Comparison of Heat Transfer Coefficient of R-12, R-134a and R-409a for Condensation Based on Existing Correlations

Abstract

The heat transfer coefficient of refrigerants R-12 (dichlorodifluoromethane), R-134a (1, 1, 1, 2, tetrafluoroethane) and R-409a (60 % R22, 25 % R124 and 15 % R142b) are compared on the basis of six existing correlations at condensing temperature 45 °C. Heat transfer coefficients are measured for horizontal tube having internal diameter 8 mm, external diameter 9.52 mm and length of 5 m, mass flux varies from 25 to 450 kg/m2sand quality (dryness fraction) varies from 0 to 1. In the comparison of three refrigerants, Bohdal correlation predict that heat transfer coefficient for R-409a is higher than R-134a and R-12 while according to Cavallini and Zecchin, Shah, Traviss, Huang and Park correlation heat transfer coefficient for R-134a is higher than R-409a and R-12.