An Investigation of Convective Evaporation of R-22 and Binary Near-Azeotropic Refrigerant Mixture R-410A in Horizontal Circular Tubes
The characteristics of convection evaporation heat transfer coefficients and two-phase flow pressure drops were measured for R-22 and binary near-azeotropic refrigerant mixture R-410A (R32/R125, 50%/50%, by weight) flowing in smooth tube with inner diameter of 6l.54 mm and micro-fin tubes with inner diameter of 6.48mm. The range of mass flux is between 100 to 400 kg/m2 sec, and data were taken at two evaporation temperature (2℃ and 10℃ respectively). The experimental results show that the heat transfer coefficient of R-410A is higher than R-22 in both smooth and micro-fin tubes, but it will be dacaied at high amss flux and high vapor quality region. Compare with smooth tubes, the heat transfer coefficients of R-22 in the micro-fin tubes increase by 150% 240% and the heat transfer coefficient of R-410A in the micro-fin tubes increase by 150% to 210%. Between experimental data and correlations proposed for the heat transfer coefficients, Wattlet's correlation can predict R-22 datain smooth tube within ±30%. For the pressure drops, Souza's correlaiton can predict the data within ±30%.
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