CN112611041B - Air conditioning unit and electronic expansion valve control method - Google Patents

Air conditioning unit and electronic expansion valve control method Download PDF

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Publication number
CN112611041B
CN112611041B CN202011505765.2A CN202011505765A CN112611041B CN 112611041 B CN112611041 B CN 112611041B CN 202011505765 A CN202011505765 A CN 202011505765A CN 112611041 B CN112611041 B CN 112611041B
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temperature
expansion valve
pressure
electronic expansion
condenser
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CN112611041A (en
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陈见兴
李根源
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Qingdao Hisense Hitachi Air Conditioning System Co Ltd
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Qingdao Hisense Hitachi Air Conditioning System Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
    • F24F5/001—Compression cycle type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F24F11/64—Electronic processing using pre-stored data
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • F24F11/84—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/89—Arrangement or mounting of control or safety devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Physics & Mathematics (AREA)
  • Fuzzy Systems (AREA)
  • Mathematical Physics (AREA)
  • Air Conditioning Control Device (AREA)

Abstract

The application discloses an air conditioning unit and an electronic expansion valve control method, wherein the air conditioning unit comprises a refrigerant circulation loop, a compressor, a condenser, an electronic expansion valve, an evaporator and a controller, and is configured to: acquiring first operation parameters, second operation parameters, third operation parameters, evaporator pressure and compressor power in the operation of the air conditioning unit, wherein the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the exhaust pressure and exhaust temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature; determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power; and controlling the opening of the electronic expansion valve through the target opening, so that the opening of the electronic expansion valve is accurately controlled, and the hysteresis motion or frequent motion of the electronic expansion valve is reduced.

Description

Air conditioning unit and electronic expansion valve control method
Technical Field
The application relates to the field of air conditioner control, in particular to an air conditioner unit and an electronic expansion valve control method.
Background
The expansion valve is a key component of the air conditioning system, and the speed and the stability of the adjustment of the expansion valve are related to the stability of the air conditioning system and the effect of refrigerating and heating, so that the comfort of a user is indirectly influenced. When the stability of the system is poor, long-term fluctuation occurs, and the service life of the air conditioning unit is further influenced. Therefore, the regulation of the expansion valve is critical in air conditioning systems. Particularly, under the low-temperature condition, the state change of the air conditioning system is sensitive, and the expansion valve needs to be accurately controlled, so that fluctuation is avoided, and balance is achieved quickly.
In the prior art, two typical control modes exist for a conventional unit, and one is based on suction superheat control. And measuring and calculating the suction superheat degree of the compressor in real time, and comparing the obtained superheat degree with a target superheat degree to control the action of the electronic expansion valve. The scheme has simple control mode, but the response of the temperature sensor is delayed compared with that of the pressure sensor, so that the calculated superheat degree is delayed, the action of the electronic expansion valve is delayed, the liquid level of the evaporator is fluctuated, and the performance of the unit is influenced. The other is based on liquid level control, which is adjusted according to the evaporator or condenser liquid level. The liquid level of the evaporator or the condenser is detected in real time, the detected liquid level is compared with the target liquid level, and the action of the electronic expansion valve is controlled, so that the method is suitable for units with low superheat degree such as full-liquid evaporators. According to the scheme, a liquid level sensor is required to be added, so that the unit cost is increased; the unit faults caused by the faults of the liquid level sensor are newly added, and the unit fault rate is improved; the liquid level measurement has certain hysteresis and fluctuation, so that the action of the electronic expansion valve is delayed, and therefore, the electronic expansion valve is periodically and frequently operated during control, and the service lives of the valve and the unit are influenced.
Therefore, how to accurately control the opening of the electronic expansion valve, and reduce the action lag and frequent actions of the electronic expansion valve is a technical problem to be solved at present.
Disclosure of Invention
The application provides an air conditioning unit for solving the technical problems of action lag and frequent action of an electronic expansion valve in the prior art, comprising:
a refrigerant circulation loop for circulating the refrigerant in a loop formed by the compressor, the condenser, the expansion valve and the evaporator;
the compressor is used for compressing the low-temperature low-pressure refrigerant gas into high-temperature high-pressure refrigerant gas and discharging the high-temperature high-pressure refrigerant gas to the condenser;
the condenser is used for radiating heat to the cooling water to condense the high-temperature and high-pressure refrigerant gas into high-temperature and high-pressure refrigerant liquid and discharging the high-temperature and high-pressure refrigerant liquid to the electronic expansion valve;
the electronic expansion valve is used for adjusting the flow of the refrigerant liquid;
an evaporator for evaporating the low-temperature low-pressure refrigerant liquid into low-temperature low-pressure refrigerant gas by absorbing heat from the chilled water and discharging the low-temperature low-pressure refrigerant gas to the compressor;
a controller configured to:
acquiring a first operation parameter, a second operation parameter, a third operation parameter, an evaporator pressure and a compressor power in the operation of the air conditioning unit;
determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power;
controlling the opening of the electronic expansion valve through the target opening;
the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the discharge pressure and discharge temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature.
In some embodiments, the controller is configured to:
comparing the target opening with the target opening at the last moment;
if the absolute value of the difference between the target opening and the target opening at the last moment is smaller than a preset value, controlling the opening of the electronic expansion valve to keep the target opening at the last moment;
and if the absolute value of the difference between the target opening and the target opening at the previous moment is greater than or equal to a preset value, adjusting the opening of the electronic expansion valve to the target opening.
In some embodiments, the controller is configured to:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second forward parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
In some embodiments, the theoretical specific enthalpy of intake air and the theoretical specific enthalpy of exhaust gas are determined according to the following formula
h(P,T)＝(p1+p2*x+p3*x^2+p4*x^3+p5*y+p6*y^2)/(1+p7*x+p8*x^2+p9*x^3+p10*y)
Wherein, P is the suction pressure or the exhaust pressure, T is the suction temperature or the exhaust temperature, P1, P2, P3, P4, P5, P6, P7, P8, P9 and P10 are preset empirical constants, x is the pressure, and y is the temperature.
In some embodiments, the theoretical specific enthalpy of the condenser effluent is determined based on the following formula:
h(P c ,T 4 )＝p1+p2*x+p3*x^2+p4*x^3+p5*x^4+p6*y+p7*y^2+p8*y^3+p9*y^4+p10*y^5；
wherein P is c For the condenser pressure, T 4 For the condenser liquid outlet temperature, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10 are preset empirical constants, x is pressure, and y is temperature.
In some embodiments, the refrigerant mass flow is determined according to the following formula:
wherein q m And h1 is the suction theoretical specific enthalpy, h2 is the discharge theoretical specific enthalpy, and N is the compressor power.
In some embodiments, the real-time refrigeration capacity is determined according to the following formula:
Q e ＝q m ＊ (h1-h4)；
wherein Q is e Q for the real-time refrigerating capacity m For the refrigerant mass flow, h1 is the suction theoretical specific enthalpy, h 4 Theoretical specific enthalpy of the condenser effluent is obtained.
In some embodiments, the target opening is determined according to the following formula:
K＝(p1+p2*Ln(x)+p3*(Ln(x))^2+p4*(Ln(x))^3+p5*Ln(y)+p6*(Ln(y))^2)/(1+p7*Ln(x)+p8*(Ln(x))^2+p9*Ln(y)+p10*(Ln(y))^2+p11*(Ln(y))^3)；
wherein K is the target opening degree, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11 are preset empirical constants, x is the real-time refrigerating capacity, and y is the condensing temperature.
Correspondingly, the application also provides a control method of the electronic expansion valve, which is applied to an air conditioning unit comprising a refrigerant circulation loop, a compressor, a condenser, the electronic expansion valve, an evaporator and a controller, and comprises the following steps:
acquiring first operation parameters, second operation parameters, third operation parameters, evaporator pressure and compressor power in the operation of the air conditioning unit, wherein the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the exhaust pressure and exhaust temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature;
determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power;
and controlling the opening of the electronic expansion valve through the target opening.
In some embodiments, the target opening degree of the electronic expansion valve is determined based on the first operation parameter, the second operation parameter, the third operation parameter, the evaporator pressure and the compressor power, specifically:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second forward parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
Compared with the prior art, the application has the following beneficial effects:
the application discloses an air conditioning unit and an electronic expansion valve control method, wherein the air conditioning unit comprises a refrigerant circulation loop, a compressor, a condenser, an electronic expansion valve, an evaporator and a controller, and is configured to: acquiring first operation parameters, second operation parameters, third operation parameters, evaporator pressure and compressor power in the operation of the air conditioning unit, wherein the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the exhaust pressure and exhaust temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature; determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power; and controlling the opening of the electronic expansion valve through the target opening, so that the opening of the electronic expansion valve is accurately controlled, and the hysteresis motion or frequent motion of the electronic expansion valve is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of an air conditioning unit according to an embodiment of the present application;
fig. 2 is a schematic flow chart of a control method of an electronic expansion valve according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the present application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.
The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Fig. 1 is a schematic view showing the structure of an air conditioning unit according to the present application, wherein the air conditioning unit performs a refrigerating cycle of the air conditioning unit by using a compressor, a condenser, an electronic expansion valve, and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and supplies a refrigerant to the air that has been conditioned and heat exchanged.
The low-temperature low-pressure refrigerant gas from the evaporator becomes the high-temperature high-pressure refrigerant gas, and the compressed refrigerant gas is discharged. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released into the cooling water through the condensation process.
The electronic expansion valve expands the liquid-phase refrigerant in a high-temperature and high-pressure state condensed in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the electronic expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator may achieve a cooling effect by exchanging heat with a material to be cooled using latent heat of evaporation of a refrigerant. In the whole cycle, the water chiller is used for preparing cold water, and then the cold water exchanges heat with indoor air through the tail ends of a fan coil and the like.
As described in the background art, in the prior art, due to the response lag of the temperature sensor, the action lag of the electronic expansion valve is caused, but in the solution based on the liquid level control, the liquid level sensor is required to be added, so that the cost is increased, and meanwhile, the liquid level measurement has certain lag and fluctuation, so as to cause the action lag of the electronic expansion valve, so that the electronic expansion valve periodically and frequently acts, therefore, the solution designs an air conditioning unit and an electronic expansion valve control method, so as to solve the problems of the action lag or the frequent action of the electronic expansion valve in the prior art.
To further describe the solution of the present application, in one example of the present application, the air conditioning unit includes:
a refrigerant circulation loop for circulating the refrigerant in a loop formed by the compressor, the condenser, the expansion valve and the evaporator;
the compressor is used for compressing the low-temperature low-pressure refrigerant gas into high-temperature high-pressure refrigerant gas and discharging the high-temperature high-pressure refrigerant gas to the condenser;
the condenser is used for radiating heat to the cooling water to condense the high-temperature and high-pressure refrigerant gas into high-temperature and high-pressure refrigerant liquid and discharging the high-temperature and high-pressure refrigerant liquid to the electronic expansion valve;
the electronic expansion valve is used for adjusting the flow of the refrigerant liquid;
an evaporator for evaporating the low-temperature low-pressure refrigerant liquid into low-temperature low-pressure refrigerant gas by absorbing heat from the chilled water and discharging the low-temperature low-pressure refrigerant gas to the compressor;
a controller configured to:
acquiring a first operation parameter, a second operation parameter, a third operation parameter, an evaporator pressure and a compressor power in the operation of the air conditioning unit;
determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power;
controlling the opening of the electronic expansion valve through the target opening;
the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the discharge pressure and discharge temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature.
In the embodiment of the application, the target opening of the electronic expansion valve of the air conditioning unit is determined by collecting a first operation parameter, a second operation parameter, a third operation parameter, an evaporator pressure and a compressor power in the operation process of the air conditioning unit, analyzing the real-time load of the air conditioning unit, wherein the target opening is the optimal opening of the electronic expansion valve determined by each operation parameter of the air conditioning unit, the opening of the electronic expansion valve is adjusted in real time according to the target opening, the first operation parameter is the suction pressure and the suction temperature of the compressor, the second operation parameter is the exhaust pressure and the exhaust temperature of the compressor, and the third operation parameter is the condenser pressure and the condenser liquid outlet temperature.
To accurately adjust the opening of the electronic expansion valve, in some embodiments, the controller is configured to:
comparing the target opening with the target opening at the last moment;
if the absolute value of the difference between the target opening and the target opening at the last moment is smaller than a preset value, controlling the opening of the electronic expansion valve to keep the target opening at the last moment;
and if the absolute value of the difference between the target opening and the target opening at the previous moment is greater than or equal to a preset value, adjusting the opening of the electronic expansion valve to the target opening.
In this embodiment, in order to avoid frequent operation of the electronic expansion valve, after the target opening of the electronic expansion valve is obtained, the target opening at this time is compared with the target opening at the previous time, if the absolute value of the difference between the target opening and the target opening at the previous time is smaller than a preset value, this means that the difference between the target opening at two times is not very large, the opening of the electronic expansion valve is not required to be adjusted, the opening of the electronic expansion valve is controlled to be kept at the target opening at the previous time, and if the absolute value of the difference between the target opening and the target opening at the previous time is not smaller than the preset value, this means that the difference between the target opening at two times is large, and the opening of the electronic expansion valve is not adjusted, which affects the performance of the air conditioning unit, so that the unnecessary adjustment operation of the electronic expansion valve is reduced by the above steps, and the service life of the electronic expansion valve is improved.
To accurately determine the target opening, in some embodiments, the controller is configured to:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second forward parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
In this embodiment, the specific process of determining the target opening degree is: the method comprises the steps of determining suction theoretical specific enthalpy of the compressor based on the first operation parameter, determining exhaust theoretical specific enthalpy of the compressor based on the second far operation parameter, determining condenser liquid outlet theoretical specific enthalpy based on the third operation parameter, further determining refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy and the exhaust theoretical specific enthalpy, determining real-time refrigerating capacity of the air conditioner unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow, and finally determining target opening degree of the electronic expansion valve based on the real-time refrigerating capacity, the evaporation temperature and the condensation temperature.
In order to obtain the theoretical specific enthalpy of intake and the theoretical specific enthalpy of exhaust, in some embodiments, the theoretical specific enthalpy of intake and the theoretical specific enthalpy of exhaust are determined according to the following formula
h(P,T)＝(p1+p2*x+p3*x^2+p4*x^3+p5*y+p6*y^2)/(1+p7*x+p8*x^2+p9*x^3+p10*y)
Wherein, P is the suction pressure or the exhaust pressure, T is the suction temperature or the exhaust temperature, P1, P2, P3, P4, P5, P6, P7, P8, P9 and P10 are preset empirical constants, x is the pressure, and y is the temperature.
In this embodiment, when the theoretical specific enthalpy of intake air is calculated, the theoretical specific enthalpy of intake air is h1 (P1, T1), and when the theoretical specific enthalpy of exhaust gas is calculated, the theoretical specific enthalpy of exhaust gas is h2 (P2, T2).
To determine the theoretical specific enthalpy of the condenser output, in some embodiments, the theoretical specific enthalpy of the condenser output is determined based on the following equation:
h(P c ,T 4 )＝p1+p2*x+p3*x^2+p4*x^3+p5*x^4+p6*y+p7*y^2+p8*y^3+p9*y^4+p10*y^5；
wherein P is c For the condenser pressure, T 4 For the condenser liquid outlet temperature, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10 are preset empirical constants, x is pressure, and y is temperature.
In the present embodiment, P c For the condenser pressure, T 4 For the temperature of the condenser effluent, the theoretical specific enthalpy of the condenser effluent is h (P c ,T 4 )。
In order to obtain the refrigerant mass flow, in a preferred embodiment of the present application, the refrigerant mass flow is determined according to the following formula:
wherein q m And h1 is the suction theoretical specific enthalpy, h2 is the discharge theoretical specific enthalpy, and N is the compressor power.
In the present embodiment, q m For the refrigerant mass flow, h1 is the suction theoretical specific enthalpy, h2 is the discharge theoretical specific enthalpy, and the compressor power N determines the refrigerant mass flow q by the suction theoretical specific enthalpy h1, the discharge theoretical specific enthalpy h2 m 。
In order to determine the real-time cooling capacity, in a preferred embodiment of the present application, the real-time cooling capacity is determined according to the following formula:
Q e ＝q m ＊(h1-h4)；
wherein Q is e Q for the real-time refrigerating capacity m For the refrigerant mass flow, h1 is the suction theoretical specific enthalpy, h 4 Theoretical specific enthalpy of the condenser effluent is obtained.
In order to determine the target opening, in a preferred embodiment of the present application, the target opening is determined according to the following formula:
K＝(p1+p2*Ln(x)+p3*(Ln(x))^2+p4*(Ln(x))^3+p5*Ln(y)+p6*(Ln(y))^2)/(1+p7*Ln(x)+p8*(Ln(x))^2+p9*Ln(y)+p10*(Ln(y))^2+p11*(Ln(y))^3)；
wherein K is the target opening degree, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11 are preset empirical constants, x is the real-time refrigerating capacity, and y is the condensing temperature.
The application discloses an air conditioning unit and an electronic expansion valve control method, wherein the air conditioning unit comprises a refrigerant circulation loop, a compressor, a condenser, an electronic expansion valve, an evaporator and a controller, and is configured to: acquiring first operation parameters, second operation parameters, third operation parameters, evaporator pressure and compressor power in the operation of the air conditioning unit, wherein the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the exhaust pressure and exhaust temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature; determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure, and the compressor power; and controlling the opening of the electronic expansion valve through the target opening, so that the opening of the electronic expansion valve is accurately controlled, and the hysteresis motion or frequent motion of the electronic expansion valve is reduced.
In order to further explain the technical idea of the present application, the present application further provides a control method of an electronic expansion valve, where the method is applied to an air conditioning unit including a refrigerant circulation loop, a compressor, a condenser, an electronic expansion valve, an evaporator and a controller, as shown in fig. 2, the specific steps of the method are as follows:
s201, acquiring a first operation parameter, a second operation parameter, a third operation parameter, an evaporator pressure and a compressor power in the operation of the air conditioning unit, wherein the first operation parameter is the suction pressure and the suction temperature of the compressor, the second operation parameter is the exhaust pressure and the exhaust temperature of the compressor, and the third operation parameter is the condenser pressure and the condenser liquid outlet temperature.
In this step, a first operation parameter, a second operation parameter, a third operation parameter, an evaporator pressure and a compressor power in the operation of the air conditioning unit are collected, so as to obtain a target opening of the electronic expansion valve through the above parameters, wherein the first operation parameter is an air suction pressure and an air suction temperature of the compressor, the second operation parameter is an air discharge pressure and an air discharge temperature of the compressor, and the third operation parameter is a condenser pressure and a condenser liquid outlet temperature.
S202, determining the target opening degree of the electronic expansion valve based on the first operation parameter, the second operation parameter, the third operation parameter, the evaporator pressure and the compressor power.
In this step, the target opening of the electronic expansion valve is determined by the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure and the compressor power.
And S203, controlling the opening of the electronic expansion valve through the target opening.
In order to accurately obtain the target opening of the electronic expansion valve, in some embodiments, the target opening of the electronic expansion valve is determined based on the first operating parameter, the second operating parameter, the third operating parameter, the evaporator pressure and the compressor power, which is specifically:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second forward parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be appreciated by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not drive the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims (8)

1. An air conditioning unit, comprising:
a refrigerant circulation loop for circulating the refrigerant in a loop formed by the compressor, the condenser, the expansion valve and the evaporator;
the compressor is used for compressing the low-temperature low-pressure refrigerant gas into high-temperature high-pressure refrigerant gas and discharging the high-temperature high-pressure refrigerant gas to the condenser;
the condenser is used for radiating heat to the cooling water to condense the high-temperature and high-pressure refrigerant gas into high-temperature and high-pressure refrigerant liquid and discharging the high-temperature and high-pressure refrigerant liquid to the electronic expansion valve;
the electronic expansion valve is used for adjusting the flow of the refrigerant liquid;
an evaporator for evaporating the low-temperature low-pressure refrigerant liquid into low-temperature low-pressure refrigerant gas by absorbing heat from the chilled water and discharging the low-temperature low-pressure refrigerant gas to the compressor;
a controller configured to:
acquiring a first operation parameter, a second operation parameter, a third operation parameter and a compressor power in the operation of the air conditioning unit;
determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter and the compressor power;
controlling the opening of the electronic expansion valve through the target opening;
the first operation parameters are the suction pressure and suction temperature of the compressor, the second operation parameters are the discharge pressure and discharge temperature of the compressor, and the third operation parameters are the condenser pressure and condenser liquid outlet temperature;
wherein the controller is configured to:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second operating parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
2. The air conditioning unit of claim 1, wherein the controller is configured to:
comparing the target opening with the target opening at the last moment;
if the absolute value of the difference between the target opening and the target opening at the last moment is smaller than a preset value, controlling the opening of the electronic expansion valve to keep the target opening at the last moment;
and if the absolute value of the difference between the target opening and the target opening at the previous moment is greater than or equal to a preset value, adjusting the opening of the electronic expansion valve to the target opening.
3. An air conditioning unit as claimed in claim 2, wherein the theoretical specific enthalpy of suction and the theoretical specific enthalpy of discharge are h (P, T) = (p1+p2 x+p3 x 2+p4 x 3+p5 y+p6 x 2)/(1+p7 x+p8 x 2+p9 x 3+p10 x y) determined according to the following formula
Wherein, P is the suction pressure or the exhaust pressure, T is the suction temperature or the exhaust temperature, P1, P2, P3, P4, P5, P6, P7, P8, P9 and P10 are preset empirical constants, x is the pressure, and y is the temperature.
4. The air conditioning assembly of claim 2, wherein the theoretical specific enthalpy of the condenser output is determined based on the following formula:
h(P c ,T 4 )＝p1+p2*x+p3*x^2+p4*x^3+p5*x^4+p6*y+p7*y^2+p8*y^3+p9*y
^4+p10*y^5；
wherein P is c For the condenser pressure, T 4 For the condenser outlet temperature, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10 are preset empirical constantsX is pressure and y is temperature.
5. The air conditioning unit of claim 2, wherein the refrigerant mass flow is determined according to the formula:
wherein q m For the refrigerant mass flow, h1 is the theoretical specific enthalpy of suction, h2 is the theoretical specific enthalpy of discharge, and N is the compressor power.
6. The air conditioning unit of claim 2, wherein the real-time cooling capacity is determined according to the following formula:
Q e ＝q m ＊(h1-h4)
wherein Q is e Q for the real-time refrigerating capacity m Is the refrigerant mass flow, h1 is the suction theoretical specific enthalpy, h 4 Theoretical specific enthalpy of the condenser effluent.
7. The air conditioning unit of claim 2, wherein the target opening is determined according to the following formula:
K＝(p1+p2*Ln(x)+p3*(Ln(x))^2+p4*(Ln(x))^3+p5*Ln(y)+p6*(Ln(y))^2)/(1+p7*Ln(x)+p8*(Ln(x))^2+p9*Ln(y)+p10*(Ln(y))^2+p11*(Ln(y))^3)；
wherein K is the target opening degree, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11 are preset empirical constants, x is the real-time refrigerating capacity, and y is the condensing temperature.
8. An electronic expansion valve control method, wherein the method is applied to an air conditioning unit comprising a refrigerant circulation loop, a compressor, a condenser, an electronic expansion valve, an evaporator and a controller, and the method comprises the following steps:
acquiring a first operation parameter, a second operation parameter, a third operation parameter and compressor power in the operation of the air conditioning unit, wherein the first operation parameter is the suction pressure and suction temperature of the compressor, the second operation parameter is the discharge pressure and discharge temperature of the compressor, and the third operation parameter is the condenser pressure and condenser liquid outlet temperature;
determining a target opening of the electronic expansion valve based on the first operating parameter, the second operating parameter, the third operating parameter and the compressor power;
controlling the opening of the electronic expansion valve through the target opening;
the target opening degree of the electronic expansion valve is determined based on the first operation parameter, the second operation parameter, the third operation parameter and the compressor power, and specifically is:
determining a theoretical specific enthalpy of suction of the compressor based on the first operating parameter;
determining a theoretical specific enthalpy of exhaust of the compressor based on the second operating parameter;
determining theoretical specific enthalpy of the condenser effluent based on the third operating parameter;
determining a refrigerant mass flow based on the compressor power, the suction theoretical specific enthalpy, and the discharge theoretical specific enthalpy;
determining the real-time refrigerating capacity of the air conditioning unit based on the suction theoretical specific enthalpy, the condenser liquid outlet theoretical specific enthalpy and the refrigerant mass flow;
and determining the target opening of the electronic expansion valve based on the real-time refrigerating capacity, the evaporating temperature and the condensing temperature, wherein the evaporating temperature is a preset constant, and the condensing temperature is determined based on the condenser pressure and the equivalent condensing temperature corresponding to the evaporating temperature.
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