Condensation heat transfer and pressure drop of low GWP R-404A alternative refrigerants (R-448A, R-449A, R-455A, R-454C) in a 5.6 mm inner diameter horizontal smooth tube

The literature survey reveals that condensation or evaporation study of R-404A alternative refrigerants are lacking. In this study, four R-404A alternative refrigerants - two short term refrigerants (GWP100≤2500: R-448A, R-449A) and two long term refrigerants (GWP100≤150: R-455A, R-454C) - including R-404A (GWP100 = 3922) were tested under condensation condition. Test range included mass flux from 80 to 400 kg m−2s−1, vapour quality from 0.2 to 0.8. Test tube had 5.6 mm inne diameter. Results showed that, at a low mass flux, heat transfer coefficients of the alternative refrigerants were approximately the same as those of R-404A. On the other hand, at a high mass flux of 400 kg m−2s−1, heat transfer coefficients of the alternative refrigerants were higher than those of R-404A. The reason was attributed to the balance of superior thermal properties, which were beneficial, and larger temperature glide, which were malign, of the alternative refrigerants compared with those of R-404A. Pressure drops of alternative refrigerants were larger than those of R-404A. Furthermore, long term refrigerants (R-454C, R-455A) yielded larger pressure drops than short term refrigerants (R-448A, R-449A), probably due to the influence of vapour density. Furthermore, data are compared with predictions by existing correlations.