Method for controlling opening of electronic expansion valve in heat pump water heater system

Abstract

The invention discloses a method for controlling the opening of an electronic expansion valve in a heat pump water heater system, and aims to provide a control method for allowing a system to avoid an area in which the air suction degree of superheat drops suddenly in the running process and allowing the coefficient of performance (COP) of the system to keep a high level. The method comprises thefollowing steps of: setting the optimum value of the change rate delta T/delta t of the air suction degree of superheat, and setting the initial opening of the expansion valve as 80 percent of total opening; taking a temperature difference between an average temperature value at an air suction port of a compressor and the saturated evaporating temperature as the air suction degree of superheat when the compressor runs to the state of the stable running of the system; measuring and calculating the air suction degree of superheat at the interval time delta t; calculating the change rate of the actual air suction degree of superheat according to the adjacent two-time air suction degree of superheat, comparing with the set optimum value of the change rate of the air suction degree of superheat, and when the change rate of the actual air suction degree of superheat is less than or equal to A, reducing the opening of the expansion valve; when the change rate of the actual air suction degreeof superheat is more than 0, increasing the opening of the expansion valve; and when the change rate of the actual air suction degree of superheat is more than A and is less than or equal to 0, maintaining the current running state.

Description

technical field [0001] The invention relates to a method for controlling the opening degree of an electronic expansion valve in a heat pump water heater system. Background technique [0002] At present, in heat pump water heater systems, most throttling elements are thermal expansion valves or capillary tubes. However, during the operation of the heat pump water heater, as the water temperature continues to rise, the condensing pressure and evaporation pressure in the system will change accordingly; Substantial changes in many parameters such as system heating capacity and refrigerant circulation. [0003] The thermal expansion valve is used as the throttling element, and the opening of the valve core is controlled by the feedback of the remote temperature sensing signal, which has a large hysteresis, and it is difficult to respond quickly and effectively to the flow change with the displacement of the compressor; and the signal feedback The hysteresis causes the parameter...

AI Technical Summary

Problems solved by technology

However, during the operation of the heat pump water heater, as the water temperature continues to rise, the condensing pressure and evaporation pressure in the system will change accordingly; Substantial changes in many parameters such as system heating capacity and refrigerant circulation

[0003] The thermal expansion valve is used as the throttling element, and the opening of the valve core is controlled by the feedback of the remote temperature sensing signal, which has a large hysteresis, and it is difficult to respond quickly and effectively to the flow change with the displacement of the compressor; and the signal feedback Hysteresis leads to periodic oscillation of parameters, and the system cannot run stably

Eventually the machine will run unstable and even damage the compressor

[0004] For this reason, some scholars have studied the use of suction superheat and exhaust superheat to control the opening of the electronic expansion valve, but the control range of the suction superheat is very narrow, and frequent adjustments to the expansion valve opening will cause large fluctuations in the system

However, the degree of superheat of the exhaust gas can only indirectly reflect the situation of the refrigerant circulation in the system, and cannot be accurately controlled.

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