An Experiment on the Heat Transfer to Substitute Refrigerant HFC134a Evaporating in a Horizontal Smooth Tube

An experiment is performed on the heat transfer to CFC12 and its alternative HFC134a evaporating in a 6m-long, 7.9mm-ID smooth tube. A double-tube-type evaporator, where heating water flows countercurrently, is used as the test section. A comparison of measured local heat transfer coefficient between HFC134a and CFC12 is made by adjusting the heat flux distributions for both fluids. Also, by a comparison between both fluids in heat transfer coefficient vs heat flux diagrams, the heat transfer coefficient of HFC134a is shown to be about 25% higher than that of CFC12 for the same saturation temperature, mass velocity, heat flux and quality. Correlations proposed by Dhar et al. and Yoshida et al. also give a higher heat transfer coefficient for HFC134a than that of CFC12, although the difference is a little smaller than that of the experimental results. From the standpoint of the heat transfer in the evaporator, HFC134a is adequate as an alternative working fluid for CFC12.