A COMPARISON OF R-22, R-134A, R-410A AND R-407C CONDENSATION PERFORMANCE IN SMOOTH AND ENHANCED TUBES: PART I, HEAT TRANSFER

Abstract

Local and average heat transfer coefficients during condensation are reported for R-22, R-134a, R-410a, and R-407c in one smooth tube and three enhanced surface tubes. The test tubes included a 3/8 inch (9.52 mm) outer diameter smooth tube, a 3/8 inch (9.52 mm) outer diameter micro-fin tube, a 5/16 inch (7.94 mm) outer diameter micro-fin tube, and a 5/8 inch (15.88 mm) outer diameter micro-fin tube. The local and average heat transfer coefficients were measured over a mass flux range of 92,100 lb/ft2 hr (125 kg/m2 s) to 442,200 lb/ft2 hr (600 kg/m2 s), and at saturation temperatures of 104 F (40 C) and 122 F (50 C). A comparison of the performance of the different refrigerants reveals that R-134a has the highest heat transfer performance followed by R-22 and R-410a which have similar performances. In general, R-407c had the lowest performance of the refrigerants tested. The micro-fin tube more than doubles the heat transfer coefficient compared to the smooth tube for all refrigerants at the low mass fluxes, but only increases the heat transfer coefficients by 50% at the highest mass flux tested. The measured heat transfer coefficients are also compared with a number of correlations for condensation.