水平内螺纹管内R410A流动凝结换热的实验研究

本文实验研究了R410A在水平内螺纹管内的流动凝结换热特性,分析了水力工况、测试管结构参数对管内制冷剂侧表面传热系数、压降的影响。结果表明:表面传热系数、压降均随着质量流速的增加、冷凝温度的降低而增大;虽然表面传热系数随着测试水Re的增加而减小,但测试水Re对压降的影响很小。利用单位压降表面传热系数对换热进行综合性能评价时发现,单位压降表面传热系数随着质量流速的增加而减小,随着冷凝温度的增大而增大。将实验数据与经典关联式的预测值进行对比,对于光滑管,除了Akers et al.关联式低估了实验数据,Shah关联式与Thome et al.关联式均高估了实验数据,并且Thome et al.关联式表现出最高的预测精度。而对于内螺纹强化管,Cavallini et al.关联式展现出最高的预测精度,而Koyama et al.关联式与Miyara et al.关联式均低估了实验数据。

Experimental Study on Flow Condensation Heat Transfer of R410A inside Horizontal Internal Ribbed Tube

In the study, the flow condensation heat transfer characteristics of R410A inside a horizontal internal ribbed tube was experimentally investigated, and the influence of hydraulic conditions and structural parameters of a test tube on the refrigerant surface coefficient of heat transfer and pressure drop inside the tube was analyzed. The experimental results indicate that the surface coefficient of heat transfer and pressure drop increase with the increase in the mass velocity and the decrease in the condensation temperature. However, the surface coefficient of heat transfer decreases with the increase in Re of the water flow, and the pressure drop is slightly affected by the Re of the water flow. The surface coefficient of heat transfer under a unit pressure drop was used to evaluate the comprehensive performance of the heat exchanger. The results reveal that it decreases with the increase in the mass velocity, and increases with the increase in the condensation temperature. The experimental data was also compared with the prediction of some classical correlations. For the smooth tube, the correlations obtained by Shah and Thome et al. overestimate the experimental data, and the Thome et al. correlation exhibits the highest prediction accuracy although the correlation obtained by Akers et al. underestimates the experimental data. With respect to the internal ribbed tube, the Cavallini et al. correlation exhibits the highest prediction accuracy, and correlations obtained by Koyama et al. and Miyara et al. underestimate the experimental data.