in the refrigerant circulation loop, and to have a dual compressor operating state in which the low-pressure compressor and the high-pressure compressor are connected in series to compress the refrigerant in the heating mode; the pressure ratio of the high-pressure compressor is configured to meet the pressure ratio required by the compression device of the heat pump system in the cooling mode when the single compressor is in the operating state; and the pressure ratio of the low-pressure compressor is configured to meet the pressure ratio required by the compression device of the heat pump system in the heating mode when the dual compressors are in the operating state together with the high-pressure compressor.

Description

Technical Field

[0001] The present disclosure relates to the technical field of heat pumps, and in particular to a heat pump system and a control method for the heat pump system. Background Art

[0002] Heat pump technology utilizes electricity and suitable low-grade heat sources, and uses a heat pump system to provide thermal energy to meet heat needs such as building heating and domestic hot water. It is the best way to efficiently convert electricity into heat.

[0003] Heat pump systems are environmentally friendly, energy-efficient, and highly efficient. In recent years, they have become increasingly common in large-scale central heating systems. In winter, when the heat source temperature drops to -15°C, a heat pump system produces 50°C hot water, requiring a compressor operating pressure ratio as high as 9.0. Existing heat pump systems primarily use two-stage centrifugal compressors as their compression device. These compressors have a maximum pressure ratio of approximately 4.5, far exceeding the required operating pressure ratio for heat pump systems operating in heating mode. In summer, when the heat pump system operates in cooling mode, the compression device operates at a pressure ratio of 3.0. Consequently, two-stage centrifugal compressors struggle to match the high pressure ratios required in heating mode and the low pressure ratios in cooling mode. Summary of the Invention

[0004] The present disclosure aims to provide a heat pump system and a control method for the heat pump system, aiming to solve the problem in the related art that a two-stage centrifugal compressor is difficult to match a high pressure ratio when operating in heating mode and a low pressure ratio when operating in cooling mode.

[0005] A first aspect of the present disclosure provides a heat pump system, comprising a refrigerant circulation circuit, the refrigerant circulation circuit comprising a main refrigerant pipeline and an evaporator, a compression device, a condenser, and a throttling device connected in sequence through the main refrigerant pipeline, the heat pump system having a cooling mode and a heating mode;

[0006] The compression device includes a low-pressure compressor and a high-pressure compressor connected in series through a main refrigerant pipeline, the inlet of the low-pressure compressor is connected to the evaporator through the main refrigerant pipeline, the outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor through the main refrigerant pipeline, and the outlet of the high-pressure compressor is connected to the condenser through the main refrigerant pipeline;

[0007] The refrigerant circulation loop further includes a switching device, the switching device being connected to the main refrigerant pipeline and configured to enable the refrigerant circulation loop to have a single compressor working state in the cooling mode and a dual compressor working state in the heating mode, wherein in the single compressor working state, the high-pressure stage compressor compresses the refrigerant in the refrigerant circulation loop, and the low-pressure stage compressor stops compressing the refrigerant, and in the dual compressor working state, the low-pressure stage compressor and the high-pressure stage compressor are connected in series and compress the refrigerant;

[0008] The pressure ratio of the high-pressure stage compressor is configured to meet the pressure ratio required by the compression device of the heat pump system in the cooling mode when the single compressor is in operation;

[0009] The pressure ratio of the low-pressure stage compressor is configured to meet the pressure ratio required by the compression device of the heat pump system in the heating mode together with the high-pressure stage compressor when the two compressors are in operation.

[0010] In some embodiments of the heat pump system,

[0011] The pressure ratio of the high-pressure stage compressor is configured to be 1.02 to 1.06 times the pressure ratio required by the compression device of the heat pump system in the cooling mode; and / or

[0012] The pressure ratio of the low-pressure stage compressor is configured to be 1.04 to 1.06 times the pressure ratio that the low-pressure stage compressor needs to bear when the two compressors are in working state and together with the high-pressure stage compressor meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0013] In the heat pump system of some embodiments, the switching device includes:

[0014] a bypass portion comprising a bypass pipeline connected to the main refrigerant pipeline in parallel with the low-pressure stage compressor; and

[0015] The switching unit is configured to selectively connect one of the bypass line and the low-pressure stage compressor to the refrigerant circulation circuit and disconnect the other from the refrigerant circulation circuit.

[0016] In the heat pump system of some embodiments, the switching unit includes a first switching valve, which is provided on the bypass line and configured to control the on-off of the bypass line.

[0017] In the heat pump system of some embodiments, the refrigerant circulation loop further includes:

[0018] a flasher connected to the main refrigerant pipeline between the condenser and the evaporator; and

[0019] The gas supply pipeline connects the gas outlet of the flasher and the compression device and is configured to supply gas to the compression device.

[0020] In the heat pump system of some embodiments, the air supply pipeline includes:

[0021] a first air supply branch connected between the gas outlet of the flash generator and the inlet of the high-pressure compressor; and / or

[0022] The second air supply branch is connected between the gas outlet of the flasher and the air supply port of the high-pressure compressor.

[0023] In the heat pump system of some embodiments, the refrigerant circulation loop further includes:

[0024] a series air supply control valve, provided on the first air supply branch, and configured to control the on-off of the first air supply branch; and

[0025] The high-pressure air supply control valve is provided on the second air supply branch and is configured to control the on-off of the second air supply branch.

[0026] In the heat pump system of some embodiments, the throttling device includes a first throttling part and a second throttling part connected through the main refrigerant pipeline, and the flasher is located on the main refrigerant pipeline between the first throttling part and the second throttling part.

[0027] In the heat pump system of some embodiments, the flash generator is installed on the condenser.

[0028] In some embodiments of the heat pump system,

[0029] The low-pressure stage compressor is a two-stage centrifugal compressor; and / or

[0030] The high-pressure stage compressor is a two-stage centrifugal compressor.

[0031] In some embodiments of the heat pump system,

[0032] The low-pressure stage compressor is mounted on the evaporator; and / or

[0033] The high-pressure stage compressor is installed on the condenser.

[0034] In some embodiments of the heat pump system,

[0035] The low-pressure stage compressor is a fixed-speed compressor; and / or

[0036] The high-pressure stage compressor is a fixed-speed compressor.

[0037] In some embodiments of the heat pump system,

[0038] The low pressure stage compressor includes adjustable inlet guide vanes; and / or

[0039] The high pressure stage compressor includes adjustable inlet guide vanes.

[0040] In the heat pump system of some embodiments, the flow paths of the low-pressure stage compressor and the high-pressure stage compressor are configured so that F2 = A*F1; wherein

[0041] F1 is the volume flow of the low-pressure stage compressor;

[0042] F2 is the volume flow of the high-pressure stage compressor;

[0043] A is a constant representing the ratio of the outlet specific volume of the high-pressure stage compressor in the cooling mode to the outlet specific volume in the heating mode.

[0044] In some embodiments, the heat pump system further includes a water circulation loop, which includes a main water line, a heat source tower and a terminal heat exchanger. The heat source tower is switchably connected to one of the evaporator and the condenser through the main water line, and the terminal heat exchanger is switchably connected to the other of the evaporator and the condenser through the main water line.

[0045] A second aspect of the present disclosure provides a method for controlling the heat pump system according to the first aspect of the present disclosure, comprising:

[0046] In the cooling mode of the heat pump system, the refrigerant circulation loop is in the single compressor working state;

[0047] In the heating mode of the heat pump system, the refrigerant circulation loop is put into the dual compressor working state.

[0048] In the control method of some embodiments,

[0049] The refrigerant circulation circuit further includes a flasher and an air supply pipeline, wherein the flasher is connected to the main refrigerant pipeline between the condenser and the evaporator, and the air supply pipeline connects the gas outlet of the flasher and the compression device and is configured to supply air to the compression device;

[0050] The control method includes supplying air from the flasher to the compression device through the air supply pipeline.

[0051] In the control method of some embodiments, supplying air from the flasher to the compression device includes:

[0052] In the cooling mode of the heat pump system, supplying air to the air supply port of the high-pressure stage compressor; and / or

[0053] In the heating mode of the heat pump system, air is supplied to the air inlet and / or air supply port of the high-pressure stage compressor.

[0054] In some embodiments of the control method, the high-pressure stage compressor includes adjustable inlet guide vanes, and the control method further includes adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor to change the supply air pressure when supplying air to the compression device.

[0055] In the control method of some embodiments,

[0056] The low-pressure stage compressor includes adjustable inlet guide vanes; and / or the high-pressure stage compressor includes adjustable inlet guide vanes;

[0057] The control method includes: in the heating mode, adjusting the opening of the adjustable inlet guide vanes of the low-pressure stage compressor and / or adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor so that the low-pressure stage compressor and the high-pressure stage compressor jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0058] In some embodiments of the control method, the control method includes: in the heating mode, fully opening the adjustable inlet guide vanes of the low-pressure stage compressor, and adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor so that the low-pressure stage compressor and the high-pressure stage compressor can jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0059] Based on the heat pump system provided by the present invention, when operating in winter heating mode, the refrigerant circulation loop can be switched to a dual-compressor working state, and a low-pressure compressor and a high-pressure compressor are used in series to compress the refrigerant to meet the high pressure ratio requirement during winter heating. At the same time, taking into account the cooling needs in summer, when operating in cooling mode, a high-pressure compressor designed according to the pressure ratio required by the cooling mode is used to independently compress the refrigerant to match the operating pressure ratio required for refrigeration, which is conducive to ensuring the high efficiency of the high-pressure compressor when operating alone in cooling mode. By switching control between single compressor operation and dual compressor series operation, the required operating pressure ratio matching in different operating modes is achieved, which is conducive to ensuring stability during high-pressure ratio operation for winter heating, and also to improving energy efficiency during low-pressure ratio operation for summer cooling.

[0060] The control method of the heat pump system according to the embodiment of the present disclosure has the advantages of the heat pump system according to the embodiment of the present disclosure.

[0061] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The drawings described herein are used to provide a further understanding of the present disclosure and constitute a part of this application. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the drawings:

[0063] Figure 1 This is a schematic diagram of a heat pump system according to an embodiment of the present disclosure, showing a refrigerant circulation loop and a water circulation loop of the heat pump system.

[0064] Figure 2 for Figure 1 Schematic diagram of the refrigerant circulation circuit of the heat pump system of the illustrated embodiment.

[0065] Figure 3 for Figure 1 Schematic diagram of the operating characteristics of the compression device of the heat pump system of the illustrated embodiment. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0067] Unless otherwise specifically stated, the relative arrangement of the parts and steps, the numerical expressions and the numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0068] In the description of the present disclosure, it should be understood that the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of the present disclosure.

[0069] In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by the directional words is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present disclosure and simplifying the description. Unless otherwise specified, these directional words 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 cannot be understood as limiting the scope of protection of the present disclosure; the directional words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself.

[0070] Figure 1 This is a schematic diagram of a heat pump system according to an embodiment of the present disclosure, showing a refrigerant circulation loop and a water circulation loop of the heat pump system. Figure 2 for Figure 1 Schematic diagram of the refrigerant circulation circuit of the heat pump system of the illustrated embodiment.

[0071] like Figure 1 and Figure 2 As shown, an embodiment of the present disclosure provides a heat pump system, including a refrigerant circulation circuit, the refrigerant circulation circuit including a main refrigerant pipeline 13 and an evaporator 3, a compression device, a condenser 4 and a throttling device connected in sequence through the main refrigerant pipeline 13. The heat pump system has a cooling mode and a heating mode. The compression device includes a low-pressure stage compressor 1 and a high-pressure stage compressor 2 connected in series through the main refrigerant pipeline 13, the inlet of the low-pressure stage compressor 1 is connected to the evaporator 3 through the main refrigerant pipeline 13, the outlet of the low-pressure stage compressor 1 is connected to the inlet of the high-pressure stage compressor 2 through the main refrigerant pipeline 13, and the outlet of the high-pressure stage compressor 2 is connected to the condenser 4 through the main refrigerant pipeline 13. The refrigerant circulation circuit also includes a switching device, which is connected to the main refrigerant pipeline 13 and is configured to enable the refrigerant circulation circuit to have a single compressor working state in the cooling mode and a dual compressor working state in the heating mode. In the single compressor working state, the high-pressure stage compressor 2 compresses the refrigerant in the refrigerant circulation loop alone, and the low-pressure stage compressor 1 stops compressing the refrigerant. In the dual compressor working state, the low-pressure stage compressor 1 and the high-pressure stage compressor 2 are connected in series and compress the refrigerant.

[0072] The pressure ratio of the high-pressure stage compressor 2 is configured to meet the pressure ratio required by the compression device of the heat pump system in the cooling mode when operating in a single compressor working state.

[0073] The pressure ratio of the low-pressure stage compressor 1 is configured to meet the pressure ratio required by the compression device of the heat pump system in the heating mode together with the high-pressure stage compressor 2 when the two compressors are operating in the working state.

[0074] According to the heat pump system of the embodiment of the present disclosure, when the heat pump system is operating in heating mode in winter, the refrigerant circulation loop can be switched to a dual-compressor working state, and the low-pressure compressor 1 and the high-pressure compressor 2 are used in series to compress the refrigerant to meet the high pressure ratio requirements during winter heating. For example, 50°C hot water can be normally produced when the heat source temperature is -15°C. At the same time, taking into account the cooling needs in summer, when the heat pump system is operating in cooling mode, only the high-pressure compressor 2 is turned on, and the high-pressure compressor 2 designed according to the pressure ratio required by the cooling mode is used to independently compress the refrigerant to match the operating pressure ratio required for cooling, which is conducive to ensuring the high efficiency of the high-pressure compressor when operating in cooling mode alone. By switching control between single-unit operation and dual-unit series operation of the compressor, the required operating pressure ratio matching in different operating modes is achieved, which is conducive to ensuring the stability of high-pressure ratio operation in winter heating, and improving the energy efficiency of low-pressure ratio operation in summer cooling.

[0075] In the heat pump system of some embodiments, the pressure ratio of the high-pressure stage compressor 2 is configured to be 1.02 to 1.05 times the pressure ratio required by the compression device of the heat pump system in the cooling mode; and / or the pressure ratio of the low-pressure stage compressor 1 is configured to be 1.04 to 1.06 times the pressure ratio that the low-pressure stage compressor 1 needs to bear when the two compressors are in working state and together with the high-pressure stage compressor 2 meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0076] The above arrangement allows unpredictable factors in actual operation of the heat pump system to be taken into account when designing the corresponding pressure ratios of the low-pressure stage compressor 1 and the high-pressure stage compressor 2, and a certain margin is reserved when designing the pressure ratio.

[0077] Figure 3 for Figure 1 Schematic diagram of the operating characteristics of the low-pressure stage compressor and the high-pressure stage compressor of the heat pump system of the embodiment shown. Figure 3 The horizontal axis F represents the volume flow rate, the vertical axis R represents the pressure ratio, and each curve represents:

[0078] L1 is the surge line;

[0079] L2 is the pipe network characteristic curve under the working state of two compressors;

[0080] L3 is the pipe network characteristic curve under the working state of a single compressor;

[0081] C1 is the characteristic curve of the compression device under the working state of two compressors;

[0082] C2 is the characteristic curve of low-pressure stage compressor 1 when the opening of its adjustable inlet guide vane is 100% under the dual compressor working state;

[0083] C3 is the characteristic curve of the high-pressure stage compressor 2 under the single compressor working state when the opening of its adjustable inlet guide vane is 100%;

[0084] C4 is the characteristic curve of the high-pressure stage compressor 2 under the single compressor working state when the opening of its adjustable inlet guide vane is less than 100%;

[0085] F1 is the volume flow of the low-pressure stage compressor 1, hereinafter referred to as the first volume flow;

[0086] F2 is the volume flow of the high-pressure stage compressor 2, hereinafter referred to as the second volume flow;

[0087] R1 is the pressure ratio of the compression device when the exhaust volume of the compression device is the first volume flow F1 under the dual compressor working state, hereinafter referred to as the first pressure ratio;

[0088] R2 is the pressure ratio of the low-pressure stage compressor 1 when the exhaust volume of the compression device is the first volume flow F1 and the opening of its adjustable inlet guide vane is 100% when the two compressors are in operation, hereinafter referred to as the second pressure ratio;

[0089] R3 is the pressure ratio of the high-pressure stage compressor 2 when the exhaust volume of the compression device is the first volume flow F1 in the dual compressor working state and the opening of its adjustable inlet guide vane is less than 100%, hereinafter referred to as the third pressure ratio;

[0090] R4 is the pressure ratio of the high-pressure stage compressor 2 when the adjustable inlet guide vane opening is 100% when the exhaust volume of the compression device is the second volume flow F2 in the single compressor working state, hereinafter referred to as the fourth pressure ratio.

[0091] The first, second, and third pressure ratios R1, R2, and R3 all correspond to the first volumetric flow rate F1. The first pressure ratio R1 refers to the total pressure ratio of the compression device for the heat pump system's heating needs. This refers to the pressure ratio of the compression device when two compressors, low-compression compressor 1 and high-pressure compressor 2, operate in series to compress the refrigerant. The first pressure ratio R1 = the second pressure ratio R2 * the third pressure ratio R3.

[0092] The fourth pressure ratio R4 corresponds to the second volume flow F2. In the single compressor working state, the high-pressure stage compressor 2 works alone to compress the refrigerant to meet the refrigeration demand of the heat pump system.

[0093] The pressure ratio required by the compression device of the heat pump system in cooling mode is the fourth pressure ratio R4. The pressure ratio of the high-pressure stage compressor 2 is configured to be 1.02 to 1.05 times the pressure ratio required by the compression device of the heat pump system in cooling mode, that is, the pressure ratio of the high-pressure stage compressor 2 is configured to be 1.02 to 1.05 times, for example, 1.03 times, of the fourth pressure ratio R4.

[0094] The pressure ratio that low-pressure compressor 1 needs to bear when the two compressors are in operation and the high-pressure compressor 2 jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode is the second pressure ratio R2. The pressure ratio of low-pressure compressor 1 is configured to be 1.01 to 1.08 times the pressure ratio that low-pressure compressor 1 needs to bear when the two compressors are in operation and the high-pressure compressor 2 jointly meet the pressure ratio required by the heat pump system in the heating mode, that is, the pressure ratio of low-pressure compressor 1 is configured to be 1.01 to 1.08 times, for example, 1.06 times, the second pressure ratio R2.

[0095] like Figure 1 and Figure 2 As shown, in some embodiments of the heat pump system, the switching device includes a bypass unit and a switching unit. The bypass unit includes a bypass line 14 connected in parallel with the low-pressure stage compressor 1. The switching unit is configured to selectively connect one of the bypass line 14 and the low-pressure stage compressor 1 to the refrigerant circulation circuit and disconnect the other from the refrigerant circulation circuit.

[0096] like Figure 1 and Figure 2 As shown, in some embodiments of the heat pump system, the switching unit includes a first switching valve 6, which is disposed on the bypass line 14 and is configured to control the opening and closing of the bypass line 14. When the first switching valve 6 is open, the refrigerant passes through the bypass line 14, and the low-pressure stage compressor 1 does not participate in the refrigerant compression. The high-pressure stage compressor 2 independently compresses the refrigerant. When the first switching valve 6 is open, the low-pressure stage compressor 1 and the high-pressure stage compressor 2 operate in series to compress the refrigerant. The first switching valve 6 is, for example, an electric valve, such as an electric butterfly valve.

[0097] In an embodiment not shown in the figure, a second switching valve can also be provided. The second switching valve can be provided on the main refrigerant pipeline 13 between the inlet of the low-pressure stage compressor 1 and the bypass pipeline 14 or on the main refrigerant pipeline 13 between the outlet of the low-pressure stage compressor 1 and the bypass pipeline 14.

[0098] like Figure 1 and Figure 2 As shown, in some embodiments of the heat pump system, the refrigerant circulation loop further includes a flash evaporator 5 and an air supply line. The flash evaporator 5 is connected to the main refrigerant line 13 between the condenser 4 and the evaporator 3. The air supply line connects the gas outlet of the flash evaporator 5 to the compression device and is configured to supply air to the compression device.

[0099] like Figure 1 and Figure 2 In the illustrated embodiment, the air supply pipeline includes at least one of a first air supply branch 15 and a second air supply branch 16. The first air supply branch 15 is connected between the gas outlet of the flasher 5 and the inlet of the high-pressure stage compressor 2. The second air supply branch 16 is connected between the gas outlet of the flasher 5 and the air supply port of the high-pressure stage compressor 2.

[0100] like Figure 1 and Figure 2 In the illustrated embodiment, the refrigerant circulation circuit includes at least one of a series air supply control valve 8 and a high-pressure air supply control valve 9. The series air supply control valve 8 is disposed on a first air supply branch 15 and is configured to control the on-off state of the first air supply branch 15. The high-pressure air supply control valve 9 is disposed on a second air supply branch 16 and is configured to control the on-off state of the second air supply branch 16.

[0101] The series air supply control valve 8 and the high-pressure air supply control valve 9 are, for example, electric valves, which can be electric butterfly valves, electric ball valves, or solenoid valves.

[0102] like Figure 1 and Figure 2 As shown, the throttling device includes a first throttling portion 11 and a second throttling portion 12 connected by a main refrigerant pipeline 13 , and the flasher 5 is located on the main refrigerant pipeline 13 between the first throttling portion 11 and the second throttling portion 12 .

[0103] In the heat pump system of some embodiments, the flash generator 5 is installed on the condenser 4 .

[0104] In some embodiments of the heat pump system, the refrigerant circulation circuit may further include a check valve disposed on the main refrigerant pipeline 13 between the outlet of the high-pressure stage compressor 2 and the condenser 4. The check valve helps prevent the high-pressure gas in the condenser 4 from flowing back when the compression device is shut down, causing the compression device to reverse.

[0105] like Figure 1 and Figure 2 As shown, in the heat pump system of some embodiments, the low-pressure stage compressor 1 and the high-pressure stage compressor 2 can both be centrifugal compressors, for example, the low-pressure stage compressor 1 is a two-stage centrifugal compressor; the high-pressure stage compressor 2 is a two-stage centrifugal compressor.

[0106] In some embodiments, to facilitate pressure ratio adjustment, the low-pressure stage compressor 1 is a fixed-speed compressor; and / or the high-pressure stage compressor 2 is a fixed-speed compressor. For example, the low-pressure stage compressor and the high-pressure stage compressor can both be fixed-speed centrifugal compressors.

[0107] The low-pressure stage compressor 1 includes adjustable inlet guide vanes; and / or the high-pressure stage compressor 2 includes adjustable inlet guide vanes. This configuration facilitates adjusting the refrigerant flow and pressure of the heat pump system according to different operating conditions of the heat pump system.

[0108] In some embodiments of the heat pump system, the flow paths of the low-pressure stage compressor 1 and the high-pressure stage compressor 2 are configured such that F2 = A*F1. F1 is the volumetric flow rate of the low-pressure stage compressor; F2 is the volumetric flow rate of the high-pressure stage compressor. A is a constant representing the ratio of the outlet specific volume of the high-pressure stage compressor 2 in cooling mode to the outlet specific volume in heating mode.

[0109] In heating mode, since the two compressors need to run in series, the refrigerant gas is compressed by the low-pressure compressor 1, and the gas specific volume decreases, so the required flow path is narrow when it reaches the high-pressure compressor 2. The high-pressure compressor 2 is designed based on the cooling mode, with a low pressure ratio, a large gas specific volume, and a wide flow path. Therefore, when designing the high-pressure compressor 2, when selecting the volume flow rate, it is necessary to design the ratio of the first volume flow rate F1 of the low-pressure compressor 1 and the second volume flow rate F2 of the high-pressure compressor 2, that is, the second volume flow rate F2 = A * the first volume flow rate F1, to ensure that the flow path of the high-pressure compressor 2 is within a reasonable range in both cooling mode and heating mode.

[0110] The constant A is described below.

[0111] The outlet specific volume V2 of the high-pressure stage compressor 2 in both cooling mode and heating mode is as follows:

[0112] V2V in / (P2 / P1)1 / k.

[0113] Where Vin is the inlet specific volume of high-pressure compressor 2, P2 is the outlet pressure of high-pressure compressor 2, P1 is the inlet pressure of high-pressure compressor 2, and k is the adiabatic index. These parameters differ between cooling mode and heating mode, resulting in different outlet specific volumes of high-pressure compressor 2 in cooling mode and heating mode. Therefore, a constant A can be used to represent the ratio of the outlet specific volume of high-pressure compressor 2 in cooling mode to the outlet specific volume in heating mode.

[0114] In the heat pump system of some embodiments, the low-pressure stage compressor 1 is installed on the evaporator 3 , and the high-pressure stage compressor 2 is installed on the condenser 4 .

[0115] like Figure 1 As shown, in the heat pump system of some embodiments, the heat pump system also includes a water circulation loop, which includes a main water line 77, a heat source tower 71 and a terminal heat exchanger 73. The heat source tower 71 is switchably connected to one of the evaporator 3 and the condenser 4 through the main water line 77, and the terminal heat exchanger 73 is switchably connected to the other of the evaporator 3 and the condenser 4 through the main water line 77.

[0116] like Figure 1 As shown, the heat pump system of the embodiment of the present disclosure includes Figure 2The refrigerant circulation circuit and water circulation circuit shown are similar to those described above. The water circulation circuit mainly includes a main water circuit 77, a heat source tower 71, a first circulating water pump 72, a terminal heat exchanger 73, a second circulating water pump 74, an operating mode switching unit 70, a concentrating device 75, a third circulating water pump 76, and a concentrating branch 78. The heat source tower 71 and the first circulating water pump 72 are connected in series via the main water circuit 77 and are switchably connected to one of the evaporator 3 and the condenser 4 via the operating mode switching unit 70. The terminal heat exchanger 73 and the second circulating water pump 74 are connected in series via the main water circuit 77 and are switchably connected to the other of the evaporator 3 and the condenser 4 via the main water circuit 77 and the operating mode switching unit 70.

[0117] For example, the operation mode switching unit 70 switches to Figure 1 In the state shown, the heat source tower 71, the first circulating water pump 72, the working mode switching unit 70 and the evaporator 3 are connected in sequence through the main water channel 77 to form a circulation loop; at the same time, the terminal heat exchanger 73, the second circulating water pump 74, the working mode switching unit 70 and the condenser 4 are connected in sequence through the main water channel 77 to form a circulation loop. At this time, the heat pump system is in heating mode.

[0118] In the refrigeration mode not shown in the figure, the working mode switching unit 70 can be switched to connect the heat source tower 71, the first circulating water pump 72, the working mode switching unit 70 and the condenser 4 in sequence through the main water channel 77 to form a circulation loop; at the same time, the terminal heat exchanger 73, the second circulating water pump 74, the working mode switching unit 70 and the evaporator 3 are connected in sequence through the main water channel 77 to form a circulation loop.

[0119] The first circulating water pump 72 is used to provide power for the circulating loop where the heat source tower 71 is located, and the second circulating water pump 72 is used to provide power for the circulating loop where the terminal heat exchanger 73 is located.

[0120] The concentrating device 75 , the third circulating water pump 76 and the concentrating branch 78 are configured to concentrate and store the antifreeze liquid.

[0121] The following combination Figure 1 and Figure 2 Describe the operation process of the embodiment of the present disclosure.

[0122] During heating mode operation, the first switching valve 6 is closed, the series air supply control valve 8 is opened, and the high-pressure air supply control valve 9 is closed. The gaseous refrigerant in the evaporator 3 is compressed by the low-pressure compressor 1 and discharged. It then enters the high-pressure compressor 2 for further compression and is discharged into the condenser 4. The liquid refrigerant in the condenser 4 undergoes primary throttling by the first throttling unit 11 and enters the flash condenser 5. The flashed gaseous refrigerant passes through the series air supply control valve 8 and mixes with the exhaust gas from the low-pressure compressor 1 before entering the high-pressure compressor 2. The flashed liquid refrigerant undergoes secondary throttling by the second throttling unit 12 and enters the evaporator 3, thus completing the cycle.

[0123] During cooling mode operation, the first switching valve 6 is open, the series air supply control valve 8 is closed, and the high-pressure air supply control valve 9 is open. The gaseous refrigerant from the evaporator 3 passes through the first switching valve 6 and directly enters the high-pressure compressor 2 for compression before being discharged into the condenser 4. The liquid refrigerant from the condenser 4 undergoes primary throttling through the first throttling unit 11 before entering the flash condenser 5. The flashed gaseous refrigerant passes through the high-pressure air supply control valve 9 and enters the air supply port of the high-pressure compressor 2. The flashed liquid refrigerant undergoes secondary throttling through the second throttling unit 12 before entering the evaporator 3, thus completing the cycle.

[0124] The present disclosure also provides a control method for a heat pump system according to the present disclosure. The control method includes: in the cooling mode of the heat pump system, operating the refrigerant circulation loop with a single compressor; in the heating mode of the heat pump system, operating the refrigerant circulation loop with two compressors.

[0125] The control method of the embodiment of the present disclosure has the same advantages as the heat pump system of the embodiment of the present disclosure.

[0126] In the control method of some embodiments, the refrigerant circulation loop also includes a flasher 5 and an air supply pipeline. The flasher 5 is connected to the main refrigerant pipeline 13 between the condenser 4 and the evaporator 3. The air supply pipeline connects the gas outlet of the flasher 5 and the compression device, and is configured to supply air to the compression device. The control method includes supplying air from the flasher 5 to the compression device.

[0127] In the control method of some embodiments, in the cooling mode of the heat pump system, air is supplied to the air supply port of the high-pressure stage compressor 2; and / or in the heating mode of the heat pump system, air is supplied to the air supply port and / or the air inlet of the high-pressure stage compressor 2.

[0128] In some embodiments of the control method, the control method further includes adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor 2 to change the supply pressure when supplying air to the compression device.

[0129] In the control method of some embodiments, the control method includes: in the heating mode, adjusting the opening of the adjustable inlet guide vanes of the low-pressure stage compressor 1 and / or adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor 2 so that the low-pressure stage compressor 1 and the high-pressure stage compressor 2 jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0130] In the control method of some embodiments, the control method includes: in the heating mode, fully opening the adjustable inlet guide vanes of the low-pressure stage compressor 1, and adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor 2 so that the low-pressure stage compressor 1 and the high-pressure stage compressor 2 can jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

[0131] According to the above description, the heat pump system and the control method of the heat pump system according to the embodiments of the present disclosure have at least one of the following advantages:

[0132] During winter heating, a low-pressure compressor and a high-pressure compressor are connected in series to compress the refrigerant, achieving the high pressure ratio required for winter heating. During summer cooling, a high-pressure compressor is used alone to compress the refrigerant, matching the required operating pressure ratio. This ensures stability during high-pressure winter heating operation and improves energy efficiency during low-pressure summer cooling operation.

[0133] When both compressors are two-stage compressors, the two compressors in series compressing the refrigerant is equivalent to compressing the refrigerant with a four-stage compressor, which is more conducive to meeting the high pressure ratio required for winter heating.

[0134] During summer cooling, a high-pressure compressor can be used to compress the refrigerant alone, which is also conducive to better matching the flow and pressure ratio, avoiding the "small horse pulling a big cart" phenomenon, and also helping to improve the operating stability of the heat pump system.

[0135] The refrigerant circulation loop of the heat pump system is equipped with a flasher. When two compressors are working, air can be supplied from the middle of the two compressors. When a single compressor is working, air can be supplied from the air supply port of the running high-pressure compressor. The pressure ratio distribution is balanced by switching the air supply, thus achieving efficient operation in dual working conditions.

[0136] The flash unit is installed on the condenser, the low-pressure compressor is installed on the evaporator, and the high-pressure compressor and flash unit are installed on the condenser, which is conducive to the compactness of the overall structure of the heat pump system and saves the installation area.

[0137] In heating mode, the two compressors are turned on at the same time, and the adjustable inlet guide vanes of the low-pressure compressor are kept fully open. By adjusting the opening of the adjustable inlet guide vanes of the high-pressure compressor, the low-pressure compressor can operate at a high pressure ratio, and the high-pressure compressor can match the remaining required pressure ratios of the compression device, ensuring that the first pressure ratio R1 = the second pressure ratio R2 * the third pressure ratio R3, realizing series operation in heating mode, which is conducive to the reliable operation of the two compressors.

[0138] The supply air pressure can be regulated by adjusting the opening of the adjustable inlet guide vanes of the high-pressure compressor. This is because adjusting the opening of the adjustable inlet guide vanes of the high-pressure compressor can control the exhaust pressure of the low-pressure compressor, thereby affecting the supply air pressure. Closing the opening of the adjustable inlet guide vanes of the high-pressure compressor increases the back pressure of the low-pressure compressor. The supply air needs to overcome this back pressure to be delivered to the high-pressure compressor. Conversely, increasing the opening of the adjustable inlet guide vanes of the high-pressure compressor reduces the back pressure of the low-pressure compressor, and the supply air pressure is appropriately reduced. Therefore, by adjusting the opening of the adjustable inlet guide vanes of the high-pressure compressor, the supply air pressure can be adjusted.

[0139] In cooling mode, the user's cooling mode needs are met by turning on the high-pressure compressor alone. At this time, the adjustable inlet guide vanes of the high-pressure compressor can be used to adjust the flow rate to meet the user's different load requirements.

[0140] The two compressors use fixed-speed compressors and utilize fixed-speed compatible pneumatic technology. The high-pressure stage compressor is designed according to the cooling mode and the low-pressure stage compressor is designed according to the heating mode. The pressure ratio is redistributed by adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor, which is conducive to achieving a large pressure ratio in the heating mode and high-efficiency operation in the cooling mode.

[0141] The low-pressure stage compressor utilizes a single-stage theoretical cycle design without air injection, while the high-pressure stage utilizes a two-stage theoretical cycle design with air injection. This facilitates air injection during operating mode switching to increase heat enthalpy and improve cooling mode efficiency. The heat pump system switches between heating and cooling modes using an air injection valve. Simultaneously, the flash ignition pressure is controlled by adjusting the opening of the high-pressure stage compressor's adjustable inlet guide vanes, facilitating pressure ratio redistribution between the low- and high-pressure stage compressors.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure and are not intended to limit them. Although the present disclosure has been described in detail with reference to preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present disclosure can still be modified or some technical features can be replaced by equivalents, which should all be included in the scope of the technical solutions claimed for protection in the present disclosure.

Claims

1. A heat pump system comprising a refrigerant circulation circuit, wherein the refrigerant circulation circuit comprises a main refrigerant pipeline (13) and an evaporator (3), a compression device, a condenser (4) and a throttling device connected in sequence via the main refrigerant pipeline (13), wherein the heat pump system has a cooling mode and a heating mode, and is characterized in that: The compression device comprises a low-pressure compressor (1) and a high-pressure compressor (2) connected in series via a main refrigerant pipeline (13); the inlet of the low-pressure compressor (1) is connected to the evaporator (3) via the main refrigerant pipeline (13); the outlet of the low-pressure compressor (1) is connected to the inlet of the high-pressure compressor (2) via the main refrigerant pipeline (13); and the outlet of the high-pressure compressor (2) is connected to the condenser (4) via the main refrigerant pipeline (13); The refrigerant circulation loop further includes a switching device, the switching device being connected to the main refrigerant pipeline (13) and being configured to enable the refrigerant circulation loop to have a single compressor working state in the cooling mode and a dual compressor working state in the heating mode. In the single compressor working state, the high-pressure stage compressor (2) compresses the refrigerant in the refrigerant circulation loop, and the low-pressure stage compressor (1) stops compressing the refrigerant. In the dual compressor working state, the low-pressure stage compressor (1) and the high-pressure stage compressor (2) are connected in series and compress the refrigerant. The pressure ratio of the high-pressure stage compressor (2) is configured to meet the pressure ratio required by the compression device of the heat pump system in the cooling mode when the single compressor is in operation; The pressure ratio of the low-pressure stage compressor (1) is configured to satisfy the pressure ratio required by the compression device of the heat pump system in the heating mode together with the high-pressure stage compressor (2) when the two compressors are in operation; The refrigerant circulation loop also includes a flasher (5) and an air supply pipeline. The flasher (5) is connected to the main refrigerant pipeline (13) between the condenser (4) and the evaporator (3). The air supply pipeline connects the gas outlet of the flasher (5) and the compression device and is configured to supply air to the compression device. The air supply pipeline includes a first air supply branch (15) and a second air supply branch (16). The first air supply branch (15) is connected between the gas outlet of the flasher (5) and the inlet of the high-pressure stage compressor (2). The second air supply branch (16) is connected between the gas outlet of the flasher (5) and the air supply port of the high-pressure stage compressor (2).

2. The heat pump system according to claim 1, characterized in that The pressure ratio of the high-pressure stage compressor (2) is configured to be 1.02 to 1.06 times the pressure ratio required by the compression device of the heat pump system in the cooling mode; and / or The pressure ratio of the low-pressure stage compressor (1) is configured to be 1.04 to 1.06 times the pressure ratio that the low-pressure stage compressor (1) needs to bear when the two compressors are in operation and the high-pressure stage compressor (2) jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

3. The heat pump system according to claim 1, characterized in that The switching device comprises: a bypass portion comprising a bypass pipeline (14) connected to the main refrigerant pipeline (13) in parallel with the low-pressure stage compressor (1); and The switching unit is configured to selectively connect one of the bypass line (14) and the low-pressure stage compressor (1) to the refrigerant circulation circuit, and disconnect the other from the refrigerant circulation circuit.

4. The heat pump system according to claim 3, characterized in that The switching unit includes a first switching valve (6), which is provided on the bypass line (14) and configured to control the on-off of the bypass line (14).

5. The heat pump system according to claim 1, characterized in that The refrigerant circulation loop further includes: a series air supply control valve (8), provided on the first air supply branch (15), configured to control the on-off of the first air supply branch (15); and The high-pressure air supply control valve (9) is provided on the second air supply branch (16) and is configured to control the on-off of the second air supply branch (16).

6. The heat pump system according to claim 1, characterized in that The throttling device includes a first throttling portion (11) and a second throttling portion (12) connected through the main refrigerant pipeline (13), and the flasher (5) is located on the main refrigerant pipeline (13) between the first throttling portion (11) and the second throttling portion (12).

7. The heat pump system according to claim 1, characterized in that The flasher (5) is mounted on the condenser (4).

8. The heat pump system according to claim 1, wherein: The low-pressure stage compressor (1) is a two-stage centrifugal compressor; and / or The high-pressure stage compressor (2) is a two-stage centrifugal compressor.

9. The heat pump system according to claim 1, characterized in that The low-pressure compressor (1) is mounted on the evaporator (3); and / or The high-pressure stage compressor (2) is mounted on the condenser (4).

10. The heat pump system according to claim 1, characterized in that The low-pressure stage compressor (1) is a fixed-speed compressor; and / or The high-pressure stage compressor (2) is a fixed-speed compressor.

11. The heat pump system according to any one of claims 1 to 10, characterized in that: The low-pressure stage compressor (1) comprises adjustable inlet guide vanes; and / or The high pressure stage compressor (2) comprises adjustable inlet guide vanes.

12. The heat pump system according to any one of claims 1 to 10, characterized in that: The flow passages of the low-pressure stage compressor (1) and the high-pressure stage compressor (2) are configured so that F2 = A*F1; in F1 is the volume flow of the low-pressure stage compressor (1); F2 is the volume flow of the high-pressure stage compressor (2); A is a constant representing the ratio of the outlet specific volume of the high-pressure stage compressor (2) in the cooling mode to the outlet specific volume in the heating mode.

13. The heat pump system according to any one of claims 1 to 10, characterized in that: The invention also includes a water circulation loop, which includes a main water line (77), a heat source tower (71) and a terminal heat exchanger (73). The heat source tower (71) is switchably connected to one of the evaporator (3) and the condenser (4) through the main water line (77), and the terminal heat exchanger (73) is switchably connected to the other of the evaporator (3) and the condenser (4) through the main water line (77).

14. A control method for a heat pump system according to any one of claims 1 to 13, characterized in that: include: In the cooling mode of the heat pump system, the refrigerant circulation loop is in the single compressor working state; In the heating mode of the heat pump system, the refrigerant circulation loop is put into the dual compressor working state.

15. The control method according to claim 14, characterized in that: The refrigerant circulation loop further includes a flasher (5) and an air supply pipeline, wherein the flasher (5) is connected to the main refrigerant pipeline (13) between the condenser (4) and the evaporator (3), and the air supply pipeline connects the gas outlet of the flasher (5) and the compression device and is configured to supply air to the compression device; The control method includes supplying air from the flasher (5) to the compression device through the air supply pipeline.

16. The control method according to claim 15, characterized in that: Supplying air from the flasher (5) to the compression device comprises: In the cooling mode of the heat pump system, supplying air to the air supply port of the high-pressure stage compressor (2); and / or In the heating mode of the heat pump system, air is supplied to the air inlet and / or the air supply port of the high-pressure stage compressor (2).

17. The control method according to claim 15, characterized in that: The high-pressure stage compressor (2) includes an adjustable inlet guide vane, and the control method further includes adjusting the opening of the adjustable inlet guide vane of the high-pressure stage compressor (2) to change the air supply pressure when supplying air to the compression device.

18. The control method according to claim 14, characterized in that: The low-pressure stage compressor (1) includes adjustable inlet guide vanes; and / or the high-pressure stage compressor (2) includes adjustable inlet guide vanes; The control method comprises: in the heating mode, adjusting the opening of the adjustable inlet guide vanes of the low-pressure stage compressor (1) and / or adjusting the opening of the adjustable inlet guide vanes of the high-pressure stage compressor (2) so that the low-pressure stage compressor (1) and the high-pressure stage compressor (2) jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

19. The control method according to claim 18, characterized in that: The control method comprises: in the heating mode, fully opening the adjustable inlet guide vanes of the low-pressure stage compressor (1), and adjusting the opening degree of the adjustable inlet guide vanes of the high-pressure stage compressor (2) so that the low-pressure stage compressor (1) and the high-pressure stage compressor (2) jointly meet the pressure ratio required by the compression device of the heat pump system in the heating mode.

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