Mass flow characteristics and empirical modeling of R744 flow through electronic expansion device

Abstract

Electronic expansion valve (EEV) takes advantages of its fast response, wide working range and accurate control and is been widely used in CO2 heat pump and air-conditioning system while the CO2 mass flow characteristics is the most crucial parameter for EEV. Different from other refrigerants, at the inlet of EEV, CO2 maintains at supercritical state. In this study, the effects of inlet pressure, inlet temperature, outlet pressure, EEV flowing area and EEV geometries on CO2 mass flowing through EEVs have been investigated under a wide operation range for three different EEVs. Meanwhile, a new empirical correlation has been developed to predict the mass flow rate of CO2 flowing through EEVs based on the experimental data. The proposed dimensionless correlation shows a good agreement with the test data. Approximately 91.8% of the experimental data within a relative deviation of ±5% for all EEVs. The average deviation and standard deviation of the predictions are 0.36% and 1.93% respectively.