Evaporation heat transfer of HFO-1123/HFC-32 (40/60 mass%) flow in a horizontal microfin tube.

A binary mixture R1123/R32 is anticipated as the new candidate to replace R410A and R32 for residential air conditioners. In this study, the experimentally quantified heat transfer coefficient and pressure drop during evaporation process in a horizontal microfin tube with an outer diameter of 6 mm is presented. The number of fins, fin height, spiral angle, and surface enlargement of the tested tube are 60, 0.269 mm, 18 deg, and 2.62, respectively. The heat transfer coefficient at a composition of 40/60 mass%, a temperature of 10 °C, and a mass flux of 200 kg m-2s-1 is almost comparable to that of R32; on the other hand, the pressure drop is somewhat lower. That is explained with the smaller surface tension and lower vapor velocity. The temperature glide is approximately 1 K at the corresponding pressure. It seems that the concerned mass transfer resistance by the volatility difference is relatively small.