Cascade heat pump system

Abstract

The utility model relates to the field of heat pumps, in particular to a cascade heat pump system. The cascade heat pump system comprises a first compressor, a first four-way valve, an evaporative condenser, an evaporator and a heat exchanger; the evaporative condenser is provided with an evaporation side and a condensation side which are in heat exchange connection, and the heat exchanger is provided with a water side and a refrigerant side which are in heat exchange connection; the first compressor, the evaporator, the first four-way valve, the condensation side of the evaporative condenser and the first expansion valve are connected to form a low-temperature stage loop; the second compressor, the evaporation side of the evaporative condenser, the refrigerant side of the heat exchanger and the second expansion valve are connected to form a high-temperature stage loop; the two ends of the refrigerant side of the heat exchanger are connected with parallel branches, the refrigerant side of the heat exchanger is connected with the condensation side of the evaporative condenser in parallel through the parallel branches, and the switching valve set controls the condensation side of the evaporative condenser and the refrigerant side of the heat exchanger to be alternately communicated between the first compressor and the evaporator. According to the cascade heat pump system, the operation efficiency under various water temperatures can be ensured.

Description

Technical Field

[0001] The present application relates to the field of heat pumps, and in particular to a cascade heat pump system. Background Art

[0002] As a clean, environmentally friendly, renewable resource application technology, heat pump technology has broad application prospects.

[0003] At present, heat pump technology is widely used in fields such as heat pump air conditioners and heat pump water heaters. A single heat pump system is difficult to meet the preparation needs of water at different temperatures, especially high-temperature hot water, and the cascade high-temperature heat pump system is born out of this need. Compared with traditional high-temperature heat pumps, the current cascade high-temperature heat pump system can meet the needs of hot water preparation over a wider range of temperatures. However, the operation mode of the cascade heat pump system is usually relatively single, and it cannot guarantee that the system maintains a high operating efficiency when water is required at different temperatures.

[0004] Therefore, how to improve the operating efficiency of the cascade heat pump system under various temperature water demands becomes a technical problem that needs to be solved by those skilled in the art. Utility Model Content

[0005] The present application provides a cascade heat pump system, which can ensure that the system maintains a high operating efficiency under various temperature water demands.

[0006] To achieve the above technical effects, the present application provides a cascade heat pump system, comprising: a first compressor, a second compressor, a first four-way valve, an evaporative condenser, an evaporator, a heat exchanger, a first expansion valve, and a second expansion valve;

[0007] The evaporative condenser is provided with an evaporation side and a condensation side connected in heat exchange, and the heat exchanger is provided with a water side and a refrigerant side connected in heat exchange;

[0008] The first compressor, the evaporator, the first four-way valve, the condensation side of the evaporative condenser, and the first expansion valve are connected to form a low-temperature circuit; the second compressor, the evaporation side of the evaporative condenser, the refrigerant side of the heat exchanger, and the second expansion valve are connected to form a high-temperature circuit;

[0009] The refrigerant side of the heat exchanger is connected to parallel branches at both ends, and the refrigerant side of the heat exchanger is connected in parallel with the condensing side of the evaporative condenser through the parallel branches. It also includes a switching valve group that controls the condensing side of the evaporative condenser and the refrigerant side of the heat exchanger to be alternately connected between the first compressor and the evaporator.

[0010] In some embodiments, the first four-way valve is provided with a C port, a D port, an E port and an S port which are switched and connected in pairs;

[0011] The first end of the evaporator is connected to the C interface of the first four-way valve, the air inlet of the first compressor is connected to the S interface of the first four-way valve, the exhaust port of the first compressor is connected to the D interface of the first four-way valve, and the E interface of the first four-way valve is respectively connected to the first end of the refrigerant side of the heat exchanger and the first end of the condensation side of the evaporative condenser;

[0012] The second end of the evaporator is respectively connected to the second end of the condensation side of the evaporative condenser and the second end of the refrigerant side of the heat exchanger;

[0013] The switching valve group includes a first solenoid valve and a second solenoid valve disposed at both ends of the condensation side of the evaporative condenser, and a third solenoid valve and a fourth solenoid valve of the parallel branch disposed at both ends of the heat exchanger.

[0014] In some embodiments, the first expansion valve is connected in series between the second end of the evaporator and the second end of the condensing side of the evaporative condenser, and the second solenoid valve is connected between the first expansion valve and the second end of the condensing side of the evaporative condenser;

[0015] The second expansion valve is connected in series between the second end of the refrigerant side of the heat exchanger and the second end of the evaporation side of the evaporative condenser;

[0016] One of the first expansion valve and the second expansion valve is connected in series with the parallel branch.

[0017] In some embodiments, the outlet of the second compressor is provided with a first isolation valve isolating the parallel branch, and the second end of the evaporation side of the evaporative condenser is provided with a second isolation valve isolating the parallel branch.

[0018] In some embodiments, a first gas-liquid separator is provided between the S interface of the first four-way valve and the air inlet of the first compressor.

[0019] In some embodiments, a second gas-liquid separator is provided between the air inlet of the second compressor and the first end of the evaporation side of the evaporative condenser.

[0020] In some embodiments, the low-temperature stage circuit is connected to a first refrigerant recovery device, and the first refrigerant recovery device is used to release the first refrigerant toward the low-temperature stage circuit or recover the first refrigerant of the low-temperature stage circuit.

[0021] In some embodiments, the high temperature stage circuit is connected to a second refrigerant recovery device, and the second refrigerant recovery device is used to release the second refrigerant toward the high temperature stage circuit or recover the second refrigerant of the high temperature stage circuit.

[0022] In some embodiments, the first refrigerant recovery device and the evaporator are connected in parallel, and a first release control valve and a first recovery control valve are respectively provided at two ends of the first refrigerant recovery device.

[0023] In some embodiments, the second refrigerant recovery device is connected in parallel with the evaporation side of the evaporative condenser, and a second release control valve and a second recovery control valve are respectively provided at both ends of the second refrigerant recovery device.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: the cascade heat pump system provided by the present application utilizes the first compressor, the evaporator, the first four-way valve, the condensing side of the evaporative condenser and the first expansion valve to form a low-temperature circuit, and utilizes the second compressor, the evaporating side of the evaporative condenser, the refrigerant side of the heat exchanger and the second expansion valve to form a high-temperature circuit, and the water side of the heat exchanger is used to pass normal temperature water and the refrigerant on the refrigerant side to exchange heat to prepare cold water or hot water of the required temperature. In addition, the refrigerant side of the heat exchanger is connected in parallel with the condensing side of the evaporative condenser through a parallel branch, so that the refrigerant side of the heat exchanger and the condensing side of the evaporative condenser are connected in parallel, and the refrigerant side of the heat exchanger and the condensing side of the evaporative condenser are controlled by the switching valve group to alternately connect between the first compressor and the evaporator.

[0025] When it is necessary to prepare low-temperature cold water, the switching valve group controls the condensing side of the evaporative condenser to be isolated from the first compressor and the evaporator, and at the same time controls the refrigerant side of the heat exchanger to be connected in series between the first compressor and the evaporator through a parallel branch to form a low-temperature stage circuit. The first four-way valve switches the low-temperature stage circuit to the refrigeration mode. The first refrigerant in the low-temperature stage circuit condenses and releases heat in the evaporator, and is sent to the refrigerant side of the heat exchanger after throttling by the first expansion valve to evaporate and absorb heat, and exchanges heat with the normal temperature water on the water side of the heat exchanger to achieve the preparation of low-temperature cold water. The settings of the parallel branch and the switching valve group realize full utilization of the characteristics of the first compressor, i.e., the low-temperature stage compressor, and the first refrigerant, i.e., the low-temperature refrigerant, to ensure that the system is at a high operating efficiency during the preparation of low-temperature cold water.

[0026] When low-temperature hot water needs to be prepared, the switching valve group controls the condensing side of the evaporative condenser to be isolated from the first compressor and the evaporator, and at the same time controls the refrigerant side of the heat exchanger to be connected in series between the first compressor and the evaporator through a parallel branch to form a low-temperature stage circuit. The first four-way valve switches the low-temperature stage circuit to the heating mode. The first refrigerant in the low-temperature stage circuit evaporates and absorbs heat in the evaporator, is compressed by the first compressor and discharged to the refrigerant side of the heat exchanger to condense and release heat, and exchanges heat with the normal temperature water on the water side of the heat exchanger to achieve the preparation of low-temperature hot water. The settings of the parallel branch and the switching valve group realize full utilization of the characteristics of the first compressor, i.e., the low-temperature stage compressor, and the first refrigerant, i.e., the low-temperature refrigerant, to ensure that the system is at a high operating efficiency during the preparation of low-temperature hot water.

[0027] When medium-temperature hot water preparation is required, the switching valve group controls the refrigerant side of the heat exchanger to be isolated from the first compressor and the evaporator, and the low-temperature stage circuit stops running; the refrigerant side of the heat exchanger and the high-temperature stage circuit composed of the second compressor, the evaporation side of the evaporative condenser, and the second expansion valve start running, the second refrigerant evaporates and absorbs heat on the evaporation side of the evaporative condenser, is compressed by the second compressor, and is sent to the refrigerant side of the heat exchanger to condense and release heat, and exchanges heat with the normal temperature water on the water side of the heat exchanger, making full use of the characteristics of the second compressor, i.e., the high-temperature stage compressor, and the characteristics of the second refrigerant, i.e., the high-temperature refrigerant, to ensure that the system maintains a high operating efficiency when medium-temperature hot water is prepared.

[0028] When high-temperature hot water preparation is required, the switching valve group controls the refrigerant side of the heat exchanger to be isolated from the first compressor and the evaporator, and at the same time controls the condensation side of the evaporative condenser to be connected in series between the first compressor and the evaporator to form a low-temperature circuit. The first four-way valve switches the low-temperature circuit to the heating mode, and the high-temperature circuit and the low-temperature circuit composed of the second compressor, the evaporation side of the evaporative condenser, the second expansion valve and the refrigerant side of the heat exchanger are cascaded through the evaporative condenser for heating. The first refrigerant in the low-temperature circuit absorbs heat in the evaporator, and after being compressed by the first compressor, it is sent to the condensation side of the evaporative condenser to condense and release heat. The second refrigerant in the high-temperature circuit evaporates and absorbs heat on the evaporation side of the evaporative condenser, absorbs the heat released by the condensation of the first refrigerant, and increases the temperature of the second refrigerant entering and discharging the second compressor, thereby increasing the condensation heat released by the second refrigerant on the refrigerant side of the heat exchanger, and exchanges heat with the normal temperature water on the water side of the heat exchanger to achieve high-temperature hot water preparation. During the cascade heating process, the low-temperature circuit and the high-temperature circuit, that is, the first compressor and the second compressor, are both in the high-efficiency operation range, thereby ensuring that the system is in an efficient operation state.

[0029] The present application realizes that the refrigerant side of the heat exchanger and the condensing side of the evaporative heat exchanger can be switched and connected between the first compressor and the evaporator to form different low-temperature stage circuits through the setting of parallel branches and switching valve groups, and fully utilizes the characteristics of the first compressor, the second compressor, the first refrigerant, and the second refrigerant, so that the cascade heat pump system maintains a high operating efficiency during the preparation of low-temperature cold water, low-temperature hot water, medium-temperature hot water and high-temperature hot water. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0033] Figure 1 A system diagram of a cascade heat pump system provided in one embodiment of the present application;

[0034] Figure 2 for Figure 1 Schematic diagram of the preparation of low-temperature cold water by a medium cascade heat pump system;

[0035] Figure 3 for Figure 1 Schematic diagram of the preparation of low-temperature hot water by a medium cascade heat pump system;

[0036] Figure 4 for Figure 1 Schematic diagram of medium-temperature hot water preparation by medium-cascade heat pump system;

[0037] Figure 5 for Figure 1 Schematic diagram of a cascade heat pump system for preparing high-temperature hot water.

[0038] Description of reference numerals:

[0039] 1-first refrigerant recovery device; 2-first release control valve; 3-first recovery control valve; 4-evaporator; 5-first four-way valve; 6-first compressor; 7-first gas-liquid separator; 8-first solenoid valve; 9-evaporative condenser; 10-second solenoid valve; 11-first expansion valve; 12-parallel branch; 13-third solenoid valve; 14-heat exchanger; 15-second expansion valve; 16-fourth solenoid valve; 17-first isolation valve; 18-second compressor; 19-second gas-liquid separator; 20-second isolation valve; 21-second refrigerant recovery device; 22-second release control valve; 23-second recovery control valve. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0041] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0042] For ease of description, spatial relative terms may be used herein to describe the relative positional relationship or movement of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", "front", "back", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure undergoes a position flip or a posture change or a motion state change, then these directional indications also change accordingly, for example: an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatial relative descriptors used herein are interpreted accordingly.

[0043] In order to solve the technical problem of low operating efficiency of cascade heat pump systems in the prior art, the present application provides a cascade heat pump system that can realize multi-mode switching operation and improve the operating efficiency of the system in the preparation process of low-temperature cold water, low-temperature hot water, medium-temperature hot water and high-temperature hot water.

[0044] It should be noted that the first compressor 6 referred to in this application is also called a low-temperature compressor, and the second compressor 18 is also called a high-temperature compressor. The high-efficiency operating ranges of the two are different, and they can be flexibly selected according to actual needs. The first refrigerant adopts a low-temperature refrigerant, which mainly participates in the circulation and heat exchange of the low-temperature stage circuit; the second refrigerant adopts a medium-temperature refrigerant or a high-temperature refrigerant, which mainly participates in the circulation and heat exchange of the high-temperature stage circuit. There is a certain difference between the evaporating temperature and the condensing temperature of the first refrigerant and the second refrigerant. They can be flexibly selected according to the water demand and the specifications of different compressors, and this application does not make specific restrictions. Unless otherwise specified, the first end of each component generally refers to Figure 1 The upper end shown, the second end refers to Figure 1 The lower end shown.

[0045] In addition, the present application does not specifically limit the temperature ranges of low-temperature hot water, medium-temperature hot water, and high-temperature hot water. Specifically, it can be flexibly set according to the characteristics of the first compressor 6, the second compressor 18, the first refrigerant, and the second refrigerant to ensure that the operation mode of the cascade heat pump system is flexibly switched according to water demand, and to ensure that the system is at a high operating efficiency at various water temperatures. Exemplarily, low-temperature hot water can be hot water at 30°C-65°C, medium-temperature hot water can be hot water at 65°C-85°C, and high-temperature hot water can be hot water above 85°C.

[0046] The embodiment of the present application provides a cascade heat pump system, as shown in the figure, mainly including a first compressor 6, a first four-way valve 5, an evaporative condenser 9, an evaporator 4, a heat exchanger 14, a first expansion valve 11 and a second expansion valve 15. The evaporative condenser 9 can generally adopt a dual-medium heat exchanger, having an evaporation side and a condensation side connected by heat exchange, the evaporation side and the condensation side are used to respectively pass different fluids, and different fluids only exchange heat at the evaporative condenser 9. The heat exchanger 14 can generally adopt a plate heat exchanger, including a refrigerant side and a water side connected by heat exchange, the refrigerant side is used to pass the refrigerant, and the water side is used to pass the normal temperature water, and the water and the refrigerant exchange heat at the heat exchanger 14 to complete the preparation of water for a specific temperature.

[0047] Among them, the first compressor 6, the evaporator 4, the first four-way valve 5, the condensing side of the evaporative condenser 9 and the first expansion valve 11 are connected to form a low-temperature circuit; the second compressor 18, the condensing side of the evaporative condenser 9, the refrigerant side of the heat exchanger 14, and the second expansion valve 15 are connected to form a high-temperature circuit. In the cascade heating mode, the low-temperature circuit and the high-temperature circuit can be connected through heat exchange of the evaporative condenser 9. In addition, the two ends of the refrigerant side of the heat exchanger 14 are also connected to parallel branches 12, so that the refrigerant side of the heat exchanger 14 is connected in parallel with the condensing side of the evaporative heat exchanger through the parallel branch 12. The cascade heat pump system also includes a switching valve group, which can alternately connect the condensing side of the evaporative heat exchanger and the refrigerant side of the heat exchanger 14 between the first compressor 6 and the evaporator 4 through a parallel branch 12, and cooperate with the first compressor 6, the evaporator 4 and the first expansion valve 11 to form different low-temperature stage circuits, thereby realizing the independent operation of the low-temperature stage circuit and the cascade operation of the high-temperature stage circuit, thereby ensuring that the cascade heat pump system is in a high operating efficiency under various temperature water demands and various operating modes.

[0048] Continue reading Figure 1 In the specific embodiment provided in the present application, the four interfaces that are switched and connected by the first four-way valve 5 are named as C interface, D interface, E interface and S interface respectively. Figure 1 The upper end is connected to the upper end shown in the figure, the S interface is connected to the air inlet of the first compressor 6; the D interface is connected to the exhaust port of the compressor, and the E interface is respectively connected to the first end of the condensation side of the evaporative condenser 9, that is, Figure 1 The upper end is connected to the first end of the refrigerant side of the heat exchanger 14. The second end of the evaporator 4 is connected to the second end of the condensation side of the evaporative condenser 9 and the second end of the refrigerant side of the heat exchanger 14, respectively.

[0049] In this embodiment, the switching valve group includes a first solenoid valve 8, a second solenoid valve 10, a third solenoid valve 13 and a fourth solenoid valve 16. The first solenoid valve 8 and the second solenoid valve 10 are arranged at both ends of the condensation side of the evaporative condenser 9, and are used to connect or isolate the condensation side of the evaporative condenser 9 between the first compressor 6 and the second end of the evaporator 4. The third solenoid valve 13 and the fourth solenoid valve 16 are respectively arranged on the parallel branches 12 at both ends of the refrigerant side of the heat exchanger 14, and are used to connect or isolate the refrigerant side of the heat exchanger 14 between the first compressor 6 and the second end of the evaporator 4.

[0050] Specifically, the first expansion valve 11 is connected in series between the second end of the evaporator 4 and the second end of the condensation side of the evaporative condenser 9, and the second solenoid valve 10 is connected between the first expansion valve 11 and the second end of the condensation side of the evaporative condenser 9. The second expansion valve 15 is connected in series between the second end of the refrigerant side of the heat exchanger 14 and the second end of the evaporation side of the evaporative condenser 9. The setting of the parallel branch 12 between the second end of the refrigerant side of the heat exchanger 14 and the second end of the evaporator 4 should ensure that only one of the first solenoid valve 8 and the second solenoid valve 10 is connected in series in the low-temperature stage circuit including the refrigerant side of the heat exchanger 14. In the illustrated embodiment, the second expansion valve 15 is connected in series with the parallel branch 12 of the second end of the refrigerant side of the heat exchanger 14, and the parallel branch 12 of the second end of the refrigerant side of the heat exchanger 14 bypasses the first expansion valve 11 and is connected to the second end of the evaporator 4. In a specific implementation, the parallel branch 12 may also be connected in series with the first expansion valve 11 , so that the parallel branch 12 bypasses the second expansion valve 15 and is connected to the second end of the refrigerant side of the heat exchanger 14 .

[0051] When low temperature cold water needs to be prepared, Figure 2 As shown, the first solenoid valve 8 and the second solenoid valve 10 shut off and control the condensing side of the evaporative condenser 9 to be isolated from the first compressor 6 and the evaporator 4; the third solenoid valve 13 and the fourth solenoid valve 16 are turned on and control the refrigerant side of the heat exchanger 14 to be connected in series between the first compressor 6 and the evaporator 4 through the parallel branch 12, thereby forming a low-temperature stage circuit.

[0052] The first four-way valve 5 switches the low-temperature circuit to the refrigeration mode, and the C interface and the D interface of the first four-way valve 5 are connected, and the E interface and the S interface are connected; the low-temperature circuit is running, and the high-temperature circuit stops running. The first refrigerant discharged by the first compressor 6 condenses and releases heat in the evaporator 4, and is throttled by the first expansion valve 11 and sent to the refrigerant side of the heat exchanger 14 for evaporation and heat absorption, and exchanges heat with the normal temperature water on the water side of the heat exchanger 14 to achieve the preparation of low-temperature cold water. The parallel branch 12 and the switching valve group are set to fully utilize the characteristics of the first compressor 6, that is, the low-temperature compressor, and the first refrigerant, that is, the low-temperature refrigerant, to ensure that the system is at a high operating efficiency during the preparation of low-temperature cold water.

[0053] When low-temperature hot water is required, Figure 3 As shown, the first solenoid valve 8 and the second solenoid valve 10 are closed to control the condensation side of the evaporative condenser 9 to be isolated from the first compressor 6 and the evaporator 4; the third solenoid valve 13 and the fourth solenoid valve 16 are opened to control the refrigerant side of the heat exchanger 14 to be connected in series between the first compressor 6 and the evaporator 4 through the parallel branch 12 to form a low-temperature stage circuit.

[0054] The first four-way valve 5 switches the low-temperature circuit to the heating mode, and the D interface and the E interface of the first four-way valve 5 are connected, and the C interface and the S interface are connected. The low-temperature circuit starts to run, and the high-temperature circuit stops running. The first refrigerant in the low-temperature circuit evaporates and absorbs heat in the evaporator 4, and enters the first compressor 6 through the C interface and the S interface of the first four-way valve 5. The high-temperature and high-pressure first refrigerant compressed by the first compressor 6 is discharged to the refrigerant side of the heat exchanger 14 through the D interface and the S interface of the first four-way valve 5 to condense and release heat, and exchanges heat with the normal temperature water on the water side of the heat exchanger 14 to achieve the preparation of low-temperature hot water. The parallel branch 12 and the switching valve group are set to fully utilize the characteristics of the first compressor 6, that is, the low-temperature compressor and the first refrigerant, that is, the low-temperature refrigerant, to ensure that the system is at a high operating efficiency during the preparation of low-temperature hot water.

[0055] When medium temperature hot water is required, such as Figure 4 As shown, the third solenoid valve 13 and the fourth solenoid valve 16 are closed to control the refrigerant side of the heat exchanger 14 to be isolated from the first compressor 6 and the evaporator 4, and the low-temperature stage circuit stops running, and the high-temperature stage circuit composed of the refrigerant side of the heat exchanger 14 and the second compressor 18, the evaporation side of the evaporative condenser 9, and the second expansion valve 15 starts running. The second refrigerant evaporates and absorbs heat on the evaporation side of the evaporative condenser 9, is compressed by the second compressor 18, and is sent to the refrigerant side of the heat exchanger 14 to condense and release heat, and exchanges heat with the normal temperature water on the water side of the heat exchanger 14, making full use of the characteristics of the second compressor 18, i.e., the high-temperature stage compressor, and the characteristics of the second refrigerant, i.e., the high-temperature refrigerant, to ensure that the system maintains a high operating efficiency when preparing medium-temperature hot water.

[0056] When high temperature hot water is required, such as Figure 5 As shown, the third solenoid valve 13 and the fourth solenoid valve 16 are closed to control the refrigerant side of the heat exchanger 14 to be isolated from the first compressor 6 and the evaporator 4, while the first solenoid valve 8 and the second solenoid valve 10 are opened to control the condensation side of the evaporative condenser 9 to be connected in series between the first compressor 6 and the evaporator 4 to form a low-temperature stage circuit. The first four-way valve 5 switches the low-temperature stage circuit to the heating mode, and the D interface and the E interface of the first four-way valve 5 are connected, and the C interface and the S interface are connected. The high-temperature stage circuit and the low-temperature stage circuit composed of the second compressor 18, the evaporation side of the evaporative condenser 9, the second expansion valve 15 and the refrigerant side of the heat exchanger 14 are cascaded through the evaporative condenser 9 for heating.

[0057] The first refrigerant in the low-temperature circuit absorbs heat in the evaporator 4, enters the first compressor 6 for compression through the C interface and the S interface of the first four-way valve 5, and the compressed first refrigerant is sent to the condensation side of the evaporative condenser 9 through the D interface and the E interface of the first four-way valve 5 to condense and release heat. The second refrigerant in the high-temperature circuit evaporates and absorbs heat on the evaporation side of the evaporative condenser 9, absorbs the heat released by the condensation of the first refrigerant, and increases the temperature of the second refrigerant entering and discharged from the second compressor 18, thereby increasing the condensation heat release of the second refrigerant on the refrigerant side of the heat exchanger 14, and exchanges heat with the normal temperature water on the water side of the heat exchanger 14 to achieve the preparation of high-temperature hot water. During the cascade heating process, the low-temperature circuit and the high-temperature circuit, that is, the first compressor 6 and the second compressor 18, are both in the high-efficiency operation range, thereby ensuring that the system is in an efficient operation state.

[0058] The present application realizes that the refrigerant side of the heat exchanger 14 and the condensing side of the evaporative heat exchanger can be switched and connected between the first compressor 6 and the evaporator 4 to form different low-temperature stage circuits through the setting of the parallel branch 12 and the switching valve group, and fully utilizes the characteristics of the first compressor 6, the second compressor 18, the first refrigerant, and the second refrigerant, so that the cascade heat pump system maintains a high operating efficiency during the preparation of low-temperature cold water, low-temperature hot water, medium-temperature hot water and high-temperature hot water. At the same time, the cascade form of the low-temperature stage circuit and the high-temperature stage circuit also expands the outlet water temperature range at the heat exchanger 14.

[0059] Understandably, Figure 1 In the illustrated embodiment, the first solenoid valve 8 and the third solenoid valve 13 may be replaced by a set of first three-way valves, and the second isolation valve 20 and the fourth solenoid valve 16 may be replaced by a set of second three-way valves.

[0060] In some embodiments, Figure 2 As shown, in order to avoid the first refrigerant entering the second compressor 18 and the evaporator 9 of the evaporator condenser 9 when the refrigerant side of the heat exchanger 14 is connected in series between the first compressor 6 and the evaporator 4 to prepare low-temperature cold water or low-temperature hot water, affecting the heat exchange efficiency when the high-temperature stage circuit is running. The cascade heat pump system provided in the embodiment of the present application also includes a first isolation valve 17 and a second isolation valve 20. The first isolation valve 17 can be set at the outlet of the second compressor 18, and the second isolation valve 20 can be set at the second end of the evaporation side of the evaporator condenser 9 to isolate the evaporation side of the evaporator condenser 9 from the parallel branch 12. When the high-temperature stage circuit is running, the third solenoid valve 13 and the fourth solenoid valve 16 are closed, and the first isolation valve 17 and the second isolation valve 20 are opened to keep the second refrigerant of the high-temperature stage circuit isolated from the first compressor 6, the evaporator 4 and the condensation side of the evaporator condenser 9 to avoid affecting the heat exchange efficiency of the low-temperature stage circuit.

[0061] In some embodiments, a first gas-liquid separator 7 is provided between the air inlet of the first compressor 6 and the S interface of the first four-way valve 5, and the first gas-liquid separator 7 is used to effectively reduce the liquid hammer phenomenon of the first compressor 6, ensure the stable operation of the first compressor 6, and extend the service life of the first compressor 6. Correspondingly, a second gas-liquid separator 19 can also be provided between the air inlet of the second compressor 18 and the first end of the evaporation side of the evaporative condenser 9 as needed, and the second gas-liquid separator 19 is used to effectively reduce the liquid hammer phenomenon of the second compressor 18, and ensure the stable operation of the second compressor 18.

[0062] When the cascade heat pump system provided in the above embodiment operates separately or in cascade in different circuits such as the low-temperature circuit or the high-temperature circuit, the corresponding refrigerant needs to be charged into the corresponding circuit. At the same time, when the operating mode is switched, the first refrigerant of the low-temperature circuit or the second refrigerant of the high-temperature circuit needs to be recovered to avoid mixing of the first refrigerant and the second refrigerant, which would affect the circulation heat exchange efficiency of the low-temperature circuit and the high-temperature circuit.

[0063] In order to improve the convenience of releasing the first refrigerant to the low-temperature circuit or recovering the first refrigerant from the low-temperature circuit, the low-temperature circuit is connected to a first refrigerant recovery device 1. The first refrigerant recovery device 1 can release the first refrigerant toward the low-temperature circuit or recover the first refrigerant of the low-temperature circuit. Specifically, the first refrigerant recovery device 1 is arranged in parallel with the evaporator 4, and a first release control valve 2 is provided at the first end of the first refrigerant recovery device 1, and the first refrigerant is released to the low-temperature circuit by opening the first release control valve 2; a first recovery control valve 3 is provided at the second end of the first refrigerant recovery device 1, and the first refrigerant of the low-temperature circuit is sucked and recovered by opening the first recovery control valve 3.

[0064] Correspondingly, in order to improve the convenience of releasing the second refrigerant to the high-temperature stage circuit or recovering the second refrigerant from the high-temperature stage circuit, the high-temperature stage circuit is connected to a second refrigerant recovery device 21. The second refrigerant recovery device 21 can release the second refrigerant toward the high-temperature stage circuit or recover the second refrigerant of the high-temperature stage circuit. Specifically, the second refrigerant recovery device 21 is arranged in parallel with the evaporation side of the evaporative condenser 9, and the first end of the second refrigerant recovery device 21 is provided with a second release control valve 22, and the second refrigerant is released to the high-temperature stage circuit by opening the second release control valve 22; the second end of the second refrigerant recovery device 21 is provided with a second recovery control valve 23, and the second refrigerant of the high-temperature stage circuit is sucked and recovered by opening the second recovery control valve 23.

[0065] The first refrigerant recovery device 1 and the second refrigerant recovery device 21 can both be in the form of a combination of a refrigerant tank and a refrigerant pump, and can release refrigerant to the corresponding circuit or recover refrigerant from the corresponding circuit by opening the corresponding release control valve, recovery control valve and refrigerant pump. The principle of releasing and recovering refrigerant by the first refrigerant recovery device 1 and the second refrigerant recovery device 21 can also refer to the prior art, and this application will not elaborate on it.

[0066] In the above embodiment, the evaporator 4 can generally adopt a finned heat exchanger, and the heat exchange efficiency between the first refrigerant and the ambient air can be improved by means of the finned heat exchanger. The heat exchanger 14 can generally adopt a plate heat exchanger, and the heat exchange efficiency between the first refrigerant or the second refrigerant and the normal temperature water can be improved by means of countercurrent heat exchange of the plate heat exchanger.

[0067] In addition, a water inlet temperature sensor and a water inlet flow valve may be provided at the water inlet of the water side of the heat exchanger 14, and a water outlet temperature sensor and a water outlet flow valve may be provided at the water outlet of the heat exchanger 14. When the water inlet temperature and the water outlet temperature deviate from the set temperature, the water flow rate involved in the heat exchange is adjusted by the water inlet flow valve and the water outlet flow valve to maintain the difference between the water outlet temperature and the set water temperature within a preset range. For example, when the water outlet temperature is higher than the set water temperature in the heating mode, the opening of the water inlet flow valve can be increased to reduce the water outlet temperature of the water outlet.

[0068] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0069] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0070] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A cascade heat pump system, characterized in that: include: A first compressor, a second compressor, a first four-way valve, an evaporative condenser, an evaporator, a heat exchanger, a first expansion valve, and a second expansion valve; The evaporative condenser is provided with an evaporation side and a condensation side connected in heat exchange, and the heat exchanger is provided with a water side and a refrigerant side connected in heat exchange; The first compressor, the evaporator, the first four-way valve, the condensation side of the evaporative condenser, and the first expansion valve are connected to form a low-temperature circuit; the second compressor, the evaporation side of the evaporative condenser, the refrigerant side of the heat exchanger, and the second expansion valve are connected to form a high-temperature circuit; The refrigerant side of the heat exchanger is connected to parallel branches at both ends, and the refrigerant side of the heat exchanger is connected in parallel with the condensing side of the evaporative condenser through the parallel branches. It also includes a switching valve group that controls the condensing side of the evaporative condenser and the refrigerant side of the heat exchanger to be alternately connected between the first compressor and the evaporator.

2. The cascade heat pump system according to claim 1, characterized in that: The first four-way valve is provided with a C interface, a D interface, an E interface and an S interface which are switched and connected in pairs; The first end of the evaporator is connected to the C interface of the first four-way valve, the air inlet of the first compressor is connected to the S interface of the first four-way valve, the exhaust port of the first compressor is connected to the D interface of the first four-way valve, and the E interface of the first four-way valve is respectively connected to the first end of the refrigerant side of the heat exchanger and the first end of the condensation side of the evaporative condenser; The second end of the evaporator is respectively connected to the second end of the condensation side of the evaporative condenser and the second end of the refrigerant side of the heat exchanger; The switching valve group includes a first solenoid valve and a second solenoid valve disposed at both ends of the condensation side of the evaporative condenser, and a third solenoid valve and a fourth solenoid valve of the parallel branch disposed at both ends of the heat exchanger.

3. The cascade heat pump system according to claim 2, characterized in that: The first expansion valve is connected in series between the second end of the evaporator and the second end of the condensation side of the evaporative condenser, and the second solenoid valve is connected between the first expansion valve and the second end of the condensation side of the evaporative condenser; The second expansion valve is connected in series between the second end of the refrigerant side of the heat exchanger and the second end of the evaporation side of the evaporative condenser; One of the first expansion valve and the second expansion valve is connected in series with the parallel branch.

4. The cascade heat pump system according to any one of claims 1 to 3, characterized in that: The outlet of the second compressor is provided with a first isolating valve for isolating the parallel branch, and the second end of the evaporation side of the evaporative condenser is provided with a second isolating valve for isolating the parallel branch.

5. The cascade heat pump system according to claim 3, characterized in that: A first gas-liquid separator is provided between the S interface of the first four-way valve and the air inlet of the first compressor.

6. The cascade heat pump system according to claim 3, characterized in that: A second gas-liquid separator is provided between the air inlet of the second compressor and the first end of the evaporation side of the evaporative condenser.

7. The cascade heat pump system according to claim 4, characterized in that: The low-temperature stage circuit is connected to a first refrigerant recovery device, and the first refrigerant recovery device is used to release the first refrigerant toward the low-temperature stage circuit or recover the first refrigerant of the low-temperature stage circuit.

8. The cascade heat pump system according to claim 7, characterized in that: The high-temperature stage circuit is connected to a second refrigerant recovery device, and the second refrigerant recovery device is used to release the second refrigerant toward the high-temperature stage circuit or recover the second refrigerant of the high-temperature stage circuit.

9. The cascade heat pump system according to claim 7, characterized in that: The first refrigerant recovery device and the evaporator are connected in parallel, and a first release control valve and a first recovery control valve are respectively provided at two ends of the first refrigerant recovery device.

10. The cascade heat pump system according to claim 8, characterized in that: The second refrigerant recovery device is connected in parallel with the evaporation side of the evaporative condenser, and two ends of the second refrigerant recovery device are respectively provided with a second release control valve and a second recovery control valve.

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