Heat pump unit and control method of heat pump unit

Abstract

The invention relates to the technical field of heat pumps, in particular to a heat pump unit and a control method of the heat pump unit, the heat pump unit comprises a first compressor, a second compressor, a first heat exchanger, an economizer, an air heat exchanger and a valve assembly, the valve assembly is suitable for switching between a first state and a second state, the first compressor, the second compressor, the first heat exchanger, a first channel of the economizer and the air heat exchanger are sequentially communicated to form a first circulation loop. In the second state, the first compressor, the first heat exchanger, the first channel of the economizer and the air heat exchanger are sequentially communicated to form a second circulation loop. The temperature of the heat supply water source is always kept at the target temperature by switching single-stage / double-stage circulation, so that the comfort level of a user can be improved, and the heat pump unit can be always kept at relatively high energy efficiency. And the first compressor and the second compressor can operate independently, so that the operation reliability of the heat pump unit is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and particularly to a heat pump unit and a control method thereof. Background Art

[0002] For ordinary air-source heat pumps, when the ambient temperature is lower than -30°C, the water temperature usually does not exceed 45°C, and the heat supply attenuation is relatively serious. It is difficult for the heat pump unit to meet the heating demand, and the heating effect is very poor at this time. However, for the heat pump units in the prior art that can adapt to meet the heating demand under ultra-low temperature conditions, they cannot be switched in time when not in ultra-low temperature or when the compressor fails, and the applicable working conditions of the heat pump unit are limited. Summary of the Invention

[0003] The present invention provides a heat pump unit and a control method thereof to solve one of the defects in the prior art. By switching between single-stage / double-stage cycles, the temperature of the hot water supply source is always maintained at the target temperature, which can not only improve the comfort of users but also keep the heat pump unit at a high energy efficiency. And the first compressor and the second compressor can both operate independently, further improving the reliability of the operation of the heat pump unit.

[0004] The present invention provides a heat pump unit, including a first compressor, a second compressor, a first heat exchanger, an economizer, an air heat exchanger, and a valve assembly. The valve assembly is adapted to switch between a first state and a second state. In the first state, the first compressor, the second compressor, the first heat exchanger, the first passage of the economizer, and the air heat exchanger are sequentially connected to form a first circulation loop; in the second state, the first compressor, the first heat exchanger, the first passage of the economizer, and the air heat exchanger are sequentially connected to form a second circulation loop.

[0005] According to the heat pump unit provided by the present invention, in the first state, the first heat exchanger, the second passage of the economizer, and the second compressor are sequentially connected to form a branch of the first circulation loop. The refrigerant in the second passage exchanges heat with the refrigerant in the first passage, causing the refrigerant in the first passage to be reheated, cooled, and liquefied again, reducing the gaseous refrigerant entering the air heat exchanger, which is beneficial to improving the heat exchange effect between the refrigerant entering the air heat exchanger and the outside air.

[0006] According to the heat pump unit provided by the present invention, the valve assembly is further adapted to switch to a third state. In the third state, the second compressor, the first heat exchanger, the first passage of the economizer, and the air heat exchanger are sequentially connected to form a third circulation loop; or, The valve assembly is further adapted to switch to a fourth state. In the fourth state, the first compressor, the air heat exchanger, the first passage of the economizer, and the first heat exchanger are sequentially connected to form a fourth circulation loop; or, The valve assembly is also adapted to switch to a fifth state, in which the second compressor, the air heat exchanger, the first passage of the economizer, and the first heat exchanger are sequentially connected to form a fifth circulation loop.

[0007] To ensure that the compressor of the heat pump unit always operates within its high-efficiency frequency range, when the actual operating frequency of the compressor is not within its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted through another state switch of the valve assembly, so as to make full use of the compressor, improve the operating efficiency of the heat pump unit and the effect of making hot water.

[0008] Through the state switch of the valve assembly, the first compressor, the second compressor, the first heat exchanger, the economizer, and the air heat exchanger are connected in series to form different refrigerant circulation loops, so as to cool the water passing through the first heat exchanger and complete the refrigerated water work of the heat pump unit.

[0009] To ensure that the compressor of the heat pump unit always operates within its high-efficiency frequency range, when the actual operating frequency of the compressor is not within its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted through another state switch of the valve assembly, and the compressor is controlled to always operate within the high-efficiency range according to the required cooling load, so as to make full use of the compressor, improve the operating energy efficiency of the heat pump unit, be more energy-saving and improve the refrigerated water effect.

[0010] According to a heat pump unit provided by the present invention, the volume of the first compressor is larger than that of the second compressor. The compression heat that can be provided and their respective operating frequencies are different, so that under different external working conditions, a heat pump unit that can meet the corresponding refrigerant compression requirements can be provided. According to a heat pump unit provided by the present invention, the heat pump unit further includes a second heat exchanger. The refrigerant outlet of the first compressor is communicated with the inlet of the heat release passage of the second heat exchanger, and the outlet of the heat release passage of the second heat exchanger is communicated with at least one of the refrigerant inlet of the second compressor and the valve assembly. It can not only recover the refrigerant discharge heat of the first compressor, but also reduce the suction temperature of the second compressor, thereby improving the operating reliability of the heat pump unit.

[0011] The present invention also provides a control method for a heat pump unit, which is applied to the heat pump unit as described above, and includes: Obtain a hot water production instruction and control the heat pump unit to start; Determine that the actual water temperature at the outlet of the heat absorption passage of the first heat exchanger is less than the first set temperature, and control the valve assembly of the heat pump unit to switch to the first state, where the first set temperature is the lower limit threshold of the target temperature; or, determine that the actual water temperature at the outlet of the heat absorption passage of the first heat exchanger is greater than or equal to the second set temperature, and control the valve assembly of the heat pump unit to switch to the second state, where the second set temperature is the upper limit threshold of the target temperature.

[0012] According to a control method of a heat pump unit provided by the present invention, after determining that the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger is greater than or equal to the second set temperature and controlling the valve assembly of the heat pump unit to switch to the second state, it further includes: Determine that the actual operating frequency of the first compressor is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the third state, where the first set frequency is the lower limit value of the rated frequency of the compressor; Determine that the actual operating frequency of the second compressor is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the second state, where the second set frequency is the upper limit value of the rated frequency of the compressor.

[0013] According to a control method of a heat pump unit provided by the present invention, it further includes: Obtain a chilled water instruction and control the valve assembly of the heat pump unit to switch to the fourth state; Or, Obtain a chilled water instruction and control the valve assembly of the heat pump unit to switch to the fourth state; Determine that the actual operating frequency of the first compressor is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the fifth state; Determine that the actual operating frequency of the second compressor is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the fourth state.

[0014] According to a control method of a heat pump unit provided by the present invention, when it is determined that the duration for which the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger is less than the first set temperature reaches the first set duration, control the valve assembly of the heat pump unit to switch to the first state; or, when it is determined that the duration for which the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger is greater than the second set temperature reaches the first set duration, control the valve assembly of the heat pump unit to switch to the second state.

[0015] According to a control method of a heat pump unit provided by the present invention, when it is determined that the duration for which the actual operating frequency of the first compressor is less than the first set frequency reaches the second set duration, control the valve assembly of the heat pump unit to switch to the third state; when it is determined that the duration for which the actual operating frequency of the second compressor is greater than the second set frequency reaches the second set duration, control the valve assembly of the heat pump unit to switch to the second state; Or, When it is determined that the duration for which the actual operating frequency of the first compressor is less than the first set frequency reaches the third set duration, control the valve assembly of the heat pump unit to switch to the fifth state; when it is determined that the actual operating frequency of the second compressor is greater than the second set frequency reaches the third set duration, control the valve assembly of the heat pump unit to switch to the fourth state.

[0016] The heat pump unit provided by the present invention forms different refrigerant circulation circuits by connecting the first compressor, the second compressor, the first heat exchanger, the economizer and the air heat exchanger in series through the state switching of the valve assembly, so as to heat the water passing through the first heat exchanger under different external ambient temperatures and complete the hot water production work of the heat pump unit.

[0017] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger is lower than the target temperature, the valve assembly switches to the first state. At this time, both the first compressor and the second compressor are turned on. The refrigerant is compressed by the first compressor and the second compressor in sequence to form a high-temperature gaseous refrigerant, which enters the heat release channel of the first heat exchanger and exchanges heat with the water in the heat absorption channel of the first heat exchanger. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as the hot water supply source. Then the refrigerant enters the first channel of the economizer to exchange heat and cool down and liquefy again. After entering the air heat exchanger, it further exchanges heat with the external air, cools down to a low-temperature liquid refrigerant and then returns to the first compressor. In this way, the first circulation circuit realizes the hot water production effect.

[0018] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger is greater than or equal to the target temperature, the valve assembly switches to the second state. At this time, the first compressor is turned on and the second compressor is turned off. The refrigerant is compressed by the first compressor to form a high-temperature gaseous refrigerant, which enters the heat release channel of the first heat exchanger and exchanges heat with the water in the heat absorption channel of the first heat exchanger. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as the hot water supply source. Then the refrigerant enters the air heat exchanger through the first channel of the economizer, further exchanges heat with the external air, cools down to a low-temperature liquid refrigerant and then returns to the first compressor. In this way, the second circulation circuit realizes the hot water production effect.

[0019] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger is lower than the target temperature, it proves that the temperature of the hot water supply source cannot reach the target temperature, and the heat pump unit needs to provide more heat to heat up the water source faster. Therefore, the first compressor and the second compressor are started together, and at the same time, the state of the valve assembly is switched to form a two-stage compression cycle. When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger is greater than or equal to the target temperature, it proves that the temperature of the hot water supply source has reached the target temperature. To continuously ensure the stable temperature of the hot water supply source, the heat pump unit does not need to provide more heat to heat up the water source. Therefore, the first compressor is started but the second compressor is turned off, and at the same time, the state of the valve assembly is switched to form a single-stage compression cycle.

[0020] The present invention provides a cryogenic high-output dual-stage compression heat pump unit, which can effectively solve the problem that the temperature of the hot water supply source cannot reach the target temperature under cryogenic conditions. At the same time, it can switch to single-stage operation under non-cryogenic conditions or when a certain compressor fails, improving the operating energy efficiency and reliability of the heat pump unit. By switching between single-stage / double-stage cycles, the temperature of the hot water supply source can always be maintained at the target temperature, which can not only improve the comfort of users but also keep the heat pump unit at a relatively high energy efficiency. Moreover, both the first compressor and the second compressor can operate independently, further improving the reliability of the operation of the heat pump unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention 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 some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic structural diagram of the heat pump unit provided by an embodiment of the present invention.

[0023] REFERENCE SIGNS: 100, the first compressor; 200, the second compressor; 300, the first heat exchanger; 400, the economizer; 500, the air heat exchanger; 600, the second heat exchanger; 710, the first control valve; 720, the second control valve; 730, the first throttle valve; 740, the second throttle valve; 750, the four-way valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0025] As Figure 1As shown in the figure, the heat pump unit provided by the embodiment of the present invention includes a first compressor 100, a second compressor 200, a first heat exchanger 300, an economizer 400, an air heat exchanger 500 and a valve assembly. The valve assembly is adapted to switch between a first state and a second state. In the first state, the first compressor 100, the second compressor 200, the first heat exchanger 300, the first passage of the economizer 400 and the air heat exchanger 500 are sequentially connected to form a first circulation loop; in the second state, the first compressor 100, the first heat exchanger 300, the first passage of the economizer 400 and the air heat exchanger 500 are sequentially connected to form a second circulation loop.

[0026] The heat pump unit of the embodiment of the present invention, through the state switching of the valve assembly, connects the first compressor 100, the second compressor 200, the first heat exchanger 300, the economizer 400 and the air heat exchanger 500 in series to form different refrigerant circulation loops, so as to heat the water passing through the first heat exchanger 300 under different external ambient temperatures and complete the hot water production work of the heat pump unit.

[0027] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger 300 is lower than the target temperature, the valve assembly switches to the first state. At this time, both the first compressor 100 and the second compressor 200 are turned on. The refrigerant is compressed by the first compressor 100 and the second compressor 200 in sequence to form a high-temperature gaseous refrigerant, which enters the heat release passage of the first heat exchanger 300 and exchanges heat with the water in the heat absorption passage of the first heat exchanger 300. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as a hot water source. Then the refrigerant enters the first passage of the economizer 400 to exchange heat and cool down and liquefy again. After entering the air heat exchanger 500, it further exchanges heat with the outside air, cools down to a low-temperature liquid refrigerant and then returns to the first compressor 100. In this way, the first circulation loop realizes the hot water production effect.

[0028] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger 300 is greater than or equal to the target temperature, the valve assembly switches to the second state. At this time, the first compressor 100 is turned on and the second compressor 200 is turned off. The refrigerant is compressed by the first compressor 100 to form a high-temperature gaseous refrigerant, which enters the heat release passage of the first heat exchanger 300 and exchanges heat with the water in the heat absorption passage of the first heat exchanger 300. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as a hot water source. Then the refrigerant enters the air heat exchanger 500 through the first passage of the economizer 400, further exchanges heat with the outside air, cools down to a low-temperature liquid refrigerant and then returns to the first compressor 100. In this way, the second circulation loop realizes the hot water production effect.

[0029] When the actual water temperature of the heat absorption passage of the first heat exchanger 300 is lower than the target temperature, it proves that the temperature of the hot water supply source cannot reach the target temperature, and the heat pump unit needs to provide more heat faster to heat up the water source. Therefore, the first compressor 100 and the second compressor 200 are started simultaneously, and at the same time, the valve assembly state is switched to form a two-stage compression cycle. When the actual water temperature of the heat absorption passage of the first heat exchanger 300 is greater than or equal to the target temperature, it proves that the temperature of the hot water supply source has reached the target temperature. To continuously ensure the stable temperature of the hot water supply source, the heat pump unit does not need to provide more heat to heat up the water source. Therefore, the first compressor 100 is started but the second compressor 200 is turned off, and at the same time, the valve assembly state is switched to form a single-stage compression cycle.

[0030] The present invention provides a super-low temperature and high-outlet-temperature two-stage compression heat pump unit, which can effectively solve the problem that the temperature of the hot water supply source cannot reach the target temperature under super-low temperature conditions, and can switch to single-stage operation in non-super-low temperature conditions or when a certain compressor fails, improving the operating energy efficiency and reliability of the heat pump unit. By switching the single-stage / double-stage cycle, the temperature of the hot water supply source is always maintained at the target temperature, which can not only improve the comfort of users, but also keep the heat pump unit at a high energy efficiency. And the first compressor 100 and the second compressor 200 can both operate independently, further improving the reliability of the operation of the heat pump unit.

[0031] According to an embodiment provided by the present invention, in the first state, the first heat exchanger 300, the second passage of the economizer 400, and the second compressor 200 are sequentially connected to form a branch of the first circulation loop. In this embodiment, the economizer 400 has a first passage and a second passage. In the first circulation loop, the first heat exchanger 300 is connected to both the first passage and the second passage of the economizer 400 to form two refrigerant flow paths. That is, after the refrigerant flows out of the first heat exchanger 300, it is divided into two paths. One path enters the first passage of the economizer 400, and the other path enters the second passage of the economizer 400. The refrigerant entering the first passage of the economizer 400 is compressed after returning to the first compressor 100 and then converges with the refrigerant flowing out of the second passage of the economizer 400 and flows into the second compressor 200. Therefore, the first compressor 100, the second compressor 200, the first heat exchanger 300, the first passage of the economizer 400, and the air heat exchanger 500 through which the refrigerant flows are the main path of the first circulation loop, and the first heat exchanger 300, the second passage of the economizer 400, and the second compressor 200 through which the refrigerant flows are the branch of the first circulation loop.

[0032] When the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger 300 is lower than the target temperature, the valve assembly switches to the first state. At this time, both the first compressor 100 and the second compressor 200 are turned on. The refrigerant is compressed by the first compressor 100 and the second compressor 200 in sequence to form a high-temperature gaseous refrigerant, which enters the heat release passage of the first heat exchanger 300 and exchanges heat with the water in the heat absorption passage of the first heat exchanger 300. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as the hot water source. Then the refrigerant enters the first passage and the second passage of the economizer 400 respectively. The refrigerant in the second passage exchanges heat with the refrigerant in the first passage to make the refrigerant in the first passage exchange heat and cool down and liquefy again, reducing the gaseous refrigerant entering the air heat exchanger 500, which is beneficial to improving the heat exchange effect between the refrigerant entering the air heat exchanger 500 and the outside air.

[0033] According to an embodiment provided by the present invention, the valve assembly is further adapted to switch to the third state. In the third state, the second compressor 200, the first heat exchanger 300, the first passage of the economizer 400 and the air heat exchanger 500 are connected in sequence to form a third circulation loop. In this embodiment, when the actual water temperature of the water outlet of the heat absorption passage of the first heat exchanger 300 is greater than or equal to the target temperature, the valve assembly switches to the second state. At this time, the first compressor 100 is turned on and the second compressor 200 is turned off, and the second circulation loop realizes the hot water production effect. Under this working condition, to ensure that the compressor of the heat pump unit always operates in its high-efficiency frequency range, when the actual operating frequency of the compressor is not in its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted by the re-state switching of the valve assembly to make full use of the compressor and improve the operating efficiency and hot water production effect of the heat pump unit.

[0034] When the actual operating frequency of the first compressor 100 is less than the first set frequency, the valve assembly switches from the second state to the third state. At this time, the first compressor 100 is turned off and the second compressor 200 is turned on. The refrigerant is compressed by the second compressor 200 to form a high-temperature gaseous refrigerant, which enters the heat release passage of the first heat exchanger 300 and exchanges heat with the water in the heat absorption passage of the first heat exchanger 300. The refrigerant releases heat and cools down, and the water absorbs heat and warms up to be used as the hot water source. Then the refrigerant enters the air heat exchanger 500 through the first passage of the economizer 400, exchanges heat with the outside air further, cools down to a low-temperature liquid refrigerant and then returns to the second compressor 200, and the third circulation loop realizes the hot water production effect in this way.

[0035] After the heat pump unit operates in the third circulation loop with the valve assembly switched to the third state for a period of time, when the actual operating frequency of the second compressor 200 is greater than the second set frequency, the valve assembly switches from the third state to the second state, and the second circulation loop operates, and the hot water production effect is realized again by the second circulation loop.

[0036] According to an embodiment provided by the present invention, the valve assembly is further adapted to switch to a fourth state. In the fourth state, the first compressor 100, the air heat exchanger 500, the first passage of the economizer 400, and the first heat exchanger 300 are sequentially connected to form a fourth circulation loop. In this embodiment, by switching the state of the valve assembly, the first compressor 100, the second compressor 200, the first heat exchanger 300, the economizer 400, and the air heat exchanger 500 are connected in series to form different refrigerant circulation loops, thereby cooling the water passing through the first heat exchanger 300 and completing the chilled water operation of the heat pump unit.

[0037] The valve assembly switches to the fourth state. At this time, the first compressor 100 is turned on and the second compressor 200 is turned off. The refrigerant is compressed by the first compressor 100 to form a high-temperature gaseous refrigerant, which enters the air heat exchanger 500 to exchange heat with the outside air. The refrigerant releases heat and cools down. Then, the refrigerant enters the heat absorption passage of the first heat exchanger 300 through the first passage of the economizer 400, and further exchanges heat with the water in the heat release passage of the first heat exchanger 300, causing the chilled water source to release heat and cool down. After warming up to a high-temperature liquid refrigerant, it returns to the first compressor 100. In this way, the fourth circulation loop realizes the chilled water effect.

[0038] According to an embodiment provided by the present invention, the valve assembly is further adapted to switch to a fifth state. In the fifth state, the second compressor 200, the air heat exchanger 500, the first passage of the economizer 400, and the first heat exchanger 300 are sequentially connected to form a fifth circulation loop. In this embodiment, when the valve assembly switches to the fourth state, the heat pump unit operates the fourth circulation loop to realize chilled water. Under this working condition, to ensure that the compressor of the heat pump unit always operates in its high-efficiency frequency range, when the actual operating frequency of the compressor is not in its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted by switching the state of the valve assembly again. According to the required cooling load, the compressor is controlled to always operate in the high-efficiency range, making full use of the compressor, improving the operating energy efficiency of the heat pump unit, being more energy-saving, and enhancing the chilled water effect.

[0039] When the actual operating frequency of the first compressor 100 is less than the first set frequency, the valve assembly switches from the fourth state to the fifth state. At this time, the first compressor 100 is turned off and the second compressor 200 is turned on. The refrigerant is compressed by the second compressor 200 to form a high-temperature gaseous refrigerant, which enters the air heat exchanger 500 to exchange heat with the outside air. The refrigerant releases heat and cools down. Then, the refrigerant enters the heat absorption passage of the first heat exchanger 300 through the first passage of the economizer 400, and further exchanges heat with the water in the heat release passage of the first heat exchanger 300, causing the chilled water source to release heat and cool down. After warming up to a high-temperature liquid refrigerant, it returns to the second compressor 200. In this way, the fifth circulation loop realizes the chilled water effect.

[0040] The heat pump unit switches the valve assembly to the fifth state. After the fifth circulation loop operates for a period of time, when the actual operating frequency of the second compressor 200 is greater than the second set frequency, the valve assembly switches from the fifth state to the fourth state, and the fourth circulation loop operates, and the hot water heating effect is realized again through this fourth circulation loop.

[0041] According to an embodiment provided by the present invention, the volume of the first compressor 100 is greater than the volume of the second compressor 200. In this embodiment, the volumes of the first compressor 100 and the second compressor 200 are different, so that when the first compressor 100 and the second compressor 200 start and operate separately, the compressed heat that can be provided and their respective operating frequencies are different, so as to provide a heat pump unit that can meet the corresponding refrigerant compression requirements under different external working conditions.

[0042] In this embodiment, in order to make the heat pump unit have higher operating energy efficiency, the volume ratio of the first compressor 100 to the second compressor 200 is about 2:1.

[0043] According to an embodiment provided by the present invention, the heat pump unit further includes a second heat exchanger 600. The refrigerant outlet of the first compressor 100 is communicated with the inlet of the heat release channel of the second heat exchanger 600, and the outlet of the heat release channel of the second heat exchanger 600 is communicated with at least one of the refrigerant inlet of the second compressor 200 and the valve assembly.

[0044] In this embodiment, when the heat pump unit is in the two-stage compression mode, the exhaust temperature of the second compressor 200 is likely to be too high, exceeding the compressor exhaust temperature limit and causing the heat pump unit to fail to operate normally. Therefore, a second heat exchanger 600 is provided between the refrigerant outlet of the first compressor 100 and the refrigerant inlet of the second compressor 200. After the refrigerant is compressed by the first compressor 100, it first enters the heat release path of the second heat exchanger 600 and exchanges heat with the water in the heat absorption path of the second heat exchanger 600. The water in the heat absorption path of the second heat exchanger 600 can be a hot water supply source, and the refrigerant heat of the first compressor 100 is used to preheat the hot water supply source for the first time. In this way, both the refrigerant discharge heat of the first compressor 100 can be recovered and the suction temperature of the second compressor 200 can be reduced, thereby improving the operating reliability of the heat pump unit.

[0045] In this embodiment, since the opening and closing of the first compressor 100 and the second compressor 200 cooperate with the switching of the valve assembly to make the heat pump unit operate different refrigerant circulation loops, the second heat exchanger 600 mainly cools the refrigerant discharged from the first compressor 100. The refrigerant discharged from the second heat exchanger 600 can directly enter the second compressor 200, or can enter the device after the first compressor 100 in the corresponding circulation loop under the switching of the valve assembly.

[0046] According to an embodiment provided by the present invention, the valve assembly includes a first control valve 710, a second control valve 720, a first throttle valve 730, a second throttle valve 740, and a four-way valve 750. A first port of the four-way valve 750 is communicated with the refrigerant outlet of the second compressor 200. A second port of the four-way valve 750 is communicated with the first heat exchanger 300. A third port of the four-way valve 750 is communicated with the refrigerant inlet of the first compressor 100. A fourth port of the four-way valve 750 is communicated with the air heat exchanger 500. A first branch pipeline is provided on the pipeline where the first compressor 100 is communicated with the second compressor 200. The first branch pipeline is communicated with the first port of the four-way valve 750. The second control valve 720 is arranged on the first branch pipeline. A second branch pipeline is provided on the pipeline where the third port of the four-way valve 750 is communicated with the refrigerant inlet of the compressor. The second branch pipeline is communicated with the refrigerant inlet of the second compressor 200. The first control valve 710 is arranged on the second branch pipeline. The first throttle valve 730 is arranged on the pipeline where the first heat exchange channel of the economizer 400 is communicated with the air heat exchanger 500. The second throttle valve 740 is arranged on the pipeline where the second heat exchange channel of the economizer 400 is communicated with the first heat exchanger 300.

[0047] In this embodiment, when the valve assembly is switched to the first state, both the first control valve 710 and the second control valve 720 are closed, both the first throttle valve 730 and the second throttle valve 740 are opened, the first port D of the four-way valve 750 is communicated with the second port C, and the third port S is communicated with the fourth port E. When the valve assembly is switched to the second state, the first control valve 710 is closed, the second control valve 720 is opened, the first throttle valve 730 is opened, the second throttle valve 740 is closed, the first port D of the four-way valve 750 is communicated with the second port C, and the third port S is communicated with the fourth port E. When the valve assembly is switched to the third state, the first control valve 710 is opened, the second control valve 720 is closed, the first throttle valve 730 is opened, the second throttle valve 740 is closed, the first port D of the four-way valve 750 is communicated with the second port C, and the third port S is communicated with the fourth port E. When the valve assembly is switched to the fourth state, the first control valve 710 is closed, the second control valve 720 is opened, the first throttle valve 730 is opened, the second throttle valve 740 is closed, the first port D of the four-way valve 750 is communicated with the fourth port E, and the third port S is communicated with the second port C. When the valve assembly is switched to the fifth state, the first control valve 710 is opened, the second control valve 720 is closed, the first throttle valve 730 is opened, the second throttle valve 740 is closed, the first port D of the four-way valve 750 is communicated with the fourth port E, and the third port S is communicated with the second port C.

[0048] The control method of the heat pump unit provided by the present invention will be described below. The control method of the heat pump unit described below can be mutually corresponding and referred to with the heat pump unit described above.

[0049] An embodiment of the present invention further provides a control method for a heat pump unit, which is applied to the heat pump unit as described in the above embodiment, and includes: Obtain a hot water production instruction and control the start of the heat pump unit; Determine that the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 is less than the first set temperature, and control the valve assembly of the heat pump unit to switch to the first state, where the first set temperature is the lower threshold of the target temperature; or, determine that the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 is greater than or equal to the second set temperature, and control the valve assembly of the heat pump unit to switch to the second state, where the second set temperature is the upper threshold of the target temperature.

[0050] In the control method of the heat pump unit according to the embodiment of the present invention, after obtaining the hot water production instruction, the heat pump unit starts to enter the hot water production mode, and judges the relationship between the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 and the first set temperature. If the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 is less than the first set temperature, the valve assembly is controlled to switch to the first state, and the first circulation loop operates to produce hot water; if the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 is greater than or equal to the second set temperature, the valve assembly switches to the second state, and the second circulation loop operates to produce hot water.

[0051] In this embodiment, the first set temperature and the second set temperature are respectively the lower threshold and the upper threshold of the target temperature. The upper threshold of the target temperature is the sum of the target temperature and the fluctuation temperature, and the lower threshold of the target temperature is the difference between the target temperature and the fluctuation temperature.

[0052] According to an embodiment provided by the present invention, after determining that the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 is greater than or equal to the second set temperature and controlling the valve assembly of the heat pump unit to switch to the second state, it further includes: Determine that the actual operating frequency of the first compressor 100 is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the third state, where the first set frequency is the lower limit value of the rated frequency of the compressor; Determine that the actual operating frequency of the second compressor 200 is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the second state, where the second set frequency is the upper limit value of the rated frequency of the compressor.

[0053] In this embodiment, when the actual water temperature of the water outlet of the heat absorption path of the first heat exchanger 300 is greater than or equal to the second set temperature and the valve assembly switches to the second state to realize hot water production in the second circulation loop, in order to ensure that the compressor of the heat pump unit always operates in its high-efficiency frequency range, when the actual operating frequency of the compressor is not in its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted by switching the state of the valve assembly again to make full use of the compressor and improve the operating efficiency and hot water production effect of the heat pump unit.

[0054] Judge the relationship between the actual operating frequency of the first compressor 100 and the first set frequency. If the actual operating frequency of the first compressor 100 is less than the first set frequency, control the valve assembly to switch from the second state to the third state, and the third circulation loop operates to produce hot water. After the third circulation loop operates for a period of time, judge the relationship between the actual operating frequency of the second compressor 200 and the second set frequency. If the actual operating frequency of the second compressor 200 is greater than the second set frequency, control the valve assembly to switch from the third state to the second state, and the second circulation loop operates to produce hot water.

[0055] In this embodiment, the first set frequency is the high-efficiency operating frequency of the first compressor 100, which can be 50 Hz, and the second set temperature is the high-efficiency operating frequency of the second compressor 200, which can be 100 Hz.

[0056] According to an embodiment provided by the present invention, the control method of the heat pump unit further includes: Obtain a chilled water instruction and control the valve assembly of the heat pump unit to switch to the fourth state.

[0057] In this embodiment, after obtaining the chilled water instruction, the heat pump unit starts to enter the chilled water mode, controls the valve assembly to switch to the fourth state, and the fourth circulation loop operates to produce chilled water. The second compressor 200 is turned off, and the second throttle valve 740 is closed. The circulation form is as follows: The first compressor 100 → the second heat exchanger 600 → the second control valve 720 → the four-way valve 750DE → the air heat exchanger 500 → the first throttle valve 730 → the economizer 400 → the first heat exchanger 300 → the four-way valve 750CS → the first compressor 100.

[0058] In the chilled water mode, when the second compressor 200 fails, this circulation also operates.

[0059] According to an embodiment provided by the present invention, after obtaining the chilled water instruction and controlling the valve assembly of the heat pump unit to switch to the fourth state, it further includes: Determine that the actual operating frequency of the first compressor 100 is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the fifth state; Determine that the actual operating frequency of the second compressor 200 is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the fourth state.

[0060] In this embodiment, in the chilled water mode, when the valve assembly switches to the fourth state and the heat pump unit operates in the fourth circulation loop to achieve chilled water, to ensure that the compressor of the heat pump unit always operates in its high-efficiency frequency range, when the actual operating frequency of the compressor is not in its suitable frequency range, the circulation loop of the heat pump unit needs to be adjusted through another state switch of the valve assembly, and the compressor is controlled to always operate in the high-efficiency range according to the required cooling load, making full use of the compressor, improving the operating energy efficiency of the heat pump unit, being more energy-saving and improving the chilled water effect.

[0061] Judge the relationship between the actual operating frequency of the first compressor 100 and the first set frequency. If the actual operating frequency of the first compressor 100 is less than the first set frequency, control the valve assembly to switch from the fourth state to the fifth state, and the fifth circulation loop operates for chilled water. After the fifth circulation loop operates for a period of time, judge the relationship between the actual operating frequency of the second compressor 200 and the second set frequency. If the actual operating frequency of the second compressor 200 is greater than the second set frequency, control the valve assembly to switch from the fifth state to the fourth state, and the fourth circulation loop operates for chilled water.

[0062] According to a control method of a heat pump unit provided by the present invention, when it is determined that the continuous duration of the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 being less than the first set temperature reaches the first set duration, control the valve assembly of the heat pump unit to switch to the first state; or, when it is determined that the continuous duration of the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300 being greater than the second set temperature reaches the first set duration, control the valve assembly of the heat pump unit to switch to the second state.

[0063] In this embodiment, in the hot water heating mode, to avoid the compressor and the heat exchanger having large fluctuations during operation and causing instability of the heat pump unit due to too frequent switching of the valve assembly, and to avoid misjudgment of the system due to the instantaneous temperature of the hot water supply source affecting the accuracy of the detection result, when judging the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger 300, only when the detected actual water temperature continuously remains less than the first set temperature for a duration reaching the first set duration, or continuously remains greater than or equal to the second set temperature for a duration reaching the first set duration, will the state of the valve assembly be switched.

[0064] When the detected actual water temperature t wo <the first set temperature t0 - △t and maintains the first set duration T, the first control valve 710 is closed, the second control valve 720 is closed, and the circulation form is as follows: The first compressor 100 → the second heat exchanger 600 → the second compressor 200 → the four-way valve 750DC → the first heat exchanger 300 → the first branch and the second branch; Among them, the first branch is: the second throttle valve 740 → the economizer 400 → the second compressor 200; the second branch is: the economizer 400 → the first throttle valve 730 → the air heat exchanger 500 → the four-way valve 750ES → the first compressor 100.

[0065] When the actual water temperature t is detected wo ≥ the second set temperature t0 + △t and maintains for the first set duration T, the second compressor 200 is turned off, and the second throttle valve 740 is turned off. The circulation form is as follows: The first compressor 100 → the second heat exchanger 600 → the second control valve 720 → the four-way valve 750DC → the first heat exchanger 300 → the economizer 400 → the first throttle valve 730 → the air heat exchanger 500 → the four-way valve 750ES → the first compressor 100.

[0066] In the hot water production mode, when the second compressor 200 fails, this cycle is also run.

[0067] According to an embodiment provided by the present invention, when it is determined that the duration for which the actual operating frequency of the first compressor 100 is less than the first set frequency reaches the second set duration, the valve assembly of the heat pump unit is controlled to switch to the third state; when it is determined that the duration for which the actual operating frequency of the second compressor 200 is greater than the second set frequency reaches the second set duration, the valve assembly of the heat pump unit is controlled to switch to the second state.

[0068] In this embodiment, in the hot water production mode, when it is necessary to control the compressor to always operate in the high-efficiency range, to avoid large fluctuations in the operation of the compressor and the heat exchanger caused by too frequent switching of the valve assembly, resulting in instability of the heat pump unit, and to avoid misjudgment of the system caused by the instantaneous temperature of the hot water supply source affecting the accuracy of the detection result, only when the duration for which the actual operating frequency of the detected first compressor 100 is continuously less than the first set frequency reaches the second set duration, or when the duration for which the actual operating frequency of the detected second compressor 200 is continuously greater than the second set frequency reaches the second set duration, will the state of the valve assembly be switched.

[0069] When it is detected that the actual operating frequency f1 of the first compressor 100 < the first set frequency fa and maintains for the second set duration t1, the first compressor 100 is turned off, and the second throttle valve 740 is turned off. The circulation form is as follows: The second compressor 200 → the four-way valve 750DC → the first heat exchanger 300 → the economizer 400 → the first throttle valve 730 → the air heat exchanger 500 → the four-way valve 750ES → the first control valve 710 → the second compressor 200.

[0070] In the hot water production mode, when the first compressor 100 fails, this cycle is also run.

[0071] When it is detected that the actual operating frequency f2 of the second compressor 200 > the second set frequency fb and maintains for the second set duration t1, the second compressor 200 is turned off, and the second throttle valve 740 is closed. The cycle form is as follows: First compressor 100 → Second heat exchanger 600 → Second control valve 720 → Four-way valve 750DC → First heat exchanger 300 → Economizer 400 → First throttle valve 730 → Air heat exchanger 500 → Four-way valve 750ES → First compressor 100.

[0072] According to an embodiment provided by the present invention, when it is determined that the duration for which the actual operating frequency of the first compressor 100 is less than the first set frequency reaches the third set duration, the valve assembly of the heat pump unit is controlled to switch to the fifth state; when it is determined that the actual operating frequency of the second compressor 200 is greater than the second set frequency for the third set duration, the valve assembly of the heat pump unit is controlled to switch to the fourth state.

[0073] In this embodiment, in the chilled water mode, when it is necessary to control the compressor to always operate in the high-efficiency range, to avoid large fluctuations in the operation of the compressor and the heat exchanger due to overly frequent switching of the valve assembly, resulting in instability of the heat pump unit, and to avoid misjudgment of the system caused by the instantaneous temperature of the hot water supply affecting the accuracy of the detection result, only when the duration for which the detected actual operating frequency of the first compressor 100 is continuously less than the first set frequency reaches the third set duration, or when the duration for which the detected actual operating frequency of the second compressor 200 is continuously greater than the second set frequency reaches the third set duration, will the state of the valve assembly be switched.

[0074] When it is detected that the actual operating frequency f1 of the first compressor 100 < the first set frequency fa and maintains for the third set duration t2, the first compressor 100 is turned off, and the second throttle valve 740 is closed. The cycle form is as follows: Second compressor 200 → Four-way valve 750DE → Air heat exchanger 500 → First throttle valve 730 → Economizer 400 → First heat exchanger 300 → Four-way valve 750CS → First control valve 710 → Second compressor 200.

[0075] In the chilled water mode, when the first compressor 100 fails, this cycle is also run.

[0076] When it is detected that the actual operating frequency f2 of the second compressor 200 > the second set frequency fb and maintains for the third set duration t2, the second compressor 200 is turned off, and the second throttle valve 740 is closed. The cycle form is as follows: The first compressor 100 → the second heat exchanger 600 → the second control valve 720 → the four-way valve 750DE → the air heat exchanger 500 → the first throttle valve 730 → the economizer 400 → the first heat exchanger 300 → the four-way valve 750CS → the first compressor 100.

[0077] In this embodiment, the third set duration may be the same as the second set duration.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat pump unit, characterized in that, Comprising a first compressor (100), a second compressor (200), a first heat exchanger (300), an economizer (400), an air heat exchanger (500) and a valve assembly, the valve assembly being adapted to switch between a first state and a second state. In the first state, the first compressor (100), the second compressor (200), the first heat exchanger (300), the first passage of the economizer (400) and the air heat exchanger (500) are sequentially connected to form a first circulation loop; in the second state, the first compressor (100), the first heat exchanger (300), the first passage of the economizer (400) and the air heat exchanger (500) are sequentially connected to form a second circulation loop.

2. The heat pump unit according to claim 1, characterized in that, In the first state, the first heat exchanger (300), the second passage of the economizer (400) and the second compressor (200) are sequentially connected to form a branch of the first circulation loop.

3. The heat pump unit according to claim 1, characterized in that, The valve assembly is further adapted to switch to a third state. In the third state, the second compressor (200), the first heat exchanger (300), the first passage of the economizer (400) and the air heat exchanger (500) are sequentially connected to form a third circulation loop; or, The valve assembly is further adapted to switch to a fourth state. In the fourth state, the first compressor (100), the air heat exchanger (500), the first passage of the economizer (400) and the first heat exchanger (300) are sequentially connected to form a fourth circulation loop; or, The valve assembly is further adapted to switch to a fifth state. In the fifth state, the second compressor (200), the air heat exchanger (500), the first passage of the economizer (400) and the first heat exchanger (300) are sequentially connected to form a fifth circulation loop.

4. The heat pump unit according to claim 1, characterized in that, The volume of the first compressor (100) is larger than the volume of the second compressor (200).

5. The heat pump unit according to any one of claims 1 to 4, characterized in that, The heat pump unit further includes a second heat exchanger (600). The refrigerant outlet of the first compressor (100) is connected to the inlet of the heat release passage of the second heat exchanger (600), and the outlet of the heat release passage of the second heat exchanger (600) is connected to at least one of the refrigerant inlet of the second compressor (200) and the valve assembly.

6. A control method for a heat pump unit, characterized in that, Applied to the heat pump unit according to any one of claims 1 to 5, comprising: Obtaining a hot water production instruction and controlling the start of the heat pump unit; Determining that the actual water temperature at the outlet of the heat absorption passage of the first heat exchanger (300) is less than a first set temperature, and controlling the valve assembly of the heat pump unit to switch to the first state, where the first set temperature is the lower threshold of the target temperature; or, determining that the actual water temperature at the outlet of the heat absorption passage of the first heat exchanger (300) is greater than or equal to a second set temperature, and controlling the valve assembly of the heat pump unit to switch to the second state, where the second set temperature is the upper threshold of the target temperature.

7. The control method of the heat pump unit according to claim 6, characterized in that, After determining that the actual water temperature at the outlet of the heat absorption passage of the first heat exchanger (300) is greater than or equal to the second set temperature and controlling the valve assembly of the heat pump unit to switch to the second state, it further includes: Determine that the actual operating frequency of the first compressor (100) is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the third state, where the first set frequency is the lower limit value of the rated frequency of the compressor; Determine that the actual operating frequency of the second compressor (200) is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the second state, where the second set frequency is the upper limit value of the rated frequency of the compressor.

8. The control method of the heat pump unit according to claim 7, characterized in that, It further includes: Obtain a chilled water instruction and control the valve assembly of the heat pump unit to switch to the fourth state; Or, Obtain a chilled water instruction and control the valve assembly of the heat pump unit to switch to the fourth state; Determine that the actual operating frequency of the first compressor (100) is less than the first set frequency, and control the valve assembly of the heat pump unit to switch to the fifth state; Determine that the actual operating frequency of the second compressor (200) is greater than the second set frequency, and control the valve assembly of the heat pump unit to switch to the fourth state.

9. The control method of the heat pump unit according to claim 6, characterized in that, Determine that the duration for which the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger (300) is less than the first set temperature reaches the first set duration, and control the valve assembly of the heat pump unit to switch to the first state; or, determine that the duration for which the actual water temperature at the outlet of the heat absorption channel of the first heat exchanger (300) is greater than the second set temperature reaches the first set duration, and control the valve assembly of the heat pump unit to switch to the second state.

10. The control method of the heat pump unit according to claim 8, characterized in that, Determine that the duration for which the actual operating frequency of the first compressor (100) is less than the first set frequency reaches the second set duration, and control the valve assembly of the heat pump unit to switch to the third state; Determine that the duration for which the actual operating frequency of the second compressor (200) is greater than the second set frequency reaches the second set duration, and control the valve assembly of the heat pump unit to switch to the second state; Or, Determine that the duration for which the actual operating frequency of the first compressor (100) is less than the first set frequency reaches the third set duration, and control the valve assembly of the heat pump unit to switch to the fifth state; Determine that the actual operating frequency of the second compressor (200) is greater than the second set frequency reaches the third set duration, and control the valve assembly of the heat pump unit to switch to the fourth state.

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