利用液晶瞬态技术测量离散缝的气膜加热效率及换热系数

采用液晶瞬态测试技术对带离散缝平板的加热效率及换热系数进行了测量。从实验结果来看主流速度较高时,吹风比大,平均效率高。在主流速度较低时,这种情况并不明显。不同吹风比下反映出的平均换热系数差别在靠近缝口的区域较明显,沿下游方向这种差别逐渐减少。同一吹风比下,主流速度较高,平均效率及平均换热系数也较高。从垂直于流动方向来看,缝中心线附近区域的效率较高,2个缝之间区域较低;而换热系数则是相邻2个缝之间的区域较高,缝中心区域较低。

New Transient-State Measurements of Film Heated Effectiveness and Heat Transfer Coefficients of the Discrete Slots with Liquid Crystal Technique

Purpose.Like Refs.4 and 5,we make use of transient liquid crystal technique.However,the transient-state measurements we did under contract have not been,to our best knowledge,found available in the open literature.In the full paper,we explain in detail how to make the transient-state measurements;in this abstract,we just list the two topics of our explanation:(a) experimental set-up;we give Figs.1 and 2 in the full paper to help explain;(b) principles and method of transient-state measurements;we derive eqs.(1) through(6) in the full paper to help explain.Figs.4 through 11 in the full paper show the results of our transient-state measurements;these results show that:(1) when the mainstream velocity is high,the higher the blow ratio is,the higher the average effectiveness is;(2) the average heat transfer coefficient near the slots is different for different blow ratios,whereas away from the slots,the differences rapidly diminish;(3) under constant blow ratio,the higher the mainstream velocity is,the higher the average effectiveness and average heat transfer coefficient are;(4) in the vertical direction of the flow,higher effectiveness appears near the centerlines of the discrete slots but higher heat transfer coefficient appears between two discrete slots.