R513A在水平螺纹管内冷凝换热性能与压降

Condensation heat transfer performance and pressure drop of R513A in horizontal microfin tubes

为研究R513A在内螺纹管中的冷凝换热性能与流动特性,通过实验对R513A在外径为12.7 mm和9.52 mm的光滑管和内螺纹管中的冷凝换热系数和压降进行分析,实验工况为:质量流速50—270 kg/(m^(2)·s),冷凝温度33、35、38、40℃。结果表明:R513A与R134a在光滑管内的冷凝换热系数差值为-18.8%—-25.5%,在螺纹管内差值为-5.5%—0.8%,螺纹管对于R513A的管内冷凝换热效果的增强更为显著;R513A的压降比R134a低5.6%—17.8%;随着管径的减小,R513A的管内冷凝换热系数和压降均增大。Oliver关联式对所测试螺纹管的管内冷凝换热系数的预测精度最高,平均误差值约为14.56%;对于管内压降的预测,所选关联式的计算结果与部分实验值存在较大误差;新拟合的压降关联式对R513A在内螺纹管内冷凝的压降预测结果较好,95.32%的数据点在30%误差线之内。

In order to investigate the condensation heat transfer performance and flow characteristics of R513A in microfin tubes,the condensation heat transfer coefficient and pressure drop of R513A in smooth and microfin tubes with outer diameters of 12.7 mm and 9.52 mm were analyzed experimentally.The experimental conditions were mass fluxes 50⁃270 kg/(m^(2)·s)and condensation temperatures 33,35,38,40℃.The results show that the R513A condensation heat transfer coefficient in the smooth tube is 18.8%⁃25.5%lower than that of R134a,and the deviation is-5.5%⁃0.8%in the microfin tube.The condensation heat transfer performance of R513A is enhanced more significantly than that of R134a in the microfin tube.The pressure drop of R513A is 5.6%⁃17.8%lower than that of R134a.When the tube diameter decreases,the condensation heat transfer coefficient and pressure drop of R513A both increase.The Oliver correlation has the highest prediction accuracy for the tested microfin tube,and the average deviation is about 14.56%.For the prediction of pressure drop,calculated results of selected correlations have large errors with some of the experimental data.The newly fitted correlation well predicts the pressure drop of R513A condensing in the microfin tube,with 95.32%of the data points within 30%error line.