Experimental investigation on boiling heat transfer and pressure drop of R245fa in a horizontal micro-fin tube水平微肋管内R245fa 沸腾换热及压降的实验研究

An experimental investigation on the boiling heat transfer and frictional pressure drop of R245fa in a 7 mm horizontal micro-fin tube was performed. The results show that in terms of flow boiling heat transfer characteristics, boiling heat transfer coefficient (HTC) increases with mass velocity of R245fa, while it decreases with the increment of saturation temperature and heat flux. With the increase of vapor quality, HTC has a maximum and the corresponding vapor quality is about 0.4, which varies with the operating conditions. When vapor quality is larger than the transition point, HTC can be promoted more remarkably at higher mass velocity or lower saturation temperature. Among the four selected correlations, KANDLIKAR correlation matches with 91.6% of experimental data within the deviation range of ±25%, and the absolute mean deviation is 11.2%. Also, in terms of frictional pressure drop characteristics of flow boiling, the results of this study show that frictional pressure drop increases with mass velocity and heat flux of R245fa, while it decreases with the increment of saturation temperature. MULLER-STEINHAGEN-HECK correlation shows the best prediction accuracy for frictional pressure drop among the four widely used correlations. It covers 84.1% of experimental data within the deviation range of ±20%, and the absolute mean deviation is 10.1%.