Four-pipe cooling and heating unit and control method thereof

Abstract

The invention relates to the technical field of heat pumps, and provides a four-pipe cooling and heating unit and a control method thereof. The four-pipe cooling and heating unit comprises a compressor, a cold water side heat exchanger, a hot water side heat exchanger and a balance heat exchanger. The compressor is provided with an exhaust port and an air suction port, a first three-way valve is arranged at the exhaust port, a second three-way valve is arranged at the air suction port, the first three-way valve is connected with one end of the hot-water-side heat exchanger and one end of the balance heat exchanger, and the second three-way valve is connected with one end of the cold-water-side heat exchanger and one end of the balance heat exchanger. The four-pipe refrigerating and heating unit at least has a refrigerating mode, a heating mode and a total heat recovery mode, and the four-pipe refrigerating and heating unit is configured to switch the refrigerating mode, the heating mode and the total heat recovery mode in response to the adjusting states of the first three-way valve and the second three-way valve. The four-pipe cooling and heating unit provided by the invention can meet the switching of multiple modes, and is simple and convenient to operate.

Description

Technical Field

[0001] The present application relates to the technical field of heat pumps, and in particular to a four-pipe refrigeration and heating unit and a control method thereof. Background Art

[0002] The four-pipe cooling and heating unit can provide cold water and hot water at the same time. It is particularly suitable for occasions that require both cold and hot sources. It is widely used in hospitals, archives, high-end hotels, constant temperature and humidity workshops, etc.

[0003] When the water temperature on the hot water side and / or the cold water side meets the requirements, the traditional four-pipe cooling and heating unit switches between the three modes of "cooling water, hot water, and hot water + cooling water" through the setting of a four-way valve. Since this switching is the switching of the entire system of the four-pipe heat pump unit, it is usually necessary to configure a larger energy storage tank to avoid large fluctuations in water temperature or frequent switching. At the same time, some units also use the setting of a balancing heat exchanger to ensure the stability of cutting in and out of the cold water side and the hot water side, but this direction often requires step-by-step adjustment of the balancing heat exchanger, which is more complicated to operate; and, under certain operating conditions, it is easy to cause the compressor to inhale liquid and be damaged, and the cold water heat exchanger to be frozen due to the evaporation temperature being too low. Summary of the Invention

[0004] Based on this, it is necessary to provide a four-pipe cooling and heating unit that meets the needs of "cooling water, hot water, hot water + cooling water", and is simple and convenient to operate, and can avoid the problem of the cold water heat exchanger being damaged by freezing due to the evaporation temperature being too low.

[0005] A four-pipe cooling and heating unit, comprising a compressor, a cold water side heat exchanger, a hot water side heat exchanger and a balancing heat exchanger; the compressor has an exhaust port and an air intake port, the exhaust port is provided with a first three-way valve, the air intake port is provided with a second three-way valve, the first three-way valve is connected to one end of the hot water side heat exchanger and one end of the balancing heat exchanger, the second three-way valve is connected to one end of the cold water side heat exchanger and one end of the balancing heat exchanger; the other end of the cold water side heat exchanger is connected to the other end of the hot water side heat exchanger through a first pipe, the other end of the cold water side heat exchanger is connected to the other end of the balancing heat exchanger through a second pipe, and the other end of the hot water side heat exchanger is connected to the other end of the balancing heat exchanger through a third pipe; the first pipe and the second pipe are connected in parallel with a first parallel point , the first pipeline and the third pipeline are connected in parallel with a second parallel point, and the first parallel point is located upstream of the second parallel point; a first one-way valve and a first expansion valve are provided on the first pipeline, and the first one-way valve is located upstream of the first parallel point, and the first expansion valve is located downstream of the second parallel point, the second pipeline is provided with a second one-way valve, and the third pipeline is provided with a second expansion valve, the second one-way valve is located upstream of the first parallel point, and the second expansion valve is located downstream of the second parallel point; the four-pipe cooling and heating unit has at least a cooling mode, a heating mode and a full heat recovery mode, and the four-pipe cooling and heating unit is configured to switch the cooling mode, the heating mode and the full heat recovery mode in response to the adjustment status of the first three-way valve and the second three-way valve.

[0006] It can be understood that the configuration of the first three-way valve and the second three-way valve can adjust the connectivity between the cold water side heat exchanger, the hot water side heat exchanger, and the balancing heat exchanger, enabling switching between the three modes. The overall operation is simple and convenient. In heating mode, the second three-way valve eliminates the need for the refrigerant to pass through the cold water side heat exchanger, thereby preventing the unevaporated refrigerant in the cold water side heat exchanger from continuing to evaporate and causing the cold water temperature to be too low. In addition, this configuration can prevent the refrigerant from migrating into the cold water side heat exchanger, resulting in excessive refrigerant entering the compressor upon restart and causing liquid hammer. In full heat recovery mode, the second three-way valve eliminates the need for the refrigerant to pass through the balancing heat exchanger, ensuring the refrigerant quantity between the cold water side heat exchanger and the hot water side heat exchanger, thereby ensuring the energy efficiency of the unit. In cooling mode, the first three-way valve eliminates the need for the refrigerant to pass through the hot water side heat exchanger, thereby reducing the impact of the hot water side heat exchanger on the refrigerant, which can cause the temperature to fail to meet the cooling requirements of the terminal water equipment.

[0007] In some of these embodiments, in the refrigeration mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the balance heat exchanger, and the second three-way valve adjusts the suction port of the compressor to communicate with the cold water side heat exchanger. The compressor, the balance heat exchanger, the second pipeline, the first expansion valve, and the cold water side heat exchanger are connected to form a refrigeration circuit; in the heating mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the hot water side heat exchanger, and the second three-way valve adjusts the suction port of the compressor to communicate with the balance heat exchanger. The compressor, the hot water side heat exchanger, the third pipeline, the second expansion valve, and the balance heat exchanger are connected to form a heating circuit; in the total heat recovery mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the hot water side heat exchanger, and the second three-way valve adjusts the suction port of the compressor to communicate with the cold water side heat exchanger. The compressor, the hot water side heat exchanger, the first pipeline, the first expansion valve, and the cold water side heat exchanger are connected to form a total heat recovery circuit.

[0008] In some of these embodiments, the four-pipe refrigeration and heating unit further has a partial heat recovery mode and a partial cold recovery mode; in the partial heat recovery mode, the first three-way valve adjusts both the hot water side heat exchanger and the balance heat exchanger to communicate with the exhaust port of the compressor, and the second three-way valve adjusts the suction port of the compressor to communicate with the cold water side heat exchanger, and both the total heat recovery circuit and the refrigeration circuit are connected; in the partial cold recovery mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the hot water side heat exchanger, and the second three-way valve adjusts both the balance heat exchanger and the cold water side heat exchanger to communicate with the suction port of the compressor, and both the total heat recovery circuit and the heating circuit are connected.

[0009] In some of these embodiments, a fourth pipeline is further provided between the suction port of the compressor and one end of the hot water side heat exchanger, and a first two-way valve is provided on the fourth pipeline; a fifth pipeline is further provided between the other end of the hot water side heat exchanger and the other end of the balance heat exchanger. The fifth pipeline is parallel to the third pipeline and has an opposite flow direction, and a third expansion valve is provided on the fifth pipeline.

[0010] In some of these embodiments, the four-pipe refrigeration and heating unit further has a defrosting mode; in the defrosting mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the balance heat exchanger, and the first two-way valve is configured to be in an open state. The compressor, the balance heat exchanger, the fifth pipeline, the third expansion valve, the hot water side heat exchanger, and the fourth pipeline are connected to form a defrosting circuit.

[0011] In some of these embodiments, the four-pipe cooling and heating unit further includes a liquid reservoir. The inlet of the liquid reservoir is connected in parallel with a first branch and a second branch, and the outlet of the liquid reservoir is connected in parallel with a third branch and a fourth branch. The first branch is connected to the hot water side heat exchanger, and the third branch is connected to the cold water side heat exchanger. The first one-way valve is provided in the first branch, and the first expansion valve is provided in the third branch. The first branch and the third branch communicate with each other to jointly define the first pipeline. The second branch is connected to the balance heat exchanger, and the second one-way valve is provided in the second branch. The second branch and the third branch communicate with each other to jointly define the second pipeline. The fourth branch is connected to the balance heat exchanger, and the second expansion valve is provided in the fourth branch. The first branch and the fourth branch communicate with each other to jointly define the third pipeline.

[0012] In some of these embodiments, a fifth branch is further connected in parallel to the outlet of the liquid reservoir. The fifth branch is connected to the hot water side heat exchanger, and the third expansion valve is provided in the fifth branch. The second branch and the fifth branch communicate with each other to jointly define the fifth pipeline.

[0013] This application also provides a control method for a four-pipe cooling and heating unit, including the following steps:

[0014] Obtain the actual cold water temperature and the actual hot water temperature;

[0015] Compare the actual cold water temperature with the set cold water loading temperature, and compare the actual hot water temperature with the set hot water loading temperature;

[0016] When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is not less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the cooling mode;

[0017] When the actual cold water temperature is not greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the heating mode;

[0018] When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the full heat recovery mode.

[0019] In some of these embodiments, during the operation cycle of the cooling mode:

[0020] Compare the actual hot water temperature with the set hot water unloading temperature, and compare the actual cold water temperature with the set cold water unloading temperature;

[0021] When the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit switches to the partial heat recovery mode;

[0022] When the actual hot water temperature is not less than the set hot water loading temperature: If the actual cold water temperature is greater than the set cold water loading temperature, the compressor in the four-pipe cooling and heating unit is loaded; if the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit is unloaded.

[0023] In some embodiments, during the operation cycle of the heating mode:

[0024] When the actual cold water temperature is greater than the set cold water loading temperature, the four-pipe cooling and heating unit switches to the partial cold recovery mode;

[0025] When the actual cold water temperature is not greater than the set cold water loading temperature: If the actual hot water temperature is less than the set hot water loading temperature, the compressor in the four-pipe cooling and heating unit is loaded; if the actual hot water temperature is greater than the set hot water unloading temperature, the compressor unloading in the four-pipe cooling and heating unit is reduced.

[0026] In some embodiments, during the operation cycle of the full heat recovery mode:

[0027] Obtain the actual operation time of the full heat recovery mode and compare the actual operation time with the set operation time;

[0028] When the actual hot water temperature is greater than the set hot water unloading temperature, the actual cold water temperature is not less than the set cold water unloading temperature, and the actual operation time is not less than the set operation time, the four-pipe cooling and heating unit switches to the partial heat recovery mode;

[0029] When the actual hot water temperature is not greater than the set hot water unloading temperature, the actual cold water temperature is less than the set cold water unloading temperature, and the actual operation time is not less than the set operation time, the four-pipe cooling and heating unit switches to the partial cold recovery mode;

[0030] When the actual hot water temperature is greater than the set hot water unloading temperature and the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit is unloaded;

[0031] When the actual hot water temperature is less than the set hot water loading temperature and the actual cold water temperature is greater than the set cold water unloading temperature, or when the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water unloading temperature, the compressor in the four-pipe cooling and heating unit loads.

[0032] In some embodiments, a first three-way valve is provided at the exhaust port of the compressor in the four-pipe cooling and heating unit. Port A of the first three-way valve is connected to the exhaust port, port B is connected to the balance heat exchanger, and port C is connected to the hot water side heat exchanger.

[0033] When the four-pipe cooling and heating unit switches from the refrigeration mode to the partial heat recovery mode, the opening degrees of port A and port C are increased; or when the four-pipe cooling and heating unit switches from the full heat recovery mode to the partial heat recovery mode, the opening degrees of port A and port C are decreased.

[0034] In some embodiments, when the opening degree between port A and port C is equal to 0, the four-pipe cooling and heating unit switches from the partial heat recovery mode to the refrigeration mode.

[0035] When the opening degree between port A and port C is equal to 100%, the four-pipe cooling and heating unit switches from the partial heat recovery mode to the full heat recovery mode.

[0036] In some embodiments, during the operation cycle of the partial heat recovery mode:

[0037] When the actual hot water temperature is less than the set hot water loading temperature and the actual operation time is greater than the set operation time, the opening degrees of port A and port C are increased.

[0038] When the actual hot water temperature is greater than the set hot water unloading temperature and the actual operation time is greater than the set operation time, the opening degrees of port A and port C are decreased.

[0039] When the actual cold water temperature is greater than the set cold water loading temperature, the compressor in the four-pipe cooling and heating unit loads.

[0040] When the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads.

[0041] In some embodiments, a second three-way valve is provided at the suction port of the compressor in the four-pipe cooling and heating unit. Port D of the second three-way valve is connected to the suction port, port E is connected to the cold water side heat exchanger, and port F is connected to the balance heat exchanger.

[0042] When the four-pipe cooling and heating unit switches from the total heat recovery mode to the partial cold recovery mode: obtain the actual ambient temperature and compare it with the set ambient temperature; when the actual ambient temperature is greater than the set ambient temperature, reduce the opening degrees of the port D and the port E to a first opening degree, and the first opening degree is greater than the opening degrees of the port D and the port F; when the actual ambient temperature is not greater than the set ambient temperature, reduce the opening degrees of the port D and the port E to a second opening degree, and the second opening degree is less than the opening degrees of the port D and the port F; or, when the four-pipe cooling and heating unit switches from the heating mode to the partial cold recovery mode, increase the opening degree between the port D and the port E.

[0043] In some embodiments, when the opening degrees of the port D and the port E are equal to 0, the four-pipe cooling and heating unit switches from the partial cold recovery mode to the heating mode;

[0044] When the opening degrees of the port D and the port E are equal to 100%, the four-pipe cooling and heating unit switches from the partial cold recovery mode to the total heat recovery mode.

[0045] In some embodiments, during the operation cycle of the partial cold recovery mode:

[0046] Compare the actual chilled water temperature with the set chilled water cut-in temperature;

[0047] When the actual chilled water temperature is greater than the set chilled water cut-in temperature, increase the opening degrees of the port D and the port E to 100%, and the four-pipe cooling and heating unit switches from the partial cold recovery mode to the total heat recovery mode;

[0048] When the actual chilled water temperature is not greater than the set chilled water cut-in temperature:

[0049] Obtain the actual pressure on the chilled water side and compare the actual pressure on the chilled water side with the set pressure on the chilled water side; when the actual pressure on the chilled water side is less than the set pressure on the chilled water side, reduce the opening degrees of the port D and the port E.

[0050] In some embodiments, when the actual pressure on the chilled water side is not less than the set pressure on the chilled water side:

[0051] When the actual chilled water temperature is greater than the set chilled water loading temperature and the actual operation time is greater than the set operation time, increase the opening degree between the port D and the port E;

[0052] When the actual cold water temperature is less than the set cold water unloading temperature and the actual running time is greater than the set running time, reduce the opening degree between the port D and the port E;

[0053] When the actual hot water temperature is less than the set hot water loading temperature, the compressor in the four-pipe cooling and heating unit loads;

[0054] When the actual hot water temperature is greater than the set hot water unloading temperature, the compressor unloading amount in the four-pipe cooling and heating unit. Brief Description of the Drawings

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0056] Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided by the present application;

[0057] Figure 2 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the cooling mode;

[0058] Figure 3 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the heating mode;

[0059] Figure 4 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the full heat recovery mode;

[0060] Figure 5 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the partial heat recovery mode;

[0061] Figure 6 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the partial cold recovery mode;

[0062] Figure 7 For Figure 1 Schematic diagram of the four-pipe cooling and heating unit provided in the defrosting mode;

[0063] Figure 8 Flow chart of the switching of each working mode of the four-pipe cooling and heating unit provided by the present application;

[0064] Figure 9This is a flow chart of the control of the first three-way regulating valve of the four-pipe cooling and heating unit provided in this application in the partial heat recovery mode;

[0065] Figure 10 This is a flow chart of the control of the second three-way regulating valve of the four-pipe cooling and heating unit provided in this application in the partial cold recovery mode.

[0066] Figure numerals: 10, compressor; 20, hot water side heat exchanger; 30, cold water side heat exchanger; 40, balancing heat exchanger; 50, liquid reservoir; 61, first three-way valve; 62, second three-way valve; 71, first one-way valve; 72, second one-way valve; 73, first expansion valve; 74, second expansion valve; 75, third expansion valve; 76, first two-way valve; 81, pressure sensor. DETAILED DESCRIPTION

[0067] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0068] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0069] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the quantity of the technical features indicated. Thus, features defined as "first" or "second" may explicitly or implicitly include at least one of these features.

[0070] In the present application, unless otherwise clearly specified or limited, a first feature being “on” or “under” a second feature may mean that the first feature is directly in contact with the second feature, or the first feature and the second feature are indirectly in contact through an intermediate medium.

[0071] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more of the related listed items.

[0072] As Figures 1 to 4 shown, an embodiment of this application provides a four-pipe refrigeration and heat pump unit, which includes a compressor 10, a cold water side heat exchanger 30, a hot water side heat exchanger 20, and a balance heat exchanger 40. The compressor 10 has an exhaust port and a suction port, and a first three-way valve 61 is arranged at the exhaust port, and a second three-way valve 62 is arranged at the suction port. The first three-way valve 61 has ports A, B, and C. Port A is connected to the exhaust port of the compressor 10, port B is connected to one end of the hot water side heat exchanger 20, and port C is connected to one end of the balance heat exchanger 40. At the same time, the second three-way valve 62 has ports D, E, and F. Port D is connected to the suction port of the compressor 10, port E is connected to one end of the cold water side heat exchanger 30, and port F is connected to one end of the balance heat exchanger 40. The other ends of the cold water side heat exchanger 30 and the hot water side heat exchanger 20 are connected through a first pipeline, and the other end of the cold water side heat exchanger 30 and the other end of the balance heat exchanger 40 are connected through a second pipeline, that is, the hot water side heat exchanger 20 and the balance heat exchanger 40 are arranged in parallel, and the other ends of the hot water side heat exchanger 20 and the balance heat exchanger 40 are connected through a third pipeline.

[0073] Among them, the first pipeline and the second pipeline are connected in parallel with a first parallel point, the first pipeline and the third pipeline are connected in parallel with a second parallel point, and the first parallel point is located upstream of the second parallel point. A first check valve 71 and a first expansion valve 73 are arranged on the first pipeline, and the first check valve 71 is located upstream of the first parallel point, and the first expansion valve 73 is located downstream of the second parallel point. A second check valve 72 is arranged on the second pipeline, and a second expansion valve 74 is arranged on the third pipeline. The second check valve 72 is located upstream of the first parallel point, and the second expansion valve 74 is located downstream of the second parallel point.

[0074] In actual use, the first three-way valve 61 is used to adjust the connection state of the hot water side heat exchanger 20 and the balance heat exchanger 40 relative to the exhaust port of the compressor 10, and the second three-way valve 62 is used to adjust the connection state of the cold water side heat exchanger 30 and the balance heat exchanger 40 relative to the suction port of the compressor 10. The four-pipe refrigeration and heat pump unit has at least a refrigeration mode, a heating mode, and a full heat recovery mode, and the four-pipe refrigeration and heat pump unit is configured to switch the refrigeration mode, the heating mode, and the full heat recovery mode in response to the adjustment states of the first three-way valve 61 and the second three-way valve 62.

[0075] The following describes the circulation of refrigerant in the four-pipe cooling and heating unit for the above three modes respectively.

[0076] like Figure 2 As shown, in cooling mode, the first three-way valve 61 regulates the connection between the exhaust port of the compressor 10 and the balancing heat exchanger 40, that is, port A is connected to port B, and port A is disconnected from port C. The second three-way valve 62 regulates the connection between the intake port of the compressor 10 and the cold water-side heat exchanger 30, that is, port D is connected to port E, and port D is disconnected from port F. At this time, the compressor 10, the balancing heat exchanger 40, the second pipeline, the first expansion valve 73, and the cold water-side heat exchanger 30 are connected to form a refrigeration circuit. This refrigeration circuit is used to generate cooling capacity. In actual use, the cold water-side heat exchanger 30 can be connected to a terminal water-using device to provide cold water to the terminal water-using device. When a terminal user requires low-temperature or cold water, the gaseous refrigerant delivered through the exhaust port of compressor 10 flows to the balancing heat exchanger 40, where it condenses and releases heat. It then expands along the second pipeline, passes through the first expansion valve 73, and flows to the cold water heat exchanger 30. After absorbing heat in the cold water heat exchanger 30, it becomes gaseous refrigerant and flows to the intake port of compressor 10. After absorbing heat in the cold water heat exchanger 30, the water temperature is lowered and supplied to the terminal user. That is, in cooling mode, the hot water heat exchanger 20 does not participate in heat exchange, the balancing heat exchanger 40 acts as a condenser, and the cold water heat exchanger 30 acts as an evaporator.

[0077] like Figure 3 As shown, in heating mode, the first three-way valve 61 regulates the connection between the exhaust port of the compressor 10 and the hot water-side heat exchanger 20, that is, port A is connected to port C, and port A is disconnected from port B. The second regulating valve regulates the connection between the intake port of the compressor 10 and the balancing heat exchanger 40, that is, port D is connected to port F, and port D is disconnected from port E. At this time, the compressor 10, the hot water-side heat exchanger 20, the third pipeline, the second expansion valve 74, and the balancing heat exchanger 40 are connected to form a heating circuit. This heating circuit is used to generate heat. In actual use, the hot water-side heat exchanger 20 can be connected to a terminal water-using device to provide hot water to the terminal device. When a terminal user requires high-temperature or hot water, the gaseous refrigerant, delivered through the exhaust port of compressor 10, flows to the hot water-side heat exchanger 20, where it condenses and releases heat. It then expands along the third pipeline, passes through the second expansion valve 74, and flows to the balancing heat exchanger 40, where it evaporates, absorbs heat, and transforms into gaseous refrigerant, which then flows to the intake port of compressor 10. The water that has absorbed heat in the hot water-side heat exchanger 20 is heated and supplied to the terminal user. That is, in heating mode, the cold water-side heat exchanger 30 does not participate in heat exchange; the hot water-side heat exchanger 20 acts as a condenser, and the balancing heat exchanger 40 acts as an evaporator.

[0078] like Figure 4As shown, in the total heat recovery mode, the first three-way valve 61 adjusts the exhaust port of the compressor 10 to communicate with the hot water side heat exchanger 20, that is: port A communicates with port C, and port A does not communicate with port B; the second three-way valve 62 adjusts the suction port of the compressor 10 to communicate with the cold water side heat exchanger 30, that is: port D communicates with port E, and port D does not communicate with port F; then the compressor 10, the hot water side heat exchanger 20, the first pipeline, the first expansion valve 73, and the cold water side heat exchanger 30 are connected as a total heat recovery circuit. That is to say, the gaseous refrigerant sent out from the exhaust port of the compressor 10 flows to the hot water side heat exchanger 20 to condense and release heat, and then flows through the first expansion valve 73 when flowing along the first pipeline and then flows to the cold water side heat exchanger 30, and then evaporates and absorbs heat in the cold water side heat exchanger 30 to become gaseous refrigerant and flows to the suction port of the compressor 10. That is, in the total heat recovery mode, the hot water side heat exchanger 20 serves as a condenser, and the cold water side heat exchanger 30 serves as an evaporator.

[0079] In summary, it can be seen that by setting the first three-way valve 61 and the second three-way valve 62, the connection state between the cold water side heat exchanger 30, the hot water side heat exchanger 20, and the balance heat exchanger 40 can be adjusted to achieve the switching of but not limited to the above three working modes, and the overall operation is simple and convenient. In the heating mode, since port D and port E of the second three-way valve 62 do not communicate, the refrigerant does not need to pass through the cold water side heat exchanger 30, thereby avoiding the cold water temperature from being too low; moreover, such a setting can prevent the refrigerant from migrating into the cold water side heat exchanger 30, resulting in too much refrigerant entering the compressor 10 during restart and causing liquid hammer. In the total heat recovery mode, since port A and port B of the first three-way valve 61 do not communicate and port D and port F of the second three-way valve 62 do not communicate, the refrigerant does not need to pass through the balance heat exchanger 40, ensuring the refrigerant amount between the cold water side heat exchanger 30 and the hot water side heat exchanger 20, and thus ensuring the energy efficiency of the unit. In the cooling mode, since port A and port C of the first three-way valve 61 do not communicate, the refrigerant does not need to pass through the hot water side heat exchanger 20, thereby avoiding the hot water temperature from being too high.

[0080] As Figure 5 and Figure 6As shown, in some embodiments, the four-pipe cooling and heating unit also has a partial heat recovery mode and a partial cold recovery mode. In the partial heat recovery mode, the first three-way valve 61 adjusts both the hot water side heat exchanger 20 and the balance heat exchanger 40 to be connected to the exhaust port of the compressor 10, that is: port A is connected to port B, and port A is connected to port C; and, the second three-way valve 62 adjusts the suction port of the compressor 10 to be connected to the cold water side heat exchanger 30, that is: port D is connected to port E, and port D is not connected to port F; at this time, both the total heat recovery circuit and the refrigeration circuit are connected. In the partial cold recovery mode, the first three-way valve 61 adjusts the exhaust port of the compressor 10 to be connected to the hot water side heat exchanger 20, that is, port A and port C are connected, and port A and port B are not connected; and, the second three-way valve 62 adjusts both the balance heat exchanger 40 and the cold water side heat exchanger 30 to be connected to the suction port of the compressor 10, that is: port D is connected to port E, and port D is connected to port F. At this time, both the total heat recovery circuit and the heating circuit are connected.

[0081] Specifically, in the partial heat recovery mode, a part of the gaseous refrigerant sent out from the exhaust port of the compressor 10 flows to the hot water side heat exchanger 20 to condense and release heat, and then flows through the first expansion valve 73 along the first pipeline and expands to flow to the cold water side heat exchanger 30; at the same time, another part of the gaseous refrigerant sent out from the exhaust port flows to the balance heat exchanger 40 to condense and release heat, and then flows through the first expansion valve 73 along the second pipeline and expands to flow to the cold water side heat exchanger 30; the refrigerant flowing to the cold water side heat exchanger 30 evaporates and absorbs heat and then flows to the suction port of the compressor 10. That is: both the hot water side heat exchanger 20 and the balance heat exchanger 40 are used as condensers, and the cold water side heat exchanger 30 is used as an evaporator. In the partial cold recovery mode, the gaseous refrigerant sent out from the exhaust port of the compressor 10 flows to the hot water side heat exchanger 20 to condense and release heat, and a part of the refrigerant flows through the second expansion valve 74 along the third pipeline and expands to flow to the balance heat exchanger 40 to evaporate and absorb heat, and then flows to the suction port of the compressor 10; at the same time, another part of the refrigerant flows through the first expansion valve 73 along the first pipeline and expands to flow to the cold water side heat exchanger 30 to evaporate and absorb heat, and then flows to the suction port of the compressor 10. That is: the hot water side heat exchanger 20 is used as a condenser, and both the balance heat exchanger 40 and the cold water side heat exchanger 30 are used as evaporators.

[0082] That is to say, in the partial heat recovery mode, part of the heat can be recovered into the hot water side heat exchanger 20, and the other part of the heat is discharged outdoors through the balance heat exchanger 40; and, in the partial cold water recovery mode, the cold quantity is distributed between the cold water side heat exchanger 30 and the balance heat exchanger 40. In this way, the stepless adjustment of partial cold recovery and partial heat recovery is satisfied, so as to ensure the stable water temperature adjustment of the terminal water using equipment when the cooling and heating loads change.

[0083] In summary, the four-pipe cooling and heating unit provided in this embodiment utilizes the setting of the first three-way valve 61 and the second three-way valve 62 to adjust the connectivity between the cold water side heat exchanger 30, the hot water side heat exchanger 20 and the balance heat exchanger 40, so that the four-pipe cooling and heating unit has the above-mentioned multiple working mode switching. Specifically, in the cooling mode, the first three-way valve 61 is adjusted to switch to the partial heat recovery mode; in the heating mode, the second three-way valve 62 is adjusted to switch to the partial cold recovery mode; in the full heat recovery mode, the first three-way valve 61 or the second three-way valve 62 is adjusted to switch to the partial heat recovery mode or the partial cold recovery mode. The specific switching method will be described in detail below, and is only used as an example here.

[0084] In some specific embodiments, the balancing heat exchanger 40 uses an air heat exchanger, which can dissipate heat into the environment or absorb heat from the environment, and its evaporation pressure will vary greatly with changes in ambient temperature. The evaporation pressure of the refrigerant in the cold water side heat exchanger 30 is relatively stable. When the water temperature is controlled at a certain temperature, the evaporation pressure of the cold water side heat exchanger 30 will vary within a smaller range according to the load size. Therefore, when there is a difference between the evaporation pressure in the balancing heat exchanger 40 and the evaporation pressure in the cold water side heat exchanger 30, the setting of the second three-way valve 62 can perform secondary throttling (i.e., proportional regulation) on the side with higher evaporation pressure, thereby ensuring the effectiveness of the regulation and further preventing the cold water side heat exchanger 30 from freezing and liquid hammer damage caused by the compressor 10.

[0085] Furthermore, both the first three-way valve 61 and the second three-way valve 62 can adopt proportional regulating valves, which can meet the switching between cooling mode, heating mode and full heat recovery mode, partial heat recovery mode and partial cold recovery mode. Taking the first three-way valve 61 as an example, when the opening of port A and port B changes, the opening of port A and port C will also change. For example, if the opening of port A and port B decreases, the opening of port A and port C increases; conversely, if the opening of port A and port B increases, the opening of port A and port C decreases. The working mode of the second three-way valve 62 is basically similar to that of the first three-way valve 61, and a similar description will be given below in combination with actual conditions, so it will not be repeated here.

[0086] In an alternative embodiment, two branches may be connected in parallel at the exhaust port of the compressor 10, respectively connected to the hot water side heat exchanger 20 and the balancing heat exchanger 40, and a second two-way valve may be provided on each branch; at the same time, two branches may be connected in parallel at the intake port, respectively connected to the cold water side heat exchanger 30 and the balancing heat exchanger 40, and a third two-way valve may be provided on each branch.

[0087] like Figures 1 to 7As shown, in an optional embodiment, a fourth pipeline is provided between the air intake of the compressor 10 and the hot water-side heat exchanger 20, and a first two-way valve 76 is provided on the fourth pipeline. Furthermore, a fifth pipeline is provided between the hot water-side heat exchanger 20 and the balancing heat exchanger 40. The fifth pipeline is connected in parallel with the third pipeline, and the flow directions thereof are opposite. A third expansion valve 75 is provided on the fifth pipeline. In this case, the four-pipe cooling and heating unit also has a defrost mode.

[0088] like Figure 7 As shown, in defrost mode, the first three-way valve 61 regulates the connection between the exhaust port of the compressor 10 and the balancing heat exchanger 40, that is, port A and port B are connected, and port A and port C are disconnected. Furthermore, the second three-way valve 62 is configured to disconnect at least port D and port F, and the second three-way valve 62 and the first expansion valve 73 work together to prevent refrigerant from passing through the second three-way valve 62. The first two-way valve 76 on the fourth line is configured to be open, connecting the compressor 10, the balancing heat exchanger 40, the fifth line, the third expansion valve 75, the hot water-side heat exchanger 20, and the fourth line to form a defrost circuit. This defrost circuit can utilize heat from the hot water-side heat exchanger 20 to defrost the balancing heat exchanger 40 in winter, and the entire four-pipe cooling and heating unit is now free of cooling load. Because the balancing heat exchanger 40 is an air heat exchanger, in low-temperature environments such as winter, moisture in the air surrounding the balancing heat exchanger 40 condenses into frost and adheres to the outside of the balancing heat exchanger 40, thereby affecting heat exchange performance. Therefore, the balancing heat exchanger 40 needs to be defrosted to melt the frost on its surface.

[0089] In actual use, the gaseous refrigerant output from the exhaust port of the compressor 10 flows to the balancing heat exchanger 40 to exchange heat with the cold air, condensing and releasing heat. It then flows along the fifth pipeline through the third expansion valve 75 to expand, then flows to the hot water side heat exchanger 20 to evaporate and absorb heat. It then flows along the fourth pipeline to the intake port of the compressor 10. The heat released by the refrigerant condensing in the balancing heat exchanger 40 can be used to defrost the balancing heat exchanger 40. In addition, in the cooling mode mentioned above, the heat released by the gaseous refrigerant delivered by the compressor 10 through the balancing heat exchanger 40 can also be used to defrost the balancing heat exchanger 40.

[0090] It is understandable that defrosting mostly occurs in a low-temperature environment. In the cooling mode, the balancing heat exchanger 40 is used as a condenser so that the refrigerant can condense and release heat, and after expansion through the first expansion valve 73, it flows to the cold water side heat exchanger 30 to evaporate and absorb heat. In this process, the heat released by the balancing heat exchanger 40 can be used for defrosting. However, since the ambient temperature itself is too low at this time, it will also affect the cold water temperature of the terminal water-using equipment. If the cooling mode is used for defrosting, the cold water will be overcooled. Therefore, the setting of the above-mentioned defrost circuit can meet the condensation heat release of the balancing heat exchanger 40 in a low-temperature environment without passing through the cold water side heat exchanger 30, achieve defrost, and reduce the impact of the defrost process on the cold water temperature; and, such a setting can also ensure the hot water temperature of the terminal water-using equipment in a low-temperature environment, reducing the impact of the ambient temperature on the hot water temperature.

[0091] like Figures 1 to 7 As shown, in an optional embodiment, the four-pipe cooling and heating unit further includes a liquid reservoir 50, with a first branch and a second branch connected in parallel to the inlet of the liquid reservoir 50, and a third branch and a fourth branch connected in parallel to the outlet of the liquid reservoir 50. One end of the first branch is connected to the hot water-side heat exchanger 20, and one end of the third branch is connected to the cold water-side heat exchanger 30. A first one-way valve 71 is provided in the first branch, and a first expansion valve 73 is provided in the third branch. The first branch, the liquid reservoir 50, and the third branch are connected to define a first pipeline for connecting the hot water-side heat exchanger 20 and the cold water-side heat exchanger 30, thereby enabling refrigerant to flow from the hot water-side heat exchanger 20 to the cold water-side heat exchanger 30. One end of the second branch is connected to the balancing heat exchanger 40, and a second one-way valve 72 is provided in the second branch. The second branch, the liquid accumulator 50, and the third branch are connected to define a second pipeline, which is used to connect the balancing heat exchanger 40 and the cold water-side heat exchanger 30, so that the refrigerant flows from the balancing heat exchanger 40 to the cold water-side heat exchanger 30. One end of the fourth branch is connected to the balancing heat exchanger 40, and a second expansion valve 74 is provided in the fourth branch. The first branch, the liquid accumulator 50, and the fourth branch are connected to define a third pipeline, which is used to connect the hot water-side heat exchanger 20 and the balancing heat exchanger 40, so that the refrigerant flows from the hot water-side heat exchanger 20 to the balancing heat exchanger 40.

[0092] Among them, the intersection point of the first branch and the second branch at the inlet of the liquid storage device 50 can be used as the first parallel connection point of the first pipeline and the second pipeline, and the intersection point of the third branch and the fourth branch at the outlet of the liquid storage device 50 is used as the second parallel connection point of the first pipeline and the third pipeline. The first one-way valve 71 is used to drain the fluid from the hot water side heat exchanger 20 to the inlet of the liquid storage device 50, and the second one-way valve 72 is used to drain the fluid from the balanced heat exchanger 40 to the inlet of the liquid storage device 50. The inlet of the first expansion valve 73 faces the outlet of the liquid storage device 50, which is used to reduce the pressure of the refrigerant in the refrigeration circuit and the total heat recovery circuit, and adjust the opening according to the evaporation pressure at the cold water side heat exchanger 30. The inlet of the second expansion valve 74 faces the outlet of the liquid storage device 50, which is used to reduce the pressure of the refrigerant in the heating circuit, and adjust the opening according to the evaporation pressure at the balanced heat exchanger 40. Specifically, a pressure sensor 81 can be provided at one end of the cold water side heat exchanger 30 facing the compressor 10 to obtain the flow pressure of the cold water side heat exchanger 30, and then obtain the evaporation pressure.

[0093] Furthermore, a fifth branch is also connected in parallel at the outlet of the liquid storage device 50. The fifth branch is connected to the hot water side heat exchanger 20. The third expansion valve 75 is provided on the fifth branch. The second branch, the liquid storage device 50 and the fifth branch are connected and communicate with each other to jointly define a fifth pipeline, so as to achieve the purpose of flowing the refrigerant from the balanced heat exchanger 40 to the hot water side heat exchanger 20. The inlet of the third expansion valve 75 faces the outlet of the liquid storage device 50, which is used to reduce the pressure of the refrigerant in the defrosting circuit, and adjust the opening according to the evaporation pressure at the hot water side heat exchanger 20.

[0094] The above setting of the liquid storage device 50 makes the refrigerant flowing through the first pipeline, the second pipeline, the third pipeline and the fifth pipeline in a fully liquid state.

[0095] In summary, in the refrigeration mode, the port A and port B of the first three-way valve 61 are connected, the port D and port E of the second three-way valve 62 are connected, the first expansion valve 73 works, and the second expansion valve 74 and the third expansion valve 75 are closed. In the heating mode, the port A and port C of the first three-way valve 61 are connected, the port D and port F of the second three-way valve 62 are connected, the second expansion valve 74 works, and the first expansion valve 73 and the third expansion valve 75 are closed. In the total heat recovery mode, the port A and port C of the first three-way valve 61 are connected, the port D and port E of the second three-way valve 62 are connected, the first expansion valve 73 works, and the second expansion valve 74 and the third expansion valve 75 are closed. In the partial heat recovery mode, the port A of the first three-way valve 61 is connected to both port C and port B, the port D and port E of the second three-way valve 62 are connected, the first expansion valve 73 works, and the second expansion valve 74 and the third expansion valve 75 are closed. In the partial cold recovery mode, the port A and port C of the first three-way valve 61 are connected, the port D of the second three-way valve 62 is connected to both port E and port F, the first expansion valve 73 and the second expansion valve 74 work, and the third expansion valve 75 is closed. In the defrosting mode, the port A and port B of the first three-way valve 61 are connected, the third expansion valve 75 works, and the first two-way valve 76 is opened.

[0096] In actual use, the cold water side heat exchanger 30 and the hot water side heat exchanger 20 respectively have delivery pipes for connecting terminal water using devices, and first temperature sensors are provided on their respective corresponding delivery pipes. The first three-way valve 61 and the second three-way valve 62 can adjust their opening degrees according to the temperature signals detected by each first temperature sensor, thereby realizing the switching of each working mode. At the same time, when the balanced heat exchanger 40 uses an air heat exchanger, the balanced heat exchanger 40 is provided with a second temperature sensor for detecting the ambient temperature. Therefore, when the four-pipe refrigeration and heating unit switches from the total heat recovery mode to the partial cold recovery mode, the second three-way valve 62 adjusts its opening degree according to the detection signal of the second temperature sensor. In addition, due to the difference in evaporation pressure between the balanced heat exchanger 40 and the cold water side heat exchanger 30, a pressure sensor 81 is provided at one end of the cold water side heat exchanger 30 facing the compressor 10, so that when the four-pipe refrigeration and heating unit switches to the partial cold recovery mode, the second three-way valve 62 can adjust its opening degree according to the detection signal of the pressure sensor 81.

[0097] As Figures 1 to 8 shown, another embodiment of the present application provides a control method for a four-pipe refrigeration and heating unit, including the following steps:

[0098] Obtain the actual cold water temperature (T 冷测 ) and the actual hot water temperature (T 热测 ) in the figure;

[0099] Compare the actual cold water temperature with the set cold water loading temperature (T冷加载 ) for comparison, comparing the actual hot water temperature with the set hot water loading temperature (T in the figure 热加载 );

[0100] When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is not less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the cooling mode;

[0101] When the actual cold water temperature is not greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the cooling mode;

[0102] When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the full heat recovery mode.

[0103] Among them, the actual cold water temperature can be the temperature at the cold water inlet where the cold water side heat exchanger 30 is connected to the terminal water using equipment, and the actual hot water temperature can be the temperature at the hot water inlet where the hot water side heat exchanger 20 is connected to the terminal water using equipment. During actual use, temperature sensors can be installed at both the cold water inlet of the cold water side heat exchanger 30 and the hot water inlet of the hot water side heat exchanger 20 to be used for real-time monitoring of the actual cold water temperature and the actual hot water temperature. The set cold water loading temperature refers to the preset temperature at which cold capacity needs to be increased, and the set hot water loading temperature refers to the preset temperature at which heat needs to be increased.

[0104] When the actual cold water temperature at the cold water inlet is greater than the set cold water loading temperature and the actual hot water temperature is not less than the set hot water loading temperature, it indicates that the cold water temperature of the terminal water using equipment (hereinafter referred to as the terminal) is relatively high, but the terminal hot water temperature is in a normal state. At this time, the cold capacity of the cold water needs to be increased. Therefore, it is necessary to switch the four-pipe cooling and heating unit to the cooling mode to increase the cold capacity of the cold water. When the actual cold water temperature is not greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, it indicates that the heat of the terminal hot water is insufficient, but the terminal cold water temperature is in a normal state. At this time, the heat of the hot water needs to be increased. Therefore, the four-pipe cooling and heating unit can be switched to the heating mode to increase the heat of the hot water. When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, it indicates that the terminal cold water temperature is too high and the terminal hot water temperature is too low. At this time, not only the cold capacity of the cold water needs to be increased, but also the heat of the hot water needs to be increased. Therefore, the four-pipe cooling and heating unit needs to be switched to the full heat recovery mode to increase the heat exchange capacity of the entire unit.

[0105] Among them, "not less than" means greater than or equal to, and "not greater than" means less than or equal to.

[0106] In the refrigeration mode, the refrigerant circulates between the compressor 10, the balance heat exchanger 40, the liquid reservoir 50, the first expansion valve 73, and the cold water side heat exchanger 30. Therefore, the opening degree of the first expansion valve 73 can be adjusted according to the superheat degree at the cold water side heat exchanger 30. If the superheat degree here is too large, the evaporation pressure is too high, and at this time, it is necessary to increase the refrigerant flow rate, that is, increase the opening degree of the first expansion valve 73; if the superheat degree here is too small, the evaporation pressure is too low, and at this time, it is necessary to decrease the refrigerant flow rate, that is, decrease the opening degree of the first expansion valve 73. In the heating mode, the refrigerant circulates between the compressor 10, the hot water side heat exchanger 20, the liquid reservoir 50, the second expansion valve 74, and the balance heat exchanger 40. The opening degree of the second expansion valve 74 can be adjusted according to the superheat degree at the balance heat exchanger 40. The specific adjustment principle is basically similar to that of the first expansion valve 73, so it will not be elaborated here.

[0107] As Figures 1 to 8 shown, in an optional embodiment, during the refrigeration mode operation cycle of the four-pipe refrigeration and heating unit, the actual cold water temperature and the actual hot water temperature are still monitored in real time and compared with the corresponding set cold water loading temperature and the set hot water loading temperature. It should be noted that after loading cold or heat for a period of time, unloading is required, otherwise it may cause the terminal cold water to be supercooled or the terminal hot water to be overheated. At this time, it is also necessary to compare the actual cold water temperature with the set cold water unloading temperature (T 冷卸载 in the figure), and the actual hot water temperature with the set hot water unloading temperature (T 热卸载 in the figure). Among them, the set cold water unloading temperature is less than the set cold water loading temperature, and the set hot water unloading temperature is greater than the set hot water loading temperature. It should be noted that the compressor 10 loading mentioned here can be to increase the power of the compressor 10, and the compressor 10 unloading can be to decrease the power of the compressor 10. This is for illustrative purposes here.

[0108] Since the hot water side heat exchanger 20 does not participate in heat exchange in the refrigeration mode, during the operation cycle of the four-pipe refrigeration and heat pump unit in the refrigeration mode, the hot water temperature will drop over time. Therefore, when the actual hot water temperature is lower than the set hot water loading temperature, it is necessary to increase the hot water heat. At this time, the four-pipe refrigeration and heat pump unit switches to the partial heat recovery mode, so that part of the refrigerant passes through the hot water side heat exchanger 20, and then releases heat to increase the terminal hot water temperature. If during the operation cycle of the four-pipe refrigeration and heat pump unit in the refrigeration mode, it is detected that the actual hot water temperature is not lower than the set hot water loading temperature, the terminal hot water temperature is in a normal state. At this time, if the actual cold water temperature is higher than the set cold water loading temperature, it means that the cold water temperature is too high and the cooling capacity needs to be increased, so the compressor 10 is loaded; if the actual cold water temperature is lower than the set cold water unloading temperature, it means that the cold water temperature meets the requirements, and the compressor 10 can be unloaded to prevent excessive cooling capacity from causing too low water temperature; if the actual cold water temperature is equal to the set cold water loading temperature, the refrigeration mode is maintained, and after a certain period of time, the comparison is continued and adjusted according to the above steps.

[0109] As Figures 1 to 8 shown, in an alternative embodiment, during the operation cycle of the four-pipe refrigeration and heat pump unit in the heating mode, the actual cold water temperature and the actual hot water temperature are still monitored in real time and compared with the corresponding set cold water loading temperature, set cold water unloading temperature, set hot water loading temperature, and set hot water unloading temperature. Since the cold water side heat exchanger 30 does not participate in heat exchange in the heating mode, during the operation of the four-pipe refrigeration and heat pump unit in the heating mode, the cold water temperature will rise over time. When the actual cold water temperature is higher than the set cold water loading temperature, it means that the cooling capacity needs to be increased to lower the water temperature, so the four-pipe refrigeration and heat pump unit switches to the partial cold recovery mode, so that the cold water side heat exchanger 30 participates in heat exchange, and part of the refrigerant passes through the cold water side heat exchanger 30 to evaporate and absorb heat to lower the terminal cold water temperature. If during the operation cycle of the four-pipe refrigeration and heat pump unit in the heating mode, it is detected that the actual cold water temperature is not higher than the set cold water loading temperature, it means that the terminal cold water temperature is in a normal state. At this time, if the actual hot water temperature is lower than the set hot water loading temperature, it means that the hot water temperature is too low and the heat needs to be increased, so the compressor 10 is loaded; if the actual hot water temperature is higher than the set hot water unloading temperature, it means that the hot water temperature meets the requirements, and the compressor 10 can be unloaded to prevent excessive heat from causing too high water temperature; if the actual hot water temperature is equal to the set hot water loading temperature, the heating mode is maintained, and after a certain period of time, the comparison is continued and adjusted according to the above steps.

[0110] As Figures 1 to 8As shown, in an alternative embodiment, during the operation cycle of the four-pipe cooling and heating unit in the full heat recovery mode, the actual chilled water temperature and the actual hot water temperature are still monitored in real time and compared with the corresponding set chilled water loading temperature, set chilled water unloading temperature, set hot water loading temperature, and set hot water unloading temperature. It should be noted that since the heat exchange amount is large in the full heat recovery mode and has a great impact on the water temperature, the actual operation time of the full heat recovery mode needs to be considered. At this time, the actual operation time also needs to be compared with the set operation time. Specifically as follows:

[0111] Obtain the actual operation time of the full heat recovery mode and compare the actual operation time with the set operation time (τ min in the figure). Among them, the set operation time can be used as the shortest operation time requirement of the unit. Such a setting is equivalent to reserving a safe operation time for the unit, which can well prevent the unit from randomly switching between the partial cold recovery mode, the full heat recovery mode, and the partial heat recovery mode, thereby preventing the balance heat exchanger 40 from being damaged due to continuously connecting to the high-pressure side and the low-pressure side (that is: acting as a condenser for a while and acting as an evaporator for a while), and improving the control reliability of the unit. Therefore, it can be judged whether it is necessary to switch to the partial heat recovery mode or the partial cold recovery mode, or whether it is necessary to load or unload the compressor 10 according to the actual operation time.

[0112] In some specific embodiments, the set operation time can be between 1 s and 600 s. Further, it can be between 10 s and 500 s. For example, the set operation time can be 1 s, 90 s, 250 s, 300 s, 450 s, or 600 s.

[0113] When the actual hot water temperature is greater than the set hot water unloading temperature, the actual chilled water temperature is not less than the set chilled water unloading temperature, and the actual operation time is not less than the set operation time, it indicates that the full heat recovery mode has been running for a period of time and meets the shortest operation time requirement, and the terminal hot water temperature meets the requirement. However, since the chilled water unloading temperature is less than the chilled water loading temperature, the terminal chilled water temperature may still be less than the set chilled water loading temperature, that is, the terminal chilled water temperature is low. Therefore, it is necessary to switch the four-pipe cooling and heating unit to the partial heat recovery mode to introduce the balance heat exchanger 40 for heat exchange to increase the heat exchange amount of the chilled water side heat exchanger 30, thereby ensuring that the terminal chilled water temperature meets the demand. At the same time, the setting of the balance heat exchanger 40 can also dissipate part of the heat exchange amount into the air, avoiding excessive heat exchange amount of the hot water side heat exchanger 20 resulting in overheating of the terminal hot water temperature, and ensuring the stability of the terminal chilled water temperature and the terminal hot water temperature.

[0114] When the actual hot water temperature is not greater than the set hot water unloading temperature, the actual cold water temperature is less than the set cold water unloading temperature, and the actual operation time is not less than the set operation time, it indicates that the total heat recovery mode has been running for some time and meets the minimum operation time requirement, and the terminal cold water temperature meets the requirement. However, since the set hot water unloading temperature is greater than the set hot water loading temperature, the actual hot water temperature may still be less than the set hot water loading temperature, that is, the terminal hot water temperature is relatively low. Therefore, it is necessary to switch the four-pipe refrigeration and heating unit to the partial cold recovery mode to introduce the balance heat exchanger 40 for heat exchange, thereby increasing the heat exchange capacity of the hot water side heat exchanger 20 and ensuring that the terminal hot water temperature meets the demand.

[0115] When the actual hot water temperature is greater than the set hot water unloading temperature, the actual cold water temperature is less than the set cold water unloading temperature, and the actual operation time is less than the set operation time, it indicates that the operation time of the four-pipe refrigeration and heating unit in the total heat recovery mode is relatively short and does not meet the minimum operation time requirement, and both the terminal hot water temperature and the terminal cold water temperature meet their respective demands. At this time, the compressor 10 unloading can be adjusted to avoid overheating or overcooling.

[0116] When the actual hot water temperature is less than the set hot water loading temperature, the actual cold water temperature is greater than the set cold water unloading temperature, and the actual operation time is less than the set operation time, it indicates that the operation time of the four-pipe refrigeration and heating unit in the total heat recovery mode is relatively short and does not meet the minimum operation time requirement, and the terminal hot water temperature is relatively low and the terminal cold water temperature is relatively high. Then, the compressor 10 loading needs to be adjusted. In an alternative embodiment, it can also be when the actual cold water temperature is greater than the set cold water loading temperature, the actual hot water temperature is less than the set hot water unloading temperature, and the actual operation time is less than the set operation time, indicating that the operation time of the four-pipe refrigeration and heating unit in the total heat recovery mode does not meet the minimum operation time requirement, and the terminal hot water temperature is relatively low and the terminal cold water temperature is relatively high. Then, the compressor 10 loading also needs to be adjusted.

[0117] In addition, when the actual hot water temperature is equal to the hot water unloading temperature, the actual cold water temperature is equal to the cold water unloading temperature, and the actual operation time is less than the set operation time, the total heat recovery mode is maintained, and after a certain time, continue to compare and adjust according to the above steps.

[0118] In actual use, the target temperature can be defined, that is, the temperature that meets the use requirements. Among them, the cold water corresponds to the cold water target temperature, and the hot water corresponds to the hot water target temperature. Then, the cold water loading temperature > the cold water target temperature > the cold water unloading temperature, and the hot water loading temperature < the hot water target temperature < the hot water unloading temperature. Among them, the cold water target temperature can be set to 7°C, the cold water unloading temperature to 6.7°C, the cold water loading temperature to 7.7°C, the hot water target temperature to 45°C, the hot water unloading temperature to 45.3°C, and the hot water loading temperature to 44.7°C.

[0119] The following specifically describes the switching of each mode in combination with the control of the first three-way valve 61 and the second three-way valve 62.

[0120] As Figures 1 to 6 and Figure 9 shown, in an alternative embodiment, when the four-pipe refrigeration and heat pump unit switches to the partial heat recovery mode, it is necessary to adjust the communication between port A and port B, and between port A and port C of the first three-way valve 61. Therefore, when switching from the refrigeration mode or the full heat recovery mode to the partial heat recovery mode, it is necessary to adjust the opening degrees of port A and port C. Specifically, when switching from the refrigeration mode to the partial heat recovery mode, since port A is connected to port B and not connected to port C (i.e., the opening degree is equal to 0) in the refrigeration mode, it is necessary to increase the opening degrees of port A and port C at this time, so as to satisfy the connection of both port B and port C to port A; when switching from the full heat recovery mode to the partial heat recovery mode, since port A is connected to port C and not connected to port B in the full heat recovery mode, it is necessary to reduce the opening degrees of port A and port C, so as to increase the opening degrees of port A and port B, and achieve the connection of both port B and port C to port A.

[0121] During the adjustment process, if the opening degrees of port A and port C of the first three-way valve 61 are adjusted to 0, then port A of the first three-way valve 61 is connected to port B and the opening degree is 100%, and the four-pipe refrigeration and heat pump unit switches to the refrigeration mode; if the opening degrees of port A and port C of the first three-way valve 61 are adjusted to 100%, then port A and port B are not connected, and the four-pipe refrigeration and heat pump unit switches to the full heat recovery mode. It should be noted that at this time, the second three-way valve 62 remains unchanged and is in the state where port D and port E are connected.

[0122] If both port A and port B, and port A and port C of the first three-way valve 61 are connected, the four-pipe refrigeration and heat pump unit switches to the partial heat recovery mode. During the operation cycle of the partial heat recovery mode:

[0123] When the actual hot water temperature is less than the set hot water loading temperature and the actual operation time is greater than the set operation time (τ 设定 ) in the figure, it means that the partial heat recovery mode has been running for a period of time and meets the shortest operation time requirement, but the terminal hot water heat is insufficient. Therefore, the opening degrees of port A and port C are increased, while the opening degrees of port A and port B are decreased, thereby increasing the refrigerant amount flowing to the hot water side heat exchanger 20, decreasing the refrigerant amount flowing to the balance heat exchanger 40, and increasing the heat exchange amount of the hot water side heat exchanger 20.

[0124] When the actual hot water temperature is greater than the set hot water unloading temperature and the actual running time is greater than the set running time, it indicates that the terminal hot water heat is sufficient. At this time, the opening degrees of port A and port C can be reduced, so that the opening degrees of port A and port B are increased, thereby reducing the refrigerant amount flowing to the hot water side heat exchanger 20 and increasing the refrigerant amount flowing to the balance heat exchanger 40, so as to dissipate the excess heat through the balance heat exchanger 40 and air cooling.

[0125] When the actual running time is less than the set running time and the actual cold water temperature is greater than the set cold water loading temperature, it indicates that part of the heat recovery mode has not met the minimum running time requirement, but the terminal cold water temperature is relatively high, which prompts the compressor 10 to load. At the same time, when the actual cold water temperature is less than the set cold water unloading temperature and the actual running time is less than the set running time, that is, the terminal cold water temperature meets the requirement, but to prevent excessive cooling capacity, the compressor 10 is prompted to unload. In addition, when the actual cold water temperature is equal to the set cold water loading temperature or the actual cold water temperature is equal to the set cold water unloading temperature and the actual running time is less than the set running time, the unit maintains the current operating state for a period of time and then compares again.

[0126] That is to say, in the partial heat recovery mode, it is possible to first judge whether the actual hot water temperature meets the requirements. When the actual hot water temperature meets the requirements, then judge whether the actual running time meets the requirements. When the actual running time does not meet the requirements, judge whether the actual cold water temperature meets the requirements to load or unload the compressor 10. In addition, when the actual hot water temperature does not meet the requirements, it is possible to directly judge whether the actual cold water temperature meets the requirements to load and unload the compressor 10.

[0127] In some specific embodiments, when switching from the refrigeration mode to the partial heat recovery mode, the opening degrees of port A and port C are adjusted to increase by the first gear; when switching from the full heat recovery mode to the partial heat recovery mode, the opening degrees of port A and port C are adjusted to decrease by the second gear. Wherein the first gear and the second gear can be between 0.5% and 20%. For example, both the first gear and the second gear are 2%. Of course, it can also be 0.5%, 10%, 15% or 20%. The specific adjustment gear can be calculated according to the water temperature difference. Specifically, when switching from the refrigeration mode to the partial heat recovery mode, the opening degrees of port A and port C are adjusted to increase by 2%; when switching from the full heat recovery mode to the partial heat recovery mode, the opening degrees of port A and port C are adjusted to decrease by 2%.

[0128] Such as Figures 1 to 6 and Figure 10As shown, in an alternative embodiment, when the four-pipe cooling and heating unit switches to the partial cold recovery mode, it is necessary to adjust the communication between port D and port E, and port D and port F of the second three-way valve 62. Therefore, when switching from the heating mode or the full heat recovery mode to the partial cold recovery mode, it is necessary to adjust the opening degrees of port D and port E.

[0129] When switching from the heating mode to the partial cold recovery mode, since port D and port F are in communication and port D and port E are not in communication in the heating mode, at this time, the opening degrees of port D and port E need to be increased by the third gear, so as to satisfy that both port E and port F are in communication with port D. Among them, the third gear is between 0.5% and 20%, such as 0.5%, 2%, 10% or 20%. Specifically, the opening degrees of port D and port E can be increased by 2%.

[0130] When switching from the full heat recovery mode to the partial cold recovery mode, since port D and channel E are in communication and port D and port F are not in communication in the full heat recovery mode, at this time, it is necessary to increase the opening degrees of port D and port F (that is, decrease the opening degrees of port D and port E), so as to satisfy that both port E and port F are in communication with port D. In the partial cold recovery mode, the balance heat exchanger 40 is used as an evaporator for evaporation and heat absorption; and, since the balance heat exchanger 40 is an air heat exchanger, the refrigerant flowing through the balance heat exchanger 40 is used for heat exchange with air for evaporation and heat absorption, so the ambient temperature will affect the evaporation pressure of the balance heat exchanger 40. Therefore, it is necessary to consider the actual ambient temperature where the balance heat exchanger 40 is located, and then adjust the opening degrees of port D and port E to satisfy the adjustment of the refrigerant amount flowing through the balance heat exchanger 40.

[0131] Exemplarily, when the four-pipe cooling and heating unit switches from the full heat recovery mode to the partial cold recovery mode:

[0132] Obtain the actual ambient temperature (T in the figure 环温测 ), and compare it with the set ambient temperature (T in the figure 设定环温 );

[0133] When the actual ambient temperature is greater than the set ambient temperature, decrease the opening degree between port D and port E;

[0134] When the actual ambient temperature is not greater than the set ambient temperature, increase the opening degree between port D and port E.

[0135] When the actual ambient temperature is higher than the set ambient temperature, it indicates that the temperature around the balancing heat exchanger 40 is higher, resulting in an increase in the evaporation pressure of the balancing heat exchanger 40. In this case, the amount of refrigerant flowing through the balancing heat exchanger 40 needs to be increased to ensure sufficient refrigerant flows to the balancing heat exchanger 40. Therefore, the openings of ports D and E can be reduced to the first opening, so that ports D, E, and F are all connected. The first opening is greater than the openings of ports D and F. This ensures that both the balancing heat exchanger 40 and the cold water-side heat exchanger 30 have sufficient heat exchange capacity to meet the heat exchange requirements of the hot water-side heat exchanger 20. Furthermore, since the refrigerant in the cold water-side heat exchanger 30 still needs to meet the terminal cold water load, the openings of ports D and E cannot be too small. For example, the 100% opening of ports D and E can be reduced by 2% (i.e., the fourth level), resulting in a first opening of 98%. In addition, precisely because the evaporation pressure of the balancing heat exchanger 40 is too large and greater than the evaporation pressure of the cold water side heat exchanger 30, the openings of ports D and F need to be smaller than those of ports D and E to achieve a secondary throttling effect.

[0136] The first opening can be between 80% and 99.5%. When the openings of the corresponding ports D and E are 100%, the fourth gear needs to be reduced. The fourth gear is between 0.5% and 20%, such as 0.5%, 2%, 10% or 20%.

[0137] When the actual ambient temperature is not greater than the set ambient temperature, it means that the temperature around the balanced heat exchanger 40 is low and can be fully used for evaporation heat exchange. Therefore, the opening of port D and port E can be reduced to the second opening, and the opening of port D and port F can be made greater than the second opening. At this time, the balanced heat exchanger 40 can be fully utilized for heat exchange, and the cooling capacity of the cold water side heat exchanger 30 can be maintained without causing the terminal cold water temperature to be too low. For example, the opening of port D and port E can be adjusted to 30%, and the opening of port D and port F reaches 70%. Among them, 30% can also be used as the initial opening when opening. The second opening can be in the range of 5%-50%, for example, it can be 5%, 30%, 45% or 50%.

[0138] In some specific embodiments, the ambient temperature is set within a range of values, having an upper limit and a lower limit. The upper limit can be the ambient temperature corresponding to a certain value at which the evaporation pressure in the balancing heat exchanger 40 is higher than the evaporation pressure in the cold water-side heat exchanger 30, while the lower limit can be the ambient temperature corresponding to a certain value at which the evaporation pressure in the balancing heat exchanger 40 is lower than the evaporation pressure in the cold water-side heat exchanger 30. Furthermore, when the refrigerant in the four-pipe cooling and heating unit is water, the ambient temperature can be set to 10°C while maintaining the outlet water temperature at 7°C.

[0139] During the adjustment process, if the opening degrees of ports D and E of the second three-way valve 62 are adjusted to 0, then ports D and F of the second three-way valve 62 are fully connected and open, and the four-pipe refrigeration and heat pump unit switches to the heating mode; if the opening degrees of ports D and E of the second three-way valve 62 are adjusted to 100%, then the four-pipe refrigeration and heat pump unit switches to the full heat recovery mode. It should be noted that at this time, the first three-way valve 61 remains unchanged and is in the state where ports A and B are connected.

[0140] If ports D and E, and ports D and F of the second three-way valve 62 are both connected, the four-pipe refrigeration and heat pump unit switches to the partial cold recovery mode. During the operation cycle of the partial cold recovery mode:

[0141] Compare the actual chilled water temperature with the set chilled water cut-in temperature (T 冷切入 ) shown in the figure. When the actual chilled water temperature is greater than the set chilled water cut-in temperature, the terminal chilled water temperature is too high, and at this time, the refrigeration capacity needs to be increased. Therefore, it is necessary to increase the opening degrees of ports D and E to 100% to switch the four-pipe refrigeration and heat pump unit from the partial cold recovery mode to the full heat recovery mode. Among them, the set chilled water cut-in temperature refers to the temperature when chilled water needs to be added.

[0142] When the evaporation pressure of the chilled water side heat exchanger 30 is less than the set evaporation pressure, it is necessary to reduce the opening degrees of ports D and E to reduce the refrigeration capacity; also, when the actual chilled water temperature is greater than the set chilled water loading temperature, it is necessary to increase the opening degrees of ports D and E to increase the refrigeration capacity. However, since the influence of the evaporation pressure on the chilled water side heat exchanger 30 has a higher priority, after the refrigerant amount flowing through the chilled water side heat exchanger 30 is reduced, the actual chilled water temperature will be higher than the set chilled water cut-in temperature after operating in the partial cold recovery mode for a period of time. At this time, it is necessary to switch the partial cold recovery mode to the full heat recovery mode to ensure the refrigerant amount flowing through the chilled water side heat exchanger 30.

[0143] When the actual chilled water temperature is not greater than the set chilled water cut-in temperature: obtain the actual pressure on the chilled water side and compare the actual pressure on the chilled water side (P 冷侧 ) shown in the figure with the set pressure on the chilled water side (i.e., the above-mentioned set evaporation pressure, P 冷设定min) for comparison; when the actual pressure on the cold water side is less than the set pressure on the cold water side, reduce the opening of port D and port E. Among them, the actual pressure on the cold water side refers to the evaporation pressure of the refrigerant in the cold water side heat exchanger 30, and the set pressure on the cold water side is the minimum evaporation pressure of the refrigerant in the cold water side heat exchanger 30. If the evaporation pressure of the cold water side heat exchanger 30 is too small, it is necessary to reduce the flow area between port D and port E, thereby increasing the evaporation pressure. It is understandable that since the actual pressure on the cold water side is too small, there may be risks in long-term operation. Therefore, in order to ensure the safety and reliability of the four-pipe cooling and heating unit, it is necessary to reduce the opening of port D and port E to form secondary throttling on the cold water side heat exchanger 30 to ensure that the evaporation pressure of the refrigerant in the cold water side heat exchanger 30 is within a safe range.

[0144] In some specific embodiments, the openings of the ports D and E can be reduced to a fifth level, which is between 5% and 25%, for example, 5%, 10%, 20% or 25%.

[0145] When the actual pressure on the cold water side is not less than the set pressure on the cold water side, it means that the evaporation pressure of the cold water side heat exchanger 30 meets the requirements, and the actual cold water temperature and the operating time of the four-pipe cooling and heating unit in the partial cold recovery mode can be judged.

[0146] When the actual cold water temperature is greater than the set cold water loading temperature, and the actual running time is greater than the set running time (τ 设定 ), it means that the partial cold recovery mode has been running for a period of time and meets the minimum operating time requirement, but the terminal cold water temperature is high, so it is necessary to increase the opening of port D and port E to the third gear (for example, increase by 2%), and reduce the opening of port D and port F, thereby increasing the amount of refrigerant flowing through the cold water side heat exchanger 30 and reducing the amount of refrigerant flowing through the balancing heat exchanger 40; and, such a setting can reduce the evaporation pressure of the cold water side heat exchanger 30, thereby reducing the superheat of the cold water side heat exchanger 30.

[0147] When the actual cold water temperature is lower than the set cold water unloading temperature and the actual operating time is longer than the set operating time, it means that the terminal cold water cooling capacity is sufficient. At this time, the opening of port D and port E can be reduced to the fourth level (for example, it can be reduced by 2%), and the opening of port D and port F can be increased, thereby increasing the refrigerant amount of the balancing heat exchanger 40 so that the heat can be dissipated through the balancing heat exchanger 40.

[0148] When the actual hot water temperature is lower than the set hot water loading temperature and the actual operation time is shorter than the set operation time, it indicates that the terminal hot water temperature is relatively low before the operation time is reached, and at this time, the compressor 10 needs to be loaded. Meanwhile, when the actual hot water temperature is higher than the set hot water unloading temperature and the actual operation time is shorter than the set operation time, it indicates that the hot water temperature of the terminal water-using equipment is too high at this time, and the compressor 10 needs to be unloaded. In addition, when the actual hot water temperature is equal to the set hot water loading temperature or the actual hot water temperature is equal to the set hot water unloading temperature, and the actual operation time is shorter than the set operation time, the unit maintains its current operating state for a period of time and then makes a comparison again.

[0149] That is to say, in the partial cold recovery mode, it is possible to first determine whether the actual cold water temperature meets the requirements. When the actual cold water temperature meets the requirements, then determine whether the actual operation time meets the requirements. When the actual operation time does not meet the requirements, determine whether the actual hot water temperature meets the requirements to load or unload the compressor 10. In addition, when the actual cold water temperature does not meet the requirements, it is possible to directly determine whether the actual hot water temperature meets the requirements to load and unload the compressor 10.

[0150] Among them, when the compressor 10 is unloaded to the minimum, it is shut down, and when it is loaded to the maximum, it is fully loaded.

[0151] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0152] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A four-pipe cooling and heating unit, characterized in that, The four-pipe cooling and heating unit includes a compressor, a cold-side heat exchanger, a hot-side heat exchanger, and a balance heat exchanger; The compressor has an exhaust port and a suction port. A first three-way valve is provided at the exhaust port, and a second three-way valve is provided at the suction port. The first three-way valve is connected to one end of the hot-side heat exchanger and one end of the balance heat exchanger, and the second three-way valve is connected to one end of the cold-side heat exchanger and one end of the balance heat exchanger; The other end of the cold-side heat exchanger is connected to the other end of the hot-side heat exchanger through a first pipeline, the other end of the cold-side heat exchanger is connected to the other end of the balance heat exchanger through a second pipeline, and the other end of the hot-side heat exchanger is connected to the other end of the balance heat exchanger through a third pipeline; A first parallel point is provided in parallel with the first pipeline and the second pipeline, and a second parallel point is provided in parallel with the first pipeline and the third pipeline. The first parallel point is located upstream of the second parallel point; A first check valve and a first expansion valve are provided on the first pipeline, and the first check valve is located upstream of the first parallel point, and the first expansion valve is located downstream of the second parallel point. A second check valve is provided on the second pipeline, and a second expansion valve is provided on the third pipeline. The second check valve is located upstream of the first parallel point, and the second expansion valve is located downstream of the second parallel point; The four-pipe cooling and heating unit has at least a cooling mode, a heating mode, and a full heat recovery mode, and the four-pipe cooling and heating unit is configured to switch the cooling mode, the heating mode, and the full heat recovery mode in response to the adjustment states of the first three-way valve and the second three-way valve.

2. The four-tube refrigeration and heat pump unit according to claim 1, wherein, In the cooling mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the balance heat exchanger, the second three-way valve adjusts the suction port of the compressor to communicate with the cold-side heat exchanger, and the compressor, the balance heat exchanger, the second pipeline, the first expansion valve, and the cold-side heat exchanger are connected to form a cooling circuit; In the heating mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the hot-side heat exchanger, the second three-way valve adjusts the suction port of the compressor to communicate with the balance heat exchanger, and the compressor, the hot-side heat exchanger, the third pipeline, the second expansion valve, and the balance heat exchanger are connected to form a heating circuit; In the full heat recovery mode, the first three-way valve adjusts the exhaust port of the compressor to communicate with the hot-side heat exchanger, the second three-way valve adjusts the suction port of the compressor to communicate with the cold-side heat exchanger, and the compressor, the hot-side heat exchanger, the first pipeline, the first expansion valve, and the cold-side heat exchanger are connected to form a full heat recovery circuit.

3. The four-pipe cooling and heating unit according to claim 2, wherein The four-pipe cooling and heating unit also has a partial heat recovery mode and a partial cold recovery mode; In the partial heat recovery mode, the first three-way valve adjusts the hot water side heat exchanger and the balance heat exchanger to be both communicated with the exhaust port of the compressor, the second three-way valve adjusts the suction port of the compressor to be communicated with the cold water side heat exchanger, and the total heat recovery circuit and the refrigeration circuit are both communicated; In the partial cold recovery mode, the first three-way valve adjusts the exhaust port of the compressor to be communicated with the hot water side heat exchanger, the second three-way valve adjusts the balance heat exchanger and the cold water side heat exchanger to be both communicated with the suction port of the compressor, and the total heat recovery circuit and the heating circuit are both communicated.

4. The four-tube refrigeration and heat pump unit according to claim 1, characterized in that, A fourth pipeline is further arranged between the suction port of the compressor and one end of the hot water side heat exchanger, and a first two-way valve is arranged on the fourth pipeline; a fifth pipeline is further arranged between the other end of the hot water side heat exchanger and the other end of the balance heat exchanger, the fifth pipeline is parallel to the third pipeline and has an opposite flow direction, and a third expansion valve is arranged on the fifth pipeline.

5. The four-tube refrigeration and heat pump unit according to claim 4, characterized in that, The four-pipe refrigeration and heat pump unit further has a defrosting mode; In the defrosting mode, the first three-way valve adjusts the exhaust port of the compressor to be communicated with the balance heat exchanger, the first two-way valve is configured to be in an open state, and the compressor, the balance heat exchanger, the fifth pipeline, the third expansion valve, the hot water side heat exchanger and the fourth pipeline are communicated to form a defrosting circuit.

6. The four-tube refrigeration and heat pump unit according to claim 4, characterized in that, The four-pipe refrigeration and heat pump unit further includes a liquid receiver, the inlet of the liquid receiver is connected in parallel with a first branch and a second branch, and the outlet of the liquid receiver is connected in parallel with a third branch and a fourth branch; The first branch is connected to the hot water side heat exchanger, the third branch is connected to the cold water side heat exchanger, a first check valve is arranged on the first branch, a first expansion valve is arranged on the third branch, and the first branch and the third branch are communicated to jointly define the first pipeline; The second branch is connected to the balance heat exchanger, a second check valve is arranged on the second branch, and the second branch and the third branch are communicated to jointly define the second pipeline; The fourth branch is connected to the balance heat exchanger, a second expansion valve is arranged on the fourth branch, and the first branch and the fourth branch are communicated to jointly define the third pipeline.

7. The four-pipe cooling and heating unit according to claim 6, characterized in that, The outlet of the liquid receiver is further connected in parallel with a fifth branch, the fifth branch is connected to the hot water side heat exchanger, a third expansion valve is arranged on the fifth branch, and the second branch and the fifth branch are communicated to jointly define the fifth pipeline.

8. A control method for a four-tube refrigeration and heat pump unit, characterized in that, The control method includes the following steps: Obtain the actual cold water temperature and the actual hot water temperature; Compare the actual cold water temperature with the set cold water loading temperature, and compare the actual hot water temperature with the set hot water loading temperature; When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is not less than the set hot water loading temperature, the four-pipe refrigeration and heat pump unit starts or switches to the refrigeration mode; When the actual cold water temperature is not greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the heating mode; When the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit starts or switches to the full heat recovery mode.

9. The control method according to claim 8, wherein During the operation cycle of the cooling mode: Compare the actual hot water temperature with the set hot water unloading temperature, and compare the actual cold water temperature with the set cold water unloading temperature; When the actual hot water temperature is less than the set hot water loading temperature, the four-pipe cooling and heating unit switches to the partial heat recovery mode; When the actual hot water temperature is not less than the set hot water loading temperature: if the actual cold water temperature is greater than the set cold water loading temperature, the compressor in the four-pipe cooling and heating unit loads; if the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads.

10. The control method according to claim 9, characterized in that, During the operation cycle of the heating mode: When the actual cold water temperature is greater than the set cold water loading temperature, the four-pipe cooling and heating unit switches to the partial cold recovery mode; When the actual cold water temperature is not greater than the set cold water loading temperature: if the actual hot water temperature is less than the set hot water loading temperature, the compressor in the four-pipe cooling and heating unit loads; if the actual hot water temperature is greater than the set hot water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads.

11. The control method according to claim 10, wherein During the operation cycle of the full heat recovery mode: Obtain the actual operation time of the full heat recovery mode and compare the actual operation time with the set operation time; When the actual hot water temperature is greater than the set hot water unloading temperature, the actual cold water temperature is not less than the set cold water unloading temperature, and the actual operation time is not less than the set operation time, the four-pipe cooling and heating unit switches to the partial heat recovery mode; When the actual hot water temperature is not greater than the set hot water unloading temperature, the actual cold water temperature is less than the set cold water unloading temperature, and the actual operation time is not less than the set operation time, the four-pipe cooling and heating unit switches to the partial cold recovery mode; When the actual hot water temperature is greater than the set hot water unloading temperature and the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads; When the actual hot water temperature is less than the set hot water loading temperature and the actual cold water temperature is greater than the set cold water unloading temperature, or when the actual cold water temperature is greater than the set cold water loading temperature and the actual hot water temperature is less than the set hot water unloading temperature, the compressor in the four-pipe cooling and heating unit loads.

12. The control method according to claim 11, wherein A first three-way valve is provided at the exhaust port of the compressor in the four-pipe cooling and heating unit. Port A of the first three-way valve is connected to the exhaust port, port B is connected to the balance heat exchanger, and port C is connected to the hot water side heat exchanger; When the four-pipe cooling and heating unit switches from the refrigeration mode to the partial heat recovery mode, increase the opening degrees of port A and port C; or, when the four-pipe cooling and heating unit switches from the full heat recovery mode to the partial heat recovery mode, decrease the opening degrees of port A and port C.

13. The control method according to claim 12, wherein When the opening degree between port A and port C is equal to 0, the four-pipe cooling and heating unit switches from the partial heat recovery mode to the refrigeration mode; When the opening degree between port A and port C is equal to 100%, the four-pipe cooling and heating unit switches from the partial heat recovery mode to the full heat recovery mode.

14. The control method according to claim 12, wherein During the operation cycle of the partial heat recovery mode: When the actual hot water temperature is less than the set hot water loading temperature and the actual operation time is greater than the set operation time, increase the opening degrees of port A and port C; When the actual hot water temperature is greater than the set hot water unloading temperature and the actual operation time is greater than the set operation time, decrease the opening degrees of port A and port C; When the actual cold water temperature is greater than the set cold water loading temperature, the compressor in the four-pipe cooling and heating unit loads; When the actual cold water temperature is less than the set cold water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads.

15. The control method according to claim 11, characterized in that A second three-way valve is provided at the suction port of the compressor in the four-pipe cooling and heating unit. Port D of the second three-way valve is connected to the suction port, port E is connected to the cold water side heat exchanger, and port F is connected to the balance heat exchanger; When the four-pipe cooling and heating unit switches from the full heat recovery mode to the partial cold recovery mode: obtain the actual ambient temperature and compare it with the set ambient temperature; when the actual ambient temperature is greater than the set ambient temperature, decrease the opening degrees of port D and port E to a first opening degree, and the first opening degree is greater than the opening degrees of port D and port F; when the actual ambient temperature is not greater than the set ambient temperature, decrease the opening degrees of port D and port E to a second opening degree, and the second opening degree is less than the opening degrees of port D and port F; or, when the four-pipe cooling and heating unit switches from the heating mode to the partial cold recovery mode, increase the opening degree between port D and port E.

16. The control method according to claim 15, wherein When the opening degrees of port D and port E are equal to 0, the four-pipe cooling and heating unit switches from the partial cold recovery mode to the heating mode; When the opening degrees of port D and port E are equal to 100%, the four-pipe cooling and heating unit switches from the partial cold recovery mode to the full heat recovery mode.

17. The control method according to claim 15, characterized in that During the operation cycle of the partial cold recovery mode; Compare the actual cold water temperature with the set cold water cut-in temperature; When the actual cold water temperature is greater than the set cold water cut-in temperature, increase the opening degrees of port D and port E to 100%, and the four-pipe cooling and heating unit switches from the partial cold recovery mode to the full heat recovery mode; When the actual cold water temperature is not greater than the set cold water cut-in temperature: obtain the actual pressure on the cold water side and compare the actual pressure on the cold water side with the set pressure on the cold water side; when the actual pressure on the cold water side is less than the set pressure on the cold water side, reduce the opening degrees of the port D and the port E.

18. The control method according to claim 17, characterized in that When the actual pressure on the cold water side is not less than the set pressure on the cold water side: When the actual cold water temperature is greater than the set cold water loading temperature and the actual running time is greater than the set running time, increase the opening degree between the port D and the port E; When the actual cold water temperature is less than the set cold water unloading temperature and the actual running time is greater than the set running time, reduce the opening degree between the port D and the port E; When the actual hot water temperature is less than the set hot water loading temperature, the compressor in the four-pipe cooling and heating unit loads; When the actual hot water temperature is greater than the set hot water unloading temperature, the compressor in the four-pipe cooling and heating unit unloads.

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