Abstract
The characteristics of convection boiling heat transfer coefficients and two-phase flow pressure drops were measured for R-134a and HFO-1234yf flowing in smooth tube with inner diameter of 3.9 mm. The range of mass flux is between 200 to 500 kg/m2s, heat flux ranging from 5.67 to 26.18 kW/m2, evaporating temperature ranging from 6℃ to 15℃. Results showed that, the heat transfer coefficients of R-134a and HFO-1234yf increase with mass flux, heat flux and saturation temperature. The effect of heat flux on the heat transfer was large at low vapor quality, the effect of mass flux on the heat transfer was large at high vapor quality, and the heat transfer coefficient of HFO-1234yf is almost same as that of R-134a. For the pressure drops, under the same experimental conditions, the pressure drops of R-134a are higher than that of HFO-1234yf. Between experimental data and correlations proposed for the heat transfer coefficients, Wattlet and Chato’s correlation can predict data in smooth tube within 50%. For the pressure drops, Friedel’s correlation can predict the data within 30%.
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