R404A在水平内螺纹管中的冷凝传热研究

经过实验与理论对比,研究了R404A在外径9.52 mm内螺纹管内局部平均冷凝换热系数。采用Cavallini纯工质与混合工质关联式分别计算的冷凝换热系数,最大偏差不到4%。在工程计算R404A内螺纹管内冷凝换热系数时,可将其以纯质来对待。分析比较Cavallini,Yu-Koyama和Kaushink-Azer关联式,各自的理论预测值和实验结果相比,表明Cavallini关联式的预测精度最高,其标准偏差为7.76%。因此Cavallini关联式对于R404A在管内的冷凝换热预测有较好的适用性。研究结果对R404A冷凝器的工程设计及其优化具有一定的参考意义。

Investigation on condensation heat transfer for R404A inside microfin-tube

The characteristics of average condensation heat transfer for R404A inside microfin tube were investigated theoretically and experimentally.Considering R404A as a pure and mixture refrigerant respectively,the condensation heat transfer coefficients inside the copper tube with an outside diameter of 9.52 mm were predicted by Cavallini correlations for pure and mixture refrigerants.The difference between two predicted condensation heat transfer coefficients increases with the vapor quality,and the maximum difference is less than 4%.It shows that R404A can be treated as pure refrigerant when calculating its in-tube condensation heat transfer coefficients for industrial application.Three correlations of Cavallini,Yu-Koyama and Kaushink-Azer were analyzed and applied to predict condensation heat transfer coefficient for R404A.Compared with the experimental data,Cavallini correlation illustrates that the highest accuracy in predicting condensation heat transfer coefficients for R404A inside microfin tubes.The standard error is 7.76%.The results are valuable for designing and optimizing R404A condensers.