Experimental study of convective boiling of refrigerants R-22 and R-410A

The two-phase heat transfer coefficient and pressure drop characteristics of refrigerants R-22 and R-410A (a binary mixture of 50% R-32 and 50% R-125) for a smooth tube with a 6.54 mm ID are presented in this study. The data were taken at an evaporation temperature of 2 C. The mass flux was between 100 kg/m{sup 2}{center_dot}s and 400 kg/m{sup 2}{center_dot}s and the heat flux was between 2.5 kW/m{sup 2} and 20 kW/m{sup 2}. Experimental data are presented in the form of quasi-local heat transfer coefficients and frictional pressure gradients. The effect of heat flux and mass flux on the heat transfer coefficients are examined in the present investigation. It is found that the heat transfer coefficients for R-410A are 10%{approximately}20% higher than those of R-22 for G = 100 kg/m{sup 2}{center_dot}s. For G = 400 kg/m{sup 2}{center_dot}s, the heat transfer coefficients for R-22, depending on the prescribed heat flux, may be higher than those of R-410A at a certain vapor quality. The pressure drop of R-410A is about 30%--40% lower than that of R-22.