Saturated vapour condensation of R410A inside a 4 mm ID horizontal smooth tube: Comparison with the low GWP substitute R32

This study performs 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 °C, 35 °C, and 40 °C, at different vapour quality and mass velocities to evaluate the specific contribution of refrigerant mass flux, mean vapour quality, and condensation temperature (pressure). The frictional pressure drops exhibit great sensitivity to all the operating variables considered, while the condensation heat transfer coefficients show great sensitivity only to refrigerant mass flux and mean vapour quality. The transition between gravity controlled and forced convection condensation occurred in the range of the equivalent Reynolds number 10,000-20,000. The Friedel (1979) correlation was able to predict properly the entire set of frictional pressure drops data, while the Akers et al. (1959) model gave a fair estimation of the forced convection condensation heat transfer coefficients. R32 exhibits condensation heat transfer coefficients and frictional pressure drops higher than those of R410A and it seems a valuable low GWP substitute for R410A.