Evaporation heat transfer coefficient and frictional pressure drop of R600a in a micro-fin tube at low mass fluxes and temperatures

In this study, the evaporation heat transfer characteristics of R600a in micro-fin and smooth tubes are investigated under the operating conditions of domestic refrigerators. The evaporation heat transfer coefficient and frictional pressure drop of R600a were measured and analyzed at various vapor qualities ranging from 0.2 to 0.9, mass fluxes from 20 to 40 kg m⁻² s⁻¹, saturation temperatures from −25 to −10 °C, and heat fluxes from 9 to 15 kW m⁻². The evaporation heat transfer characteristics of R600a in the micro-fin and smooth tubes were compared in terms of the enhancement factor, penalty factor, and enhancement parameter. The micro-fin tube was preferable under low mass flux conditions, resulting in a higher enhancement parameter. Additionally, because of the poor prediction of the existing correlations, new empirical correlations for the evaporation heat transfer coefficient and frictional pressure drop of R600a in the micro-fin tube were proposed with high accuracy. These results can be used to design evaporators for domestic refrigerators under low saturation temperature and mass flux conditions.