内肋-光滑组合式圆管内流动沸腾换热试验

Experimental study on flow boiling heat transfer in fin-smooth-combined circular tube

为探究分段结构对管内流动沸腾过程的影响,采用试验方法分析了制冷剂R245fa在光滑管、内肋管以及采用前肋-后光滑组合管中的流动沸腾换热特性。以质量流速为100~350 kg/(m^(2)·s)、热流密度为9.36~55.84 kW/m^(2)、试验管进口过冷度约为2℃进行试验,并以光滑管的流动换热特性为基准,对比不同试验管的换热系数增强比例(enhancement factor,EF)和价值因子(merit factor,MF)。研究结果表明:内肋管和前肋-后光滑组合管的换热性能均优于全光滑管;在低质量流速时,内肋管的EF高于前肋-后光滑组合管,即内肋管换热效果更好;而随着质量流速的增加,前肋-后光滑组合管的EF逐渐高于内肋管,达到1.7左右;内肋管的MF在低质量流速时高于前肋-后光滑组合管,但在较高质量流速以及较高热流密度条件下,前肋-后光滑组合管的MF要高于内肋管,即前肋-后光滑组合管的综合性能更好。

In order to explore the effect of the segmented structure on the flow boiling process in the tube,the flow boiling heat transfer characteristics of refrigerant R245fa in the smooth tube,microfin tube,and combined one with fin-smooth form fin-smooth-combined tube were studied experimentally.The experimental conditions were as follows:mass flux 100-350 kg/(m^(2)·s),heat flux 9.36-55.84 kW/m^(2),inlet subcooling 2℃.Based on the flow and heat transfer characteristics of the smooth tube,the enhancement factor(EF)and merit factor(MF)of the test tubes were compared.It is found that the EF of the microfin tube is higher than that of the fin-smooth one fin-smooth-combined tube at low mass flux,that is,the heat transfer performance of the microfin tube is better.However,with the increase of the mass flux,the EF of the fin-smooth tube fin-smooth-combined tube gradually exceeds that of the microfin tube,reaching about 1.7.In addition,t The MF of the microfin tube is higher than that of the fin-smooth one fin-smooth-combined tube at low mass flux,while the MF of the microfin tube is lower than that of the fin-smooth one fin-smooth-combined tube under the condition of high mass flux and heat flux,which means that the comprehensive performance of the fin-smooth tube fin-smooth-combined tube is better.