Numerical Investigation During Condensation of R134a Inside a Smooth and Dimpled Tube: Comparison with low-GWP Alternatives R1234yf, R1234ze and R290

The international community limits the usage of higher global warming potential (GWP) refrigerants like R134a in refrigeration and air-conditioning systems. In view of this, the present study focuses on the low-GWP alternatives to R134a during condensation inside a smooth and dimpled tube. The refrigerants considered for this study are propane (R290), 2,3,3,3-tetrafluoropropene (R1234yf), and 1,3,3,3-tetrafluoropropene (R1234ze). The geometric specifications of smooth and dimple tubes are 8.38 mm ID with 1.5 m length. The operating conditions are saturation temperature of 40 degrees C, mass flux ranging between 50 and 200 kg m(-2) s(-1), and dryness fraction of 0.5 and 0.75. The flow field was assumed to be transient, three-dimensional and turbulent while the VOF model was used to solve the governing equations. The effect of mass flux and dryness fraction was studied with R134a and its alternatives. The simulated void fraction values are compared with experimental values and empirical correlations. In this study, the total pressure drop was reduced by 15 and 20% with smooth tube and 11 and 16.7% with dimpled tube by using R1234yf at the quality of 0.5 and 0.75. However, it was increased with R290 and R1234ze. The power consumption was reduced by using R1234yf as a substitute to R134a and the thermophysical properties are quite similar.