Evaporation heat transfer and pressure drop of the interim (R-448A, R-449A) and long term (R-455A, R-454C) low GWP R-404A alternative refrigerants in a smooth tube

Due to the global warming issue, R-404A phases out, and new alternative refrigerants are emerging. In this study, four R-404A alternative refrigerants - two interim refrigerants (R-448A, R-449A) and two long term refrigerants (R-455A, R-454C) - including R-404A were tested in a 5.6 mm inner diameter tube under evaporation condition. The test range included the mass flux from 90 to 300 kg/m²s, heat flux from 5 to 15 kW/m², and vapor quality from 0.2 to 0.8. The saturation temperature was 10 °C. The results showed that, at a low mass flux, the heat transfer coefficients of R-404A were higher than those of the alternative refrigerants. At a high mass flux and high quality, on the other hand, the reverse was true - the heat transfer coefficients of R-404A were lower than those of the alternative refrigerants. The pressure drops of the alternative refrigerants were larger than those of R-404A. Finally, the data are compared with the predictions by existing correlations.