Experimental investigation on flow condensation characteristics of binary mixture in a rectangular micro-channel

A flow condensation experimental study with binary mixture in a horizontal rectangle 1 mm-channel was carried out. The flow patterns, heat transfer characteristics and frictional pressure gradients were analyzed based on the parametric study. Pure refrigerants R134a, R245fa and their three mixtures R134a/R245fa (70/30, 30/70 and 10/90 by wt%) were selected in this study. The impacts of mass flux, saturation temperature and wall subcooled temperature on the flow condensation were discussed. Flow pattern transition characteristic was studied and an annular-intermittent flow transition criterion considering the composition and temperature glide was proposed. The heat transfer deterioration was discussed and the mass transfer resistance was characterized by some physics parameters and working conditions. The frictional pressure gradient of zeotropic mixture was weakened because of the temperature glide. New prediction methods of heat transfer coefficient and frictional pressure gradient for R134a/R245fa were developed, and both the prediction correlations showed satisfactory accuracy.