Evaporation heat transfer of R-32, R-134a, R-32/134a, and R-32/125/134a inside a horizontal smooth tube

Evaporative heat transfer coefficients of R-32, R-134a, R-32/134a, and R-407C (R-32/125/134a: 23/25/52 wt%) have been measured in a horizontal smooth tube. Experiments were conducted for test section average temperatures of −12.0–17.0°C, with a mass flux of 240–1060 kg m−2 s−1, and a heat flux of 4.1–28.6 kW m−2. Evaporative heat transfer characteristics of R-407C as a possible alternative to R-22 have been compared with those of R-22. A new correlation based on superposition model for pure refrigerants and refrigerant mixtures was presented. Experimental results were compared with several correlations which predict evaporative heat transfer characteristics. Comparison with the experimental data in the open literature showed that our correlation gave a satisfactory result.