Investigation on the Properties of Supercritical CO2 Fluid and its Heat Transfer Characteristics

The obvious characteristics of transcritical CO2 cycle are that the heat rejection process takes place in the supercritical region. The thermophysical properties of supercritical CO2 change dramatically with the temperature and pressure near the critical region, which results in the momentum and energy exchange and buoyant force change in the heat flux direction, so it should be treated as “variable properties”. According to the characteristics of CO2 specific heat, the correlation of the pseudocritical temperature is obtained and the pseudocritical region is defined. The heat transfer features of CO2 under supercritical pressure are different from those of the conventional refrigerants. In order to compare the heat transfer performance of supercritical CO2 fluid and the conventional refrigerants, the contrast investigation on the heat transfer treatment principle, the heat transfer mechanism and the thermophysical properties are mainly presented in this paper.