Cascade heat pump system

Abstract

This application relates to the field of heat pump technology, and particularly to a cascade heat pump system. The cascade heat pump system includes a first compressor, a second compressor, an evaporator, an evaporator-condenser, and a condenser heat exchanger. The evaporator-condenser has an evaporator side and a condenser side connected by heat exchange. The first compressor, the condenser side of the evaporator-condenser, and the evaporator are connected in series to form a primary loop. The condenser heat exchanger has a refrigerant side and a water side connected by heat exchange. The second compressor, the refrigerant side of the condenser heat exchanger, and the evaporator side of the evaporator-condenser are connected in series to form a secondary loop. It also includes a parallel branch and a switching valve assembly. The parallel branch connects the evaporator and the secondary loop, connecting the evaporator and the evaporator side of the evaporator-condenser in parallel. The switching valve assembly is used to switch the evaporator side of the evaporator-condenser and the evaporator alternately connected to the second compressor and the condenser heat exchanger. The cascade heat pump system provided by this application can utilize multiple heat sources, improve system operating efficiency, and meet diverse user needs.

Description

Technical Field

[0001] This application relates to the field of heat pumps, and more particularly to a cascade heat pump system. Background Technology

[0002] Encouraging the use of green energy to replace current fossil fuels, heat pump technology, as a clean, environmentally friendly, and renewable resource application technology, has broad application prospects.

[0003] Currently, heat pump technology is widely used in heat pump air conditioners and heat pump water heaters. For industries such as industrial manufacturing, aquaculture, and slaughtering, where water temperatures above 80℃ are required, single heat pump systems cannot meet the demand for high-temperature hot water production. Therefore, cascade high-temperature heat pump systems have emerged to address this need. Compared to traditional high-temperature heat pumps, current cascade high-temperature heat pump systems can provide hot water up to 85℃ at temperatures below -25℃, saving more than 50% in costs. However, cascade high-temperature heat pumps have low cooling efficiency, and while a few multi-heat-source heat pumps can switch between different heat sources, the actual operation still relies on a single heat source, failing to achieve the combined utilization of two or more heat sources. Summary of the Invention

[0004] This application provides a cascade heat pump system that can utilize multiple heat sources in combination, improve system operating efficiency, and meet diverse user needs.

[0005] To achieve the above-mentioned technical effects, this application provides a cascade heat pump system, including a first compressor, a second compressor, an evaporator, an evaporative condenser, and a condensing heat exchanger;

[0006] The evaporator-condenser has an evaporator side and a condenser side connected by heat exchange. The first compressor, the condenser side of the evaporator-condenser and the evaporator are connected in series to form a primary circuit.

[0007] The condensing heat exchanger has a refrigerant side and a water side with heat exchange connection. The second compressor, the refrigerant side of the condensing heat exchanger and the evaporation side of the evaporating condenser are connected in series to form a two-stage loop.

[0008] It also includes a parallel branch and a switching valve group. The parallel branch connects the evaporator and the secondary circuit, connecting the evaporator and the evaporator-condenser evaporator side in parallel. The switching valve group is used to switch the evaporator-condenser side and the evaporator alternately connected to the second compressor and the condenser heat exchanger.

[0009] In some embodiments, the secondary circuit is provided with a four-way valve, the first end of the evaporator side of the evaporator-condenser, the second end of the refrigerant side of the condenser-heat exchanger, and the air inlet and exhaust port of the second compressor are respectively connected to the four connectors of the four-way valve.

[0010] In some embodiments, the switching valve group includes a three-way switching valve located at both ends of the evaporation side of the evaporator-condenser, with two ports of the three-way switching valve connected in series to the secondary circuit, and the third port of the three-way switching valve connected to both ends of the parallel branch respectively.

[0011] In some embodiments, the switching valve group includes a first switching valve located at both ends of the evaporator side of the evaporator-condenser and a second switching valve located at both ends of the parallel branch and the evaporator.

[0012] In some embodiments, a first isolation valve for isolating the parallel branch is provided between the first compressor and the evaporator, and a second isolation valve for isolating the parallel branch is provided on the condensing side between the evaporator and the evaporator-condenser.

[0013] In some embodiments, the primary circuit is provided with a first refrigerant recovery device, which is capable of releasing first refrigerant into the primary circuit or recovering the first refrigerant from the primary circuit, and a first control valve is provided at the outlet of the first refrigerant recovery device.

[0014] The secondary circuit or the parallel branch is equipped with a second refrigerant recovery device. The second refrigerant recovery device is capable of releasing second refrigerant into the secondary circuit or recovering second refrigerant from the secondary circuit. The outlet of the second refrigerant recovery device is equipped with a second control valve.

[0015] In some embodiments, the second refrigerant recovery device is located in the parallel branch, and a third isolation valve is provided between the second refrigerant recovery device and the primary circuit.

[0016] In some embodiments, the inlet of the first compressor is provided with a first gas-liquid separator; and / or, the inlet of the second compressor is provided with a second gas-liquid separator.

[0017] In some embodiments, the water side of the condenser heat exchanger is provided with an inlet and an outlet that are interconnected, and the outlet is provided with an outlet water temperature regulation module;

[0018] When the outlet water temperature requirement of the outlet water temperature regulation module is greater than the first temperature, the primary circuit and the secondary circuit cascade heating.

[0019] When the outlet water temperature requirement of the outlet water temperature regulation module is less than the first temperature, the switching valve group switches to conduct the single-stage heating of the secondary circuit or switches to conduct the parallel branch to cooperate with the refrigerant side single-stage heating of the evaporator, the compressor and the condenser heat exchanger.

[0020] In some embodiments, a liquid receiver is provided between the evaporation side of the evaporator-condenser and the refrigerant side of the condenser-heat exchanger.

[0021] In some embodiments, the evaporator is provided with a first temperature sensor for detecting the ambient temperature of the evaporator, and the evaporator-condenser is provided with a second temperature sensor for detecting the ambient temperature of the evaporator-condenser.

[0022] Compared with the prior art, the technical solution provided in this application has the following advantages: When the system needs heating and the water outlet temperature of the condenser heat exchanger is required to be higher than the first temperature, the primary circuit and the secondary circuit adopt cascade heating. At this time, the switching valve group switches the connection between the evaporator side of the evaporator condenser and the second compressor and the condenser heat exchanger; the first refrigerant in the primary circuit absorbs heat at the evaporator, enters the first compressor for compression, and then flows to the condenser side of the evaporator condenser to release heat, heating the second refrigerant on the evaporator side of the evaporator condenser, i.e., the secondary circuit, increasing the temperature of the second refrigerant before entering the second compressor, increasing the temperature of the second refrigerant discharged from the second compressor, and thus increasing the heat release of the second refrigerant on the refrigerant side of the condenser heat exchanger, ensuring the water outlet temperature of the condenser heat exchanger and improving the heating efficiency.

[0023] When the system requires heating and the water outlet temperature of the condenser heat exchanger is required to be lower than the first temperature, the primary circuit stops operating. Based on the outlet temperature requirement, the switching valve group switches the connection between the evaporator side of the evaporator condenser and the second compressor and condenser heat exchanger, or connects the evaporator with the second compressor and condenser heat exchanger through parallel branches and switching valve groups. Using the environment where the evaporator or the evaporator side of the evaporator condenser is located as a heat source, the second compressor and condenser heat exchanger form a circulation loop with one of the evaporator and the evaporator side of the evaporator condenser to achieve single-stage heating, heating the water entering the condenser heat exchanger to the required temperature and reducing system energy consumption.

[0024] The aforementioned cascade heat pump system utilizes the cascade of primary and secondary circuits. The switching valve group connects the second compressor and condenser heat exchanger alternately with the evaporator or the evaporator-condenser side through parallel branches and secondary circuits. This allows for heat absorption from three heat sources: the environment where the evaporator is located, the environment where the evaporator-condenser is located, and the condenser side of the evaporator-condenser. This meets the needs for preparing hot water at different temperatures, improves the system's heating efficiency, and reduces system energy consumption. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0028] Figure 1 This is a schematic diagram of a cascade heat pump system provided in one embodiment of this application;

[0029] Figure 2 for Figure 1 A schematic diagram of the first heating mode of a cascade heat pump system;

[0030] Figure 3 for Figure 1 A schematic diagram of the second heating mode of a cascade heat pump system;

[0031] Figure 4 for Figure 1 A schematic diagram of the third heating mode of a cascade heat pump system;

[0032] Figure 5 for Figure 1 A schematic diagram of the cooling mode of a cascade heat pump system;

[0033] Figure 6 This is a schematic diagram of a cascade heat pump system provided in another embodiment of this application.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1-Evaporator; 2-Parallel branch; 3-Second switching valve; 4-First isolation valve; 5-First gas-liquid separator; 6-First compressor; 7-Evaporator-condenser; 8-First throttle valve; 9-Second isolation valve; 10-First refrigerant recovery device; 11-Second refrigerant recovery device; 12-Second control valve; 13-First switching valve; 14-Four-way valve; 15-Second compressor; 16-Second gas-liquid separator; 17-Condensing heat exchanger; 18-Liquid receiver; 19-Second throttle valve; 20-First control valve. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0038] For ease of description, spatial relative terms may be used in the text to describe the relative position or movement of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "front," "back," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure undergoes a positional flip, orientation change, or change of motion, these directional indications will change accordingly. For instance, an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can 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 in the text will be interpreted accordingly.

[0039] To address the technical problem of low heating efficiency and high system energy consumption caused by the inability of existing heat pump systems to utilize multiple heat sources, this application provides a cascade heat pump system that can utilize multiple heat sources, improve system operating efficiency, and meet diverse user needs.

[0040] The evaporator and condenser sides of the evaporator-condenser 7 refer only to the primary and secondary circuits operating under cascade heating conditions, and do not limit the phase change type of the refrigerant on the corresponding sides. That is, in different modes, the evaporator side of the evaporator-condenser 7 can experience both heat absorption through evaporation of liquid refrigerant and heat release through condensation of gaseous refrigerant. The first end of the evaporator side of the evaporator-condenser 7 is... Figure 1The upper end shown is the second end of the evaporation side of the evaporator-condenser 7. Figure 1 The lower end shown; the first end of the refrigerant side of the condensing heat exchanger 17 is Figure 1 The lower end shown is the second end on the refrigerant side of the condensing heat exchanger 17. Figure 1 The lower end is shown; the first end of evaporator 1 is Figure 1 The lower end shown is the second end of evaporator 1. Figure 1 The lower end is shown.

[0041] See Figure 1 This application provides a cascade heat pump system that can not only perform cascade heating of primary and secondary loops to improve heating efficiency and outlet water temperature, but also perform single-stage heating with the help of different heat sources to reduce system energy consumption and meet water demand at different temperatures. The cascade heat pump system mainly includes a first compressor 6, a second compressor 15, an evaporator 1, an evaporator-condenser 7, and a condenser-heat exchanger 17. The evaporator-condenser 7 has an evaporator side and a condenser side connected by heat exchange. The first compressor 6, the condenser side of the evaporator-condenser 7, and the evaporator 1 are connected in series to form a primary circuit, which is used to introduce the first refrigerant. The condenser-heat exchanger 17 has a refrigerant side and a water side connected by heat exchange. The second compressor 15, the refrigerant side of the condenser-heat exchanger 17, and the evaporator side of the evaporator-condenser 7 are connected in series to form a secondary circuit, which is used to introduce the second refrigerant. It also includes a parallel branch 2 and a switching valve assembly. The parallel branch 2 connects the evaporator 1 and the secondary circuit, connecting the evaporator 1 and the evaporator side of the evaporator-condenser 7 in parallel. The switching valve assembly is used to switch the evaporator side of the evaporator-condenser 7 and the evaporator 1 alternately connected to the second compressor 15 and the condenser-heat exchanger 17. The setting of the throttling valves in the primary and secondary circuits can refer to existing cascade systems. This application does not make any improvements to the throttling valves and other related components, so they will not be described in detail here.

[0042] The aforementioned cascade heat pump system can utilize three heat sources to achieve three heating modes. Combined with the operating frequency adjustment of the first compressor 6 and the second compressor 15, it can meet the needs of preparing hot water at high temperatures and different water temperatures, satisfying users' hot water needs while improving heating efficiency and reducing system energy consumption.

[0043] In the first heating mode, when the system needs heating and the water outlet temperature of the condenser heat exchanger 17 is required to be higher than the first temperature (e.g., 80°C), the primary and secondary circuits adopt cascade heating.

[0044] See Figure 1 and Figure 2At this time, the switching valve group switches the connection between the evaporator side of the evaporator condenser 7 and the second compressor 15 and the condenser heat exchanger 17. The first refrigerant in the primary circuit absorbs heat at the evaporator 1, enters the first compressor 6 for compression, and then flows to the condenser side of the evaporator condenser 7 to release heat. This heats the second refrigerant on the evaporator side of the evaporator condenser 7, which is also the secondary circuit, thereby increasing the temperature of the second refrigerant before it enters the second compressor 15 and increasing the temperature of the second refrigerant discharged from the second compressor 15. This, in turn, increases the heat release of the second refrigerant on the refrigerant side of the condenser heat exchanger 17, ensuring the outlet water temperature on the water side of the condenser heat exchanger 17 and improving the heating efficiency.

[0045] When the system requires heating and the water outlet temperature of the condenser heat exchanger 17 is required to be lower than the first temperature, the system adopts a single-stage heating method and selects a second or third heating mode according to different outlet temperature requirements and the temperature status of different heat sources.

[0046] For the second heating mode, please refer to... Figure 1 and Figure 3 When the system requires heating and the water outlet temperature of the condenser heat exchanger 17 is required to be lower than the first temperature, the evaporator 1 is connected to the second compressor 15 and the condenser heat exchanger 17 via parallel branch 2 and switching valve group according to the outlet temperature requirement. Utilizing the environment where the evaporator 1 is located as a heat source, the second refrigerant absorbs heat at the evaporator 1 and enters the second compressor 15. The second compressor 15 compresses the second refrigerant and discharges it to the refrigerant side of the condenser heat exchanger 17 for condensation and heat release, exchanging heat with the water on the water side of the condenser heat exchanger 17 to heat the water on the water side of the condenser heat exchanger 17 to the required temperature. In other words, in this mode, a single-stage heating circuit consisting of the second compressor 15, the refrigerant side of the condenser heat exchanger 17, and the evaporator 1 can meet the water temperature requirement, reducing system energy consumption.

[0047] For the third heating mode, please refer to... Figure 1 and Figure 4 Using the environment surrounding the evaporator-condenser 7 as a heat source, the second refrigerant absorbs heat on the evaporation side of the evaporator-condenser 7 and enters the second compressor 15. The second compressor 15 compresses the second refrigerant and discharges it to the refrigerant side of the condenser heat exchanger 17, where it condenses and releases heat. This heat exchange occurs with the water on the water side of the condenser heat exchanger 17, heating the water to the required temperature. In other words, in this mode, a single-stage heating system consisting of the second compressor 15, the condenser heat exchanger 17, and the evaporation side of the evaporator-condenser 7 can meet the water temperature requirements, reducing system energy consumption.

[0048] It should be noted that the selection of the second and third heating modes can be based on the outlet water temperature requirement, or it can be determined based on the ambient temperature of the condenser side of evaporator 1 and evaporator-condenser 7. The mode with the higher ambient temperature can be selected as the heat source to reduce system energy consumption.

[0049] In other words, the required outlet water temperature and the ambient temperature are switched by the switching valve group to connect the evaporator side of the evaporator condenser 7 with the second compressor 15 and the condenser heat exchanger 17, or the evaporator 1 with the second compressor 15 and the condenser heat exchanger 17 through the parallel branch 2 and the switching valve group. Using the environment where the evaporator side of the evaporator 1 or the evaporator condenser 7 is located as a heat source, the second compressor 15, the condenser heat exchanger 17 and one of the evaporator sides of the evaporator 1 and the evaporator condenser 7 can form a circulation loop to achieve single-stage heating, heating the water introduced into the water side of the condenser heat exchanger 17 to the required temperature and reducing system energy consumption.

[0050] The aforementioned cascade heat pump system utilizes the cascade of primary and secondary circuits. The switching valve group connects the second compressor 15 and the condensing heat exchanger 17 alternately with the evaporator 1 or the evaporator-condenser 7 via the parallel branch 2 and the secondary circuit. This enables heat absorption from three heat sources: the environment where the evaporator 1 is located, the environment where the evaporator-condenser 7 is located, and the condensing side of the evaporator-condenser 7. This meets the requirements for preparing hot water at different temperatures, improves the system's heating efficiency, and reduces system energy consumption.

[0051] It should be noted that during the switching process between different modes, the refrigerant in different circuits should be recovered first to avoid refrigerant mixing. For example, when a cascade heat pump system is in cascade heating mode, or in the first heating mode, the first refrigerant can be introduced into the primary circuit and the second refrigerant into the secondary circuit. When switching from the first heating mode to other heating modes, the first refrigerant in the primary circuit should be recovered to avoid mixing of the first and second refrigerants. Specifically, the second refrigerant is used in the circuits corresponding to the second and third heating modes. When switching between the second and third heating modes, or switching back to the first heating mode, the second refrigerant must be recovered first, and then the first and second refrigerants are released into the corresponding circuits. The following will describe the switching process between the second and third heating modes and the corresponding refrigerant release and recovery process using different embodiments. The release and recovery of the refrigerant can be done manually, but preferably, an automatic recovery device is used according to corresponding control commands.

[0052] See also Figure 1 and Figure 5 The cascade heat pump system provided in this application embodiment also includes a four-way valve 14 disposed in the secondary circuit. With the help of the four-way valve 14, the refrigerant of the second compressor 15 and the condensing heat exchanger 17 can be connected to the evaporation side of the evaporating condenser 7 and one of the evaporators 1 through the switching valve group and the parallel branch 2 to achieve refrigeration. That is, the cascade heat pump system provided in this application embodiment can also be used for refrigeration or to produce chilled water.

[0053] The four-way valve 14 has four connectors, named C connector, D connector, E connector, and S connector. The exhaust port of the second compressor 15 is connected to the D connector of the four-way valve 14, and the intake port of the second compressor 15 is connected to the S connector of the four-way valve 14. The first end of the parallel branch 2 and the evaporator side of the evaporator condenser 7 is connected to the C connector of the four-way valve 14. The second end of the refrigerant side of the condenser heat exchanger 17 is connected to the E connector of the four-way valve 14. The first end of the refrigerant side of the condenser heat exchanger 17 is connected to the second end of the evaporator side of the evaporator condenser 7. A second throttling valve 19 is installed between the first end of the refrigerant side of the condenser heat exchanger 17 and the second end of the evaporator side of the evaporator condenser 7. The second end of the parallel branch 2 is connected between the second throttling valve 19 and the second end of the evaporator side of the evaporator condenser 7.

[0054] Evaporator 1 is connected in series in parallel branch 2. The inlet of the first compressor 6 is connected to the first end of evaporator 1, the outlet of the first compressor 6 is connected to the first end of the condensing side of evaporator condenser 7, the second end of evaporator condenser 7 is connected to the second end of evaporator 1, and the first throttle valve 8 is set between the second end of evaporator condenser 7 and the second end of evaporator 1.

[0055] In cooling mode, the D and C connectors of the four-way valve 14 are connected, and the E and S connectors are connected. The flow direction of the second refrigerant is: the exhaust port of the second compressor 15 - the D connector of the four-way valve 14 - the C connector of the four-way valve 14 - the refrigerant side of the evaporator 1 - the E connector of the four-way valve 14 - the S connector of the four-way valve 14 - the air inlet of the second compressor 15.

[0056] In cooling mode, the flow direction of the second refrigerant can also be: discharge port of the second compressor 15 - D connector of the four-way valve 14 - C connector of the four-way valve 14 - evaporator side of the evaporator-condenser 7 - refrigerant side of the condenser heat exchanger 17 - E connector of the four-way valve 14 - S connector of the four-way valve 14 - inlet of the second compressor 15. Specifically, the switching valve group can be controlled to switch the connection of different loops according to the temperature of the environment where the evaporator 1 and the evaporator-condenser 7 are located. Preferably, the condenser of the refrigeration cycle is the one with the lower ambient temperature between the evaporator 1 and the evaporator side of the evaporator-condenser 7.

[0057] In heating mode, connectors D and E of the four-way valve 14 are connected, and connectors S and C are connected. The refrigerant circulation process for different heating modes is as follows:

[0058] In the first heating mode: the flow direction of the first refrigerant is: discharge port of the first compressor 6 - condensing side of the evaporator-condenser 7 - evaporator 1 - air inlet of the first compressor 6. The flow direction of the second refrigerant is: discharge port of the second compressor 15 - D connector of the four-way valve 14 - E connector of the four-way valve 14 - condensing heat exchanger 17 - evaporator-condenser 7 - C connector of the four-way valve 14 - S connector of the four-way valve 14 - air inlet of the second compressor 15.

[0059] In the second heating mode, there is no first refrigerant in the system circuit, and the flow direction of the second refrigerant is: the exhaust port of the second compressor 15 - the D connector of the four-way valve 14 - the E connector of the four-way valve 14 - the condenser heat exchanger 17 - the evaporator 1 - the C connector of the four-way valve 14 - the S connector of the four-way valve 14 - the air inlet of the second compressor 15.

[0060] In the third heating mode, there is no first refrigerant in the system circuit, and the flow direction of the second refrigerant is: the exhaust port of the second compressor 15 - the D connector of the four-way valve 14 - the E connector of the four-way valve 14 - the condensing heat exchanger 17 - the evaporating side of the evaporating condenser 7 - the C connector of the four-way valve 14 - the S connector of the four-way valve 14 - the air inlet of the second compressor 15.

[0061] The following describes the setup of the switching valve group and the switching process for different modes:

[0062] In some embodiments, see Figure 1 The switching valve assembly includes a first switching valve 13 and a second switching valve 3. The first switching valve 13 is located at both ends of the evaporator side of the evaporator-condenser 7, and is used to control the connection between the two ends of the evaporator side of the evaporator-condenser 7 and the C-connector of the four-way valve 14 and the condenser heat exchanger 17, respectively. The second switching valve 3 is used to control the connection between the two ends of the evaporator 1 and the C-connector of the four-way valve 14 and the condenser heat exchanger 17, respectively. In the first heating mode and the third heating mode, the first switching valve 13 is open and the second switching valve 3 is closed, so that the switching valve assembly connects the two ends of the evaporator side of the evaporator-condenser 7 to the C-connector of the four-way valve 14 and the refrigerant side of the condenser heat exchanger 17, respectively. In the second heating mode, the first switching valve 13 is closed and the second switching valve 3 is open, so that the switching valve assembly connects the two ends of the evaporator 1 to the C-connector of the four-way valve 14 and the refrigerant side of the condenser heat exchanger 17, respectively.

[0063] In other embodiments, see Figure 5Alternatively, a pair of three-way valves can replace the first switching valve 13 and the second switching valve 3 in the switching valve assembly. The pair of three-way valves are located at both ends of the evaporator side of the evaporator-condenser 7. Two ports of the three-way valves are connected in series to the secondary circuit, and the third ports of the pair of three-way valves are connected to both ends of the evaporator 1. Specifically, the three ports of one of the three-way valves are connected to the C-connector of the four-way valve 14, the first end of the evaporator 1, and the first end of the evaporator side of the evaporator-condenser 7, respectively; the three ports of the other three-way valve are connected to the first end of the refrigerant side of the condenser heat exchanger 17, the second end of the evaporator 1, and the second end of the evaporator side of the evaporator-condenser 7, respectively.

[0064] Continue reading Figure 1 To prevent the second refrigerant from flowing to the first compressor 6 in the second heating mode, a first isolation valve 4 is installed between the first compressor 6 and the evaporator 1 to isolate the first compressor 6 and the parallel branch 2. Simultaneously, to prevent the second refrigerant from flowing to the condensing side of the evaporator condenser 7, a second isolation valve 9 is installed between the evaporator 1 and the condensing side of the evaporator condenser 7. In the second heating mode, by closing the first isolation valve 4 and the second isolation valve 9, the flow path of the second refrigerant to the first compressor 6 and the condensing side of the evaporator condenser 7 is cut off.

[0065] To facilitate the release of the first and second refrigerants to the primary and secondary circuits respectively, and the recovery of the first refrigerant in the primary circuit and the second refrigerant in the secondary circuit, the cascade heat pump system is also equipped with a first refrigerant recovery device 10 and a second refrigerant recovery device 11. A first control valve 20 is installed at the outlet of the first refrigerant recovery device 10. The release and recovery of the first refrigerant are achieved by adjusting the operating state of the first refrigerant recovery device 10 and the on / off state of the first control valve 20. A second refrigerant recovery device 11 is installed on the secondary circuit or parallel branch 2. A second control valve 12 is installed at the outlet of the second refrigerant recovery device 11. The release and recovery of the second refrigerant are achieved by adjusting the operating state of the second refrigerant recovery device 11 and the on / off state of the second control valve 12.

[0066] For example, when the system switches from the first heating mode to the cooling mode, the first refrigerant recovery device 10 needs to first recover the first refrigerant in the primary circuit, and then control the switching valve group and the four-way valve 14 to switch to the cooling mode.

[0067] The first refrigerant recovery device 10 and the second refrigerant recovery device 11 can be in the form of a refrigerant tank combined with a power pump. The power pump pumps gas into or extracts gas from the refrigerant tank, changing the pressure inside the refrigerant tank to release or recover the corresponding refrigerant. To prevent the power pump from extracting the refrigerant from the refrigerant tank, a deformable or sliding isolator can be installed inside the refrigerant tank. The isolator divides the refrigerant tank into two independent chambers, a first chamber and a second chamber. The power pump can be connected to the first chamber, while the corresponding refrigerant is stored in the second chamber. The volume of the second chamber is changed by the deformation of the isolator or its movement relative to the refrigerant tank, thereby changing the pressure in the second chamber.

[0068] The above is merely an illustrative description of the working process of the first refrigerant recovery device 10 and the second refrigerant recovery device 11, and does not limit the first refrigerant recovery device 10 and the second refrigerant recovery device 11 to only adopt this type of structure. It is also applicable to other devices that can achieve relative refrigerant release and recovery. For example, the first refrigerant recovery device 10 and the second refrigerant recovery device 11 may both include a refrigerant recovery module and a refrigerant release module. The refrigerant recovery module can draw in the corresponding refrigerant from the system, while the refrigerant release module can charge the corresponding refrigerant into the system.

[0069] When the second refrigerant recovery device 11 is installed in the parallel branch 2, a third isolation valve is also required, or the second switching valve 3 should be positioned appropriately to isolate the second refrigerant recovery device 11 from the primary circuit. Specifically, the second switching valve 3 or the added third isolation valve should be positioned between the second refrigerant recovery device 11 and the second end of the evaporator 1, and the second switching valve 3 or the third isolation valve must maintain the second refrigerant recovery device 11 in a state of isolation from the condensing side of the evaporator-condenser 7. Figure 1 As shown, when the second switching valve 3 is located between the second refrigerant recovery device 11 and the second end of the evaporator 1, there is no need to add a third isolation valve.

[0070] In some embodiments, to prevent liquid slugging in the first compressor 6 and the second compressor 15, a first gas-liquid separator 5 is provided at the inlet of the first compressor 6, and correspondingly, a second gas-liquid separator 16 can be provided at the inlet of the second compressor 15. To ensure the stability of the system during refrigeration, a liquid receiver 18 can also be provided on the refrigerant side of the second throttle valve 19 and the condenser heat exchanger 17 as needed.

[0071] The condenser heat exchanger 17 has an interconnected inlet and outlet on its water side. In different heating modes, by introducing cold water into the inlet, hot water at the desired temperature can be obtained from the outlet. The outlet can be equipped with an outlet temperature regulation module. By setting the target outlet temperature using this module, the system controller receives the target outlet temperature and selects an appropriate heating mode accordingly. For example, if the target outlet temperature is higher than the first temperature, neither the second nor the third heating mode can meet the need for high-temperature hot water preparation, and the system adopts the first heating mode, which uses a cascade heating of the primary and secondary loops. When the target outlet temperature is lower than the first temperature, the system selects either the second or third heating mode as needed.

[0072] Furthermore, the cascade heat pump system provided in this application embodiment can also be equipped with a first temperature sensor for detecting the ambient temperature of the evaporator 1 and a second temperature sensor for detecting the ambient temperature of the evaporator condenser 7. The first and second temperature sensors are connected to the system controller so that the controller can select a suitable heating / cooling mode based on the ambient temperature of the evaporator 1 and the evaporator condenser 7.

[0073] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0074] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0075] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A cascade heat pump system, characterized in that, It includes a first compressor, a second compressor, an evaporator, an evaporative condenser, and a condensing heat exchanger; The evaporator-condenser has an evaporator side and a condenser side connected by heat exchange. The first compressor, the condenser side of the evaporator-condenser and the evaporator are connected in series to form a primary circuit. The condensing heat exchanger has a refrigerant side and a water side with heat exchange connection. The second compressor, the refrigerant side of the condensing heat exchanger and the evaporation side of the evaporating condenser are connected in series to form a two-stage loop. It also includes a parallel branch and a switching valve group. The parallel branch connects the evaporator and the secondary circuit, connecting the evaporator and the evaporator-condenser evaporator side in parallel. The switching valve group is used to switch the evaporator-condenser evaporator side and the evaporator alternately connected to the second compressor and the condenser heat exchanger. The primary circuit is equipped with a first refrigerant recovery device, which is capable of releasing first refrigerant into the primary circuit or recovering first refrigerant from the primary circuit. The outlet of the first refrigerant recovery device is equipped with a first control valve. The secondary circuit or the parallel branch is equipped with a second refrigerant recovery device. The second refrigerant recovery device is capable of releasing second refrigerant into the secondary circuit or recovering second refrigerant from the secondary circuit. The outlet of the second refrigerant recovery device is equipped with a second control valve.

2. The cascade heat pump system according to claim 1, characterized in that, The secondary circuit is equipped with a four-way valve, and the first end of the evaporator side of the evaporator-condenser, the second end of the refrigerant side of the condenser-heat exchanger, the air inlet and the air outlet of the second compressor are respectively connected to the four connectors of the four-way valve.

3. The cascade heat pump system according to claim 2, characterized in that, The switching valve group includes three-way switching valves located at both ends of the evaporator side of the evaporator-condenser. Two ports of the three-way switching valves are connected in series to the secondary circuit, and the third port of the three-way switching valves is connected to both ends of the parallel branch.

4. The cascade heat pump system according to claim 2, characterized in that, The switching valve group includes a first switching valve located at both ends of the evaporator side of the evaporator-condenser and a second switching valve located at both ends of the parallel branch of the evaporator.

5. The cascade heat pump system according to claim 1, characterized in that, A first isolation valve for isolating the parallel branch is provided between the first compressor and the evaporator, and a second isolation valve for isolating the parallel branch is provided on the condensing side between the evaporator and the evaporator-condenser.

6. The cascade heat pump system according to claim 1, characterized in that, The second refrigerant recovery device is located in the parallel branch, and a third isolation valve is provided between the second refrigerant recovery device and the primary circuit.

7. The cascade heat pump system according to claim 1, characterized in that, The first compressor has a first gas-liquid separator at its air inlet; and / or the second compressor has a second gas-liquid separator at its air inlet.

8. The cascade heat pump system according to claim 1, characterized in that, The condenser heat exchanger has an inlet and an outlet that are interconnected on the water side, and the outlet is equipped with an outlet water temperature regulation module. When the outlet water temperature requirement of the outlet water temperature regulation module is greater than the first temperature, the primary circuit and the secondary circuit cascade heating. When the outlet water temperature requirement of the outlet water temperature regulation module is less than the first temperature, the switching valve group switches to conduct the single-stage heating of the secondary circuit or switches to conduct the parallel branch to cooperate with the refrigerant side single-stage heating of the evaporator, the second compressor and the condenser heat exchanger.

9. The cascade heat pump system according to claim 1, characterized in that, The evaporator is equipped with a first temperature sensor for detecting the ambient temperature of the evaporator, and the evaporator-condenser is equipped with a second temperature sensor for detecting the ambient temperature of the evaporator-condenser.

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