Four-pipe unit

Abstract

The four-pipe unit comprises a compressor unit, a cold water heat exchanger, a hot water heat exchanger, a first throttling element, a heat storage phase change tank, a cold storage phase change tank, a first pipeline, a first switch valve assembly, a second pipeline, a second switch valve assembly and a third pipeline, the cold water heat exchanger is provided with a port O and a port P, and the hot water heat exchanger is provided with a port R and a port T. A heat storage phase change material is arranged in the heat storage phase change tank, a cold storage phase change material is arranged in the cold storage phase change tank, one end of the first pipeline can be connected with an air outlet of the compressor unit, the other end of the first pipeline is connected with the first end and a T opening of the heat storage phase change tank in parallel through the first switch valve assembly, and one end of the second pipeline is connected with the second end and an R opening of the heat storage phase change tank in parallel. The other end of the first throttling element is connected with the liquid inlet end and the O port of the cold storage phase change tank in parallel through the second switch valve assembly, one end of the third pipeline is connected with the liquid outlet end and the P port of the cold storage phase change tank in parallel, and the other end of the third pipeline is connected with an air inlet of the compressor unit.

Description

Technical Field

[0001] This application relates to the field of air conditioning unit technology, and in particular to a four-pipe unit. Background Technology

[0002] For locations where both cooling and heating are required, and temperature and humidity must be maintained within a specific range, the four-pipe air source heat pump unit has emerged. Employing self-balancing technology, it can provide both cooling and heating year-round, offering advantages such as high efficiency, energy saving, stability, reliability, adaptability, and environmental friendliness. It can be widely used in locations with simultaneous cooling and heating needs, or where temperature and humidity requirements are specific, such as hospitals, commercial complexes, museums, hotels, and indoor swimming pools.

[0003] When a four-pipe air source heat pump unit is in heat recovery mode, it can provide hot water and cold water simultaneously. However, when the heating and cooling demands of the four-pipe air source heat pump unit are unbalanced, the excess energy is usually dissipated into the external environment, which will result in a waste of heat or cooling capacity. Summary of the Invention

[0004] Therefore, it is necessary to provide a four-pipe air source heat pump unit to solve the above problems.

[0005] A four-pipe unit includes a compressor unit, a chilled water heat exchanger, a hot water heat exchanger, a first throttling element, a thermal phase change tank, a cold phase change tank, a first pipeline, a first switching valve assembly, a second pipeline, a second switching valve assembly, and a third pipeline. The chilled water heat exchanger has an O port and a P port, and the hot water heat exchanger has an R port and a T port. The thermal phase change tank contains thermal phase change material, and the cold phase change tank contains cold phase change material. One end of the first pipeline is connected to the outlet of the compressor unit, and the other end is connected in parallel to the first end and the T port of the thermal phase change tank via the first switching valve assembly. One end of the second pipeline is connected in parallel to the second end and the R port of the thermal phase change tank, and the other end is connected to one end of the first throttling element. The other end of the first throttling element is connected in parallel to the inlet and the O port of the cold phase change tank via the second switching valve assembly. One end of the third pipeline is connected in parallel to the outlet and the P port of the cold phase change tank, and the other end is connected to the inlet of the compressor unit.

[0006] In one embodiment, the thermal storage phase change tank is provided with a thermally conductive material, which is mixed with the thermal storage phase change material; or, the thermally conductive material divides the thermal storage phase change material into multiple heat exchange units; the cold storage phase change tank is provided with a thermally conductive material, which is mixed with the cold storage phase change material; or, the thermally conductive material divides the cold storage phase change material into multiple heat exchange units.

[0007] In one embodiment, the first switching valve assembly includes a first solenoid valve and a second solenoid valve. The first solenoid valve is connected to a first pipeline and a first end of the thermal storage phase change tank, and the second solenoid valve is connected to the first pipeline and a T-port. The second switching valve assembly includes a third solenoid valve and a fourth solenoid valve. The third solenoid valve is connected to a first throttling element and the liquid inlet of the cold storage phase change tank, and the fourth solenoid valve is connected to the first throttling element and an O-port. When the four-pipe unit is in heat recovery mode, the first solenoid valve is closed, the second solenoid valve is open, the third solenoid valve is closed, and the fourth solenoid valve is open. Furthermore, during the operation of the four-pipe unit in heat recovery mode, when the heat demand of the four-pipe unit is less than the cooling demand, the first solenoid valve is open and the second solenoid valve is closed; when the heat demand of the four-pipe unit is greater than the cooling demand, the third solenoid valve is open and the fourth solenoid valve is closed.

[0008] In one embodiment, the four-pipe unit further includes a balancing heat exchanger, a four-way valve, a fourth pipeline, a fifth pipeline, and a sixth pipeline. The balancing heat exchanger has ports A and B. The four-way valve has ports D, E, S, and C. Port D connects to the outlet of the compressor unit, port E connects to the first pipeline, port S connects to the third pipeline, and port C connects to port A. The second pipeline includes a first section, a second section, a third section, and a fourth section connected sequentially from port R to a first throttling element. The second section is equipped with a first check valve that allows unidirectional flow from the first section to the third section. The fourth pipeline connects port B at one end and the connection between the second and third sections at the other end. The fourth pipeline is equipped with a second check valve that allows unidirectional flow from port B to the second pipeline. The fifth pipeline connects port B and the second check valve at one end and the connection between the third and fourth sections at the other end. The fifth pipeline is equipped with a third check valve and a second throttling element connected in series. The second throttling element is located close to the second pipeline, and the third check valve allows unidirectional flow from the second throttling element to the fourth pipeline.

[0009] In one embodiment, the four-pipe unit further includes a chilled water inlet pipe, a chilled water outlet pipe, a fifth solenoid valve, and a sixth solenoid valve. The chilled water heat exchanger and the cold storage phase change tank each have an inlet and an outlet. The fifth solenoid valve is connected to the chilled water inlet pipe and the inlet of the cold storage phase change tank. The sixth solenoid valve is connected to the chilled water inlet pipe and the inlet of the chilled water heat exchanger. The outlet of the cold storage phase change tank and the outlet of the chilled water heat exchanger are respectively connected to the chilled water outlet pipe.

[0010] In one embodiment, when the four-pipe unit is in single-cooling mode, port D is connected to port C, port E is connected to port S, the first throttling element is open, the second throttling element is closed, the third solenoid valve is closed, the fourth solenoid valve is open, the fifth solenoid valve is closed, and the sixth solenoid valve is open.

[0011] In one embodiment, the four-pipe unit operates in a cold storage mode before operating in a single cooling mode, and when the four-pipe unit is in the cold storage mode, the third solenoid valve is open, the fourth solenoid valve is closed, the fifth solenoid valve is closed, and the sixth solenoid valve is closed.

[0012] In one embodiment, when the four-pipe unit is operating in single-cooling mode, the fifth solenoid valve opens and the sixth solenoid valve closes when the actual outlet temperature of the chilled water outlet pipe is greater than the target outlet temperature of the chilled water or when the cooling demand of the four-pipe unit increases.

[0013] In one embodiment, the phase change point of the cold storage phase change material in the cold storage phase change tank is defined as A1, the evaporation temperature in the cold water heat exchanger is defined as B1, the target outlet temperature of the chilled water is defined as C1, and C1-Y1>A1>B1+X1; wherein, 0.5K≤X1≤2K, 3K≤Y1≤5K.

[0014] In one embodiment, the four-pipe unit further includes a hot water inlet pipe, a hot water outlet pipe, a seventh solenoid valve, and an eighth solenoid valve. The hot water heat exchanger and the thermal storage phase change tank each have an inlet and an outlet. The seventh solenoid valve is connected to the hot water inlet pipe and the inlet of the thermal storage phase change tank, the eighth solenoid valve is connected to the hot water inlet pipe and the inlet of the hot water heat exchanger, and the outlet of the thermal storage phase change tank and the outlet of the hot water heat exchanger are respectively connected to the hot water outlet pipe.

[0015] In one embodiment, when the four-pipe unit is in single heating mode, port D is connected to port E, port C is connected to port S, the first throttling element is closed, the second throttling element is open, the first solenoid valve is closed, the second solenoid valve is open, the seventh solenoid valve is closed, and the eighth solenoid valve is open.

[0016] In one embodiment, the four-pipe unit operates in heat storage mode before operating in single heating mode, and when the four-pipe unit is in heat storage mode, the first solenoid valve is open, the second solenoid valve is closed, the fifth solenoid valve is closed, the seventh solenoid valve is closed, and the eighth solenoid valve is closed.

[0017] In one embodiment, when the four-pipe unit is operating in single heating mode, when the actual outlet water temperature of the hot water outlet pipe is less than the target outlet water temperature or when the heat demand of the four-pipe unit increases, the seventh solenoid valve opens and the eighth solenoid valve closes.

[0018] In one embodiment, the phase change point of the heat storage phase change material in the heat storage phase change tank is defined as A2, the condensation temperature in the hot water heat exchanger is defined as B2, the target hot water outlet temperature is defined as C2, and C2+Y2<A2<B2-X2, where 2K≥X2≥0.5K, 5K≥Y2≥3K.

[0019] In one embodiment, the four-pipe unit further includes a sixth pipeline, one end of which is connected between the third check valve and the second throttling element, and the other end is connected between the first section and the second section. Furthermore, the sixth pipeline is provided with a fourth check valve that allows unidirectional flow from the fifth pipeline to the second pipeline.

[0020] In one embodiment, when the four-pipe unit is in defrosting mode, port D is connected to port C, port E is connected to port S, the first throttling element is closed, the second throttling element is open, the first solenoid valve is closed, the second solenoid valve is open, the seventh solenoid valve is closed, and the eighth solenoid valve is open; or, the first solenoid valve is open, the second solenoid valve is closed, the seventh solenoid valve is closed, and the eighth solenoid valve is closed.

[0021] Compared with existing technologies, the four-pipe unit provided in this application connects the compressor unit, hot water heat exchanger, first throttling element, and cold water heat exchanger to form a refrigerant circulation loop. The hot water heat exchanger provides hot water, and the cold water heat exchanger provides cold water. Since the thermal storage phase change tank is connected to the refrigerant circulation loop via a first switching valve assembly and is configured in parallel with the hot water heat exchanger, when the heat demand in the refrigerant circulation loop is less than the cooling demand, the first switching valve assembly can be controlled to allow the refrigerant to enter the thermal storage phase change tank and exchange heat with the thermal storage phase change material, thereby storing the excess heat in the refrigerant circulation loop in the thermal storage phase change tank. Similarly, since the cold storage phase change tank is connected to the refrigerant circulation loop via a second switching valve assembly and is configured in parallel with the cold water heat exchanger, when the heat demand in the refrigerant circulation loop is greater than the cooling demand, the second switching valve assembly can be controlled to allow the refrigerant to enter the cold storage phase change tank and exchange heat with the cold storage phase change material, thereby storing the excess cold energy in the refrigerant circulation loop in the cold storage phase change tank. Thus, compared to the method of directly dissipating excess energy to the external environment in related structures, the four-pipe unit provided in this application can store excess heat in a thermal phase change tank and excess cold in a cold phase change tank, thereby effectively avoiding the waste of heat or cold. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the four-control unit provided in this application;

[0024] Figure 2 Partial schematic diagram of the four-control unit provided in this application Figure 1 ;

[0025] Figure 3 Partial schematic diagram of the four-control unit provided in this application Figure 2 ;

[0026] Figure 4 A schematic diagram of the four-pipe unit provided in this application in single-cooling mode;

[0027] Figure 5 A schematic diagram of the four-pipe unit in cold storage mode provided for this application;

[0028] Figure 6 A schematic diagram of the four-pipe unit provided in this application in single heating mode;

[0029] Figure 7 A schematic diagram of the four-pipe unit in heat storage mode provided for this application;

[0030] Figure 8 A schematic diagram of the four-pipe unit in heat recovery mode provided for this application;

[0031] Figure 9 A schematic diagram of the four-pipe unit in defrost mode provided in this application.

[0032] Reference numerals: 100, Four-pipe unit; 10, Compressor unit; 11, Air inlet; 12, Air outlet; 13, Make-up air inlet; 21, Chilled water heat exchanger; 211, Water inlet; 212, Water outlet; 22, Hot water heat exchanger; 31, First throttling element; 41, Thermal storage phase change tank; 411, Second refrigerant passage; 412, Hot water flow path; 413, First end; 414, Second end; 42, Cold storage phase change tank; 421, First refrigerant passage; 422, Chilled water flow path; 51, First pipeline; 52, First switching valve assembly; 521, First solenoid valve; 522, Second solenoid valve; 53, Second pipeline; 531, First section; 532, Second section; 532a, First check valve; 533, Third section; 533a, Dryer filter; 533b, Liquid receiver. ; 534, Fourth section; 54, Second switching valve assembly; 541, Third solenoid valve; 542, Fourth solenoid valve; 55, Third pipeline; 551, Gas-liquid separator; 56, Fourth pipeline; 561, Second check valve; 57, Fifth pipeline; 571, Third check valve; 572, Second throttling element; 58, Sixth pipeline; 581, Fourth check valve; 60, Balanced heat exchanger; 70, Four-way valve; 81, Chilled water inlet pipe; 82, Chilled water outlet pipe; 83, Fifth solenoid valve; 84, Sixth solenoid valve; 85, Hot water inlet pipe; 86, Hot water outlet pipe; 87, Seventh solenoid valve; 88, Eighth solenoid valve; 90, Economizer; 901, First channel; 902, Second channel; 91, Fifth check valve; 92, Third throttling element; 93, Ninth solenoid valve. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application's specification are for illustrative purposes only and do not represent the only possible implementation.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0036] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0038] Please see Figure 1 and Figure 8 This application provides a four-pipe unit 100, which includes a compressor unit 10, a chilled water heat exchanger 21, a hot water heat exchanger 22, a first throttling element 31, a thermal phase change tank 41, a cold phase change tank 42, a first pipeline 51, a first switching valve assembly 52, a second pipeline 53, a second switching valve assembly 54, and a third pipeline 55. The chilled water heat exchanger 21 has an O port and a P port, and the hot water heat exchanger 22 has an R port and a T port. The thermal phase change tank 41 contains thermal phase change material, and the cold phase change tank 42 contains cold phase change material. One end of a pipe 51 can be connected to the outlet 12 of the compressor unit 10, and the other end is connected in parallel to the first end 413 and the T port of the heat storage phase change tank 41 through the first switching valve assembly 52. ​​One end of the second pipe 53 is connected in parallel to the second end 414 and the R port of the heat storage phase change tank 41, and the other end is connected to one end of the first throttling element 31. The other end of the first throttling element 31 is connected in parallel to the liquid inlet and the O port of the cold storage phase change tank 42 through the second switching valve assembly 54. One end of the third pipe 55 is connected in parallel to the liquid outlet and the P port of the cold storage phase change tank 42, and the other end is connected to the inlet 11 of the compressor unit 10.

[0039] It is understandable that the compressor unit 10, the hot water heat exchanger 22, the first throttling element 31, and the cold water heat exchanger 21 can be connected to form a refrigerant circulation loop, with the hot water heat exchanger 22 providing hot water and the cold water heat exchanger 21 providing cold water. Since the heat storage phase change tank 41 is connected to the above-mentioned refrigerant circulation loop and is set in parallel with the hot water heat exchanger 22 through the first switching valve assembly 52, when the heat demand in the above-mentioned refrigerant circulation loop is less than the cooling demand, the refrigerant can be controlled by the first switching valve assembly 52 to enter the heat storage phase change tank 41 and exchange heat with the heat storage phase change material, thereby storing the excess heat in the refrigerant circulation loop in the heat storage phase change tank 41. Similarly, since the cold storage phase change tank 42 is connected to the refrigerant circulation loop and is arranged in parallel with the chilled water heat exchanger 21 via the second switching valve assembly 54, when the heat demand in the refrigerant circulation loop is greater than the cooling demand, the refrigerant can be allowed to enter the cold storage phase change tank 42 and exchange heat with the cold storage phase change material by controlling the second switching valve assembly 54, thereby storing the excess cooling capacity in the refrigerant circulation loop in the cold storage phase change tank 42. Thus, compared to the method of directly dissipating excess energy to the external environment in related structures, the four-pipe unit 100 provided in this application can store excess heat in the heat storage phase change tank 41 and excess cooling capacity in the cold storage phase change tank 42, thereby effectively avoiding the waste of heat or cooling capacity.

[0040] Optionally, the surface of the thermal storage phase change tank 41 is provided with an insulation layer. External heat dissipation equipment can also be used to dissipate heat from the thermal storage phase change tank 41 to avoid exceeding its energy storage limit. Similarly, the external surface of the cold storage phase change tank 42 is provided with an insulation layer. External cooling equipment can also be used to dissipate heat from the cold storage phase change tank 42 to avoid exceeding its energy storage limit.

[0041] Optionally, the compressor unit 10 includes one or more compressors, which can be scroll, screw, rotary, etc. A temperature sensor and a pressure sensor are provided at the outlet 12 of the compressor unit 10. A gas-liquid separator 551 is also provided on the third pipeline 55. The chilled water heat exchanger 21 and the hot water heat exchanger 22 can be configured as shell-and-tube heat exchangers.

[0042] Alternatively, in one embodiment, as Figure 2 , Figure 3 and Figure 8As shown, the first switching valve assembly 52 includes a first solenoid valve 521 and a second solenoid valve 522. The first solenoid valve 521 is connected to the first pipeline 51 and the first end 413 of the thermal storage phase change tank 41, and the second solenoid valve 522 is connected to the first pipeline 51 and the T-port. The second switching valve assembly 54 includes a third solenoid valve 541 and a fourth solenoid valve 542. The third solenoid valve 541 is connected to the first throttling element 31 and the liquid inlet of the cold storage phase change tank 42, and the fourth solenoid valve 542 is connected to the first throttling element 31 and the O-port. When... When the four-pipe unit 100 is in heat recovery mode, the first solenoid valve 521 is closed, the second solenoid valve 522 is open, the third solenoid valve 541 is closed, and the fourth solenoid valve 542 is open. Furthermore, during the operation of the four-pipe unit 100 in heat recovery mode, when the heat demand of the four-pipe unit 100 is less than the cooling demand, the first solenoid valve 521 is open and the second solenoid valve 522 is closed; when the heat demand of the four-pipe unit 100 is greater than the cooling demand, the third solenoid valve 541 is open and the fourth solenoid valve 542 is closed.

[0043] Specifically, the cold storage phase change tank 42 is provided with a first refrigerant channel 421. One end of the first refrigerant channel 421 is connected to a first throttling element 31 via a third solenoid valve 541, and the other end is connected to a third pipeline 55. When the third solenoid valve 541 is open, the refrigerant can flow through the first refrigerant channel 421 and exchange heat with the cold storage phase change material in the cold storage phase change tank 42. The heat storage phase change tank 41 is provided with a second refrigerant channel 411. One end of the second refrigerant channel 411 is connected to a first pipeline 51 via a first solenoid valve 521, and the other end is connected to a second pipeline 53. When the first solenoid valve 521 is open, the refrigerant can flow through the second refrigerant channel 411 and exchange heat with the heat storage phase change material in the heat storage phase change tank 41. Understandably, during the operation of the four-pipe unit 100 in heat recovery mode, when the heat demand of the four-pipe unit 100 is less than the cooling demand, heat accumulates in the hot water heat exchanger 22. By opening the first solenoid valve 521 and closing the second solenoid valve 522, not only can the heat storage phase change tank 41 share the heat, but further heat accumulation in the hot water heat exchanger 22 can also be prevented. Similarly, when the heat demand of the four-pipe unit 100 is greater than the cooling demand, by opening the third solenoid valve 541 and closing the fourth solenoid valve 542, not only can the cold storage phase change tank 42 share the cooling load, but further cold load accumulation in the cold water heat exchanger 21 can also be prevented.

[0044] Of course, in another embodiment, during the operation of the four-pipe unit 100 in heat recovery mode, when the heat demand of the four-pipe unit 100 is less than the cooling demand, both the first solenoid valve 521 and the second solenoid valve 522 are opened. Furthermore, after the heat storage phase change tank 41 shares the heat, the heat demand of the four-pipe unit 100 is greater than the heat released by the refrigerant condensation in the hot water heat exchanger 22. When the heat demand of the four-pipe unit 100 is greater than the cooling demand, both the third solenoid valve 541 and the fourth solenoid valve 542 are opened. Furthermore, after the cooling capacity is shared by the cold storage phase change tank 42, the cooling demand of the four-pipe unit 100 is greater than the heat absorbed by the refrigerant evaporation in the cold water heat exchanger 21.

[0045] In other embodiments, an electric three-way valve may be used instead of the first solenoid valve 521 and the second solenoid valve 522. Alternatively, an electric three-way valve may be used instead of the third solenoid valve 541 and the fourth solenoid valve 542.

[0046] Please continue reading. Figure 1 and Figure 8 The four-pipe unit 100 also includes a balancing heat exchanger 60, a four-way valve 70, a fourth pipeline 56, a fifth pipeline 57, and a sixth pipeline 58. The balancing heat exchanger 60 has ports A and B, and the four-way valve has ports D, E, S, and C. Port D connects to the outlet 12 of the compressor unit, port E connects to the first pipeline 51, port S connects to the third pipeline 55, and port C connects to port A. The second pipeline 53 includes a first section 531, a second section 532, a third section 533, and a fourth section 534 connected sequentially from port R to the first throttling element 31. The second section 532 is equipped with a first one-way valve 53 that allows unidirectional flow from the first section 531 to the third section 533. 2a; The fourth pipeline 56 is connected to port B at one end and to the connection between the second section 532 and the third section 533 at the other end. The fourth pipeline 56 is provided with a second one-way valve 561 that allows unidirectional flow from port B to the second pipeline 53. The fifth pipeline 57 is connected between port B and the second one-way valve 561 at one end and to the connection between the third section 533 and the fourth section 534 at the other end. The fifth pipeline 57 is provided with a third one-way valve 571 and a second throttling element 572 connected in series. The second throttling element 572 is located close to the second pipeline 53. The third one-way valve 571 allows unidirectional flow from the second throttling element 572 to the fourth pipeline 56.

[0047] Optionally, the third section 533 is further provided with a dryer filter 533a and a liquid receiver 533b connected in series, wherein the liquid receiver 533b is located close to the second section 532. The four-pipe unit 100 also includes an economizer 90, which has a first channel 901 and a second channel 902. One end of the first channel 901 is connected to the dryer filter 533a, and the other end is connected to the third section 533. The second channel 902 is provided with a fifth check valve 91, a ninth solenoid valve 93, and a third throttling element 92 connected in series. One end of the second channel 902 is connected to the connection between the first channel 901 and the third section 533, and the other end is connected to the gas supply port 13 of the compressor unit 10. The refrigerant flowing out of the dryer filter 533a flows through the first channel 901 and then splits into two branches. One branch flows into the third section 533, and the other branch flows sequentially through the ninth solenoid valve 93, the third throttling element 92, and the fifth check valve 91, and then flows into the gas supply port 13 of the compressor unit 10. Among them, the Economist 90 adopts a rear-mounted mode.

[0048] In this way, multiple parallel and independent refrigerant circulation loops are formed using the compressor unit 10 and the four-way valve 70. For example, the compressor unit 10, the balance heat exchanger 60, the first throttling element 31, and the chilled water heat exchanger 21 are connected to form one refrigerant circulation loop, in which case the chilled water heat exchanger 21 can provide chilled water; the compressor unit 10, the hot water heat exchanger 22, the second throttling element 572, and the balance heat exchanger 60 are connected to form another refrigerant circulation loop, in which case the hot water heat exchanger 22 can provide hot water. Therefore, when the four-pipe unit 100 switches operating modes, it can switch part of the refrigerant circulation loop without switching the entire compressor system, which helps to reduce water temperature fluctuations.

[0049] The balance heat exchanger 60 can be an air-side heat exchanger or a water-cooled heat exchanger. For example, the balance heat exchanger 60 can be configured with a copper tube and aluminum tooth structure.

[0050] Please see Figures 1 to 3The four-pipe unit 100 also includes a chilled water inlet pipe 81, a chilled water outlet pipe 82, a fifth solenoid valve 83, and a sixth solenoid valve 84. The chilled water heat exchanger 21 and the cold storage phase change tank 42 each have an inlet 211 and an outlet 212. The fifth solenoid valve 83 connects to the chilled water inlet pipe 81 and the inlet 211 of the cold storage phase change tank 42. The sixth solenoid valve 84 connects to the chilled water inlet pipe 81 and the inlet 211 of the chilled water heat exchanger 21. The outlet 212 of the cold storage phase change tank 42 and the outlet 212 of the chilled water heat exchanger 21 are respectively connected to the chilled water outlet pipe 82. An electric three-way valve can be used to replace the fifth solenoid valve 83 and the sixth solenoid valve 84. The four-pipe unit 100 also includes a hot water inlet pipe 85, a hot water outlet pipe 86, a seventh solenoid valve 87, and an eighth solenoid valve 88. The hot water heat exchanger 22 and the thermal storage phase change tank 41 each have an inlet 211 and an outlet 212. The seventh solenoid valve 87 connects the hot water inlet pipe 85 and the inlet 211 of the thermal storage phase change tank 41, and the eighth solenoid valve 88 connects the hot water inlet pipe 85 and the inlet 211 of the hot water heat exchanger 22. The outlet 212 of the thermal storage phase change tank 41 and the outlet 212 of the hot water heat exchanger 22 are respectively connected to the hot water outlet pipe 86. An electric three-way valve can be used to replace the seventh solenoid valve 87 and the eighth solenoid valve 88.

[0051] The four-pipe unit also includes a sixth pipe 58, one end of which is connected between the third check valve 571 and the second throttling element 572, and the other end is connected between the first section 531 and the second section 532. Furthermore, the sixth pipe 58 is provided with a fourth check valve 581 that allows unidirectional flow from the fifth pipe 57 to the second pipe 53.

[0052] Specifically, the cold storage phase change tank 42 is equipped with a chilled water flow path 422, which connects to the inlet 211 and outlet 212 of the heat storage phase change tank 41. When the fifth solenoid valve 83 is opened, chilled water in the chilled water inlet pipe 81 can enter the chilled water flow path 422 and exchange heat with the cold storage phase change material in the cold storage phase change tank 42 to cool it down. The heat storage phase change tank 41 is equipped with a hot water flow path 412, which connects to the inlet 211 and outlet 212 of the heat storage phase change tank 41. When the seventh solenoid valve 87 is opened, hot water in the hot water inlet pipe 85 can enter the hot water flow path 412 and exchange heat with the heat storage phase change material in the heat storage phase change tank 41 to heat it up. The chilled water flow path 422 of the cold storage phase change tank 42 and the chilled water heat exchanger 21 are connected to the same end through the chilled water inlet pipe 81 and the chilled water outlet pipe 82. The hot water flow path 412 in the heat storage phase change tank 41 is connected to the hot water heat exchanger 22 through the hot water inlet pipe 85 and the hot water outlet pipe 86 to the same end.

[0053] The following describes the other operating modes of the four-pipe unit 100.

[0054] Single cooling mode

[0055] Please see Figures 1 to 4 When the four-pipe unit is in single cooling mode, port D is connected to port C, port E is connected to port S, the first throttling element 31 is open, the second throttling element 572 is closed, the third solenoid valve 541 is closed, the fourth solenoid valve 542 is open, the fifth solenoid valve 83 is closed, and the sixth solenoid valve 84 is open.

[0056] It is understandable that when the four-pipe unit is in single cooling mode, the refrigerant flow direction is: outlet 12 of compressor unit 10 - D port - C port - balance heat exchanger 60 - second check valve 561 - first throttling element 31 - fourth solenoid valve 542 - chilled water heat exchanger 21 - inlet 11 of compressor unit 10.

[0057] Cold storage mode

[0058] Please see Figure 1 and Figure 5 Before the four-pipe unit 100 operates in single cooling mode, it first operates in cold storage mode. When the four-pipe unit 100 is in cold storage mode, the third solenoid valve 541 is open, the fourth solenoid valve 542 is closed, the fifth solenoid valve 83 is closed, and the sixth solenoid valve 84 is closed.

[0059] Understandably, when the four-pipe unit 100 performs cold storage, the refrigerant flow direction is: compressor unit 10 outlet 12 - D port - C port - balance heat exchanger 60 - second one-way valve 561 - first throttling element 31 - third solenoid valve 541 - cold storage phase change tank 42 - compressor unit 10 inlet 11. In this way, by utilizing the refrigerant entering the cold storage phase change tank 42 and evaporating to absorb heat, the cold storage phase change material completes cold storage.

[0060] Furthermore, during the operation of the four-pipe unit 100 in single-cooling mode, when the actual outlet water temperature of the chilled water outlet pipe 82 is greater than the target outlet water temperature of the chilled water, or when the cooling demand of the four-pipe unit 100 increases, the fifth solenoid valve 83 opens and the sixth solenoid valve 84 closes.

[0061] Understandably, by opening the fifth solenoid valve 83 and closing the sixth solenoid valve 84, chilled water in the chilled water inlet pipe 81 enters the cold storage phase change tank 42 through the fifth solenoid valve 83. The cold storage phase change material in the cold storage phase change tank 42 evaporates and absorbs heat, thereby reducing the actual outlet water temperature of the chilled water outlet pipe 82. In this way, the cold storage phase change tank 42 serves as a temporary transition, which helps to stabilize the actual outlet water temperature of the chilled water.

[0062] The phase change point of the cold storage phase change material in the cold storage phase change tank 42 is defined as A1, the evaporation temperature in the chilled water heat exchanger 21 is defined as B1, and the target outlet temperature of the chilled water is defined as C1, where C1-Y1>A1>B1+X1; and 0.5K≤X1≤2K, 3K≤Y1≤5K. That is, the phase change point A1 of the cold storage phase change material in the cold storage phase change tank 42 is close to and higher than the evaporation temperature B1 in the chilled water heat exchanger 21, and lower than the target outlet temperature C1 of the chilled water. When the values ​​of X1 and Y1 conflict, priority is given to ensuring that the phase change point A1 of the cold storage phase change material in the cold storage phase change tank 42 is close to and higher than the evaporation temperature B1 in the chilled water heat exchanger 21.

[0063] Because the phase change point A1 of the cold storage phase change material in the cold storage phase change tank 42 is close to and higher than the evaporation temperature B1 in the chilled water heat exchanger 21, it can be ensured that the cold storage phase change material continuously releases heat and undergoes a phase change during the cold storage process in the cold storage phase change tank 42, thereby utilizing the latent heat of the cold storage phase change material. Furthermore, because the phase change point A1 of the cold storage phase change material in the cold storage phase change tank 42 is lower than the target chilled water outlet temperature C1, when the actual outlet temperature of the chilled water outlet pipe 82 is higher than the target chilled water outlet temperature, or when the cooling demand of the four-pipe unit 100 increases, a temperature difference is formed between the cold storage phase change material and the chilled water. The cold storage phase change material can continuously absorb heat from the chilled water and undergo a phase change, and its temperature remains constant during the phase change process until the phase change is complete.

[0064] Among them, the cold storage phase change material can be a pure alkane, or a mixture of substances with similar phase change points such as paraffin, alcohol, aldehyde, ether, etc.; it can also be a mixture of a certain alkane with other substances added to change its phase change point.

[0065] For example, in one embodiment, the evaporation temperature T within the cold water heat exchanger 21 is... e =5℃, target outlet temperature of chilled water T cg =7℃, the cold storage phase change material is n-tetradecane, and its phase change point (freezing point) is 5.5℃.

[0066] Single heating mode

[0067] Please see Figures 1 to 6 When the four-pipe unit 100 is in single heating mode, port D is connected to port E, port C is connected to port S, the first throttling element 31 is closed, the second throttling element 572 is open, the first solenoid valve 521 is closed, the second solenoid valve 522 is open, the seventh solenoid valve 87 is closed, and the eighth solenoid valve 88 is open.

[0068] It is understandable that when the four-pipe unit 100 is in single heating mode, the refrigerant flow direction is as follows: outlet 12 of compressor unit 10 - D port - E port - second solenoid valve 522 - hot water heat exchanger 22 - first check valve 532a - second throttling element 572 - third check valve 571 - balance heat exchanger 60 - C port - S port - gas-liquid separator 551 - inlet 11 of compressor unit 10.

[0069] Heat storage mode

[0070] Please see Figures 1 to 7 Before the four-pipe unit 100 operates in single heating mode, it first operates in heat storage mode. When the four-pipe unit 100 is in heat storage mode, the first solenoid valve 521 is open, the second solenoid valve 522 is closed, the fifth solenoid valve 83 is closed, the seventh solenoid valve 87 is closed, and the eighth solenoid valve 88 is closed.

[0071] Understandably, when the four-pipe unit 100 performs heat storage, the refrigerant flow direction is: compressor unit 10 outlet 12 - D port - E port - first solenoid valve 521 - heat storage phase change tank 41 - first one-way valve 532a - second throttling element 572 - third one-way valve 571 - balance heat exchanger 60 - C port - S port - gas-liquid separator 551 - compressor unit 10 inlet 11. In this way, by utilizing the refrigerant entering the heat storage phase change tank 41 and condensing to release heat, the heat storage phase change material completes heat storage.

[0072] Furthermore, during the operation of the four-pipe unit 100 in single heating mode, when the actual outlet water temperature of the hot water outlet pipe 86 is less than the target outlet water temperature, or when the heat demand of the four-pipe unit 100 increases, the seventh solenoid valve 87 opens and the eighth solenoid valve 88 closes.

[0073] Understandably, by opening the seventh solenoid valve 87 and closing the eighth solenoid valve 88, the hot water in the hot water inlet pipe 85 enters the heat storage phase change tank 41 through the seventh solenoid valve 87. The heat storage phase change material in the heat storage phase change tank 41 condenses and releases heat, thereby reducing the actual outlet water temperature of the hot water outlet pipe 86. In this way, the heat storage phase change tank 41 serves as a temporary transition, which helps to stabilize the actual outlet water temperature.

[0074] The phase change point of the thermal storage phase change material in the thermal storage phase change tank 41 is defined as A2, the condensation temperature in the hot water heat exchanger 22 is defined as B2, and the target hot water outlet temperature is defined as C2. Furthermore, C2 + Y2 < A2 < B2 - X2, where 2K ≥ X2 ≥ 0.5K and 5K ≥ Y2 ≥ 3K. That is, the phase change point A2 of the thermal storage phase change material in the thermal storage phase change tank 41 is close to and lower than the condensation temperature B2 in the hot water heat exchanger 22, and higher than the target hot water outlet temperature C2. When the values ​​of Y2 and X2 conflict, priority is given to ensuring that the phase change point A2 of the thermal storage phase change material is close to and lower than the condensation temperature B2 in the hot water heat exchanger 22.

[0075] Because the phase change point A2 of the thermal storage phase change material in the thermal storage phase change tank 41 is close to and lower than the condensation temperature B2 in the hot water heat exchanger 22, it can be ensured that the cold storage phase change material continuously absorbs heat and undergoes phase change during the heat storage process in the thermal storage phase change tank 41, thereby utilizing the latent heat of the thermal storage phase change material. Furthermore, because the phase change point A2 of the cold storage phase change material in the thermal storage phase change tank 41 is higher than the target hot water outlet temperature C2, when the actual outlet temperature of the hot water outlet pipe 86 is greater than the target chilled water outlet temperature, or when the heat demand of the four-pipe unit 100 increases, a temperature difference is formed between the thermal storage phase change material and the hot water. The thermal storage phase change material can continuously absorb heat from the hot water and undergo phase change, and its temperature remains constant during the phase change process until the phase change is complete.

[0076] Among them, the heat storage phase change material can be a pure alkane, or a mixture of substances with similar phase change points such as paraffin, alcohol, aldehyde, ether, etc.; it can also be a mixture of a certain alkane with other substances added to change its phase change point.

[0077] For example, in one embodiment, the condensation temperature T within the hot water heat exchanger 22 c =40℃, target hot water outlet temperature T rg =35℃, the heat storage phase change material is configured as n-eicosane, whose phase change point (melting point) is 36.4℃; or, the heat storage phase change material is configured as cyclopentane, whose phase change point (boiling point) is 36.1℃; or, the heat storage phase change material is configured as myristol, whose phase change point (melting point) is 37.8℃.

[0078] Defrosting mode

[0079] Please see Figures 1 to 9 When the four-pipe unit 100 is in defrosting mode, port D is connected to port C, port E is connected to port S, the first throttling element 31 is closed, the second throttling element 572 is open, the first solenoid valve 521 is closed, the second solenoid valve 522 is open, the seventh solenoid valve 87 is closed, and the eighth solenoid valve 88 is open; or, the first solenoid valve 521 is open, the second solenoid valve 522 is closed, the seventh solenoid valve 87 is closed, and the eighth solenoid valve 88 is closed.

[0080] It is understandable that when the four-pipe unit 100 is in defrost mode, the refrigerant flow direction is: compressor unit 10 outlet 12 - D port - C port - balance heat exchanger 60 - second one-way valve 561 - second throttling element 572 - fourth one-way valve 581 - hot water heat exchanger 22 - second solenoid valve 522 - E port - S port - gas-liquid separator 551 - compressor unit 10 inlet 11; or, the refrigerant flow direction is: compressor unit 10 outlet 12 - D port - C port - balance heat exchanger 60 - second one-way valve 561 - second throttling element 572 - fourth one-way valve 581 - heat storage phase change tank 41 - first solenoid valve 521 - E port - S port gas-liquid separator 551 - compressor unit 10 inlet 11. In the previous structure, the refrigerant could only absorb heat from the hot water through the hot water heat exchanger 22 for defrosting, which would cause the hot water supply to be interrupted. However, in this embodiment, the refrigerant can absorb heat from the heat storage phase change material in the heat storage phase change tank 41 for defrosting, or the refrigerant can absorb heat from the hot water through the hot water heat exchanger 22 for defrosting. Therefore, the hot water supply does not need to be interrupted for a short period of time during the defrosting period.

[0081] The thermal storage phase change tank 41 contains a thermally conductive material, which is mixed with the thermal storage phase change material; or, the thermally conductive material divides the thermal storage phase change material into multiple heat exchange units. The cold storage phase change tank 42 contains a thermally conductive material, which is mixed with the cold storage phase change material; or, the thermally conductive material divides the cold storage phase change material into multiple heat exchange units.

[0082] Thermally conductive materials are used to improve the thermal conductivity inside the thermal storage phase change tank 41 and the cold storage phase change tank 42. For example, the thermally conductive materials can be expanded graphite, foamed metal, nanomaterials, or inorganic salts.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A four-pipe unit, characterized in that, The four-pipe unit (100) includes a compressor unit (10), a cold water heat exchanger (21), a hot water heat exchanger (22), a first throttling element (31), a thermal storage phase change tank (41), a cold storage phase change tank (42), a first pipeline (51), a first switching valve assembly (52), a second pipeline (53), a second switching valve assembly (54), and a third pipeline (55). The cold water heat exchanger (21) has an O port and a P port, and the hot water heat exchanger (22) has an R port and a T port. The heat storage phase change tank (41) is equipped with heat storage phase change material, and the cold storage phase change tank (42) is equipped with cold storage phase change material. One end of the first pipeline (51) can be connected to the outlet (12) of the compressor unit (10), and the other end is connected in parallel to the first end (413) of the heat storage phase change tank (41) and the T port through the first switching valve assembly (52). One end of the second pipeline (53) is connected in parallel to the second end (414) of the heat storage phase change tank (41) and the R port, and the other end is connected to one end of the first throttling element (31). The other end of the first throttling element (31) is connected in parallel to the liquid inlet of the cold storage phase change tank (42) and the O port through the second switching valve assembly (54). One end of the third pipeline (55) is connected in parallel to the liquid outlet of the cold storage phase change tank (42) and the P port, and the other end is connected to the air inlet (11) of the compressor unit (10).

2. The four-pipe unit according to claim 1, characterized in that, The heat storage phase change tank (41) is provided with a thermally conductive material, which is mixed with the heat storage phase change material; or, the thermally conductive material divides the heat storage phase change material into multiple heat exchange units. The cold storage phase change tank (42) is provided with a thermally conductive material, which is mixed with the cold storage phase change material; or, the thermally conductive material divides the cold storage phase change material into multiple heat exchange units.

3. The four-pipe unit according to claim 1 or 2, characterized in that, The first switching valve assembly (52) includes a first solenoid valve (521) and a second solenoid valve (522). The first solenoid valve (521) is connected to the first pipeline (51) and the first end (413) of the thermal storage phase change tank (41). The second solenoid valve (522) is connected to the first pipeline (51) and the T-port. The second switching valve assembly (54) includes a third solenoid valve (541) and a fourth solenoid valve (542). The third solenoid valve (541) is connected to the first throttling element (31) and the liquid inlet of the cold storage phase change tank (42). The fourth solenoid valve (542) is connected to the first throttling element (31) and the O-port. When the four-pipe unit (100) is in heat recovery mode, the first solenoid valve (521) is closed, the second solenoid valve (522) is open, the third solenoid valve (541) is closed, and the fourth solenoid valve (542) is open. Furthermore, during the operation of the four-pipe unit (100) in the heat recovery mode, when the heat demand of the four-pipe unit (100) is less than the cooling demand, the first solenoid valve (521) is open and the second solenoid valve (522) is closed; when the heat demand of the four-pipe unit (100) is greater than the cooling demand, the third solenoid valve (541) is open and the fourth solenoid valve (542) is closed.

4. The four-pipe unit according to claim 3, characterized in that, The four-pipe unit (100) further includes a balance heat exchanger (60), a four-way valve (70), a fourth pipeline (56), a fifth pipeline (57), and a sixth pipeline (58). The balance heat exchanger (60) has an A port and a B port. The four-way valve has a D port, an E port, an S port, and a C port. The D port is connected to the outlet (12) of the compressor unit. The E port is connected to the first pipeline (51). The S port is connected to the third pipeline (55). The C port is connected to the A port. The second pipeline (53) includes a first section (531), a second section (532), a third section (533) and a fourth section (534) connected in sequence from the R port to the first throttling element (31), and the second section (532) is provided with a first check valve (532a) that unidirectionally flows from the first section (531) to the third section (533); The fourth pipeline (56) is connected to the B port at one end and to the connection point of the second section (532) and the third section (533) at the other end. Furthermore, the fourth pipeline (56) is provided with a second one-way valve (561) that allows one-way flow from the B port to the second pipeline (53). One end of the fifth pipeline (57) is connected between port B and the second one-way valve (561), and the other end is connected to the connection between the third section (533) and the fourth section (534). The fifth pipeline (57) is provided with a third one-way valve (571) and a second throttling element (572) connected in series. The second throttling element is located close to the second pipeline (53), and the third one-way valve (571) is unidirectionally connected from the second throttling element (572) to the fourth pipeline (56).

5. The four-pipe unit according to claim 4, characterized in that, The four-pipe unit (100) also includes a chilled water inlet pipe (81), a chilled water outlet pipe (82), a fifth solenoid valve (83) and a sixth solenoid valve (84), and the chilled water heat exchanger (21) and the cold storage phase change tank (42) respectively have an inlet (211) and an outlet (212); The fifth solenoid valve (83) is connected to the chilled water inlet pipe (81) and the inlet (211) of the cold storage phase change tank (42). The sixth solenoid valve (84) is connected to the chilled water inlet pipe (81) and the inlet (211) of the cold water heat exchanger (21). The outlet (212) of the cold storage phase change tank (42) and the outlet (212) of the cold water heat exchanger (21) are respectively connected to the chilled water outlet pipe (82).

6. The four-pipe unit according to claim 5, characterized in that, When the four-pipe unit is in single cooling mode, port D is connected to port C, port E is connected to port S, the first throttling element (31) is open, the second throttling element (572) is closed, the third solenoid valve (541) is closed, the fourth solenoid valve (542) is open, the fifth solenoid valve (83) is closed, and the sixth solenoid valve (84) is open.

7. The four-pipe unit according to claim 6, characterized in that, Before the four-pipe unit (100) operates in single cooling mode, it first operates in cold storage mode. When the four-pipe unit (100) is in cold storage mode, the third solenoid valve (541) is open, the fourth solenoid valve (542) is closed, the fifth solenoid valve (83) is closed, and the sixth solenoid valve (84) is closed.

8. The four-pipe unit according to claim 6 or 7, characterized in that, When the four-pipe unit (100) is operating in single cooling mode, when the actual outlet temperature of the chilled water outlet pipe (82) is greater than the target outlet temperature of the chilled water, or when the cooling demand of the four-pipe unit (100) increases, the fifth solenoid valve (83) opens and the sixth solenoid valve (84) closes.

9. The four-pipe unit according to claim 8, characterized in that, The phase change point of the cold storage phase change material in the cold storage phase change tank (42) is defined as A1, the evaporation temperature in the cold water heat exchanger (21) is defined as B1, the target outlet temperature of the chilled water is defined as C1, and C1-Y1>A1>B1+X1; where 0.5K≤X1≤2K, 3K≤Y1≤5K.

10. The four-pipe unit according to claim 5, characterized in that, The four-pipe unit (100) also includes a hot water inlet pipe (85), a hot water outlet pipe (86), a seventh solenoid valve (87) and an eighth solenoid valve (88). The hot water heat exchanger (22) and the heat storage phase change tank (41) are respectively provided with an inlet (211) and an outlet (212). The seventh solenoid valve (87) is connected to the hot water inlet pipe (85) and the inlet (211) of the heat storage phase change tank (41). The eighth solenoid valve (88) is connected to the hot water inlet pipe (85) and the inlet (211) of the hot water heat exchanger (22). The outlet (212) of the heat storage phase change tank (41) and the outlet (212) of the hot water heat exchanger (22) are respectively connected to the hot water outlet pipe (86).

11. The four-pipe unit according to claim 10, characterized in that, When the four-pipe unit (100) is in single heating mode, port D is connected to port E, port C is connected to port S, the first throttling element (31) is closed, the second throttling element (572) is open, the first solenoid valve (521) is closed, the second solenoid valve (522) is open, the seventh solenoid valve (87) is closed, and the eighth solenoid valve (88) is open.

12. The four-pipe unit according to claim 11, characterized in that, Before the four-pipe unit (100) operates in single heating mode, it first operates in heat storage mode. When the four-pipe unit (100) is in heat storage mode, the first solenoid valve (521) is open, the second solenoid valve (522) is closed, the fifth solenoid valve (83) is closed, the seventh solenoid valve (87) is closed, and the eighth solenoid valve (88) is closed.

13. The four-pipe unit according to claim 11 or 12, characterized in that, When the four-pipe unit (100) is operating in single heating mode, when the actual outlet temperature of the hot water outlet pipe (86) is less than the target outlet temperature of the hot water or when the heat demand of the four-pipe unit (100) increases, the seventh solenoid valve (87) opens and the eighth solenoid valve (88) closes.

14. The four-pipe unit according to claim 13, characterized in that, The phase change point of the heat storage phase change material in the heat storage phase change tank (41) is defined as A2, the condensation temperature in the hot water heat exchanger (22) is defined as B2, the target outlet temperature of the hot water is defined as C2, and C2+Y2<A2<B2-X2, where 2K≥X2≥0.5K, 5K≥Y2≥3K.

15. The four-pipe unit according to claim 10, characterized in that, The four-pipe unit also includes a sixth pipeline (58), one end of which is connected between the third check valve (571) and the second throttling element (572), and the other end is connected between the first section (531) and the second section (532). Furthermore, the sixth pipeline (58) is provided with a fourth check valve (581) that allows unidirectional flow from the fifth pipeline (57) to the second pipeline (53).

16. The four-pipe unit according to claim 15, characterized in that, When the four-pipe unit (100) is in defrosting mode, the D port is connected to the C port, the E port is connected to the S port, the first throttling element (31) is closed, and the second throttling element (572) is open. The first solenoid valve (521) is closed, the second solenoid valve (522) is open, the seventh solenoid valve (87) is closed, and the eighth solenoid valve (88) is open; or, the first solenoid valve (521) is open, the second solenoid valve (522) is closed, the seventh solenoid valve (87) is closed, and the eighth solenoid valve (88) is closed.

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