水平小管内R290的凝结换热特性实验

EXPERIMENTAL STUDY ON CONDENSATION HEAT TRANSFER CHARACTERISTICS OF R290 FLOWING IN HORIZONTAL SMALL TUBE

以管内径为4 mm的水平光滑铜管,质量流速100~250 kg/(m^2·s),热流密度5~10 kW/m^2,饱和温度分别为40、50、55℃,干度0~1,对R290(丙烷)进行凝结换热实验。结果表明:提高质量流速或增大热流密度,均可增大凝结换热系数;而饱和温度升高则会使凝结换热系数减小;此外,随着凝结过程的进行,干度逐渐降低,凝结换热系数通常也随之减小,仅在热流密度过大时出现先增后减的现象。最后,选取6种经典的凝结换热关联式计算凝结换热系数,并与实验结果对比,Cavallini关联式和Bohdal关联式的预测效果较好。

The condensation heat transfer characteristics of R290(propane)is studied experimentally while flowing inside a 4 mm ID horizontal smooth copper tube,and condensation heat transfer coefficients is got under different experimental conditions which include mass flux(100-250 kg/(m^2·s)),heat flux(5-10 kW/m^2),the saturated temperature(40,50 and 55 ℃) and the quality(0-1). The results show that the condensation heat transfer coefficient of R290 can be improved by increasing the mass flow rate or heat flux density,while the condensation heat transfer coefficient will be decreased with the increase of saturation temperature. Also,the condensation heat transfer coefficient generally decreases with the vapor quality decreasing,but increases at first and then decreases in the case of excessive heat flux. except that it increases at first but then decreases under excessive heat flux with the vapor quality decreasing. Finally,comparing the experimental results with the data of condensation heat transfer coefficients respectively got by six classical correlation equations selected in the paper,it can be concluded that the two correlations proposed by Cavallini and Bohdal are more accurate.