Condensation heat transfer coefficients of HCFC22, R410A, R407C and HFC134a at various temperatures on a plain horizontal tube

Abstract

In this study, external condensation heat transfer coefficients (HTCs) of HCFC22, R410A, R407C, and HFC134a were measured on a smooth horizontal tube at 30, 39, and 50℃ with the wall subcooling of 3-8℃. The results showed that condensation HTCs decreased for all fluids tested with an increase in temperature. This is due mainly to such properties as the saturated liquid density and liquid thermal conductivity. These properties decrease as the temperature increase and accordingly HTCs decrease. The condensation HTCs of R410A are 9.2~19.7% higher than those of HCFC22 while those of R134a are 2.5~10.2% lower than those of HCFC22. Condensation HTCs of R407C, nonazeotropic mixture, are 29.4~34.3% lower than those of HCFC22. Overall, the HTCs of R407C are much lower than those of HCFC22, HFC134a and R410A due to the mass transfer resistance in a diffusion vapor film. Condensation HTCs of HCFC22 and HFC134a are higher than those calculated by Nusselt’s equation by 7.7~11.8% and 4.0~11.1% respectively. On the other hand, HTCs of R407C measured on plain tube, however, are not well predicted by these well-known prediction correlations due to the introduction of mass transfer resistance associated with non-azeotropic mixtures.