Evaporation Heat Transfer Characteristics of R-290 in a Micro Fin Tube

Hydrocarbons are very suitable alternative refrigerants, because of their low GWP and ODP. These alternative refrigerants have been expected to have different heat transfer characteristics from that of HCFC-22 when the phase is changed in the evaporator. Thus, in this study, evaporation heat transfer coefficient, pressure drop and flow regimes of pure R-290(Propane) inside a micro fin tube were experimentally investigated. The length of test section was 500 mm and average diameter of a micro fin copper tube was 8.62 min. Test conditions were as follows: saturation temperature 5℃ mass velocity 100, 150 kg/m2s heat flux 10, 20 kW/m2 inlet quality 0.08 - 1.0. The observed flow regimes agreed with that of Breber's flow map. However, annular flow pattern appeared at the low quality, which was different from the flow pattern in a smooth tube. Pressure drop of R-290 was three times higher than that of R-22 at the same mass velocity and heat flux. Among the local surface temperature difference in circumferential direction of a micro fin tube, temperature difference of upper part was smallest and lower one was largest. Evaporation heat transfer coefficient of R-290 was two times higher than that of R-22 at the same mass velocity and heat flux.