稳态与瞬态冲击射流换热性能实验对比

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 Nu_D 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 Nu_D and impact time t. The Nu_D 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%.