横向层流中多孔冲击射流强化传热的实验研究

Experimental investigation on heat transfer enhancement by multiple impinging jets in laminar cross-flow

为研究横向层流中多孔冲击射流对平板传热特性的影响,搭建了多孔冲击射流强化传热实验台架,研究了横向层流中不同射流速度比r(10≤r≤30)和不同射流高度(20≤L/d≤80)下多孔冲击射流对加热陶瓷平板对流换热的影响,分析了对流换热系数和相对努塞尔数的变化规律,讨论了多孔冲击射流强化传热的物理机理。结果显示,相对努塞尔数随射流速度比的增大而增大,最大的相对努塞尔数为1.98。此外,多孔冲击射流高度并非越小越好,而是存在一个最佳射流高度。当r较小时,相对努塞尔数随多孔射流高度的增加而减小;当r较大时,相对努塞尔数随多孔射流高度的增加先增大后减小。

In order to study the influence of multiple impinging jets on the convective heat transfer from a flat plate in laminar cross-flow,an experimental setup was built. The effect of multiple impinging jets on convective heat transfer from a heated ceramic plate was investigated under different jet velocity ratio r（ 10≤r≤30） and different jet height（ 20≤L /d≤80）. The change law of convective heat transfer coefficient and the relative Nusselt number were analyzed,and the physical mechanism of heat transfer enhancement by multiple impinging jets was discussed. Results revealed that the relative Nusselt number increased with the jet velocity ratio,and the highest relative Nusselt number of 1. 98 was obtained. In addition,it was found that smaller jet height did not always result in better heat transfer,and there was an optimized jet height. In case that the jet velocity ratio r was relative small,the relative Nusselt number always decreased with the jet height,whereas when the jet velocity ratio r was relative large,the relative Nusselt number increased firstly and followed by a decrease trend as the jet height increased.