水平微肋管内R513A冷凝换热特性研究
Study on condensation heat exchange characteristics of R513A in horizontal micro-fin tubes
摘要：
采用实验方法研究了R513A在光管和不同齿密度微肋管内的冷凝换热性能,并通过对比冷凝换热系数实验值与关联式的预测值,探究了现有关联式对R513A的适用性,实验在冷凝温度33、35、38 ℃,质量流速50～150 kg/(m2·s)的工况范围内进行。实验结果表明:冷凝换热系数随质量流速的增大而增大,在低质量流速区域,微肋管的冷凝换热系数增长幅度更大;随着齿密度的增加,管内换热面积增大,但管内表面张力作用增强,相应的流动阻力增强,强化传热作用被削弱;与R134a相比,微肋管对R513A的强化传热效果更优;对于光管,Bashar关联式的预测效果最佳,Cavallini关联式与Dobson关联式在低质量流速区域的预测误差偏大;对于微肋管,Yu关联式的预测效果最理想,Cavallini关联式与Kedzierski关联式均低估了管内冷凝换热特性。以Kedzierski关联式为基础,拟合了新的修正关联式,修正关联式的预测值与实验值的一致性较好,其平均绝对误差与标准差分别为7.8%、8.5%。
Abstract：
The condensation heat exchange performance of R513A in a smooth tube and micro-fin tubes with different tooth densities is studied experimentally.By comparing the experimental value of the condensation heat exchange coefficient with the prediction value of the correlation,the applicability of the existing correlation to R513A is explored.The experiment is carried out in the range of condensation temperature 33,35,38 ℃ and mass flux from 50 to 150 kg/(m2·s).The experimental results show that the condensation heat exchange coefficient increases with the increase of mass flux,and the increase range of condensation heat exchange coefficient of the micro-fin tube is larger in the region of low mass flux.With the increase of tooth density,the heat exchange area in the tube increases,but the surface tension increases,the corresponding flow resistance increases,and the function of enhanced heat transfer is weakened.Compared with R134a,the enhanced heat transfer effect of the micro-fin tube on R513A is better.For the smooth tube,the prediction effect of the Bashar correlation is the best,while the prediction errors of the Cavallini correlation and the Dobson correlation are larger in the region of low mass flux.For micro-fin tubes,the prediction effect of the Yu correlation is the best,and both the Cavallini correlation and the Kedzierski correlation underestimate the condensation heat exchange characteristics in the tube.Based on the Kedzierski correlation,a new modified correlation is fitted.The prediction value of the modified correlation is in good agreement with the experimental value,and the average absolute error and the standard deviation are 7.8% and 8.5%,respectively.
Keywords:R513A; micro-fin tube; condensation heat exchange; enhanced heat transfer; correlation