Condensation heat transfer and pressure drop of azeotropic mixture refrigerant R32/R1270 inside horizontal small-diameter tubes.

This paper describes an experimental study on condensation heat transfer and pressure drop using the small-diameter tube and refrigerants R410A and R32, along with the azeotropic mixture R32/R1270 (70 mass% R32; 30 mass% R1270 (propylene)), which was used as a test refrigerant existing at the azeotropic point. The experimental apparatus was a vapor compression heat pump system. Smooth and internally helically grooved small-diameter tubes were used as test tubes. The test heat exchanger consisted of four double-tube test sections with countercurrent flow. In each test section, a test tube in an annulus was cooled by cooling water, and the refrigerant flowed within an inner tube. The condensation temperature was maintained at 35°C, and the refrigerant mass flux ranged from 320 to 750 kg/(m2s). The experimental values for condensation heat transfer and pressure drop were compared with values obtained for R32 and R410A refrigerants and with the results of previous studies.