Control method of a heating system

Abstract

The present application relates to the field of heating and ventilation technology, and particularly relates to a control method of a heating system. The present application aims to solve the problems of high cost and high risk of refrigerant leakage existing in the current heat pump heating. For this purpose, the heating system of the present application comprises a heat pump cycle and a water cycle, the heat pump cycle comprises a variable displacement compressor, a tubular heat exchanger, a throttling device and an evaporator connected through a refrigerant pipeline, the water cycle comprises an indoor radiator and the tubular heat exchanger connected through a heat exchange pipeline, the refrigerant in the heat pump cycle and the circulating water in the water cycle exchange heat in the tubular heat exchanger, the variable displacement compressor has two compression cylinders, and the control method comprises: acquiring an outdoor environment temperature; determining a working mode of the variable displacement compressor according to a temperature interval in which the outdoor environment temperature is located; and controlling the variable displacement compressor to operate based on the working mode. The present application has good heating effect, low cost, low risk of leakage and good heat pump heating effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heating and ventilation technology, in particular to a control method of a heating system. BACKGROUND

[0002] To achieve the above-mentioned goal, the heating method in rural areas or areas without central heating in China is changed from coal-fired heating to heat pump heating or air heater heating. Although the above-mentioned heating method solves the problem of carbon emission, it inevitably brings the following defects: for heat pump heating, directly using air conditioning to heat, the outlet temperature is high, the outlet is dry, and the outlet range is uneven, which makes the human body very uncomfortable, and the heat pump heating needs multiple indoor units, which also has the problems of high cost and refrigerant leakage.

[0003] Correspondingly, there is a need in the art for a new technical solution to solve the above-mentioned problems. SUMMARY

[0004] In order to solve at least one of the above-mentioned problems in the prior art, that is, to solve the problem of high cost and high risk of refrigerant leakage existing in the current heat pump heating, the present application provides a control method of a heating system, the heating system comprising a heat pump cycle and a water cycle, the heat pump cycle comprising a variable displacement compressor, a tubular heat exchanger, a throttling device and an evaporator connected by a refrigerant pipeline, the water cycle comprising an indoor radiator and the tubular heat exchanger connected by a heat exchange pipeline, the refrigerant in the heat pump cycle and the circulating water in the water cycle exchange heat in the tubular heat exchanger, the variable displacement compressor has two compression cylinders, and the control method comprises:

[0005] obtaining an outdoor environment temperature;

[0006] determining the working mode of the variable displacement compressor according to the temperature interval of the outdoor environment temperature;

[0007] controlling the variable displacement compressor to operate based on the working mode;

[0008] Wherein, the working mode of the variable displacement compressor includes a double-cylinder mode and a double-stage mode, in the double-cylinder mode, the two compression cylinders of the variable displacement compressor compress the refrigerant separately, and in the double-stage mode, the two compression cylinders of the variable displacement compressor compress the refrigerant in sequence.

[0009] In the preferred technical solution of the above-mentioned control method of the heating system, the step of "determining the working mode of the variable displacement compressor according to the temperature interval of the outdoor environment temperature" further comprises:

[0010] If the outdoor environment temperature is greater than or equal to a first temperature threshold, the working mode of the variable displacement compressor is determined to be a double-stage mode.

[0011] In the preferred technical scheme of the control method of the heating system, the control method further comprises:

[0012] PID control is performed on the variable displacement compressor according to the indoor ambient temperature.

[0013] In the preferred technical scheme of the control method of the heating system, the step of determining the working mode of the variable displacement compressor according to the temperature range in which the outdoor ambient temperature is located further comprises:

[0014] If the outdoor ambient temperature is less than the first temperature threshold and greater than or equal to the second temperature threshold, the working mode of the variable displacement compressor is determined to be the double-cylinder mode.

[0015] In the preferred technical scheme of the control method of the heating system, the step of determining the working mode of the variable displacement compressor according to the temperature range in which the outdoor ambient temperature is located further comprises:

[0016] If the outdoor ambient temperature is less than the second temperature threshold, the working mode of the variable displacement compressor is determined to be the double-stage mode.

[0017] In the preferred technical scheme of the control method of the heating system, the first temperature threshold is any value in the range of 4-10℃; and / or

[0018] The second temperature threshold is any value in the range of -10-0℃.

[0019] In the preferred technical scheme of the control method of the heating system, the refrigerant and the circulating water adopt convective heat exchange in the tube heat exchanger.

[0020] In the preferred technical scheme of the control method of the heating system, a water tank is further arranged on the heat exchange pipeline, a liquid level sensor is arranged in the water tank, a water replenishment valve is arranged on the water tank, the water replenishment valve is in communication with a water source, and the control method further comprises:

[0021] Obtaining the actual liquid level of the water tank;

[0022] Comparing the actual liquid level with a lower liquid level threshold;

[0023] When the actual liquid level is less than the lower liquid level threshold, the water replenishment valve is controlled to be opened until the liquid level in the water tank reaches an upper liquid level threshold.

[0024] In the preferred technical scheme of the control method of the heating system, a pressure relief valve is further arranged on the heat exchange pipeline, and a pressure sensor is further arranged on the heat exchange pipeline, and the control method further comprises:

[0025] Obtaining the actual pressure of the heat exchange pipeline;

[0026] comparing the actual pressure with a preset pressure threshold value;

[0027] when the actual pressure is greater than the preset pressure threshold value, controlling the pressure relief valve to open until the pressure of the heat exchange pipeline is less than the preset pressure threshold value.

[0028] In the preferred technical scheme of the control method of the heating system, a circulating water pump is further arranged on the heat exchange pipeline, and the control method further comprises:

[0029] controlling the circulating water pump to operate during the operation of the variable displacement compressor.

[0030] The technical scheme of the present application can achieve the same effect as central heating by using a heat pump cycle to heat the water circulation, and has a lower cost than multi-terminal air conditioning, and the refrigerant does not participate in indoor circulation, so there is no risk of refrigerant leakage. By arranging a variable displacement compressor and determining the working mode of the variable displacement compressor based on the temperature range of the outdoor environment temperature, the capacity of the variable displacement compressor can be controlled based on the load during heating, so that the compressor is always in an optimal operating state for efficient operation, and the heating effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0031] The present application will be described below with reference to the accompanying drawings. In the drawings:

[0032] Figure 1 is a system diagram of the heating system of the present application (double-cylinder mode);

[0033] Figure 2 is a system diagram of the heating system of the present application (double-stage mode);

[0034] Figure 3 is a flowchart of the control method of the heating system of the present application;

[0035] Figure 4 is a logic diagram of one possible implementation process of the control method of the heating system of the present application.

[0036] List of reference signs

[0037] 1, variable displacement compressor; 11, first compression cylinder; 12, second compression cylinder; 13, first port; 14, second port; 15, third port; 16, fourth port; 17, exhaust port; 2, tubular heat exchanger; 3, throttling device; 4, evaporator; 5, heat exchange pipeline; 6, indoor radiator; 71, first four-way valve; 72, second four-way valve; 8, gas-liquid separator; 91, water tank; 92, pressure relief valve; 93, circulating water pump. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that the embodiments are only used to explain the technical principles of the present application, and are not intended to limit the scope of protection of the present application. For example, although the steps in the following examples are described in a certain order, those skilled in the art can understand that, in order to achieve the effect of the present embodiment, the steps do not have to be executed in such an order, and they can be executed simultaneously (in parallel) or in a reversed order, and these simple changes are within the scope of protection of the present application.

[0039] It should be noted that in the embodiments of the present application, the terms "first", "second", "third", "fourth" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. In addition, "a plurality of" in the embodiments of the present application refers to two or more.

[0040] It should also be noted that in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through an intermediate medium, or internal communication of two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0041] Firstly, the heating system of the present application is described. Figure 1 and Figure 2 The heating system of the present application is described.

[0042] As shown in Figure 1 and Figure 2 , the heating system of the present application includes a heat pump cycle and a water cycle. The heat pump cycle includes a variable displacement compressor 1, a second four-way valve 72, a tube heat exchanger 2, a throttling device 3 and an evaporator 4 connected by a refrigerant pipeline, and the water cycle includes an indoor radiator 6 and the tube heat exchanger 2 connected by a heat exchange pipeline 5, the refrigerant in the heat pump cycle and the circulating water in the water cycle exchange heat in the tube heat exchanger 2, so as to realize the adjustment of indoor temperature by the indoor radiator 6. Among them, the tube heat exchanger 2 in the present application can be a double-pipe heat exchanger, or a tube-shell heat exchanger.

[0043] Preferably, the variable displacement compressor 1 has two compression cylinders. Specifically, the variable displacement compressor 1 is internally provided with a first compression cylinder 11 and a second compression cylinder 12, and four ports and an exhaust port 17 are formed on the compressor housing, wherein the first port 13 is in communication with the suction port of the first compression cylinder 11, the second port 14 is in communication with the discharge port of the first compression cylinder 11, the third port 15 is in communication with the suction port of the second compression cylinder 12, and the discharge port of the second compression cylinder 12 is in communication with the exhaust port 17, and the fourth port 16 is in communication with the exhaust port 17 through the interior of the housing.

[0044] The variable displacement compressor 1 is further provided with a first four-way valve 71, which has four interfaces a, b, c, and d, wherein the first interface a is in communication with the fourth port 16, the second interface b is in communication with the second port 14, and the third interface c is in communication with the third port 15. The four-way valve is internally provided with a moving part, which moves within the four-way valve when the four-way valve is powered on or off, to achieve communication and blocking between different interfaces.

[0045] The variable displacement compressor 1 is further provided with a gas-liquid separator 8, the inlet of which is in communication with the second four-way valve 72, and the outlet of which is in communication with the two compression cylinders of the variable displacement compressor 1. Specifically, one outlet of the gas-liquid separator 8 is directly in communication with the first port 13, and the other outlet of the gas-liquid separator 8 is in communication with the third port 15 indirectly through the fourth interface d of the first four-way valve 71.

[0046] In the above arrangement, the working modes of the variable displacement compressor 1 include a double-cylinder mode and a double-stage mode. Specifically, Figure 1 , when the first four-way valve 71 is powered off, the double-cylinder mode is adopted, in which the two compression cylinders of the variable displacement compressor 1 compress the refrigerant separately. Specifically, part of the refrigerant discharged from the evaporator 4 enters the first compression cylinder 11 from the first port 13 after passing through the gas-liquid separator 8, is compressed by the first compression cylinder 11, and is then discharged from the second port 14, enters the housing through the second interface b and the first interface a of the first four-way valve 71, and is finally discharged from the exhaust port 17. Another part of the refrigerant passes through the gas-liquid separator 8, enters the second compression cylinder 12 from the third port 15 through the fourth interface d and the third interface c of the first four-way valve 71, is compressed in the second compression cylinder 12, and is then discharged from the exhaust port 17.

[0047] Specifically, Figure 2, the first four-way valve 71 is powered on in the double-stage mode. In this mode, the two compression cylinders of the variable displacement compressor 1 compress the refrigerant in turn. Specifically, the first interface a and the fourth interface d of the first four-way valve 71 are cut off by the moving piece, the refrigerant discharged by the evaporator 4 passes through the gas-liquid separator 8 and enters the first compression cylinder 11 through the first port 13, is compressed by the first compression cylinder 11 and discharged through the second port 14, then passes through the second interface b and the third interface c of the first four-way valve 71, enters the second compression cylinder 12 through the third port 15, and is twice compressed by the second compression cylinder 12 and discharged through the exhaust port 17.

[0048] In the water circulation, the heat exchange pipeline 5 is further provided with a water tank 91, a pressure relief valve 92 and a circulating water pump 93. The water tank 91 is provided with a liquid level sensor, and a water supplement valve is arranged on the water tank 91 and communicates with a water source. When the water amount in the heat exchange pipeline 5 decreases, the water tank 91 can be supplemented with water through the water supplement valve. The heat exchange pipeline 5 is further provided with a pressure sensor, which detects the pressure of the heat exchange pipeline 5. When the pressure of the heat exchange pipeline 5 is too high, the pressure relief valve 92 is used to relieve the pressure of the heat exchange pipeline 5 to maintain stable pressure. The circulating water pump 93 is used to drive the water in the heat exchange pipeline 5 to circulate, so as to transfer the heat of the jacket heat exchanger to the indoor radiator 6 to adjust the indoor temperature.

[0049] Those skilled in the art can understand that the arrangement of the above-mentioned air conditioner is only preferred, and those skilled in the art can adjust the structure of the above-mentioned air conditioner without departing from the principles of the present application, so that the present application is applicable to more specific application scenarios. For example, the switching between the double-cylinder mode and the double-pole mode of the variable displacement compressor 1 can not be realized through the first four-way valve 71, but a plurality of valve groups can be arranged to realize the switching by controlling the opening and closing of each valve in the valve group. For another example, the specific structure of the variable displacement compressor 1 is not fixed, and those skilled in the art can adjust the structure of the variable displacement compressor 1, such as changing the number, position and connection relationship of the ports, under the premise of realizing the switching between the double-cylinder mode and the double-stage mode. For another example, the arrangement of the water tank 91, the pressure relief valve 92 and the circulating water pump 93 is not necessary, and those skilled in the art can choose according to specific needs. For another example, the second four-way valve 72 can also not be arranged.

[0050] The following refers to Figure 3 The control method of the heating system of the present application is introduced.

[0051] As Figure 3 shown, in order to solve the problems of high cost and high risk of refrigerant leakage existing in the existing heat pump heating, the control method of the heating system of the present application comprises:

[0052] S101, acquiring the outdoor environment temperature. For example, the outdoor environment temperature is acquired by a temperature sensor arranged outdoors.

[0053] S103, determine the working mode of the variable displacement compressor according to the temperature interval in which the outdoor environment temperature is located. For example, the working mode of the compressor includes a double-cylinder mode and a double-stage mode. In the double-cylinder mode, the refrigerant flows through two compression cylinders of the compressor for compression, and in the double-stage mode, the refrigerant flows through two compression cylinders of the compressor for compression in sequence. The working mode of the compressor is selected according to the interval in which the outdoor environment temperature is located, so that the compressor is adapted to the current heating load.

[0054] S105, control the variable displacement compressor to operate based on the working mode. For example, after the working mode is determined, the compressor is controlled to operate in the working mode.

[0055] The technical solution of the present application can achieve the same effect as central heating by using a heat pump cycle to heat the water circulation, and has a lower cost than multi-terminal air conditioning. The refrigerant does not participate in indoor circulation, and there is no risk of refrigerant leakage. By setting a variable displacement compressor and determining the working mode of the variable displacement compressor based on the temperature interval in which the outdoor environment temperature is located, the capacity of the variable displacement compressor can be controlled based on the load during heating, so that the compressor is always in an optimal operating state for efficient operation, and the heating effect is good.

[0056] The preferred embodiments of the present application are described below.

[0057] In one embodiment, the step of "determining the working mode of the variable displacement compressor according to the temperature interval in which the outdoor environment temperature is located" further includes: if the outdoor environment temperature is greater than or equal to a first temperature threshold, determining the working mode of the variable displacement compressor as a double-stage mode; if the outdoor environment temperature is less than the first temperature threshold and greater than or equal to a second temperature threshold, determining the working mode of the variable displacement compressor as a double-cylinder mode; and if the outdoor environment temperature is less than the second temperature threshold, determining the working mode of the variable displacement compressor as a double-stage mode.

[0058] Specifically, the first temperature threshold is any value in 4-10℃, and the second temperature threshold is any value in -10-0℃. In the following embodiments, the first temperature threshold is 7℃, and the second temperature threshold is -5℃. When the outdoor ambient temperature is greater than or equal to 7℃, the indoor load is small, and the compressor is controlled to operate in the two-stage mode. The two-stage compression of the refrigerant can reduce the operating frequency and noise of the compressor, reduce the heat loss of the compressor, and realize the efficient and power-saving operation of the compressor. When the outdoor ambient temperature is less than 7℃ and greater than or equal to -5℃, the outdoor ambient temperature decreases, the indoor load increases, and more heating capacity is required. At this time, the compressor is controlled to operate in the two-cylinder mode, which can achieve greater exhaust capacity at the same frequency, thereby improving the heating and heating effect. When the outdoor ambient temperature is less than -5℃, the outdoor ambient temperature is low, the indoor load is large, and a high condensing temperature is required to realize heat exchange. The ordinary compressor can achieve this by increasing the compression ratio, but the increase of the compression ratio not only does not increase the exhaust temperature too much, but also causes the refrigerant to be at risk of leakage, and instead reduces the heating effect. The compressor operating mode is switched to the two-stage mode in the application, which can achieve a larger compression ratio at a lower operating frequency, thereby meeting the condensing temperature requirement.

[0059] Of course, the above-mentioned temperature interval division and compressor operating mode selection are only preferred, and in other embodiments, those skilled in the art can adjust the temperature interval division method, such as dividing more temperature intervals or reducing fewer temperature intervals, and then adjusting the operating mode of the compressor for each temperature interval to realize the efficient and stable operation of the compressor.

[0060] In an embodiment, the control method further comprises: when the outdoor ambient temperature is greater than or equal to the first temperature threshold, PID controlling the variable displacement compressor according to the indoor ambient temperature.

[0061] Specifically, when the outdoor ambient temperature is greater than or equal to 7℃, the indoor load is small, and the compressor operates stably. Only the PID control of the compressor by the indoor ambient temperature can completely meet the heating and heating requirements.

[0062] Those skilled in the art can understand that the PID control of the frequency of the compressor is only a preferred technical solution, and those skilled in the art can select other control methods.

[0063] In one embodiment, the refrigerant and the circulating water adopt counterflow heat exchange in the tubular heat exchanger. Specifically, the flow direction of the refrigerant in the tubular heat exchanger is opposite to the flow direction of the circulating water in the tubular heat exchanger, that is, the two adopt counterflow heat exchange, which can improve the heat exchange effect. Preferably, the refrigerant flows from top to bottom in the tubular heat exchanger, which can reduce the refrigerant pressure loss by using gravity and improve the efficiency of the refrigerant system. The circulating water flows from bottom to top in the tubular heat exchanger, and the inlet cold water is first subjected to counterflow heat exchange with the medium-temperature and medium-pressure refrigerant and then subjected to counterflow heat exchange with the high-temperature and high-pressure refrigerant, and is heated to high-temperature hot water entering the indoor.

[0064] It can be understood that counterflow heat exchange is only a preferred embodiment, and those skilled in the art can also adopt other heat exchange modes to realize heat exchange between the refrigerant and the circulating water.

[0065] In one embodiment, the control method further comprises: obtaining an actual liquid level of the water tank; comparing the actual liquid level with a lower liquid level threshold; and when the actual liquid level is less than the lower liquid level threshold, controlling the water supplement valve to open until the liquid level in the water tank reaches an upper liquid level threshold.

[0066] Specifically, when the actual liquid level of the water tank is lower than the lower liquid level threshold, the water amount in the heat exchange pipeline is insufficient and needs to be supplemented, at which time the water supplement valve is opened to supplement water into the water tank to maintain sufficient water amount in the heat exchange pipeline.

[0067] Of course, automatic water supplement is only a preferred embodiment, and in other embodiments, the water supplement step can be omitted and water can be supplemented manually.

[0068] In one embodiment, the control method further comprises: obtaining an actual pressure of the heat exchange pipeline; comparing the actual pressure with a preset pressure threshold; and when the actual pressure is greater than the preset pressure threshold, controlling the pressure relief valve to open until the pressure of the heat exchange pipeline is less than the preset pressure threshold.

[0069] Specifically, an excessively large pressure of the heat exchange pipeline can easily cause the circulating pipeline to burst and leak, and by obtaining the pressure of the heat exchange pipeline and opening the pressure relief valve to release pressure when the actual pressure is greater than the preset pressure threshold until the pressure of the heat exchange pipeline is less than the preset pressure threshold, the pressure of the heat exchange pipeline can be maintained stable to avoid pipeline burst.

[0070] Of course, the step of releasing pressure by the pressure relief valve is not necessary, and those skilled in the art can select it based on specific application scenarios.

[0071] In one embodiment, the control method further comprises: controlling the circulating water pump to operate during the operation of the variable displacement compressor. Specifically, since the refrigerant and the circulating water adopt counterflow heat exchange in the tubular heat exchanger and the circulating water flows in from the bottom and out from the top, the stability of heat exchange can be ensured by controlling the circulating water pump to operate to circulate heat to the heat sink in time.

[0072] Of course, the circulation water pump is not necessarily provided, and the circulating water in the heat exchange pipeline can also circulate under the action of the temperature difference when the circulation water pump is not provided.

[0073] The following will be described in combination with Figure 4 A possible operation process of the air conditioner of the present application will be briefly described.

[0074] As Figure 4 shown, in a possible operation process:

[0075] S201, in the heat pump circulation heating process, the outdoor environment temperature Tout is obtained, and then S202 is executed.

[0076] S202, whether Tout≥7℃ is established? If yes, S204 is executed; otherwise, if not, S203 is executed.

[0077] S203, further judging whether Tout<-5℃ is established? If yes, S206 is executed, otherwise, if not, S205 is executed.

[0078] S204, controlling the compressor to run in the double-stage mode, and the frequency of the compressor is PID adjusted according to the indoor environment temperature.

[0079] S205, controlling the compressor to run in the double-cylinder mode.

[0080] S206, controlling the compressor to run in the double-stage mode.

[0081] It should be noted that although the detailed steps of the method of the present application are described in detail above, the skilled in the art can combine, split and change the order of the above steps without deviating from the basic principles of the present application. The technical solutions modified in this way do not change the basic concept of the present application, and therefore fall within the protection scope of the present application.

[0082] The skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments means 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 can be used in any combination.

[0083] It should be noted that although the detailed steps of the method of the present application are described in detail above, the skilled in the art can combine, split and change the order of the above steps without deviating from the basic principles of the present application. The technical solutions modified in this way do not change the basic concept of the present application, and therefore fall within the protection scope of the present application.

[0084] So far, the technical solution of the present application has been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.

Claims

1. A control method of a heating system, characterized by, The heating system comprises a heat pump cycle and a water cycle, the heat pump cycle comprises a variable displacement compressor, a tube heat exchanger, a throttling device and an evaporator which are connected by refrigerant pipelines, the water cycle comprises an indoor radiator and the tube heat exchanger which are connected by heat exchange pipelines, the refrigerant in the heat pump cycle and the circulating water in the water cycle exchange heat in the tube heat exchanger, the variable displacement compressor has two compression cylinders, and the control method comprises: obtaining an outdoor environment temperature; determining a working mode of the variable displacement compressor according to a temperature interval in which the outdoor environment temperature is located; controlling the variable displacement compressor to operate based on the working mode; wherein the working mode of the variable displacement compressor comprises a double-cylinder mode and a double-stage mode, in the double-cylinder mode, the two compression cylinders of the variable displacement compressor compress refrigerant separately, and in the double-stage mode, the two compression cylinders of the variable displacement compressor compress refrigerant successively; the step of "determining a working mode of the variable displacement compressor according to a temperature interval in which the outdoor environment temperature is located" further comprises: if the outdoor environment temperature is greater than or equal to a first temperature threshold, determining that the working mode of the variable displacement compressor is the double-stage mode; if the outdoor environment temperature is less than the first temperature threshold and greater than or equal to a second temperature threshold, determining that the working mode of the variable displacement compressor is the double-cylinder mode; if the outdoor environment temperature is less than the second temperature threshold, determining that the working mode of the variable displacement compressor is the double-stage mode.

2. The control method of a heating system according to claim 1, characterized by, The control method further comprises: performing PID control on the variable displacement compressor according to an indoor environment temperature.

3. The control method of a heating system according to claim 1, characterized by, The first temperature threshold is any value in 4-10℃; and / or The second temperature threshold is any value in -10-0℃.

4. The control method of a heating system according to any one of claims 1 to 3, characterized in that, The refrigerant and the circulating water adopt convection heat exchange in the tube heat exchanger.

5. The control method of a heating system according to any one of claims 1 to 3, characterized in that, A water tank is further arranged on the heat exchange pipeline, a liquid level sensor is arranged in the water tank, a water replenishing valve is arranged on the water tank, the water replenishing valve is connected with a water source, and the control method further comprises: obtaining an actual liquid level of the water tank; comparing the actual liquid level with a lower liquid level threshold; when the actual liquid level is less than the lower liquid level threshold, controlling the water replenishing valve to open until the liquid level in the water tank reaches an upper liquid level threshold.

6. The control method of a heating system according to any one of claims 1 to 3, characterized by, A pressure relief valve is further arranged on the heat exchange pipeline, a pressure sensor is further arranged on the heat exchange pipeline, and the control method further comprises: obtaining an actual pressure of the heat exchange pipeline; comparing the actual pressure with a preset pressure threshold; when the actual pressure is greater than the preset pressure threshold, controlling the pressure relief valve to open until the pressure of the heat exchange pipeline is less than the preset pressure threshold.

7. The control method of a heating system according to claim 1, wherein A circulating water pump is further arranged on the heat exchange pipeline, and the control method further comprises: controlling the circulating water pump to operate in the process that the variable displacement compressor operates.

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