An experimental study compared the heat transfer characteristics of two-phase flow condensation of alternative zeotropic refrigerant mixtures to R-502 inside air/refrigerant horizontal enhanced surface tubing. The alternatives considered in this study are R-507, R-404A, R-407B, and R-408A. It was evident from the condensation experimental data that R-407B has the lowest heat transfer rate compared to the other blends in the investigated range of refrigerant mass flow rates and heat flux. Furthermore, experimental data on the two-phase condensation pressure gradient across the test section at different Reynolds numbers showed that R-404A has the highest convective pressure drop among the blends under investigation.

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