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（英文）

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%.

本文对R245fa在7 mm水平微肋管内的沸腾传热特性和摩擦压降特性进行了实验研究.结果表明,在流动沸腾传热特性方面,沸腾传热系数(HTC)随着R245fa质量速度的增加而增大,随着饱和温度和热流密度的增加而减小.随着干度的增加,HTC存在最大值,对应的干度约为0.4,其值随工作条件的变化而变化.当干度大于过渡点时,较高的质量速度或较低的饱和温度下可以显著增加HTC.在所选四个关联式中,KANDLIKAR的预测值与91.6%实验值的偏差在±25%以内,绝对平均误差为11.2%.此外,关于流动沸腾的摩擦压降特性,本研究结果表明,摩擦压降随着R245fa的质量速度和热流密度的增加而增加,随着饱和温度的升高而减小.在四种常用的关联式中,MULLER-STEINHAGEN-HECK对R245fa摩擦压降值的预测最准确,预测值与84.1%的实验值偏差在±20%以内,绝对平均误差为10.1%.