MECHANISM OF HEAT REMOVAL BY HEAT TRANSPORT VORTEX

在这种情况下，热输运涡由冲击射流的更新涡和混合对流的固定涡组成。本文通过对冲击射流和混合对流换热特性的研究，探讨了旋涡在冲击射流中的传热和强化换热作用。第一阶段，研究了冲击射流在单股圆形射流和冲击射流瞬态过程中的换热特性。实验采用热敏液晶和（r，g，B）方法。研究了喷管形状和姿态对局部换热的影响。将冲击射流实验扩展到四个方形排列的圆形喷嘴。局部努塞尔数的二维行为对应于在冲击表面上的油膜法的流动显示。平均努塞尔数用几何函数和Re^<2/3>表示。环形喷嘴的冲击换热也被捕获在二维地图。在第二阶段，对水平三壁方管内混合对流换热和流动特性进行了数值模拟和实验研究。流动行为取决于壁面和入口流体之间的相对温差。壁面附近的流体向后流动以补偿浮力引起的流动。随着Richardson数的增加，流动反转的大小也随之增加。在侧壁加热和冷却过程中，在纵向和横截面上都产生了旋涡流动，这些流动行为传递热量并影响壁面的局部换热。最后的报告由冲击射流和混合对流两章组成。

In the present case, heat transport vortexes are composed of the renewal vortex by impinging jet and fixed vortex by the mixed convection. We studied on how vortex transports heat and contributes to heat transfer enhancement by examining the characteristics of the impingement heat transfer and the mixed convection.In the first stage, the heat transfer characteristics on impinging jet were studied on a single circular jet and in transient process. Experiment was performed using thermosensitive liquid crystal and (r,g,b) method. Effects of the shape and the attitude of the nozzle were investigated on the local heat transfer. Experiments on impinging jet were expanded to four circular nozzles arranged in square-type. The two-dimensional behavior of the local Nusselt number was corresponded to the flow visualization by oil film method on the impingement surface. The average Nusselt number was expressed by the geometric function and Re^<2/3>. Impingement heat transfer by annular nozzle was also captured in two-dimensional map. Experimental formulas of the local Nusselt number were obtained in power-law expressions of r/r_p (r_p : position of local Nusselt number)for the major and minor flow regions.In the second stage, the heat transfer and flow characteristics of mixed convection in a horizontal square duct with three heat transfer walls were examined numerically and experimentally. The flow behavior depends on the relative temperature difference between wall and inlet fluid. The fluid near the wall flows backward to compensate the buoyancy induced flow. The size of the flow reversal increases with increase of Richardson number. In side wall heating and cooling, a swirl flow is generated longitudinally and at the cross section, several vortexes can be found. These flow behavior transports heat and affects the local heat transfer on the walls.The final report is composed of two chapters on impinging jet and mixed convection.