Method for controlling electronic expansion valve of trans-critical carbon dioxide heat pump system

Abstract

The invention discloses a method for controlling an electronic expansion valve of a trans-critical carbon dioxide heat pump system. The method includes the following steps that first, an exhaust pressure value is collected; second, water route control parameters are determined; third, the optimal exhaust pressure of the trans-critical carbon dioxide heat pump system is confirmed; fourth, the exhaust pressure is adjusted; fifth, the COP in the steady state of the system is calculated; and sixth, the optimal exhaust pressure is verified through particle swarm optimization (PSO). By adoption of the method, the exhaust pressure can be controlled through matching of opening degree adjustment of the electronic expansion valve and exhaust temperature variation, the sampling speed is high, precision is also high, time delay is small, robustness is high, and the defect of liquid return hidden danger caused by avoidance of the excessively-high exhaust temperature of a compressor in a traditionalexhaust temperate control method is overcome. According to the method, pressure control can be conducted on refrigerating systems like the trans-critical carbon dioxide heat pump system with strong nonlinear characteristics, and higher adjustment control capacity can be achieved when the trans-critical carbon dioxide heat pump system operates under different working conditions.

Description

technical field [0001] The invention belongs to the technical field of heating, ventilation, refrigeration and heat pumps, and relates to a method for controlling an electronic expansion valve of a transcritical carbon dioxide heat pump system. Background technique [0002] In recent years, with the continuous destruction of the greenhouse effect and the ozone layer, research institutions and their government departments have begun to pay more attention to refrigerants that do not damage the ozone layer. Natural refrigerants have also received more and more attention. CO 2 The refrigerant is an environmentally friendly refrigerant, with an ozone layer-destroying potential value ODP=0, which does not destroy the ozone layer, and does not need to be recycled and regenerated. Its global warming potential index GWP=1 is an ideal natural refrigerant. As early as the 1880s, CO 2 It has been introduced into the field of refrigeration and air conditioning, and has been used for ...

AI Technical Summary

Problems solved by technology

However, the discharge temperature control method is easy to bring back the hidden danger of liquid in order to ensure the discharge temperature of the compressor, which affects the safety of the system operation.

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