Control method of heat pump system, heat pump system, air conditioner and water heater

Abstract

The invention relates to the technical field of household appliances, and particularly provides a control method of a heat pump system, the heat pump system, an air conditioner and a water heater. Specifically, the heat pump system is additionally provided with a bypass tank, a bypass valve and a bypass pipeline, the bypass tank is provided with an inlet, a first outlet and a second outlet, the inlet communicates with the outlet end of the throttling element, the first outlet communicates with the inlet end of the gas-liquid separator through the bypass pipeline, and the second outlet communicates with the inlet end of the evaporator. The control method comprises the steps that in the first starting stage, the opening degree of the bypass valve is controlled so that the superheat degree of the evaporator can be within a first preset interval; after the set conditions are met, a second starting stage is started, the opening degree of the bypass valve is controlled so that the superheat degree of the evaporator can be within a second preset interval, and the second preset interval is smaller than the first preset interval; and closing the bypass valve at the end of the second starting phase. The starting performance of the heat pump system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of household appliances, and specifically provides a control method for a heat pump system, a heat pump system, an air conditioner and a water heater. Background Art

[0002] Heat pump systems are mainly used in household appliances such as air conditioners and water heaters. Existing heat pump systems mainly include a compressor, a condenser, a throttling element, an evaporator and a gas-liquid separator that are connected in sequence.

[0003] However, when the existing heat pump system is started in heating mode, the liquid refrigerant in the evaporator will migrate to the gas-liquid separator, causing the system to lack liquid. The performance degradation during the startup process will cause the actual operating energy efficiency of the system to decrease, thereby affecting user satisfaction.

[0004] Therefore, this field needs a new technical solution to solve the above problems. Summary of the invention

[0005] The present invention aims to solve the above technical problem, that is, to solve the problem that the existing heat pump system will experience performance degradation during the process of starting in heating mode.

[0006] In a first aspect, the present invention provides a control method for a heat pump system, the heat pump system comprising a compressor, a condenser, a throttling element, an evaporator and a gas-liquid separator connected in sequence, the heat pump system further comprising a bypass tank, a bypass valve and a bypass pipeline, the bypass tank having an inlet, a first outlet and a second outlet, the inlet being connected to the outlet end of the throttling element, the first outlet being connected to the inlet end of the gas-liquid separator through the bypass pipeline so that the gaseous refrigerant in the bypass tank can flow into the gas-liquid separator along the bypass pipeline, the second outlet being connected to the inlet end of the evaporator, the bypass valve being arranged on the bypass pipeline, the process of starting the heat pump system in a heating mode comprising a first startup stage and a second startup stage, the control method comprising:

[0007] In the first startup stage, the opening of the bypass valve is controlled so that the superheat of the evaporator is within a first preset range;

[0008] When the set conditions are met, the second startup stage is entered, and in the second startup stage, the opening of the bypass valve is controlled so that the superheat of the evaporator is within a second preset range, wherein the second preset range is smaller than the first preset range;

[0009] When the second startup phase is over, the bypass valve is closed.

[0010] In the preferred technical solution of the control method of the heat pump system, the set condition is that the difference between the pressure of the bypass tank and the pressure of the evaporator is less than or equal to a set value.

[0011] In a preferred technical solution of the control method of the heat pump system, the pressure of the evaporator is the pressure at the outlet end of the evaporator.

[0012] In a preferred technical solution of the control method of the heat pump system, the first outlet is located at the top end of the bypass tank, and the second outlet is located at the bottom end of the bypass tank.

[0013] In a preferred technical solution of the control method of the heat pump system, the inlet is located at the top of the bypass tank.

[0014] In a preferred technical solution of the control method of the heat pump system, a guide pipe is provided in the bypass tank, a top end of the guide pipe is connected to the inlet, and a bottom end of the guide pipe extends toward the bottom of the bypass tank.

[0015] In the preferred technical solution of the control method of the heat pump system, the step of "controlling the opening of the bypass valve so that the superheat of the evaporator is within the first preset range" specifically includes:

[0016] Obtaining the superheat of the evaporator;

[0017] comparing the superheat of the evaporator with the first preset interval;

[0018] If the superheat of the evaporator is less than the first preset range, increasing the opening of the bypass valve;

[0019] If the superheat of the evaporator is greater than the first preset interval, reducing the opening of the bypass valve;

[0020] The step of “controlling the opening of the bypass valve so that the superheat of the evaporator is within a second preset range” specifically includes:

[0021] comparing the superheat of the evaporator with the second preset interval;

[0022] If the superheat of the evaporator is greater than the second preset range, reducing the opening of the bypass valve;

[0023] If the superheat of the evaporator is less than the second preset range, the opening of the bypass valve is increased.

[0024] In the preferred technical solution of the control method of the heat pump system, the throttling element is an electronic expansion valve.

[0025] In a second aspect, the present invention further provides a heat pump system, comprising a controller, wherein the controller is configured to execute the above control method.

[0026] In a third aspect, the present invention further provides a water heater, comprising the above-mentioned heat pump system.

[0027] In a fourth aspect, the present invention further provides an air conditioner, comprising the above-mentioned heat pump system.

[0028] When adopting the above technical scheme, the heat pump system of the present invention is newly added with a bypass tank, a bypass pipeline and a bypass valve arranged on the bypass pipeline. The bypass tank is connected in series between the throttling element and the evaporator, and the bypass pipeline connects the bypass tank with the gas-liquid separator. During the start-up of the heat pump system in heating mode, the bypass valve can be opened to allow the gaseous refrigerant in the bypass tank to flow directly into the gas-liquid separator from the bypass pipeline to reduce the flow rate of the gaseous refrigerant in the evaporator, thereby avoiding the migration of liquid refrigerant from the evaporator to the gas-liquid separator in the initial stage of startup, thereby improving the startup performance of the system; in addition, during the startup process, the opening of the bypass valve is controlled by the superheat of the evaporator, so that the opening of the bypass valve can be accurately controlled, further improving the startup performance of the heat pump system.

[0029] Furthermore, by setting the set condition so that the difference between the pressure of the bypass tank and the pressure of the evaporator is less than or equal to the set value, the heat pump system can accurately enter the second start-up stage from the first start-up stage to avoid the liquid refrigerant in the evaporator from flowing back toward the bypass tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0031] Figure 1 is a connection schematic diagram of the heat pump system of the present invention;

[0032] Figure 2 It is a flow chart of the control method of the heat pump system of the present invention.

[0033] List of reference numerals:

[0034] 1. Compressor; 2. Condenser; 3. Throttling element; 4. Evaporator; 5. Gas-liquid separator; 6. Bypass tank; 7. Bypass valve; 8. Bypass pipeline; 61. First outlet; 62. Second outlet; 63. Inlet; 64. Guide pipe. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0036] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that, in the description of the present invention, although the various steps of the control method of the present invention are described in this application in a specific order, these orders are not restrictive, and those skilled in the art may perform the steps in different orders without departing from the basic principles of the present invention.

[0037] It should be noted that in the description of the present invention, the terms "inside", "outside", "upper", "lower", "top", "bottom" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0038] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "setting", "connection" and "installation" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Specifically, the present invention provides a heat pump system, such as Figure 1 As shown, the heat pump system of the present invention comprises a compressor 1, a condenser 2, a throttling element 3, an evaporator 4 and a gas-liquid separator 5 which are connected in sequence. The throttling element 3 is preferably an electronic expansion valve.

[0040] Specifically, the compressor 1, the condenser 2, the throttling element 3, the evaporator 4 and the gas-liquid separator 5 are connected in sequence through the refrigerant pipeline. When the heat pump system is operating in the heating mode, the refrigerant discharged from the compressor 1 flows along the refrigerant pipeline through the condenser 2, the throttling element 3, the evaporator 4 and the gas-liquid separator 5 in sequence, and then returns to the compressor 1.

[0041] The above-mentioned components are all common components of the existing heat pump system, and the present invention will not introduce them in detail.

[0042] Compared with existing heat pump systems, such as Figure 1 As shown, the heat pump system of the present invention further includes a bypass tank 6 , a bypass valve 7 and a bypass pipeline 8 .

[0043] Among them, the bypass tank 6 has an inlet 63, a first outlet 61 and a second outlet 62. The inlet 63 is connected to the outlet end of the throttling element 3. The first outlet 61 is connected to the inlet end of the gas-liquid separator 5 through the bypass pipeline 8 so that the gaseous refrigerant in the bypass tank 6 can flow into the gas-liquid separator 5 along the bypass pipeline 8. The second outlet 62 is connected to the inlet end of the evaporator 4, and the bypass valve 7 is arranged on the bypass pipeline 8.

[0044] That is to say, on the basis of the existing heat pump system, the heat pump system of the present invention is newly added with a bypass tank 6, a bypass pipeline 8 and a bypass valve 7 arranged on the bypass pipeline 8. The bypass tank 6 is connected in series between the throttling element 3 and the evaporator 4. The bypass pipeline 8 connects the bypass tank 6 with the gas-liquid separator 5. During the start-up of the heat pump system in heating mode, the bypass valve 7 can be opened to allow the gaseous refrigerant in the bypass tank 6 to flow directly from the bypass pipeline 8 into the gas-liquid separator 5 to reduce the flow rate of the gaseous refrigerant in the evaporator 4, thereby avoiding the migration of liquid refrigerant from the evaporator 4 to the gas-liquid separator 5 in the initial stage of startup, thereby improving the startup performance of the system.

[0045] Preferably, if Figure 1 As shown, the first outlet 61 of the bypass tank 6 is located at the top end of the bypass tank 6 , and the second outlet 62 of the bypass tank 6 is located at the bottom end of the bypass tank 6 .

[0046] By arranging the first outlet 61 and the second outlet 62 of the bypass tank 6 at the top and the bottom of the bypass tank 6 respectively, it is more conducive to improving the starting performance of the heat pump system.

[0047] Specifically, the bypass tank 6 stores refrigerant, wherein the gaseous refrigerant in the bypass tank 6 is located at the upper part of the bypass tank 6. By arranging the first outlet 61 at the top of the bypass tank 6, during the startup of the heat pump system, it is conducive to the gaseous refrigerant in the bypass tank 6 to be smoothly discharged from the first outlet 61 and enter the bypass pipeline 8, and then flow toward the gas-liquid separator 5 along the bypass pipeline 8. The liquid refrigerant in the bypass tank 6 is located at the lower part of the bypass tank 6. By arranging the second outlet 62 at the bottom end of the bypass tank 6, during the startup of the heat pump system, it is conducive to the liquid refrigerant in the bypass tank 6 to be smoothly discharged from the second outlet 62 and enter the refrigeration pipeline, and then flow toward the evaporator 4 along the refrigerant pipeline.

[0048] Preferably, if Figure 1 As shown, the inlet 63 of the bypass tank 6 is located at the top end of the bypass tank 6 .

[0049] For example, Figure 1 As shown, the inlet 63 and the first outlet 61 of the bypass tank 6 are both arranged at the top end of the bypass tank 6, wherein the inlet 63 is located on the right side and the first outlet 61 is located on the left side.

[0050] Preferably, if Figure 1 As shown, a guide pipe 64 is provided in the bypass tank 6 of the present invention, the top end of the guide pipe 64 is communicated with the inlet 63 , and the bottom end of the guide pipe 64 extends toward the bottom of the bypass tank 6 .

[0051] By providing a guide pipe 64 in the bypass tank 6 to guide the refrigerant entering from the inlet 63 toward the bottom end of the bypass tank 6, it is possible to better avoid the liquid refrigerant entering from the inlet 63 from being discharged from the first outlet 61 to ensure the startup performance of the heat pump system.

[0052] For example, Figure 1 As shown, the guide pipe 64 is a straight pipe and is vertically arranged in the bypass tank 6. The top end of the guide pipe 64 is connected to the inlet 63, and the bottom end of the guide pipe 64 is located in the middle and lower part of the bypass tank 6. There is a certain distance between the bottom end of the guide pipe 64 and the first outlet 61. The present invention does not limit the specific value of the distance. Those skilled in the art can flexibly set the specific value of the distance based on experiments or experience; in addition, there is also a certain distance between the bottom end of the guide pipe 64 and the bottom of the bypass tank 6. The present invention does not limit the specific value of the distance. Those skilled in the art can flexibly set the specific value of the distance based on experiments or experience, as long as it can ensure that the refrigerant can smoothly enter the bypass tank 6.

[0053] It should be noted that the guide tube 64 of the present invention is not limited to a vertical setting. For example, a person skilled in the art may also tilt the guide tube 64 in actual applications. Such flexible adjustment and change does not deviate from the principle and scope of the present invention and should be limited within the protection scope of the present invention.

[0054] In addition, it should be noted that the shape of the guide tube 64 of the present invention is not limited to the above-mentioned straight tube. For example, those skilled in the art may also set the guide tube 64 to an arc tube or an S-shaped tube, etc. in actual applications. Such adjustments and changes to the specific shape of the guide tube 64 do not deviate from the principle and scope of the present invention and should be limited within the protection scope of the present invention.

[0055] Of course, the present invention preferably sets the guide pipe 64 as a straight pipe, and makes the guide pipe 64 vertically arranged in the bypass tank 6, which has a simple structure, is easy to install, and saves costs.

[0056] Based on the heat pump system described above, the present invention further provides a control method for the heat pump system. The process of starting the heat pump system in the heating mode of the present invention includes a first start-up phase and a second start-up phase. Figure 2 As shown, the control method of the present invention comprises the following steps:

[0057] S100: In the first startup stage, the opening of the bypass valve 7 is controlled so that the superheat of the evaporator 4 is within a first preset range;

[0058] S200: When the set conditions are met, the second startup phase is entered. In the second startup phase, the opening of the bypass valve 7 is controlled so that the superheat of the evaporator 4 is within a second preset range, wherein the second preset range is smaller than the first preset range;

[0059] S300: When the second startup phase ends, the bypass valve 7 is closed.

[0060] That is to say, the present invention divides the startup process of the heat pump system into two stages, namely, the first startup stage and the second startup stage. In the first startup stage and the second startup stage, the opening of the bypass valve 7 is controlled by the superheat of the evaporator 4, wherein the superheat of the evaporator 4 can reflect whether the liquid refrigerant migrates out of the evaporator 4 during the system startup process, and can also reflect the degree of utilization of the heat exchange area of ​​the evaporator 4 during the startup process. The superheat of the evaporator 4 is positively correlated with the opening of the bypass valve 7, that is, the superheat of the evaporator 4 increases with the increase of the opening of the bypass valve 7, and decreases with the decrease of the opening of the bypass valve 7.

[0061] In the first startup stage, by keeping the bypass valve 7 at a relatively large opening, a large amount of gaseous refrigerant in the bypass tank 6 directly enters the gas-liquid separator 5 along the bypass pipe 8, so as to slow down the flow rate of the refrigerant in the evaporator 4 and avoid the liquid refrigerant in the evaporator 4 from migrating to the gas-liquid separator 5. After entering the second startup stage, by keeping the bypass valve 7 at a relatively small opening, the pressure in the bypass tank 6 is restored, so as to avoid the liquid refrigerant in the evaporator 4 from flowing back toward the bypass tank 6. In this way, the opening of the bypass valve 7 can be accurately controlled, thereby further improving the startup performance of the heat pump system.

[0062] It should be noted that the present invention does not limit the specific range value of the first preset interval. In practical applications, those skilled in the art can flexibly set the specific range value of the first preset interval based on experiments or experience, as long as the liquid refrigerant in the evaporator 4 can be prevented from migrating toward the gas-liquid separator 5.

[0063] In addition, it should be noted that the present invention does not limit the specific range value of the second preset interval. In practical applications, those skilled in the art can flexibly set the specific range value of the second preset interval based on experiments or experience, as long as the liquid refrigerant in the evaporator 4 can be prevented from flowing back to the bypass tank 6.

[0064] In addition, it should be noted that the second startup phase ends, that is, the heat pump system completes startup and enters the stable operation phase, and during the normal operation of the heat pump system, the bypass valve 7 is kept closed. Among them, it can be judged whether the heat pump system has reached a stable operation state by detecting the suction temperature of the compressor 1, the exhaust temperature of the compressor 1, the suction pressure of the compressor 1, the exhaust pressure of the compressor 1, the cooling capacity of the heat pump system, or the heating capacity of the heat pump system and other operating parameters.

[0065] Preferably, the setting condition is that the difference between the pressure of the bypass tank 6 and the pressure of the evaporator 4 is less than or equal to a set value.

[0066] Exemplarily, the setting value A=50kPa. In the first startup stage, after the superheat of the evaporator 4 is maintained in the first preset interval, the opening of the bypass valve 7 remains unchanged, and the pressure P1 in the bypass tank 6 and the pressure P2 of the evaporator 4 are obtained respectively. Then, the difference △P between the pressure P1 of the bypass tank 6 and the pressure P2 of the evaporator 4 is calculated, △P=P1-P2, and then △P is compared with the setting value A. If △P>50kPa, the second startup stage is not entered, and the opening of the bypass valve 7 remains unchanged. If △P≤50kPa, the second startup stage is entered, and the opening of the bypass valve 7 needs to be reduced to reduce the superheat of the evaporator 4 to within the second preset interval. When the superheat of the evaporator 4 is maintained in the second preset interval, the opening of the bypass valve 7 remains unchanged until the end of the second startup stage, and the bypass valve 7 can be closed to complete the startup process, and the heat pump system enters a stable operation stage.

[0067] It should be noted that the set value is not limited to the above-mentioned 50 kPa. For example, the set value can also be set to 55 kPa or 45 kPa, etc. In actual applications, those skilled in the art can flexibly set the specific value of the set value based on experiments or experience, as long as the critical line defined by the set value can enable the heat pump system to enter the second startup stage in time to avoid the liquid refrigerant in the evaporator 4 from flowing back to the bypass tank 6.

[0068] In addition, it should be noted that the set condition is not limited to the difference between the pressure of the bypass tank 6 and the pressure of the evaporator 4 being less than or equal to the set value. For example, the set condition can also be set to the start-up time reaching the set time, and so on. Those skilled in the art can adjust the specific content of the set condition in actual application, as long as the heat pump system can enter the second start-up stage in time through the limitation of the set condition to avoid the situation where the liquid refrigerant in the evaporator 4 flows back to the bypass tank 6.

[0069] Of course, the present invention preferably sets the setting condition such that the difference between the pressure of the bypass tank 6 and the pressure of the evaporator 4 is less than or equal to the set value, so that the heat pump system can enter the second startup stage from the first startup stage at a more accurate time point.

[0070] Preferably, the pressure of the evaporator 4 is the pressure at the outlet end of the evaporator 4 .

[0071] Preferably, in step S100, the step of "controlling the opening of the bypass valve 7 so that the superheat of the evaporator 4 is within the first preset range" specifically includes:

[0072] S110: Obtaining the superheat of the evaporator 4;

[0073] S120: comparing the superheat of the evaporator 4 with a first preset interval;

[0074] S130: If the superheat of the evaporator 4 is less than the first preset range, the opening of the bypass valve 7 is increased;

[0075] S140: If the superheat of the evaporator 4 is greater than the first preset range, the opening of the bypass valve 7 is reduced.

[0076] Exemplarily, the superheat △T of the evaporator 4 is the difference between the outlet temperature T1 of the evaporator 4 and the temperature T2 of the middle coil of the evaporator 4, that is, △T=T1-T2, and the first preset interval is 10 to 20°C. When the heat pump system is started in heating mode, the bypass valve 7 is first opened with a preset opening (the specific value can be determined according to the test), and then the outlet temperature T1 of the evaporator 4 and the temperature T2 of the middle coil of the evaporator 4 are detected respectively, and the superheat △T of the evaporator 4 is calculated. If △T≤10°C, the opening of the bypass valve 7 is increased to increase the superheat of the evaporator 4. Conversely, if △T≥20°C, the opening of the bypass valve 7 is reduced to reduce the superheat of the evaporator 4. In the first startup stage, the superheat △T of the evaporator 4 is set between 10 and 20°C.

[0077] It should be noted that the range value of the first preset interval is not limited to 10 to 20°C as mentioned above. For example, the range value of the first preset interval can also be set to 8 to 18°C, 8 to 20°C or 12 to 22°C, etc. Technical personnel in this field can set the specific range of the first preset interval based on experiments or experience in actual applications, as long as the range defined by the first preset interval can avoid the liquid refrigerant in the evaporator 4 from migrating toward the gas-liquid separator 5.

[0078] Preferably, in step S200, the step of "controlling the opening of the bypass valve 7 so that the superheat of the evaporator 4 is within the second preset range" specifically includes:

[0079] S210: comparing the superheat of the evaporator 4 with a second preset interval;

[0080] S220: If the superheat of the evaporator 4 is greater than the second preset interval, the opening of the bypass valve 7 is reduced;

[0081] S230: If the superheat of the evaporator 4 is less than the second preset interval, the opening of the bypass valve 7 is increased.

[0082] Exemplarily, the second preset interval is 0 to 5°C. If the superheat △T of the evaporator 4 is ≤0°C, the opening of the bypass valve 7 is increased to increase the superheat of the evaporator 4. Conversely, if △T≥5°C, the opening of the bypass valve 7 is decreased to reduce the superheat of the evaporator 4. In the second startup stage, the superheat △T of the evaporator 4 is maintained between 0 and 5°C.

[0083] It should be noted that the range value of the second preset interval is not limited to 0 to 5°C as mentioned above. For example, the range value of the first preset interval can also be set to 0 to 4°C or 1 to 6°C, etc. Technical personnel in this field can set the specific range of the second preset interval based on experiments or experience in actual applications, as long as the range defined by the second preset interval can avoid the liquid refrigerant in the evaporator 4 from flowing back to the bypass tank 6.

[0084] The present invention also provides a water heater, which includes the heat pump system introduced above.

[0085] The water heater includes an outer shell and an inner tank installed inside the outer shell. The condenser 2 of the heat pump system is installed on the outer wall of the inner tank. When the heat pump system operates in heating mode, the heat released by the condenser 2 is transferred to the inside of the inner tank through the inner tank to heat the water in the inner tank.

[0086] It should be noted that the controller of the heat pump system is the controller of the water heater, and the controller can execute the control method introduced above.

[0087] The present invention further provides an air conditioner, which includes the heat pump system introduced above.

[0088] The air conditioner includes an indoor unit and an outdoor unit, the evaporator 4 is installed in the indoor unit, and the compressor 1, condenser 2, throttling element 3, bypass tank 6, bypass valve 7, bypass pipeline 8 and gas-liquid separator 5 are all installed in the outdoor unit.

[0089] It should be noted that the controller of the heat pump system is the controller of the air conditioner, and the controller can execute the control method introduced above.

[0090] It should be noted that the control method provided in this embodiment can be stored as a program in a computer-readable storage medium. The storage medium includes a number of instructions for enabling a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor to perform some steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes.

[0091] Those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims of the present application, any one of the claimed embodiments may be used in any combination.

[0092] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A control method for a heat pump system, wherein the heat pump system comprises a compressor, a condenser, a throttling element, an evaporator and a gas-liquid separator connected in sequence, characterized in that: The heat pump system further includes a bypass tank, a bypass valve and a bypass pipeline. The bypass tank has an inlet, a first outlet and a second outlet. The inlet is communicated with the outlet end of the throttling element. The first outlet is communicated with the inlet end of the gas-liquid separator through the bypass pipeline so that the gaseous refrigerant in the bypass tank can flow into the gas-liquid separator along the bypass pipeline. The second outlet is communicated with the inlet end of the evaporator. The bypass valve is arranged on the bypass pipeline. The process of starting the heat pump system in heating mode includes a first startup stage and a second startup stage. The control method includes: In the first startup stage, the opening of the bypass valve is controlled so that the superheat of the evaporator is within a first preset range; When the set conditions are met, the second startup stage is entered, and in the second startup stage, the opening of the bypass valve is controlled so that the superheat of the evaporator is within a second preset range, wherein the second preset range is smaller than the first preset range; When the second startup phase is over, the bypass valve is closed.

2. The control method of the heat pump system according to claim 1, characterized in that: The setting condition is that the difference between the pressure of the bypass tank and the pressure of the evaporator is less than or equal to a setting value.

3. The control method of the heat pump system according to claim 2, characterized in that: The pressure of the evaporator is the pressure at the outlet end of the evaporator.

4. The control method of the heat pump system according to claim 1, characterized in that: The first outlet is located at the top end of the bypass tank, and the second outlet is located at the bottom end of the bypass tank.

5. The control method of the heat pump system according to claim 1, characterized in that: The inlet is located at the top end of the bypass tank.

6. The control method of the heat pump system according to claim 5, characterized in that: A guide pipe is provided in the bypass tank, the top end of the guide pipe is communicated with the inlet, and the bottom end of the guide pipe extends toward the bottom of the bypass tank.

7. The control method of the heat pump system according to any one of claims 1 to 6, characterized in that: The step of "controlling the opening of the bypass valve so that the superheat of the evaporator is within a first preset range" specifically includes: Obtaining the superheat of the evaporator; comparing the superheat of the evaporator with the first preset interval; If the superheat of the evaporator is less than the first preset range, increasing the opening of the bypass valve; If the superheat of the evaporator is greater than the first preset range, reducing the opening of the bypass valve; The step of "controlling the opening of the bypass valve so that the superheat of the evaporator is within a second preset range" specifically includes: comparing the superheat of the evaporator with the second preset interval; If the superheat of the evaporator is greater than the second preset interval, reducing the opening of the bypass valve; If the superheat of the evaporator is less than the second preset range, the opening of the bypass valve is increased.

8. A heat pump system, comprising a controller, characterized in that: The controller is configured to be able to execute the control method according to any one of claims 1 to 7.

9. A water heater, characterized in that: The water heater comprises the heat pump system of claim 8.

10. An air conditioner, characterized in that: The air conditioner comprises the heat pump system according to claim 8.

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