Characteristics of condensing and evaporating heat transfer using hydrocarbon refrigerants

This paper discusses the heat transfer characteristics of R-290 (propane), R-600a (iso-butane) and R-1270 (propylene) as an environment-friendly refrigerant and R-22 as a HCFCs refrigerant for condensing and evaporating. An experiment was performed for a conventional vapor compression type heat pump system. The test section was a horizontal double-pipe heat exchanger. A tube diameter of 12.70 mm with 1.315 mm wall thickness was used for this experiment. The experimental results show that the local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient for R-1270 was a maximum value and for R-22 was a minimum value among the refrigerant tested. The experimental results of comparing the condensing heat transfer coefficients agreed satisfactorily to the referenced simulation data such as the Cavallini–Zecchin’s correlation for all refrigerants. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were higher to those of R-22. The average evaporating heat transfer coefficient increased with the increase of mass velocity. The results show that the evaporating heat transfer coefficients in hydrocarbon refrigerants were higher than that of R-22. The experimental results for all the refrigerants in general agreed with Kandlikar’s correlation for the evaporating heat transfer.