Effects of Saturation Temperature Variation Due to Pressure Drop of Working Fluid in Heat Exchanger on Heat Transfer Performance

The working fluid flowing through a heat transfer tube experiences a decrease in pressure and a corresponding decrease in saturation temperature. The effect of the saturation temperature drop on the heat transfer performance of a heat exchanger was analyzed under air-conditioner condensing condition, air-conditioner evaporating condition, and refrigerator evaporating condition. The thermodynamic analysis results show that the difference between the heat transfer capacity of the heat exchanger evaluated considering the pressure drop of the saturated refrigerant, and the heat transfer capacity evaluated under the assumption that there is no pressure loss, were 2.3% at minimum and 91.1% at maximum. The rate of change of heat transfer capacity was the largest in the order of R600a, R1234yf, R134a, R410A, and R32. Heat exchanger performance simulation under practical air-conditioner operating conditions showed that the heat transfer capacity was reduced by 0.72% due to refrigerant pressure drop under the condensing condition, while the heat transfer capacity was increased by 26.55% under the evaporating condition. The lower the operating temperature of the refrigerant, the greater the effect of the pressure drop of the refrigerant on the heat transfer capacity of the heat exchanger