Air source heat pump cold and hot water unit and control method thereof

Abstract

The application provides an air source heat pump cold and hot water unit and a control method thereof. The cold and hot water unit comprises a compressor, an outdoor heat exchanger, a throttling element, a water side heat exchanger and a flow path switching valve which are connected by pipelines to form a refrigerant main circulation. The flow path switching valve can switch the air source heat pump cold and hot water unit between a cooling mode and a heating mode. The unit further comprises a controllable on-off bypass heat exchange pipeline and a bypass heat exchanger. The bypass heat exchange pipeline can guide the refrigerant discharged from the compressor into the bypass heat exchanger and then return to the refrigerant main circulation. The refrigerant in the refrigerant inlet pipeline of the water side heat exchanger can exchange heat with the refrigerant in the bypass heat exchange pipeline in the bypass heat exchanger. The application effectively prevents the water side heat exchanger from freezing and cracking due to the low water temperature of the water side heat exchanger during high load refrigeration operation or defrosting.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of air conditioning technology, and particularly relates to an air source heat pump cold and hot water unit and a control method thereof. BACKGROUND

[0002] At present, the air source heat pump cold and hot water unit on the market often has the case of water-side heat exchanger freeze damage when running in an ultra-low temperature or low temperature environment, which is mostly caused by two cases. On the one hand, the water-side heat exchanger cannot perform water circulation for a long time due to abnormal shutdown or long-time non-operation of the unit, and the water in the heat exchanger is not drained, so the water-side heat exchanger is prone to freeze after the water temperature is lower than the freezing point. On the other hand, the water temperature decreases rapidly during high-load refrigeration of the unit, so that the temperature in the water-side heat exchanger is too low to cause the freeze damage of the jacket pipe, or the heat exchange capacity of the unit is reduced due to frosting of the outdoor unit during heating operation in a low temperature condition, at which time the unit needs to be controlled to perform reverse circulation for defrosting. At this time, if the water system flow fluctuates or water flow accumulates, the water-side heat exchanger is prone to freeze crack as the water temperature gradually decreases, thereby causing the unit to be unable to operate normally. Therefore, a reliable control system is needed to prevent such a situation from occurring. SUMMARY

[0003] Therefore, the present application provides an air source heat pump cold and hot water unit and a control method thereof, which can solve the technical problem of freeze and crack of the water-side heat exchanger of the air source heat pump cold and hot water unit in the prior art due to too low water temperature during high-load refrigeration operation or defrosting of the water-side heat exchanger.

[0004] In order to solve the above problems, the present application provides an air source heat pump cold and hot water unit, which comprises a compressor, an outdoor heat exchanger, a throttling element, a water-side heat exchanger and a flow path switching valve connected by pipelines to form a refrigerant main circulation, wherein the flow path switching valve can switch the air source heat pump cold and hot water unit between a refrigeration mode and a heating mode, and further comprises a controllable on-off bypass heat exchange pipeline and a bypass heat exchanger. The bypass heat exchange pipeline can guide the refrigerant discharged from the compressor into the bypass heat exchanger and then return to the refrigerant main circulation. The refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger can exchange heat with the refrigerant in the bypass heat exchanger.

[0005] In some embodiments, the bypass heat exchange pipeline has a bypass electromagnetic valve, and the opening degree of the bypass electromagnetic valve is adjustable.

[0006] In some embodiments, the air source heat pump cold and hot water unit further comprises a flash evaporator, the compressor is a charge boosting enthalpy compressor, the flash evaporator is connected between the water side heat exchanger and the outdoor side heat exchanger, and a charge pipe of the flash evaporator is communicated with a charge port of the compressor, the throttling element comprises a first throttling element and a second throttling element, and the first throttling element and the second throttling element are respectively arranged on a connecting pipeline between the flash evaporator and the water side heat exchanger and a connecting pipeline between the flash evaporator and the outdoor side heat exchanger.

[0007] In some embodiments, a flow outlet of a refrigerant outflow section of the bypass heat exchange pipeline is communicated with the flash evaporator; and / or, a charge electromagnetic valve is arranged on a charge pipeline between the flash evaporator and the compressor.

[0008] In some embodiments, a one-way valve is connected to the refrigerant outflow section.

[0009] In some embodiments, the air source heat pump cold and hot water unit further comprises a regenerator, and refrigerant in a suction pipeline of the compressor and refrigerant in the refrigerant outflow section can form heat exchange in the regenerator.

[0010] In some embodiments, a refrigerant inlet of the bypass heat exchange pipeline is connected to a refrigerant pipeline between the flow path switching valve and the outdoor side heat exchanger.

[0011] The application further provides a control method of the air source heat pump cold and hot water unit.

[0012] The real-time temperature T1 of refrigerant in a refrigerant inlet pipeline of the water side heat exchanger is obtained.

[0013] The size relationship between a difference AT of the real-time temperature T1 of the refrigerant and a freeze-proof temperature set value T0 and a freeze-proof preset difference a is determined, wherein T1, T0 and a are constants greater than 0.

[0014] The bypass heat exchange pipeline is controlled according to the size relationship.

[0015] In some embodiments, controlling the bypass heat exchange pipeline according to the size relationship comprises:

[0016] When AT≤a, the bypass heat exchange pipeline is controlled to be turned on.

[0017] When AT>a, the bypass heat exchange pipeline is controlled to be turned off.

[0018] In some embodiments, after the bypass heat exchange pipeline is turned on, the opening degree of a bypass electromagnetic valve on the bypass heat exchange pipeline is controlled, and the opening degree of the bypass electromagnetic valve is negatively related to the size of AT.

[0019] In some embodiments, when the refrigerant flow inlet of the bypass heat exchange pipeline is connected to the refrigerant pipeline between the flow path switching valve and the outdoor heat exchanger, before acquiring the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger, the method further comprises acquiring the operating mode of the air source heat pump chiller-heater unit, and when the operating mode is the refrigeration mode, acquiring the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger again.

[0020] The air source heat pump chiller-heater unit and the control method thereof provided by the application can effectively prevent the freezing and cracking of the water-side heat exchanger caused by the low water temperature of the water-side heat exchanger during the high-load refrigeration operation or the defrosting process of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The system schematic diagram of the air source heat pump chiller-heater unit of the embodiment of the application is shown in the figure, and the arrows in the figure show the flow direction of the refrigerant during the refrigeration mode of the unit.

[0022] The signs are as follows:

[0023] 1, compressor; 2, outdoor heat exchanger; 3, water-side heat exchanger; 4, flow path switching valve; 5, flash evaporator; 51, air supplementing electromagnetic valve; 61, first throttling element; 62, second throttling element; 7, heat regenerator; 8, gas-liquid separator; 100, bypass heat exchange pipeline; 101, bypass heat exchanger; 102, bypass electromagnetic valve; 103, one-way valve. DETAILED DESCRIPTION

[0024] Reference Figure 1As shown, according to the embodiment of the present application, an air source heat pump cold and hot water unit is provided, comprising a compressor 1, an outdoor heat exchanger 2, a throttling element, a water side heat exchanger 3, and a flow path switching valve 4 connected by pipelines to form a refrigerant main circulation, wherein the unit water circuit in the water side heat exchanger 3 realizes heat exchange with the refrigerant in the refrigerant main circulation, and the water side heat exchanger 3 can be understood as an indoor heat exchanger, the switching of the passage of the flow path switching valve 4 can switch the air source heat pump cold and hot water unit between the cooling mode and the heating mode, specifically, the flow path switching valve 4 can be a four-way reversing valve, the air source heat pump cold and hot water unit further comprises a controllable on-off bypass heat exchange pipeline 100 and a bypass heat exchanger 101, the bypass heat exchange pipeline 100 can guide the refrigerant discharged by the compressor 1 into the bypass heat exchanger 101 and then return to the refrigerant main circulation, and the refrigerant in the refrigerant inlet pipeline of the water side heat exchanger 3 can exchange heat with the refrigerant in the bypass heat exchange pipeline 100 in the bypass heat exchanger 101. In this technical solution, when the water side heat exchanger 3 is detected to have a freezing risk, the bypass heat exchange pipeline 100 is controlled to be conducted, so that part of the high-temperature and high-pressure refrigerant discharged by the compressor 1 is guided to the bypass heat exchanger 101 to heat and warm the refrigerant entering the water side heat exchanger 3, thereby effectively preventing the phenomenon of water side heat exchanger freezing and cracking caused by too low water temperature of the water side heat exchanger during high-load refrigeration operation or defrosting process (objectively, the unit is also operated in cooling mode at this time).

[0025] In some embodiments, the bypass heat exchange pipeline 100 has a bypass electromagnetic valve 102, and the opening of the bypass electromagnetic valve 102 is adjustable, specifically, the opening of the bypass electromagnetic valve 102 can be controlled and adjusted according to the freezing risk of the water side heat exchanger 3, for example, when the refrigerant temperature in the refrigerant inlet pipeline of the water side heat exchanger 3 is too low, the opening of the bypass electromagnetic valve 102 is controlled to be large at this time, and the amount of high-temperature and high-pressure refrigerant guided into the bypass heat exchanger 101 is large, which can warm up more quickly, and vice versa, when the refrigerant temperature in the refrigerant inlet pipeline of the water side heat exchanger 3 is relatively not too low, the opening of the bypass electromagnetic valve 102 is controlled to be small, and only a small amount of high-temperature and high-pressure refrigerant is guided into the water side heat exchanger 3, which can be maintained in a relatively safe (i.e. no freezing risk) state, and when the refrigerant temperature in the refrigerant inlet pipeline of the water side heat exchanger 3 is relatively high, there is obviously no risk of freezing and cracking at this time, and the opening of the bypass electromagnetic valve 102 can be reduced to zero at this time, i.e. the bypass heat exchange pipeline 100 is cut off.

[0026] In some embodiments, the air source heat pump cold and hot water unit further comprises a flash evaporator 5, the compressor 1 is a charge heat compression machine, the suction port of the compressor 1 is connected with a gas-liquid separator 8, the flash evaporator 5 is connected between the water side heat exchanger 3 and the outdoor side heat exchanger 2, and the charge pipe of the flash evaporator 5 is communicated with the charge port of the compressor 1, the throttling element comprises a first throttling element 61 and a second throttling element 62, the first throttling element 61 and the second throttling element 62 are respectively arranged on the connecting pipeline between the flash evaporator 5 and the water side heat exchanger 3 and the connecting pipeline between the flash evaporator 5 and the outdoor side heat exchanger 2, the compressor 1 adopts the charge heat compression machine, and the flash evaporator 5 and the corresponding charge pipe are additionally arranged in the main refrigerant circulating pipeline, so that the unit of the application has higher energy efficiency in a low temperature environment, the charge pipe between the flash evaporator 5 and the compressor 1 is provided with a charge electromagnetic valve 51, and whether the compressor 1 is charged and heated is controlled by the on-off of the charge electromagnetic valve 51.

[0027] In one embodiment, the outlet of the refrigerant outflow section of the bypass heat exchange pipeline 100 can be guided into the accumulator in the main refrigerant circulating pipeline, and when the flash evaporator 5 is arranged, the outlet of the refrigerant outflow section of the bypass heat exchange pipeline 100 is communicated with the flash evaporator 5, that is, the function of the accumulator is realized by using the flash evaporator 5, and the system structure is simplified. A one-way valve 103 is connected to the refrigerant outflow section, and the one-way valve 103 only allows the refrigerant to flow into the flash evaporator 5 and cannot flow in the opposite direction.

[0028] In some embodiments, the air source heat pump cold and hot water unit further comprises a regenerator 7, the refrigerant in the suction pipe of the compressor 1 and the refrigerant in the refrigerant outflow section can form heat exchange in the regenerator 7, so that the suction superheat degree of the compressor 1 can be improved, and the liquid strike problem caused by liquid carrying in the suction of the compressor 1 can be effectively prevented.

[0029] In a preferred embodiment, the refrigerant inlet of the bypass heat exchange pipeline 100 is connected to the refrigerant pipeline between the flow path switching valve 4 and the outdoor side heat exchanger 2, that is, the refrigerant of the bypass heat exchange pipeline 100 is introduced from the refrigerant after flowing out of the flow path switching valve 4. It should be noted that an oil return device (not shown in the figure) is usually arranged between the exhaust port of the compressor 1 and the flow path switching valve 4, and the refrigerant is directly introduced from the exhaust port of the compressor 1, which can cause the lubricating oil to enter the branch and then enter other flow paths of the system, so that the compressor 1 cannot effectively return oil. In addition, the pressure difference of the refrigerant flowing through the flow path switching valve 4 from the exhaust port will change, which will have certain influence on the performance of the unit in the refrigeration process.

[0030] According to the embodiment of the present application, the control method of the air source heat pump hot and cold water unit is also provided, which comprises: obtaining the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger 3; judging the size relationship between the difference AT of the real-time temperature T1 and the anti-freezing temperature setting value T0 and the anti-freezing preset difference a, wherein T1, T0 and a are constants greater than 0, generally, T0 is generally set to 3-5℃, and AT is reasonably selected according to actual needs; and controlling the on-off of the bypass heat exchange pipeline 100 according to the size relationship. Specifically, the control of the on-off of the bypass heat exchange pipeline 100 according to the size relationship comprises: when AT≤a, the temperatures of T1 and T0 are relatively close at this time, and there is a risk of low-temperature freezing, therefore, the bypass heat exchange pipeline 100 is controlled to be turned on, so that part of the high-temperature and high-pressure refrigerant discharged by the compressor 1 is guided to the bypass heat exchanger 101 to exchange heat with the refrigerant entering the water-side heat exchanger 3, so as to heat the water entering the water-side heat exchanger 3, thereby effectively preventing the water-side heat exchanger 3 from freezing and cracking in the case of water flow fluctuation or temperature sudden drop; and when AT>a, it is indicated that the temperature difference between T1 and T0 is large, and the water temperature is high and there is no freezing risk, and the bypass heat exchange pipeline 100 is controlled to be turned off. It should be noted that the judgment of the size relationship between AT and a should be based on the continuous state of the preset time period, for example, AT≤a or AT>a is continuously detected within 10 seconds, so as to prevent the control from jumping back and forth.

[0031] In a preferred embodiment, after the bypass heat exchange pipeline 100 is turned on, the opening degree of the bypass electromagnetic valve 102 on the bypass heat exchange pipeline 100 is controlled, and the opening degree of the bypass electromagnetic valve 102 is negatively related to the size of AT, that is, the larger the AT, the smaller the opening degree of the bypass electromagnetic valve 102 at this time until the opening degree is adjusted to 0, and vice versa, the smaller the AT, the larger the opening degree of the bypass electromagnetic valve 102 at this time. In this technical solution, the opening degree of the bypass electromagnetic valve 102 is adjusted by the size of AT, which can ensure the anti-freezing effect while preventing the high-temperature refrigerant from adversely affecting the air conditioning system, and ensure the heating and cooling performance of the unit. The size of the opening degree K of the bypass electromagnetic valve 102 is related to AT, for example, K=λ*(T1-T0), wherein λ is a setting coefficient, which can be obtained according to experimental data fitting.

[0032] In some embodiments, when the refrigerant flow inlet of the bypass heat exchange pipeline 100 is connected to the refrigerant pipeline between the flow path switching valve 4 and the outdoor side heat exchanger 2, before obtaining the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water side heat exchanger 3, the method further comprises obtaining the operating mode of the air source heat pump cold and hot water unit, and when the operating mode is the refrigeration mode, the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water side heat exchanger 3 is obtained again. Since the anti-freezing requirement is generated in the high-load refrigeration working condition or the defrosting working condition, the foregoing control method of the present application preferably can perform the subsequent control logic when it is confirmed that the unit is operating in the refrigeration mode, so as to simplify the control difficulty of the unit.

[0033] It should be noted that when the unit is refrigerating in summer, the outlet water temperature drops quickly due to unstable water flow, low low-pressure, or when the unit is operating at high load, and when the water temperature is too low, the unit protection will be stopped or even the water side heat exchanger 3 will be frozen. During the long heating cycle of the unit in winter, the heat exchange capacity of the outdoor heat exchanger 2 gradually decreases after frosting, and at this time, defrosting is needed for the outdoor heat exchanger 2. The defrosting process adopts reverse circulation, and at this time, the water side heat exchanger 3 is an evaporator, which is extremely easy to freeze in the case of low temperature. In these two operating conditions, the temperature sensor on the refrigerant inlet pipe of the water side heat exchanger 3 detects the inlet pipe temperature T1 of the water side heat exchanger 3 (i.e. the real-time temperature T1 of the refrigerant in the foregoing, the same below), and if T1-T0≤a is continuously detected within a certain period of time (for example, within 10 seconds), the bypass electromagnetic valve 102 is opened, and the size of the opening degree K of the bypass electromagnetic valve 102 has a relationship of K=f(T1-T0) with a (for example, K=λ*(T1-T0), where λ is a set coefficient, which can be obtained according to experimental data fitting). The high-temperature gaseous refrigerant from the compressor 1 flows into the bypass branch (i.e. the foregoing bypass heat exchange pipeline 100, the same below), first exchanges heat with the throttled refrigerant through the bypass heat exchanger 101, thereby increasing the refrigerant temperature at the inlet of the water side heat exchanger 3, and preventing the water side heat exchanger 3 from being frozen in the case of water flow fluctuation or temperature sudden drop; then enters the heat regenerator 7 to exchange heat with the refrigerant entering the compressor 1, so that the refrigerant at the inlet is further superheated; finally, the refrigerant passing through the heat regenerator 7 enters the flash evaporator 5 through the one-way valve 103, and circulates with the main road refrigerant; if T1-T0>a is continuously detected within a certain period of time (for example, within 10 seconds), the bypass electromagnetic valve 102 is closed, and the system performs normal main road refrigerant circulation without refrigerant flowing through the bypass branch.

[0034] It should be noted that the air source heat pump cold and hot water unit of the present application reduces the refrigerant heat absorption from the water side during the defrosting process, prevents large indoor temperature fluctuations, and avoids the problem of inaccurate anti-freezing detection of the unit due to water flow fluctuation.

[0035] Those skilled in the art can easily understand that the advantageous technical features of the above-mentioned modes can be freely combined and superimposed without conflict.

[0036] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An air source heat pump hot and cold water unit comprising a compressor (1), an outdoor heat exchanger (2), a throttling element, a water heat exchanger (3), and a flow path switching valve (4) connected by pipes to form a main refrigerant circuit, wherein, The passage switching of the flow path switching valve (4) can switch the air source heat pump cold and hot water unit between the cooling mode and the heating mode, characterized in that further comprising a controllable on-off bypass heat exchange pipeline (100) and a bypass heat exchanger (101), the bypass heat exchange pipeline (100) can guide the refrigerant discharged by the compressor (1) into the bypass heat exchanger (101) and then return to the main refrigerant circulation, and the refrigerant in the refrigerant inlet pipeline of the water side heat exchanger (3) can exchange heat with the refrigerant in the bypass heat exchange pipeline (100) in the bypass heat exchanger (101).

2. The air source heat pump chiller-heater unit of claim 1, wherein, The bypass heat exchange pipeline (100) is provided with a bypass electromagnetic valve (102), and the opening of the bypass electromagnetic valve (102) is adjustable.

3. The air source heat pump chiller-heater unit of claim 1, wherein, Further comprising a flash evaporator (5), the compressor (1) is a charge gas enthalpy increasing compressor, the flash evaporator (5) is connected between the water side heat exchanger (3) and the outdoor side heat exchanger (2), the charge gas pipeline of the flash evaporator (5) is communicated with the charge gas inlet of the compressor (1), the throttling element comprises a first throttling element (61) and a second throttling element (62), and the first throttling element (61) and the second throttling element (62) are respectively arranged on the connecting pipelines of the flash evaporator (5) and the water side heat exchanger (3) and the connecting pipelines of the flash evaporator (5) and the outdoor side heat exchanger (2).

4. The air source heat pump chiller-heater unit of claim 3, wherein, The outlet of the refrigerant outflow section of the bypass heat exchange pipeline (100) is communicated with the flash evaporator (5); and / or, the charge gas pipeline between the flash evaporator (5) and the compressor (1) is provided with a charge gas electromagnetic valve (51).

5. The air source heat pump chiller-heater unit of claim 4, wherein, The refrigerant outflow section is connected with a check valve (103).

6. The air source heat pump chiller-heater unit of claim 4, wherein, Further comprising a regenerator (7), the refrigerant in the suction pipeline of the compressor (1) and the refrigerant in the refrigerant outflow section can form heat exchange in the regenerator (7).

7. The air source heat pump chiller-heater unit of claim 1, wherein, The refrigerant inlet of the bypass heat exchange pipeline (100) is connected to the refrigerant pipeline between the flow path switching valve (4) and the outdoor side heat exchanger (2).

8. A control method of the air source heat pump cold and hot water unit according to any one of claims 1 to 7, comprising: obtaining the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water side heat exchanger (3); judging the size relationship between the difference AT of the real-time temperature T1 of the refrigerant and the antifreeze temperature set value T0 and the antifreeze preset difference a, wherein T1, T0 and a are constants greater than 0; controlling the on-off of the bypass heat exchange pipeline (100) according to the size relationship.

9. The control method of an air source heat pump chiller-heater unit according to claim 8, characterized in that, controlling the on-off of the bypass heat exchange pipeline (100) according to the size relationship comprises: when AT≤a, controlling the bypass heat exchange pipeline (100) to be turned on; when AT>a, controlling the bypass heat exchange pipeline (100) to be turned off.

10. The control method of an air source heat pump chiller-heater unit according to claim 9, wherein, After the bypass heat exchange pipeline (100) is turned on, the opening of the bypass electromagnetic valve (102) on the bypass heat exchange pipeline (100) is adjusted, and the opening of the bypass electromagnetic valve (102) is negatively related to the size of AT.

11. The control method of an air source heat pump chiller-heater unit according to claim 8, wherein, When the refrigerant flow inlet of the bypass heat exchange pipeline (100) is connected to the refrigerant pipeline between the flow path switching valve (4) and the outdoor heat exchanger (2), before acquiring the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger (3), it further comprises acquiring the operating mode of the air source heat pump cold and hot water unit, and when the operating mode is the refrigeration mode, the real-time temperature T1 of the refrigerant in the refrigerant inlet pipeline of the water-side heat exchanger (3) is acquired again.

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