新式環保冷媒R-1234ze與R-134a於外徑9.52mm微鰭管與平滑管內之沸騰對流熱傳與壓降分析與比較

Abstract

The characteristics of convection boiling heat transfer coefficients and two-phase flow pressure drops were measured for R-134a and R-1234ze flowing in micro-fin and smooth tube with outer diameter of 9.52 mm. The range of mass flux is between 60 to 200 kg/m2s, heat flux ranging from 5 to 15 kW/m2, evaporating temperature ranging from 10℃ to 20℃. Results showed that the heat transfer coefficients of R-134a and R-1234ze increase with mass flux, heat flux, quality and saturation temperature. The effect of heat flux on the heat transfer coefficient is significant at low vapor quality, the effect of mass flux on the heat transfer coefficient is significant at high vapor quality, and the heat transfer coefficient of R-1234ze shows the same trend of R-134a. For the pressure drop, under the same experimental conditions, the pressure drop of R-1234ze is higher than that of R-1234ze.The heat transfer coefficient and pressure drop in micro-fin tube are both larger than that in smooth tube. Enhancement of micro-fin to smooth tube is better at mass flux of 100 kg/m2s. Between experimental data and correlations proposed for the heat transfer coefficients, Wu correlation can predict data in micro-fin tube within 50%. Liu and Winterton correlation can predict data in smooth tube within 50%. For the pressure drops, Filho correlation can predict the data within 50% in micro-fin tube. Collier and Thome correlation can predict the data within 50% in smooth tube.