A method for controlling a return of liquid in a heat pump system

Abstract

A kind of back liquid control method of heat pump system, the heat pump system, including compressor, first heater and oil pool temperature sensor are arranged in the bottom oil pool of compressor, frequency conversion fan is arranged in the side of evaporator, condensation temperature sensor is arranged at the outlet of refrigerant side of plate heat exchanger, obtain oil pool temperature TOIL by detecting and through oil pool temperature sensor, obtain condensation temperature TC by detecting and through condensation temperature sensor, the central controller of heat pump system is electrically connected with frequency conversion fan, timer, oil pool temperature sensor, electronic expansion valve, first heater, condensation temperature sensor respectively.The condensation temperature TC in the heat pump system is compared with the oil pool temperature TOIL of compressor in the present application, back liquid is controlled, the possibility of back liquid of heat pump system is greatly reduced, to ensure the long-term stable and reliable operation of heat pump system.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of back fluid control method of heat pump system. BACKGROUND

[0002] In heat pump system, liquid strike is one of the important factors leading to compressor serious damage, once the liquid strike phenomenon appears, it will often cause compressor damage, and even cylinder explosion and other consequences, and then it can cause the motor of compressor to burn and pollute system pipeline etc..Since compressor damage often causes great economic loss to user, such as leading to important equipment in refrigeration environment to appear fault, need to replace damaged compressor and clean contaminated pipeline etc..Therefore, it is particularly important to prevent compressor from liquid strike.

[0003] Chinese patent document No.CN 106679239A disclosed a kind of compressor oil return control method and device, air conditioning system, wherein the method includes: obtaining the high pressure and low pressure of the compressor to be measured in the state of starting;The high pressure is converted into first saturated temperature value, and the low pressure is converted into second saturated temperature value;Obtain the third temperature value of the compressor to be measured, and the fourth temperature value of the suction of the compressor to be measured;According to the first difference between the third temperature value and the first saturated temperature value, and the second difference between the fourth temperature value and the second saturated temperature value, the working state of the compressor to be measured is controlled.This kind of oil return control method is not ideal in actual use effect, and needs to be improved. SUMMARY

[0004] The purpose of the present application is to provide a kind of back fluid control method of heat pump system reliable in operation, to overcome the deficiencies in prior art.

[0005] A kind of back fluid control method of heat pump system designed according to this purpose, it is characterized in that the heat pump system, including compressor, the high pressure outlet of the compressor is connected with the refrigerant side inlet of plate heat exchanger through electromagnetic four-way valve, the refrigerant side outlet of plate heat exchanger is connected with one end of evaporator through electronic expansion valve, the other end of evaporator is connected with the low pressure inlet of compressor through electromagnetic four-way valve, first heater and oil pool temperature sensor are arranged in the bottom oil pool of compressor, frequency conversion fan is arranged on the side of evaporator, condensation temperature sensor is arranged at the refrigerant side outlet of plate heat exchanger, obtain oil pool temperature TOIL by detecting with oil pool temperature sensor, obtain condensation temperature TC by detecting with condensation temperature sensor, the central controller of heat pump system is electrically connected with frequency conversion fan, timer, oil pool temperature sensor, electronic expansion valve, first heater, condensation temperature sensor respectively, when operating, including the following steps:

[0006] Step one, system power on, enter step two;

[0007] Step two, normal operation, enter step three;

[0008] Step three, through the central controller to collect the oil pool temperature TOIL and condensing temperature TC, and calculate N value, N = TOIL-TC; enter step four;

[0009] Step four, the central controller judges whether N≥A is true, when it is true, enter step two, otherwise enter step five; wherein, M is the first safety value, the value range of M is 5℃-10℃;

[0010] Step five, the central controller judges whether A>N≥B is true, when it is true, enter step six, otherwise enter step nineteen; wherein, B is the second safety value, the value range of B is -2℃-2℃;

[0011] Step six, on the basis of the current frequency converter fan speed, the central controller increases its speed by 50r / min, after time T, enter step seven; the value range of T is 5s-5min;

[0012] Step seven, the central controller judges whether N≥A is true, when it is true, enter step two, otherwise enter step eight;

[0013] Step eight, the central controller judges whether the current speed of the frequency converter fan reaches its maximum allowable speed, when it is true, enter step nine, otherwise enter step six;

[0014] Step nine, on the basis of the current electronic expansion valve opening, the central controller closes its opening by 10P, enter step ten;

[0015] Step ten, the central controller judges whether N≥A is true, when it is true, enter step two, otherwise enter step eleven;

[0016] Step eleven, the central controller judges whether the opening of the electronic expansion valve reaches its minimum allowable opening, when it is true, enter step twelve, otherwise enter step nine;

[0017] Step twelve, the central controller starts the first heater, enter step thirteen;

[0018] Step thirteen, the central controller judges whether N≥A is true, when it is true, enter step two, otherwise enter step eighteen;

[0019] Step eighteen, stop;

[0020] Step nineteen, the central controller adjusts the speed of the frequency converter fan to the maximum speed, adjusts the opening of the electronic expansion valve to the minimum opening; and simultaneously starts the first heater; after time T, enter step twenty;

[0021] Step twenty, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step twenty-one;

[0022] Step twenty-one, the central controller judges whether A>N≥B is established, when it is established, enters step six, otherwise enters step twenty-two;

[0023] Step twenty-two, stop.

[0024] Further, the bottom oil pool of the compressor is further provided with a second heater and a third heater, and when the central controller judges that N≥A is not established in step thirteen, enters step fourteen;

[0025] Step fourteen, the central controller starts the second heater, and enters step fifteen;

[0026] Step fifteen, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step sixteen;

[0027] Step sixteen, the central controller starts the third heater, and enters step seventeen;

[0028] Step seventeen, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step eighteen.

[0029] The present application controls the backflow by comparing the condensing temperature TC and the compressor oil pool temperature TOIL in the heat pump system, and when the heat pump system is normally operated, the temperature difference between the compressor oil pool temperature TOIL and the condensing temperature TC should be above 5-10℃; if the temperature difference is lower than this, the backflow is possible. According to this characteristic, the present application controls the backflow, greatly reduces the possibility of backflow of the heat pump system, and thus ensures the long-term stable and reliable operation of the heat pump system. BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 It is a structural schematic view of an embodiment of the present application.

[0031] Fig. 2 It is a control principle diagram of the present application.

[0032] Fig. 3 It is a control block diagram of the present application.

[0033] In the figure: 1 is an evaporator, 2 is an ambient temperature sensor, 3 is an electromagnetic four-way valve, 4 is a return gas temperature sensor, 5 is an exhaust pressure sensor, 6 is an exhaust temperature sensor, 7 is a plate heat exchanger, 8 is a flow sensor, 9 is an exhaust valve, 10 is an electronic expansion valve, 11 is a return gas pressure sensor, 12 is a compressor, 13 is an inlet water temperature sensor, 14 is a water pump, 15 is an outlet water temperature sensor, 21 is a variable frequency fan, 22 is a first heater, 23 is an oil pool temperature sensor, and 24 is a condensation temperature sensor. DETAILED DESCRIPTION

[0034] The application will be further described below in conjunction with the accompanying drawings and examples.

[0035] Reference Figs. 1-3 A return liquid control method for a heat pump system, the heat pump system comprising a compressor 12, a high-pressure outlet of the compressor 12 being connected to a refrigerant-side inlet of a plate heat exchanger 7 through an electromagnetic four-way valve 3, a refrigerant-side outlet of the plate heat exchanger 7 being connected to one end of an evaporator 1 through an electronic expansion valve 10, the other end of the evaporator 1 being connected to a low-pressure inlet of the compressor 12 through the electromagnetic four-way valve 3, a first heater 22 and an oil pool temperature sensor 23 being arranged in an oil pool at the bottom of the compressor 12, a variable frequency fan 21 being arranged on the side of the evaporator 1, a condensation temperature sensor 24 being arranged at the refrigerant-side outlet of the plate heat exchanger 7, the oil pool temperature TOIL being detected and obtained by the oil pool temperature sensor 23, and the condensation temperature TC being detected and obtained by the condensation temperature sensor 24, a central controller of the heat pump system being electrically connected to the variable frequency fan 21, a timer, the oil pool temperature sensor 23, the electronic expansion valve 10, the first heater 22, and the condensation temperature sensor 24.

[0036] According to the temperature difference N between the compressor oil pool temperature TOIL and the condensation temperature TC, the system operation return liquid condition is divided into three regions, which are 1) a return liquid safety region, N≥A, 2) a return liquid control region, A>N≥B, and 3) a severe return liquid region, B>N.

[0037] Wherein, N=TOIL-TC, A is a first safety value, the value range of A is 5℃-10℃, B is a second safety value, the value range of B is -2℃-2℃, and N is a temperature difference value.

[0038] In the operation of the heat pump system, the temperature difference value N between the compressor oil pool temperature TOIL and the condensation temperature TC is timely detected and compared to determine the interval of the temperature difference value N.

[0039] When the temperature difference value N is in the return liquid safety region, the heat pump system is not adjusted and normally operated.

[0040] When the temperature difference value N is in the liquid return control area, that is, the heat pump system runs in the liquid return control area, the central controller first controls the variable frequency air fan to speed up the speed of the variable frequency air fan. Every 10 seconds, the speed of the variable frequency air fan is increased by 50 r / min or 10% on the basis of the current speed. The central controller judges whether the heat pump system runs in the liquid return safety area every time the speed is adjusted. Otherwise, the speed of the variable frequency air fan is always adjusted to the highest speed.

[0041] If the variable frequency air fan is adjusted to the highest speed, and the heat pump system still runs in the liquid return control area, the central controller adjusts the opening of the electronic expansion valve. Every 30 seconds, the opening is reduced by 10P. The central controller judges whether the heat pump system runs in the liquid return safety area every time. Otherwise, the opening of the electronic expansion valve is gradually reduced until the heat pump system runs in the liquid return safety area. Otherwise, the opening of the electronic expansion valve is always adjusted until the minimum opening of the electronic expansion valve allowed by the heat pump system.

[0042] If the opening of the electronic expansion valve has been adjusted to the minimum opening, and the heat pump system still cannot reach the liquid return safety area, the first heater 22 provided in the bottom oil pool of the compressor 12 needs to be turned on for electric heating. If the heat pump system can run in the liquid return safety area after the first heater 22 is turned on for electric heating, the system continues to run normally. If the heat pump system cannot run back to the liquid return safety area after the first heater 22 is turned on, the system stops running after 3 minutes.

[0043] In this embodiment, a second heater and / or a third heater can be added in the bottom oil pool of the compressor 12 to control the heating process and ensure that the heat pump system can run in the liquid return safety area.

[0044] Specific operations include the following steps:

[0045] Step one, power on the system, enter step two;

[0046] Step two, normal operation, enter step three;

[0047] Step three, the central controller collects the oil pool temperature TOIL and the condensation temperature TC, and calculates the value N, N = TOIL-TC; enter step four;

[0048] Step four, the central controller judges whether N≥A is true. When it is true, enter step two, otherwise enter step five; where A is the first safety value, the value range of A is 5℃-10℃;

[0049] Step five, the central controller judges whether A>N≥B is true. When it is true, enter step six, otherwise enter step nineteen; where B is the second safety value, the value range of B is -2℃-2℃;

[0050] Step six, on the basis of the current variable frequency fan speed, the speed of the variable frequency fan is increased by 50 r / min, and after a time T, step seven is entered; the value of T is in the range of 5 s to 5 min;

[0051] Step seven, the central controller judges whether N≥A is true, when it is true, step two is entered, otherwise step eight is entered;

[0052] Step eight, the central controller judges whether the current speed of the variable frequency fan 21 reaches its maximum allowable speed, when it is true, step nine is entered, otherwise step six is entered;

[0053] Step nine, on the basis of the current opening of the electronic expansion valve, the opening of the electronic expansion valve is closed by 10P, and step ten is entered;

[0054] Step ten, the central controller judges whether N≥A is true, when it is true, step two is entered, otherwise step eleven is entered;

[0055] Step eleven, the central controller judges whether the opening of the electronic expansion valve 10 reaches its minimum allowable opening, when it is true, step twelve is entered, otherwise step nine is entered;

[0056] Step twelve, the central controller starts the first heater 22, and step thirteen is entered;

[0057] Step thirteen, the central controller judges whether N≥A is true, when it is true, step two is entered, otherwise step eighteen is entered;

[0058] Step eighteen, stop;

[0059] Step nineteen, the central controller adjusts the speed of the variable frequency fan to the maximum speed, adjusts the opening of the electronic expansion valve to the minimum opening, and simultaneously starts the first heater 22; after a time T, step twenty is entered.

[0060] After the judgment of step five, the heat pump system is in a severe backflow area, so the central controller controls the variable frequency fan, the electronic expansion valve and the first heater 22 to adjust or start working at the same time.

[0061] Step twenty, the central controller judges whether N≥A is true, when it is true, step two is entered, otherwise step twenty-one is entered;

[0062] Step twenty-one, the central controller judges whether A>N≥B is true, when it is true, step six is entered, otherwise step twenty-two is entered;

[0063] Step twenty-two, stop.

[0064] Further, the bottom oil pool of the compressor 12 is also provided with a second heater and a third heater, and when N≥A is not true in step thirteen, step fourteen is entered.

[0065] Step fourteen, the central controller opens the second heater, and enters step fifteen;

[0066] Step fifteen, the central controller judges whether N>=A is true, when it is true, it enters step two, otherwise it enters step sixteen;

[0067] Step sixteen, the central controller opens the third heater, and enters step seventeen;

[0068] Step seventeen, the central controller judges whether N>=A is true, when it is true, it enters step two, otherwise it enters step eighteen.

[0069] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. The terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0070] The basic principles and main features of the present application and the advantages of the present application have been shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of controlling a return of refrigerant in a heat pump system, characterized by The heat pump system, including compressor (12), the high pressure outlet of compressor (12) is connected with the refrigerant side inlet of plate heat exchanger (7) through electromagnetic four-way valve (3), the refrigerant side outlet of plate heat exchanger (7) is connected with one end of evaporator (1) through electronic expansion valve (10), the other end of evaporator (1) is connected with the low pressure inlet of compressor (12) through electromagnetic four-way valve (3), the bottom oil pool of compressor (12) is provided with first heater (22) and oil pool temperature sensor (23), the side of evaporator (1) is provided with variable frequency fan (21), the refrigerant side outlet of plate heat exchanger (7) is provided with condensation temperature sensor (24), the oil pool temperature TOIL is detected and obtained through oil pool temperature sensor (23), the condensation temperature TC is detected and obtained through condensation temperature sensor (24), the central controller of heat pump system is electrically connected with variable frequency fan (21), timer, oil pool temperature sensor (23), electronic expansion valve (10), first heater (22), condensation temperature sensor (24), when operating, including the following steps: Step one, the system is powered on, and enters step two; Step two, normal operation, enter step three; Step three, the oil pool temperature TOIL and the condensation temperature TC are collected by the central controller, and N value is calculated, N=TOIL-TC;Enter step four; Step four, the central controller judges whether N≥A is established, when it is established, enter step two, otherwise enter step five;Wherein, A is the first safety value, the value range of A is 5℃-10℃; Step five, the central controller judges whether A>N≥B is established, when it is established, enter step six, otherwise enter step nineteen;Wherein, B is the second safety value, the value range of B is-2℃-2℃; Step six, on the basis of the current speed of variable frequency fan, the speed of the central controller is increased by 50r / min, after time T, enter step seven;The value range of T is 5s-5min; Step seven, the central controller judges whether N≥A is established, when it is established, enter step two, otherwise enter step eight; Step eight, the central controller judges whether the current speed of variable frequency fan (21) reaches the maximum speed, when it is established, enter step nine, otherwise enter step six; Step nine, on the basis of the current opening of electronic expansion valve, the opening of the central controller is closed by 10P, enter step ten; Step ten, the central controller judges whether N≥A is established, when it is established, enter step two, otherwise enter step eleven; Step eleven, the central controller judges whether the opening of electronic expansion valve (10) reaches the minimum opening, when it is established, enter step twelve, otherwise enter step nine; Step twelve, the central controller starts first heater (22), enter step thirteen; Step thirteen, the central controller judges whether N≥A is established, when it is established, enter step two, otherwise enter step eighteen; Step eighteen, stop; Step nineteen, the central controller adjusts the speed of variable frequency fan to the maximum speed, adjusts the opening of electronic expansion valve to the minimum opening, and simultaneously starts first heater (22);After time T, enter step twenty; Step twenty, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step twenty-one; Step twenty-one, the central controller judges whether A>N≥B is established, when it is established, enters step six, otherwise enters step twenty-two; Step twenty-two, stop.

2. The method of claim 1, wherein the method further comprises: The bottom oil pool of the compressor (12) is also provided with a second heater and a third heater, and when the central controller judges that N≥A is not established in step thirteen, it enters step fourteen; Step fourteen, the central controller starts the second heater and enters step fifteen; Step fifteen, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step sixteen; Step sixteen, the central controller starts the third heater and enters step seventeen; Step seventeen, the central controller judges whether N≥A is established, when it is established, enters step two, otherwise enters step eighteen.

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