R410A and its low-GWP substitute R32 condensation inside a 4 mm horizontal smooth tube

This paper presents the comparative analysis of R32 and R410A condensation inside a 4 mm ID smooth tube. The experimental tests were carried out at three different saturation temperatures, 30, 35, and 40 °C, at decreasing vapour quality to evaluate the specific contribution of refrigerant mass flux, mean vapour quality, and saturation temperature (pressure). The heat transfer coefficients exhibit great sensitivity to refrigerant mass flux and mean vapour quality and a transition region between gravity controlled and forced convection condensation was found for an equivalent Reynolds number in the range 10,000 - 20,000. The forced convection condensation heat transfer coefficients were sufficiently well predicted by Akers et al. (1959) model. R32 exhibits heat transfer coefficients higher than those of R410A under the same operating conditions and it seems a valuable low GWP substitute for R410A.