In this study the boiling heat transfer characteristics of R290 in a 1

2

and 4 mm horizontal micro-tube were investigated experimentally. The effects of mass flow rate [50-600 kg/(m2?s)]

quality (0-1)

and heat flux (5-20 kW/m2) on the boiling heat transfer coefficient at a saturation temperature of 15 °C were analyzed. The results showed that increased mass flow velocity can enhance the heat transfer coefficient and the influence of mass flow rate on the heat transfer coefficient with low quality is smaller than that with high quality. The heat transfer coefficient increased with the increased heat flux

and the effect of critical quality on the heat transfer coefficient was apparent in 2 and 1 mm tubes. The heat transfer coefficient tended to decrease precipitously for 2 and 1 mm tubes. The transverse heat transfer coefficient increased with the decreasing pipe diameter under some conditions. In addition

this study also verified the adaptability of some existing correlations of R290.