Experimental Evaluation of Condensation of R32 and R134a over a Plain Tube

Abstract

The rise in demand for universal energy, combined with environmental concerns, prompted a search for a new technology that was compatible with the existing scenario. Nowadays, most conventional refrigerants are being phased out due to environmental restrictions, which has led to the development of alternative refrigerants. Such newly developed alternative refrigerants need further experimental assessment regarding their thermophysical properties. The current work has experimentally looked at the heat transfer phenomena that occur when the refrigerants R32 and R134a condense over a single horizontal plain tube at saturation temperatures of 40–50 °C, wall sub-cooling temperatures ranging from 3 °C to 11 °C, and heat fluxes of 8–31 kW/m2. The results showed that at a saturation temperature of 40 °C, R32 and R134a have a coefficient of condensation heat transfer about 4.0–9.0% higher than that at saturation temperatures of 45 °C and 50 °C. At the same wall sub-cooling temperature, R32 has a 50–55% higher condensing-side heat transfer coefficient than R134a. The validation of the experimental condensing-side heat transfer coefficient with Nusselt’s model revealed a deviation of ±10%. Further, a modified correlation based on Nusselt’s model predicted the experimental condensing-side heat transfer coefficient with an error band of ±5%.