小间距冲击凹柱面靶板换热特性实验

Experiment of heat transfer on concave surface in single jet impingement cooling system in small jet-to-target space

利用热膜法，实验研究了小间距下单孔冲击受限凹面靶板的局部换热特性。通过改变冲击Re数（20000～30000），冲击间距和冲击孔直径之比H／D（0．2～1．0）等参数，重点分析冲击靶面周向和轴向的局部换热系数及其分布规律。结果表明：小冲击间距工况下，由于滞止区内高压区作用。气流被加速，靶面轴向上出现除滞止点以外的第二个强化换热峰值，并且随着冲击间距的减小，该效应越加明显；当H／D较小时，由于冲击导管端壁表面的限制，冲击射流在凹面靶板的周向形成冲击射流，显著提升了周向的局部换热效果，周向上也出现了二次强化换热峰值。随着H／D的增加，周向二次强化峰值迅速消失。实验中当H／D=0．2时，凹面靶板的换热效果达到最佳。

The characteristics of local heat transfer on concave target surface in single jet impingement under small jet- to-target spacing was studied. Impingement Reynolds number was in the range of 20 000 - 30 000, and the ratio of the jet impingement distance to the diameter of the jet hole H/D was 0, 2 - 1.0. And the secondary heat transfer peak in axial direction was observed because of the acceleration of cooling air, which was induced by the high pressure in jet stagnation region. These secondary peak of heat transfer is much more distinguished in small jet-to-target spacing such as H/D = 0.2. In radial direction, the secondary peak of heat transfer was also observed because of the spray jet in radial, which was induced by the too small distance between end wall of impingement nozzle and concave surface. With the increasing of H/D, the secondary peak of heat transfer in radial direction disappeared rapidly. All the results show that the heat transfer increased with the increasing of impingement Reynold number and the decreasing of H/D. The maximum local and average heat transfer can be achieved in the case of H/D = 0. 2.