CN117006720A - Cascade heat pump system and control method thereof - Google Patents

Abstract

The application relates to the technical field of cascade heat pumps, in particular to a cascade heat pump system and a control method thereof, and aims to solve the problem of low operation energy efficiency of the existing cascade heat pump system. The cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, wherein the high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger, the low-pressure refrigerant circulation loop is provided with a second compressor, a fluorine pump, an intermediate heat exchanger, a second throttling component and a second heat exchanger, the second compressor and the fluorine pump are arranged in parallel, and the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop can exchange heat through the intermediate heat exchanger. According to the cascade heat pump system, the second compressor and the fluorine pump are controlled to operate in a parallel mode, so that the second compressor is effectively prevented from being in an operating state all the time, and the operating energy efficiency of the cascade heat pump system is effectively improved.

Description

Cascade heat pump system and its control method

Technical field

The present invention relates to the technical field of cascade heat pumps, and specifically provides a cascade heat pump system and a control method thereof.

Background technique

Cascade heat pump systems generally include a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop. The high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop exchange heat through a shared intermediate heat exchanger to achieve the purpose of providing high-temperature hot water. However, the existing cascade heat pump system still needs to operate in cascade outside the rated operating conditions, for example, when the outdoor ambient temperature is relatively high, that is, it still needs to be operated under conditions where the temperature difference between the evaporation temperature and the condensation temperature is small. Two levels of compression, resulting in The loss is large, which in turn leads to low operating energy efficiency of the cascade heat pump system, resulting in energy waste.

Accordingly, the art needs a new cascade heat pump system and its control method to solve the above technical problems.

Contents of the invention

The present invention aims to solve the above technical problems, that is, to solve the problem of low operating energy efficiency of the existing cascade heat pump system.

In a first aspect, the present invention provides a cascade heat pump system, which includes a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop,

The high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling member and an intermediate heat exchanger,

The low-pressure refrigerant circulation loop is provided with a second compressor, a fluorine pump, the intermediate heat exchanger, a second throttling member and a second heat exchanger, wherein the second compressor and the fluorine pump are in a Parallel setup,

The high-pressure refrigerant circulation circuit and the low-pressure refrigerant circulation circuit are configured to enable heat exchange through the intermediate heat exchanger.

In the preferred technical solution of the above cascade heat pump system, the low-pressure refrigerant circulation loop is also provided with a three-way valve,

The three-way valve includes an inlet and two outlets. The inlet of the three-way valve is connected to the main path of the low-pressure refrigerant circulation circuit. The first outlet of the three-way valve is connected to the inlet of the second compressor. The air port is connected, and the second outlet of the three-way valve is connected with the air inlet of the fluorine pump.

In the preferred technical solution of the above cascade heat pump system, a solar collector is also provided on the low-pressure refrigerant circulation loop, and the solar collector is disposed between the second throttling member and the second heat exchanger. between devices.

In the preferred technical solution of the above cascade heat pump system, the cascade heat pump system also includes a bypass branch,

The bypass branch is connected to the low-pressure refrigerant circulation circuit, and the first end of the bypass branch is connected between the second throttling member and the solar collector. The second end is connected between the solar collector and the second heat exchanger,

A bypass valve is provided on the bypass branch, and the bypass valve is configured to control the access of the solar thermal collector to the low-pressure refrigerant circulation loop by controlling its own opening and closing state.

In the preferred technical solution of the above cascade heat pump system, the cascade heat pump system also includes a water exchange circuit,

A part of the water exchange circuit is provided in the first heat exchanger so that the water in the water exchange circuit can exchange heat with the refrigerant in the high-pressure refrigerant circulation loop through the first heat exchanger.

In the preferred technical solution of the above-mentioned cascade heat pump system, a first gas separation device is further provided on the high-pressure refrigerant circulation circuit, and the first gas separation device is disposed at the air inlet of the first compressor.

In the preferred technical solution of the above cascade heat pump system, a second gas separation device is also provided on the low-pressure refrigerant circulation circuit, and the second gas separation device is provided at the air inlet of the second compressor.

On the other hand, the present invention also provides a control method for a cascade heat pump system. The cascade heat pump system includes a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop.

The high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling member and an intermediate heat exchanger,

The low-pressure refrigerant circulation loop is provided with a second compressor, a fluorine pump, the intermediate heat exchanger, a second throttling member and a second heat exchanger, wherein the second compressor and the fluorine pump are in a Parallel setup,

The high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are configured to enable heat exchange through the intermediate heat exchanger,

The low-pressure refrigerant circulation circuit is also provided with a three-way valve. The three-way valve includes an inlet and two outlets. The inlet of the three-way valve is connected to the main path of the low-pressure refrigerant circulation circuit. The three-way valve The first outlet is connected to the air inlet of the second compressor, and the second outlet of the three-way valve is connected to the air inlet of the fluorine pump,

A solar collector is also provided on the low-pressure refrigerant circulation loop, and the solar collector is provided between the second throttling member and the second heat exchanger,

The cascade heat pump system further includes a bypass branch, the first end of the bypass branch is connected between the second throttling member and the solar collector, and the bypass branch has The second end is connected between the solar collector and the second heat exchanger, and a bypass valve is provided on the bypass branch;

When the high-pressure refrigerant circulation loop is operating, the control method includes:

Get light irradiance;

Control the connection state of the bypass branch and the operating state of the solar collector according to the light irradiance and the preset light irradiance;

Get the outdoor ambient temperature;

The communication state of the three-way valve and the operating states of the second compressor and the fluorine pump are controlled according to the outdoor ambient temperature and the preset ambient temperature.

In the preferred technical solution of the above control method, the step of "controlling the connection state of the bypass branch and the operating state of the solar collector according to the light irradiance and the preset light irradiance" is specific include:

If the light irradiance is greater than or equal to the preset light irradiance, control the bypass branch to be disconnected and the solar collector to operate;

If the light irradiance is less than the preset light irradiance, the bypass branch is controlled to be connected and the solar collector does not operate.

In the preferred technical solution of the above control method, the step of "controlling the communication status of the three-way valve and the operating status of the second compressor and the fluorine pump according to the outdoor ambient temperature and the preset ambient temperature" Specifically include:

If the outdoor ambient temperature is greater than or equal to the preset ambient temperature, control the inlet and second outlet of the three-way valve to communicate, the second compressor does not operate and the fluorine pump operates;

If the outdoor ambient temperature is lower than the preset ambient temperature, the inlet of the three-way valve is controlled to communicate with the first outlet, the second compressor operates and the fluorine pump does not operate.

When the above technical solution is adopted, the cascade heat pump system of the present invention controls the second compressor and the fluorine pump to operate selectively by setting the second compressor and the fluorine pump in parallel, effectively preventing the second compressor from always being in the operating status, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

Description of the drawings

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic structural diagram of the cascade heat pump system of the present invention;

Figure 2 is a flow chart of the main steps of the control method of the present invention;

Figure 3 is a specific step flow chart of a preferred embodiment of the control method of the present invention;

Reference signs:

1. High-pressure refrigerant circulation circuit; 11. First compressor; 12. First heat exchanger; 13. First throttling component; 14. Intermediate heat exchanger; 15. First gas separation device;

2. Low-pressure refrigerant circulation circuit; 21. Second compressor; 22. Fluorine pump; 23. Second throttling component; 24. Second heat exchanger; 25. Heat exchange fan; 26. Three-way valve; 27. Solar energy Heat collector; 28. Second gas separation device;

3. Bypass branch; 31. Bypass valve;

4. Replace the hot water line.

Detailed ways

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application situations. For example, the cascade heat pump system described in the present invention can be a household cascade heat pump system or an industrial cascade heat pump system. This is not limiting. Those skilled in the art can design their own according to actual needs. Determine the application occasions of the cascade heat pump system of the present invention. Such changes related to application scenarios do not deviate from the basic principles of the present invention and belong to the protection scope of the present invention.

It should be noted that in the description of this preferred embodiment, unless otherwise explicitly stated and limited, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, it can be a direct connection, it can be an indirect connection through an intermediate medium, or it can be an internal connection between two components. , therefore cannot be construed as a limitation of the present invention. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In addition, it should be noted that in the description of the present invention, although the various steps of the control method of the present invention are described in a specific order, these orders are not limiting and do not deviate from the basic principles of the present invention. Under the premise, those skilled in the art can perform the steps in different orders.

First refer to Figure 1, which is a schematic structural diagram of the cascade heat pump system of the present invention. As shown in Figure 1, the cascade heat pump system of the present invention includes a high-pressure refrigerant circulation circuit 1 and a low-pressure refrigerant circulation circuit 2. The high-pressure refrigerant circulation circuit 1 is provided with a first compressor 11, a first heat exchanger 12, a first The throttling member 13 and the intermediate heat exchanger 14. The low-pressure refrigerant circulation circuit 2 is provided with a second compressor 21, a fluorine pump 22, an intermediate heat exchanger 14, a second throttling member 23 and a second heat exchanger 24, wherein , the second compressor 21 and the fluorine pump 22 are arranged in parallel, and the high-pressure refrigerant circulation circuit 1 and the low-pressure refrigerant circulation circuit 2 are arranged to exchange heat through the intermediate heat exchanger 14. Based on the above structural arrangement, the cascade heat pump system of the present invention controls the second compressor 21 and the fluorine pump 22 to operate selectively by arranging the second compressor 21 and the fluorine pump 22 in parallel, effectively preventing the second compressor 21 from always running. is in the operating state, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

It should be noted that the present invention does not place any restrictions on the specific types of refrigerants flowing in the high-pressure refrigerant circulation circuit 1 and the low-pressure refrigerant circulation circuit 2 and the heat exchange sources of the first heat exchanger 12 and the second heat exchanger 24. Technicians can set it themselves according to the actual situation. As a specific implementation, the refrigerant in the high-pressure refrigerant circulation circuit 1 is refrigerant R134a, and the refrigerant in the low-pressure refrigerant circulation circuit 2 is refrigerant R410A. The heat exchange source of the second heat exchanger 24 is an air source to further reduce the energy consumption of the cascade heat pump system and improve the operating energy efficiency; specifically, the cascade heat pump system also includes a heat exchange fan 25. The hot air fan 25 is arranged near the second heat exchanger 24 to improve the heat exchange effect between the air and the refrigerant in the second heat exchanger 24 .

In addition, it should be noted that the present invention does not place any restrictions on the specific structure of the intermediate heat exchanger 14. It can be a shell-and-tube heat exchanger or a plate heat exchanger. Those skilled in the art can make their own decisions based on the actual situation. set up. In this specific embodiment, the intermediate heat exchanger 14 is preferably a plate heat exchanger to effectively improve the heat exchange efficiency of the cascade heat pump system.

Specifically, the intermediate heat exchanger 14 includes a first heat exchange channel and a second heat exchange channel. The refrigerant in the high-pressure refrigerant circulation circuit 1 flows through the first heat exchange channel, and the refrigerant in the low-pressure refrigerant circulation circuit 2 flows through the first heat exchange channel. The second heat exchange channel, the first heat exchange channel and the second heat exchange channel are arranged in a staggered manner to achieve the purpose of heat exchange between the refrigerant in the high-pressure refrigerant circulation circuit 1 and the refrigerant in the low-pressure refrigerant circulation circuit 2.

In addition, it should be noted that the present invention does not apply to the first compressor 11, the second compressor 21, the fluorine pump 22, the first throttling member 13, the second throttling member 23, the first heat exchanger 12, the second There are no restrictions on the specific structure and specific model of the heat exchanger 24; the first compressor 11 and the second compressor 21 can be variable frequency compressors or fixed frequency compressors. Preferably, the first compressor 11 and the second compressor 21 can be variable frequency compressors or fixed frequency compressors. The compressor 21 is a variable frequency compressor in order to control the operating status of the cascade heat pump system; the fluorine pump 22 can be a fluorine-lined centrifugal pump, a fluorine-lined magnetic pump, or a fluorine-lined self-priming pump; first The throttling member 13 and the second throttling member 23 may be electronic expansion valves, capillary tubes, or thermal expansion valves; the first heat exchanger 12 and the second heat exchanger 24 may be plate heat exchangers, or It can be a shell and tube heat exchanger, which is not limiting. Those skilled in the art can set it themselves according to the actual situation.

Furthermore, the low-pressure refrigerant circulation circuit 2 is also provided with a three-way valve 26. The three-way valve 26 includes an inlet (port a in Figure 1) and two outlets. The inlet of the three-way valve 26 is connected to the main path of the low-pressure refrigerant circulation circuit 2. connected, the first outlet of the three-way valve 26 (port b in Figure 1) is connected with the air inlet of the second compressor 21, and the second outlet of the three-way valve 26 (port c in Figure 1) is connected with the inlet of the fluorine pump 22 The breath is connected. The three-way valve 26 is configured to selectively connect the second compressor 21 and the fluorine pump 22 to the low-pressure refrigerant circulation circuit 2 by controlling its own communication state. When port a and port b of the three-way valve 26 are connected, the second compressor 21 is connected to the low-pressure refrigerant circulation circuit 2; when port a and port c of the three-way valve 26 are connected, the fluorine pump 22 is connected to the low-pressure refrigerant cycle. In loop 2. It should be noted that the present invention does not place any restrictions on the specific structure and type of the three-way valve 26, and those skilled in the art can set it themselves according to the actual situation.

Preferably, the low-pressure refrigerant circulation circuit 2 is also provided with a solar collector 27 , and the solar collector 27 is disposed between the second throttling member 23 and the second heat exchanger 24 . The solar collector 27 can be used to supplement the heat of the refrigerant in the low-pressure refrigerant circulation circuit 2, which can not only make full use of renewable solar energy, but also further improve the operating energy efficiency of the cascade heat pump system.

Further, the cascade heat pump system also includes a bypass branch 3, which is connected to the low-pressure refrigerant circulation circuit 2, and the first end of the bypass branch 3 is connected to the second throttling member 23 and solar energy. Between the heat collectors 27, the second end of the bypass branch 3 is connected to between the solar collector 27 and the second heat exchanger 24. The bypass branch 3 is provided with a bypass valve 31. The bypass valve 31 It is configured to be able to control the connection of the solar collector 27 to the low-pressure refrigerant circulation circuit 2 by controlling its own opening and closing state.

It should be noted that the present invention does not place any restrictions on the specific structure and type of the solar collector 27 and the bypass valve 31. The solar collector 27 can be a flat plate collector, a concentrating collector, or It can be a plane mirror collector; the bypass valve 31 can be a hydraulic control valve or an electromagnetic control valve. These are not restrictive, and those skilled in the art can set them according to the actual situation.

Further preferably, the cascade heat pump system also includes a hot water exchange circuit 4, and the water in the hot water exchange circuit 4 is the heat exchange source of the first heat exchanger 12; specifically, a part of the hot water exchange circuit 4 is provided in the first heat exchanger 12. In the heat exchanger 12 , the water in the water exchange circuit 4 passes through the first heat exchanger 12 to exchange heat with the refrigerant in the high-pressure refrigerant circulation circuit 1 .

In addition, in this specific embodiment, the high-pressure refrigerant circulation circuit 1 is also provided with a first gas separation device 15 , and the first gas separation device 15 is provided at the air inlet of the first compressor 11 . The low-pressure refrigerant circulation circuit 2 is also provided with a second gas separation device 28 , and the second gas separation device 28 is disposed at the air inlet of the second compressor 21 . The arrangement of the first gas separation device 15 and the second gas separation device 28 can effectively avoid the problem of liquid slugging in the first compressor 11 and the second compressor 21 and effectively ensure the service life of the first compressor 11 and the second compressor 21 . It should be noted that the present invention does not place any restrictions on the specific structures of the first gas separation device 15 and the second gas separation device 28, and those skilled in the art can set them according to actual conditions.

Further, the cascade heat pump system also includes a temperature sensor, a light irradiance sensor and a controller (not shown in the figure). The temperature sensor can obtain the ambient temperature near the cascade heat pump system, so The optical irradiance sensor can detect the optical irradiance near the solar collector 27, and the controller can obtain the ambient temperature detected by the temperature sensor and the optical irradiance detected by the optical irradiance sensor, so The controller can also control the connection status of the bypass branch 3 and the three-way valve 26 as well as the operating status of the solar collector 27, the second compressor 21 and the fluorine pump 22, etc., which are not limiting.

It should be noted that the present invention does not place any restrictions on the specific number and location of the temperature sensors and the light irradiance sensors, as long as the ambient temperature and light irradiance can be obtained. Those skilled in the art can determine The situation sets itself. In addition, those skilled in the art can understand that the present invention does not place any restrictions on the specific structure and model of the controller, and the controller can be the original controller of the cascade heat pump system, or it can be It is a controller set up separately for executing the control method of the present invention. Those skilled in the art can set the structure and model of the controller according to actual needs.

Next, refer to Figure 2, which is a flow chart of the main steps of the control method of the present invention. As shown in Figure 2, based on the cascade heat pump system described in the above embodiment, the control method of the present invention mainly includes the following steps:

S1: Obtain light irradiance;

S2: Control the connection status of the bypass branch and the operating status of the solar collector according to the light irradiance and the preset light irradiance;

S3: Get the outdoor ambient temperature;

S4: Control the connection status of the three-way valve and the operating status of the second compressor and fluorine pump according to the outdoor ambient temperature and the preset ambient temperature.

When the high-pressure refrigerant circulation loop 1 is running, first, in step S1, the controller obtains the light irradiance; of course, the present invention does not place any restrictions on the specific acquisition timing and acquisition method of the light irradiance. The controller can obtain the information in real time or at certain intervals. This is not restrictive, and those skilled in the art can set it themselves according to the actual situation. Preferably, the controller obtains the light irradiance in real time so as to promptly and effectively adjust the operating status of the cascade heat pump system, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

Next, in step S2, the controller controls the connection state of the bypass branch 3 and the operating state of the solar collector 27 according to the light irradiance and the preset light irradiance.

It should be noted that the present invention does not place any restrictions on the specific control method of the controller to control the connection state of the bypass branch 3 and the operating state of the solar collector 27. The controller can control the light irradiance. Compare or compare with the preset light irradiance, and then control the connection state of the bypass branch 3 and the operating state of the solar collector 27 according to the comparison result or the comparison result; of course, this is not Limitations can be set by those skilled in the art according to actual conditions.

In addition, it should be noted that the present invention does not place any restrictions on the specific setting value of the preset light irradiance. Persons skilled in the art can set it according to the actual operating conditions of the cascade heat pump system, or It is obtained according to the actual usage needs of the user, and this is not restrictive.

In addition, in step S3, the controller acquires the outdoor ambient temperature near the cascade heat pump system; of course, the present invention does not place any restrictions on the specific acquisition timing and acquisition method of the outdoor ambient temperature. The device can be obtained in real time or at a certain interval. This is not restrictive. Those skilled in the art can set it by themselves according to the actual situation. Preferably, the controller obtains the outdoor ambient temperature in real time so as to promptly and effectively adjust the operating status of the cascade heat pump system, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

Next, in step S4, the controller controls the communication state of the three-way valve 26 and the operating states of the second compressor 21 and the fluorine pump 22 according to the outdoor ambient temperature and the preset ambient temperature.

It should be noted that the present invention does not place any restrictions on the specific setting value of the preset ambient temperature. Persons skilled in the art can set it according to the actual operating conditions of the cascade heat pump system, or according to the actual use of the user. Requirements acquisition, none of this is restrictive.

In addition, it should be noted that the present invention does not place any restrictions on the specific control method by which the controller controls the connection state of the three-way valve 26 and the operating states of the second compressor 21 and the fluorine pump 22. The outdoor ambient temperature and the preset ambient temperature are compared or compared, and then the connection status of the three-way valve 26 and the operating status of the second compressor 21 and the fluorine pump 22 are controlled based on the comparison result or the comparison result.

In addition, it should be noted that the present invention does not place any restrictions on the specific execution order of steps S1 and S3. Steps S1 and S3 can be executed at the same time or one after another in no particular order. Those skilled in the art can proceed according to actual conditions. The situation sets itself.

Referring next to Figure 3, Figure 3 is a specific step flow chart of a preferred embodiment of the control method of the present invention. As shown in Figure 3, based on the cascade heat pump system described in the above embodiment, the control method of the preferred embodiment of the present invention includes the following steps:

S101: Obtain light irradiance;

S102: If the light irradiance is greater than or equal to the preset light irradiance, the bypass branch is controlled to be disconnected and the solar collector operates;

S103: If the light irradiance is less than the preset light irradiance, the bypass branch is controlled to be connected and the solar collector does not operate;

S104: Get the outdoor ambient temperature;

S105: If the outdoor ambient temperature is greater than or equal to the preset ambient temperature, the inlet and second outlet of the three-way valve are controlled to be connected, the second compressor does not run and the fluorine pump runs;

S106: If the outdoor ambient temperature is lower than the preset ambient temperature, the inlet of the three-way valve is controlled to be connected to the first outlet, the second compressor runs and the fluorine pump does not run.

When the high-pressure refrigerant circulation loop 1 is running, first, in step S101, the controller obtains light irradiance; of course, the present invention does not place any restrictions on the specific acquisition timing and acquisition method of the light irradiance. The controller can obtain the information in real time or at certain intervals. This is not restrictive, and those skilled in the art can set it themselves according to the actual situation. Preferably, the controller obtains the light irradiance in real time so as to promptly and effectively adjust the operating status of the cascade heat pump system, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

Then, the controller controls the connection state of the bypass branch 3 and the operating state of the solar collector 27 according to the light irradiance and the preset light irradiance. It should be noted that the present invention does not place any restrictions on the specific setting value of the preset light irradiance. Those skilled in the art can set it according to the actual operating conditions of the cascade heat pump system, or according to the user's requirements. For actual use requirements acquisition, this is not restrictive.

Specifically, in step S102, if the light irradiance is greater than or equal to the preset light irradiance, the controller controls the bypass branch 3 to be disconnected and the solar collector 27 to operate; at this time , the bypass valve 31 is in a closed state, and the refrigerant in the low-pressure refrigerant circulation circuit 2 flows out from the second throttling member 23 , flows through the solar collector 27 and then flows to the second heat exchanger 24 .

Further, in step S103, if the light irradiance is less than the preset light irradiance, the controller controls the bypass branch 3 to be connected and the solar collector 27 not to operate; at this time, the bypass The bypass valve 31 is in an open state, and the refrigerant in the low-pressure refrigerant circulation circuit 2 flows out from the second throttling member 23 , flows through the bypass valve 31 and then flows to the second heat exchanger 24 .

In addition, in step S104, the controller obtains the outdoor ambient temperature near the cascade heat pump system; of course, the present invention does not impose any restrictions on the specific timing and acquisition method of the outdoor ambient temperature. The device can be obtained in real time or at a certain interval. This is not restrictive. Those skilled in the art can set it by themselves according to the actual situation. Preferably, the controller obtains the outdoor ambient temperature in real time so as to promptly and effectively adjust the operating status of the cascade heat pump system, thereby effectively improving the operating energy efficiency of the cascade heat pump system.

Then, the controller controls the communication state of the three-way valve 26 and the operating states of the second compressor 21 and the fluorine pump 22 according to the outdoor ambient temperature and the preset ambient temperature. It should be noted that the present invention does not place any restrictions on the specific setting value of the preset ambient temperature. Persons skilled in the art can set it according to the actual operating conditions of the cascade heat pump system, or according to the actual use of the user. Requirements acquisition, none of this is restrictive.

Specifically, in step S105, if the outdoor ambient temperature is greater than or equal to the preset ambient temperature, the controller controls the inlet (port a) and the second outlet (port c) of the three-way valve 26 to communicate, The second compressor 21 does not operate and the fluorine pump 22 operates.

Further, in step S106, if the outdoor ambient temperature is less than the preset ambient temperature, the controller controls the inlet (a port) of the three-way valve to communicate with the first outlet (b port), and the second compression The machine 21 is running and the fluorine pump 22 is not running.

Based on the above arrangement, in the cascade heat pump system of the present invention, the second compressor 21 does not operate and the fluorine pump 22 operates during the high temperature season; during the cascade operation during the low temperature season, the second compressor 21 operates and the fluorine pump 22 does not operate. , which can not only improve the operating energy efficiency of the cascade heat pump system under high temperature working conditions, but also improve the operating energy efficiency of the cascade heat pump system under low temperature working conditions. In addition, when the light irradiance of the cascade heat pump system of the present invention is high, the solar collector 27 is connected to the low-pressure refrigerant circulation loop 2, which can make full use of renewable solar energy and further improve the efficiency of the cascade heat pump. The operating energy efficiency of the system.

It should be noted that the present invention does not place any restrictions on the specific execution order of step S101 and step S104. Steps S101 and step S104 can be executed at the same time or one after the other in no particular order. Those skilled in the art can set them according to the actual situation. . Preferably, step S101 and step S104 are executed simultaneously to further improve the operating energy efficiency of the cascade heat pump system.

In addition, it should be noted that the operation mode of the cascade heat pump system of the present invention is not limited to the above situation. Those skilled in the art can set the operation mode of the cascade heat pump system according to the actual situation; technology in the art Personnel can understand that changes in the specific operating mode of the cascade heat pump system do not deviate from the basic principles of the present invention and still fall within the protection scope of the present invention.

So far, the technical solution of the present invention has been described with reference to the preferred embodiments shown in the drawings. However, those skilled in the art can easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to relevant technical features, and technical solutions after these modifications or substitutions will fall within the protection scope of the present invention.

Claims (10)

1. A cascade heat pump system is characterized in that the cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop,

the high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger,

the low-pressure refrigerant circulation loop is provided with a second compressor, a fluorine pump, the intermediate heat exchanger, a second throttling component and a second heat exchanger, wherein the second compressor and the fluorine pump are arranged in parallel,

the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are arranged to be capable of exchanging heat through the intermediate heat exchanger.

2. The cascade heat pump system of claim 1, wherein the low-pressure refrigerant circulation circuit is further provided with a three-way valve,

the three-way valve comprises an inlet and two outlets, the inlet of the three-way valve is connected with the main path of the low-pressure refrigerant circulation loop, the first outlet of the three-way valve is connected with the air inlet of the second compressor, and the second outlet of the three-way valve is connected with the air inlet of the fluorine pump.

3. The cascade heat pump system of claim 1, wherein a solar heat collector is further disposed on the low pressure refrigerant circulation loop, the solar heat collector being disposed between the second throttle member and the second heat exchanger.

4. The cascade heat pump system of claim 3, further comprising a bypass branch,

the bypass branch is connected with the low-pressure refrigerant circulation loop, the first end of the bypass branch is connected between the second throttling component and the solar heat collector, the second end of the bypass branch is connected between the solar heat collector and the second heat exchanger,

the bypass branch is provided with a bypass valve, and the bypass valve is arranged to control the condition that the solar heat collector is connected into the low-pressure refrigerant circulation loop by controlling the opening and closing states of the bypass valve.

5. The cascade heat pump system of any of claims 1-4, further comprising a heat exchange waterway,

and a part of the heat exchange waterway is arranged in the first heat exchanger so that water in the heat exchange waterway exchanges heat with the refrigerant in the high-pressure refrigerant circulation loop through the first heat exchanger.

6. The cascade heat pump system according to any one of claims 1-4, further comprising a first gas separation device disposed on the high-pressure refrigerant circulation circuit, the first gas separation device being disposed at a gas inlet of the first compressor.

7. The cascade heat pump system according to any one of claims 1-4, wherein a second gas separation device is further provided on the low-pressure refrigerant circulation circuit, the second gas separation device being provided at a gas inlet of the second compressor.

8. A control method of a cascade heat pump system is characterized in that the cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop,

the high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger,

the low-pressure refrigerant circulation loop is provided with a second compressor, a fluorine pump, the intermediate heat exchanger, a second throttling component and a second heat exchanger, wherein the second compressor and the fluorine pump are arranged in parallel,

the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are arranged to be capable of exchanging heat through the intermediate heat exchanger,

the low-pressure refrigerant circulation loop is also provided with a three-way valve, the three-way valve comprises an inlet and two outlets, the inlet of the three-way valve is connected with the main path of the low-pressure refrigerant circulation loop, the first outlet of the three-way valve is connected with the air inlet of the second compressor, the second outlet of the three-way valve is connected with the air inlet of the fluorine pump,

the low-pressure refrigerant circulation loop is also provided with a solar heat collector which is arranged between the second throttling component and the second heat exchanger,

the cascade heat pump system further comprises a bypass branch, wherein a first end of the bypass branch is connected between the second throttling component and the solar heat collector, a second end of the bypass branch is connected between the solar heat collector and the second heat exchanger, and a bypass valve is arranged on the bypass branch;

under the condition that the high-pressure refrigerant circulation loop operates, the control method comprises the following steps:

acquiring irradiance;

controlling the communication state of the bypass branch and the operation state of the solar heat collector according to the irradiance and the preset irradiance;

acquiring outdoor environment temperature;

and controlling the communication state of the three-way valve and the running states of the second compressor and the fluorine pump according to the outdoor environment temperature and the preset environment temperature.

9. The control method according to claim 8, wherein the step of controlling the communication state of the bypass branch and the operation state of the solar collector according to the irradiance of light and the preset irradiance of light specifically includes:

if the irradiance is greater than or equal to the preset irradiance, controlling the bypass branch not to be communicated and the solar collector to operate;

and if the irradiance is smaller than the preset irradiance, controlling the bypass branch to be communicated and the solar heat collector not to operate.

10. The control method according to claim 8, wherein the step of controlling the communication state of the three-way valve and the operation states of the second compressor and the fluorine pump according to the outdoor ambient temperature and the preset ambient temperature specifically includes:

if the outdoor ambient temperature is greater than or equal to the preset ambient temperature, controlling the inlet of the three-way valve to be communicated with a second outlet, wherein the second compressor is not operated and the fluorine pump is operated;

and if the outdoor environment temperature is smaller than the preset environment temperature, controlling the inlet of the three-way valve to be communicated with the first outlet, wherein the second compressor is operated and the fluorine pump is not operated.