稳态与瞬态冲击射流换热性能实验对比

Experimental Comparison of Heat Transfer Performance Between Steady and Transient Impinging Jet

关键词:  单孔冲击射流  热色液晶  传热强化  实验对比

Key words:  Single hole impingement  Thermochromic liquid crystal  Heat transfer augmentation  Experimental comparison

摘要:

为了对比研究稳态与瞬态单孔冲击射流的传热性能，采用热色液晶测温技术获取实验件被冲击表面的传热系数分布。实验中改变了冲击雷诺数Re和冲击孔直径比L/d，利用工业相机拍摄实验件凹表面颜色变化过程，计算并对比两种射流条件下局部努塞尔数[NuD]的分布，并与文献值进行比较。研究表明相对于稳态冲击射流，瞬态冲击射流的传热性能更佳。通过记录整个冲击射流过程，得到[NuD]随时间t变化关系。驻点附近[NuD]随冲击的进行逐渐减小并趋于稳定。随冲击雷诺数Re增大或冲击孔直径比L/d接近6，瞬态冲击射流的强化传热效果逐渐明显，强化效果可达15%以上。

Abstract:

In order to compare the heat transfer performance of the steady and transient single hole impingement jets， the heat transfer coefficient distribution of the impact surface was obtained by thermochromic liquid crystal. In the study， the impact Reynolds number Re and the impact distance to diameter ratio L/d were changed. The color change process of the concave surface of the experimental part was photographed by the industrial camera. The local Nusselt number [NuD] distribution of two kinds of jet conditions was calculated and compared. In addition， the results were compared with the literature value. The research shows that the heat transfer performance is better than that of steady jet under transient jet impingement. By recording the whole impinging jet process， the relationship was obtained between [NuD] and impact time t. The [NuD] around stagnation point gradually decreases with the impact going and tends to be stable. With the increase of the Re or L/d close to 6， the heat transfer enhancement effect of transient impinging jet is obvious， and the enhancement result is more than 15%.