Water source heat pump unit and low-temperature start preheating control method thereof

Abstract

The application discloses a water source heat pump unit and a preheating control method for low-temperature starting of the water source heat pump unit. The water source heat pump unit comprises an oil separator, a liquid storage tank, a gas-liquid separator and a water preheating system. The water preheating system comprises a heat source, a flow regulating valve communicated through a pipeline in sequence, a coil pipe located in the oil separator, the liquid storage tank and the gas-liquid separator, and a one-way valve. The pipeline introduces hot water into the coil pipe, and is used for heating refrigerant in the oil separator, the liquid storage tank and the gas-liquid separator when the water source heat pump unit starts in a low-temperature state. The water source heat pump system can quickly supply heat when starting in a low-temperature state, and the user experience is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of air conditioning, in particular to a water source heat pump unit and a low-temperature start preheating control method thereof. BACKGROUND

[0002] The water source heat pump unit has advantages such as high energy efficiency, small occupation, and good economic payback rate, which cannot be compared with air source multi-split units. In particular, compared with air source heat pump units, the total cost (initial investment + operation cost) of the water source heat pump unit will be lower than that of the air source heat pump unit after about 1.5 years of operation. This feature makes the current market share of water source heat pumps increase year by year.

[0003] The existing water source heat pump unit is generally placed in a machine room or outdoors. During heating, the high-temperature and high-pressure gaseous refrigerant discharged by the compressor directly enters the indoor heat exchanger and exchanges heat with indoor air, and the condensation heat of the high-temperature and high-pressure gaseous refrigerant is discharged to the indoor side. However, during the holiday in winter or the shutdown for maintenance and other factors, the unit may be shut down or on standby for a period of time (more than 4 hours), and the temperature at which the unit is located may be low. For example, the outdoor temperature in northern China can be as low as -20℃ or lower. At this time, the gaseous refrigerant in the system will gradually condense due to the decrease in the ambient temperature, forming liquid refrigerant. After a long time of placement, the liquid refrigerant is mainly concentrated in the liquid storage tank, the gas-liquid separator, and the oil separator. When the unit is started and operated, the compressor first heats the low-temperature liquid refrigerant during the initial work. Since the liquid refrigerant is in the gas-liquid separator, the liquid storage tank, and the oil separator, the compressor has less suction of refrigerant, and there is large heat loss in the pipeline and components, resulting in poor heating effect. This leads to a long time of no heating to the indoor side, prolongs the heating time, and thus affects the user experience and the heating effect. SUMMARY

[0004] The present application provides a water source heat pump unit and a low-temperature start preheating control method to solve the technical problem of long heating time in the low-temperature state in the prior art.

[0005] The water source heat pump unit provided by the present application includes an oil separator, a liquid storage tank, a gas-liquid separator, and a water preheating system. The water preheating system is used to heat the refrigerant in the oil separator, the liquid storage tank, and the gas-liquid separator when the water source heat pump unit starts in a low-temperature state.

[0006] The water preheating system includes a heat source, a flow regulating valve, a coil located in the oil separator, the liquid storage tank, and the gas-liquid separator, and a check valve. The pipeline introduces hot water into the coil to heat the refrigerant.

[0007] The heat source of the water preheating system is an electric heater, a boiler, or high-pressure exhaust of part of the heat pump unit.

[0008] The water source heat pump unit comprises a compressor, an oil separator, a four-way valve, an outdoor heat exchanger, an electronic expansion valve and a liquid storage tank which are connected by pipelines.

[0009] Further, a high-pressure inlet pipeline of the four-way valve leads to a first branch, the other end of the first branch being connected to the liquid storage tank, and a pressurizing valve is arranged on the first branch.

[0010] Further, an oil return pipeline of the oil separator is provided with an oil return temperature sensor, an oil return electromagnetic valve and a pressure reducing device.

[0011] Further, a gas outlet pipeline of the gas-liquid separator is provided with an outlet pipeline temperature sensor.

[0012] Preferably, the outdoor heat exchanger is a water-cooled plate heat exchanger, and an inlet pipeline temperature sensor is arranged on a refrigerant inlet pipeline of the water-cooled plate heat exchanger.

[0013] Further, the water source heat pump system further comprises an over-cooler, and an outlet of the liquid storage tank is divided into two branches, one of which enters the over-cooler and then is connected to an indoor unit through a valve, and the other of which enters the over-cooler through an electronic expansion valve of the over-cooler and then is connected to the gas-liquid separator through a second branch.

[0014] Further, an over-cooling electromagnetic valve is arranged on the second branch, and a third branch is led out between the over-cooling electromagnetic valve and the over-cooler, the other end of the third branch being connected to a gas supplementing opening of the compressor, and a spray enthalpy valve is arranged on the third branch.

[0015] The application further provides a preheating control method for the water source heat pump unit, when the heat pump unit is started in a low-temperature state, a water preheating system is started to heat refrigerant in the oil separator, the liquid storage tank and the gas-liquid separator.

[0016] Preferably, the preheating control method is started when the following conditions are met simultaneously:

[0017] The shutdown time is greater than a first set time t1;

[0018] The refrigerant inlet pipeline temperature of the outdoor heat exchanger is detected to be less than a first set temperature T1 for a continuous time t2;

[0019] The outlet pipeline temperature of the gas-liquid separator is detected to be less than a second set temperature T2 for a continuous time t3;

[0020] The oil return temperature is detected to be less than a third set temperature T3 for a continuous time t4;

[0021] The water inlet temperature is detected to be greater than or equal to a fourth set temperature T4 for a continuous time t5.

[0022] In an embodiment, the first set time t1 is 5 hours, the first set temperature T1, the second set temperature T2, the third set temperature T3 are all 5℃, and the fourth set temperature T4 is 20℃.

[0023] Preferably, when the water preheating system is turned on, the following steps are performed:

[0024] S1. Keep the opening degree of the water amount adjusting valve as P1 for continuous time t6;

[0025] S2. Determine whether the saturation temperature corresponding to the system condensing pressure is less than or equal to a set value C1. If yes, keep the current opening degree of the water amount adjusting valve; if no, reduce the opening degree P2 of the water amount adjusting valve;

[0026] S3. Keep running for continuous time t7, and determine whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to a set value C2. If yes, reduce the opening degree P3 of the water amount adjusting valve; if no, keep the current opening degree unchanged;

[0027] S4. Keep running for continuous time t8, and determine whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to a set value C3. If yes, reduce the opening degree P4 of the water amount adjusting valve; if no, keep the current opening degree unchanged.

[0028] In an embodiment, the following parameters are respectively: time t6, time t7 and time t8 are 5 minutes; opening degree P1 is 100%, opening degree P2 is 25%, opening degree P3 is 30%, and opening degree P4 is 40%; set value C1 is 25℃, set value C2 is 30℃, and set value C3 is 40℃.

[0029] Preferably, when the water preheating system is running, the supercooling valve electromagnetic valve and the oil return electromagnetic valve are opened, the compressor controls the frequency according to the system target capacity and target high pressure, the heating electronic expansion valve, the indoor electronic expansion valve, the injection expansion valve and the supercooling electronic expansion valve are all adjusted to the maximum opening degree.

[0030] Preferably, the preheating control method controls the water preheating system to be turned off when any one of the following conditions is met:

[0031] The heat pump unit has been running for more than or equal to t9;

[0032] The saturation temperature corresponding to the system condensing pressure is detected to be greater than or equal to a set value C4 for continuous time t10;

[0033] The system is shut down, stopped or stopped at a temperature set point.

[0034] In an embodiment, time t9 is 30 minutes, time t10 is 10 minutes, and set value C4 is 40℃.

[0035] This invention adds a water preheating system to the existing water source heat pump system to preheat the refrigerant in the gas-liquid separator, liquid storage tank and oil separator when the unit starts at low temperature, so as to achieve the purpose of rapid heating after the unit has been placed at low temperature for a long time, thereby improving the user experience and the effect of rapid heating. Attached Figure Description

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, wherein:

[0037] Figure 1 This is a system diagram of the water source heat pump unit proposed in this invention;

[0038] Figure 2 This is a flowchart of the low-temperature start-up preheating control method proposed in this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the invention and do not constitute a limitation thereof.

[0040] like Figure 1 As shown, the water source heat pump unit includes a compressor 1, an oil separator 2, a four-way valve 3, an outdoor heat exchanger 4, an electronic expansion valve 5, a liquid storage tank 6, and a gas-liquid separator 14, all connected by pipelines. Preferably, the outdoor heat exchanger 4 is a water-cooled plate heat exchanger, and its refrigerant inlet pipe is equipped with an inlet pipe temperature sensor 16. A one-way valve 7 is installed on the high-pressure pipeline from the refrigerant outlet of the oil separator to the four-way valve. A high-pressure sensor 9 is installed at the outlet of the one-way valve. A first branch 8 is led out from the outlet pipeline of the one-way valve, and the other end of the first branch is connected to the liquid storage tank 6. A pressure-boosting valve 10 is installed on the first branch near the liquid storage tank. The function of the first branch is to inject gaseous refrigerant into the liquid storage tank when the refrigerant in the pipeline is insufficient, thereby pressurizing the liquid storage tank and forcing the refrigerant in the liquid storage tank out into the system pipeline. The oil return pipeline of the oil separator 2 is equipped with an oil return temperature sensor 11, an oil return solenoid valve 12, and a pressure-reducing device 13. The oil is depressurized by the pressure reducing device 13 and then returned to the compressor 1. The gas outlet of the gas-liquid separator 14 is connected to the suction port of the compressor through a pipe, and the outlet pipe is equipped with an outlet pipe temperature sensor 15.

[0041] Furthermore, the water source heat pump system also includes a subcooler 17. The outlet of the liquid storage tank 6 is divided into two branches. One branch enters the subcooler 17 for subcooling and then connects to the indoor unit through a valve. The other branch enters the subcooler after being cooled by the subcooler's electronic expansion valve 18, and then connects to the gas-liquid separator 14 through a second branch 19. A subcooling solenoid valve 20 is provided on the second branch. A third branch 21 is led out between the subcooling solenoid valve and the subcooler, and its other end is connected to the gas injection port of the compressor 1. An enthalpy injection valve 22 is provided on the third branch.

[0042] In the heating cycle, the high-temperature and high-pressure gas refrigerant discharged by the compressor 1 is sent to the indoor unit for heating through the oil separator 2, the four-way valve 3 and the valve, the medium-temperature liquid refrigerant returned by the indoor unit passes through the cooler 17, the liquid accumulator 6, the electronic expansion valve 5 to the outdoor heat exchanger 4, and the refrigerant is gasified in the outdoor heat exchanger and then returns to the compressor 1 through the four-way valve 3 and the gas-liquid separator 14.

[0043] In the winter low-temperature state and when the unit is stopped for a long time, a large amount of liquid refrigerant will be accumulated in the oil separator, the liquid accumulator and the gas-liquid separator, and if the heating cycle is started at this time, the system heating will be delayed. In order to solve this problem, the water preheating system is added to the existing heat pump system, and the refrigerant in the gas-liquid separator, the liquid accumulator and the oil separator is heated by using hot water, so that the unit can quickly produce heating effect when it is started after being placed for a long time in low temperature.

[0044] As shown in Figure 1 The water preheating system of the present application is shown by the dotted line in the figure, which comprises a flow regulating valve 23 and a coil 24 located at the bottom of the oil separator, the liquid accumulator and the gas-liquid separator, which are sequentially connected by pipelines. A one-way valve 25 is arranged on the pipeline of the water system. The heat source of the water preheating system can be an external electric heater, a boiler or part of the high-pressure exhaust of the heat pump unit. The water in the preheating water system is heated and then enters the system through the water inlet side, passes through the flow regulating valve 23 to the liquid accumulator 6, then to the gas-liquid separator 14, and then to the oil separator 2 and is discharged from the water outlet side, and returns to the heat source. A water pump is also arranged in the preheating water system. The preheating water is usually heated to 20℃.

[0045] Figure 2 The flow chart of the low-temperature starting preheating control method of the present application.

[0046] When the following conditions are met at the same time, the water preheating system is started:

[0047] The shutdown time is greater than the first set time t1;

[0048] The temperature of the refrigerant inlet pipe of the outdoor heat exchanger is detected to be less than the first set temperature T1 for t2 consecutive times;

[0049] The temperature of the gas-liquid separator outlet pipe is detected to be less than the second set temperature T2 for t3 consecutive times;

[0050] The oil return temperature is detected to be less than the third set temperature T3 for t4 consecutive times;

[0051] The water inlet temperature is detected to be greater than or equal to the fourth set temperature T4 for t5 consecutive times.

[0052] When the water preheating system is started, the following steps are performed:

[0053] S1. Keep the opening of water flow regulating valve as P1 for continuous time t6;

[0054] S2. Determine whether the saturation temperature corresponding to the system condensing pressure is less than or equal to the set value C1. If yes, keep the current opening of water flow regulating valve; if no, decrease the opening P2 of water flow regulating valve.

[0055] S3. For continuous running time t7, determine whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to the set value C2. If yes, decrease the opening P3 of water flow regulating valve; if no, keep the current opening unchanged.

[0056] S4. For continuous running time t8, determine whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to the set value C3. If yes, decrease the opening P4 of water flow regulating valve; if no, keep the current opening unchanged.

[0057] The above steps continue until the water flow regulating valve is closed and the water preheating operation is exited.

[0058] When the water preheating system is running, open the supercooler electromagnetic valve 23 and the oil return electromagnetic valve 12. The compressor frequency is controlled according to the target capacity and the target high pressure. The heating electronic expansion valve, the indoor electronic expansion valve, the injection expansion valve and the supercooler electronic expansion valve are all adjusted to the maximum opening.

[0059] The water preheating system is closed when any of the following conditions is met:

[0060] The continuous running time of the heat pump unit is greater than or equal to t9;

[0061] The saturation temperature corresponding to the system condensing pressure is detected to be greater than or equal to the set value C4 for continuous time t10;

[0062] The system is shut down, stopped or stopped at the temperature set point.

[0063] In an embodiment, the water preheating system is controlled in the following mode:

[0064] The water preheating system is started to run when the system detects that the following conditions are met at the same time: the shutdown time is greater than or equal to 5 hours, the refrigerant inlet pipe temperature is less than 5℃, the gas-liquid separator outlet pipe temperature is less than 5℃, the oil return temperature is less than 5℃, and the water inlet temperature is greater than or equal to 20℃.

[0065] When the water preheating operation is entered, the water flow regulating valve 23 is opened, and hot water enters the liquid storage tank 6, the gas-liquid separator 14 and the oil separator 2 in turn, and exchanges heat with the refrigerant through the coil 24 arranged in these components. During operation, the water flow regulating valve is controlled according to the system high pressure feedback. When the high pressure meets certain conditions, the water flow regulating valve is closed.

[0066] When the heat pump system detects that the water preheating cycle is in progress, open the supercooler solenoid valve 20 and the oil return solenoid valve 12, the compressor frequency is controlled according to the system target capacity and the target high pressure control frequency, the electronic expansion valve 5, the indoor electronic expansion valve, the injection expansion valve 22 and the supercooler electronic expansion valve 18 are all adjusted to the maximum opening.

[0067] When the system detects any of the following conditions, control the water preheating cycle to end: the unit continuous operation time is greater than or equal to 30 minutes, or the system condensing pressure corresponding to the saturation temperature is greater than or equal to 40℃, or the system is shut down, or the set temperature point is reached and the system is shut down.

[0068] The low-temperature start preheating control method provided by the application can be used for ordinary air-cooled heat pumps, water source heat pumps and water source multi-split units.

[0069] The above is only a specific embodiment of the application. It should be noted that any modification, equivalent replacement and change made within the spirit and framework of the application should be included in the protection scope of the application.

Claims

1. A water source heat pump unit comprising an oil separator, a receiver tank, and a gas-liquid separator, characterized by, The water preheating system comprises a heat source, a flow regulating valve, a coil pipe arranged in the oil separator, the liquid storage tank and the gas-liquid separator, and a one-way valve.

2. The water source heat pump unit of Claim 1, wherein, The heat source of the water preheating system is an electric heater, a boiler or high-pressure exhaust gas of the water source heat pump unit.

3. The water source heat pump unit of claim 1, wherein, The water source heat pump unit comprises a compressor, an oil separator, a four-way valve, an outdoor heat exchanger, an electronic expansion valve and a liquid storage tank.

4. The water source heat pump unit of claim 3, wherein, The high-pressure inlet pipe of the four-way valve leads to a first branch, the other end of the first branch being connected to the liquid storage tank, and a pressurizing valve being arranged on the first branch.

5. The water source heat pump unit of claim 3, wherein, An oil return temperature sensor, an oil return electromagnetic valve and a pressure reducing device are arranged on the oil return pipe of the oil separator.

6. The water source heat pump unit of claim 3, wherein, An outlet pipe temperature sensor is arranged on the gas outlet pipe of the gas-liquid separator.

7. The water source heat pump unit of claim 3, wherein, The outdoor heat exchanger is a water-cooled plate heat exchanger, and an inlet pipe temperature sensor is arranged on the refrigerant inlet pipe of the outdoor heat exchanger.

8. The water source heat pump unit of claim 3, wherein, A subcooler is further arranged, and the outlet of the liquid storage tank is divided into two branches, one of which is connected to the subcooler and then connected to the indoor unit through a valve, and the other of which is connected to the subcooler through an electronic expansion valve of the subcooler and then connected to the gas-liquid separator through a second branch.

9. The water source heat pump unit of claim 8, wherein, A subcooling electromagnetic valve is arranged on the second branch, and a third branch is led out between the subcooling electromagnetic valve and the subcooler, the other end of the third branch being connected to the air supplementing port of the compressor, and a spray enthalpy valve being arranged on the third branch.

10. A low temperature start preheating control method for the water source heat pump unit according to any one of claims 1-9, characterized in that, When the water source heat pump unit is started in a low-temperature state, the water preheating system is started first and the following steps are performed: S1. The opening degree of the water amount regulating valve is kept as P1 for a continuous time t6; S2. It is determined whether the saturation temperature corresponding to the system condensing pressure is less than or equal to a set value C1, if yes, the water amount regulating valve is kept at the current opening degree; if no, the opening degree of the water amount regulating valve is reduced by P2; S3. It is determined whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to a set value C2 for a continuous running time t7, if yes, the opening degree of the water amount regulating valve is reduced by P3; if no, the current opening degree is kept unchanged; S4. It is determined whether the saturation temperature corresponding to the system condensing pressure is greater than or equal to a set value C3 for a continuous running time t8, if yes, the opening degree of the water amount regulating valve is reduced by P4; if no, the current opening degree is kept unchanged.

11. The low-temperature start-up preheat control method of claim 10, wherein, The water preheating system is started when the following conditions are met simultaneously: The shutdown time is greater than or equal to a first set time t1; The refrigerant inlet pipe temperature of the outdoor heat exchanger is less than a first set temperature T1 for a continuous time t2; The outlet pipe temperature of the gas-liquid separator is less than a second set temperature T2 for a continuous time t3; The oil return temperature is less than a third set temperature T3 for a continuous time t4; The water inlet temperature of the outdoor heat exchanger is greater than or equal to a fourth set temperature T4 for a continuous time t5.

12. The low-temperature start-up pre-heat control method of claim 11, wherein, The first set time t1 is 5 hours, the first set temperature T1, the second set temperature T2 and the third set temperature T3 are all 5℃, and the fourth set temperature T4 is 20℃.

13. The subzero starting preheat control method of claim 10 wherein, The following parameters are respectively: time t6, time t7 and time t8 are 5 minutes; opening degree P1 is 100%, opening degree P2 is 25%, opening degree P3 is 30%, and opening degree P4 is 40%; the set value C1 is 25℃, the set value C2 is 30℃, and the set value C3 is 40℃.

14. The subzero starting preheat control method of claim 10 wherein, When the water preheating system is running, the supercooling electromagnetic valve and the oil return electromagnetic valve are opened, the compressor operating frequency is controlled according to the system target capacity and the target high pressure control frequency, the heating electronic expansion valve, the indoor electronic expansion valve, the spray electronic expansion valve and the supercooler electronic expansion valve are all adjusted to the maximum opening degree.

15. The subzero starting preheat control method of claim 10 wherein, The water preheating system is closed when any of the following conditions is met: The continuous running time of the heat pump unit is greater than or equal to t9; The continuous time t10 detects that the saturation temperature corresponding to the system condensing pressure is greater than or equal to the set value C4; The system is shut down, stopped or stopped at the temperature set point.

16. The subzero starting preheat control method of claim 15 wherein, The time T9 is 30 minutes, the time t10 is 10 minutes, and the set value C4 is 40℃.

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