阵列射流冲击复合不同肋化表面的沸腾特性

阵列射流冲击冷却技术可以有效地解决高热流密度器件的散热问题，为了验证受冲击表面强化传热结构对优化两相射流冷却性能的有效性，结合高速显微摄像手段，研究了不同肋化表面结构形态对受限式阵列射流冷却的流动、传热特性的影响。设计了2种含不同肋化表面形态:光滑切割针肋（0.6 mm×0.6 mm×1.0 mm）、外覆多孔烧结层的粗糙针肋（粒径为73~53 μm）。实验使用无水乙醇为工质，以光滑表面的射流冷却热沉为对照组，入口温度均为20℃，在固定工质流量7.5 mL/s下，随着加热热流密度由5 W/cm2增加至100 W/cm2时，热沉的换热系数均持续上升但增幅逐渐减小，未明显观察到沸腾相变的发生。对固定热流密度82.6 W/cm2、80.5 W/cm2改变工质流量（射流雷诺数）的实验工况，当工质流量由7.5 mL/s逐渐降低至1.0 mL/s时，可以非常明显地观测到射流腔内部工质由分层湍流逐步进入泡状流、弹状流及环状流，其分别对应起始沸腾区、核态沸腾区及膜态沸腾区。 

Boiling characteristics of array jet impingement with various pin-finned surfaces

Array jet impingement cooling technology can effectively solve the heat dissipation problem of high heat flux devices. In order to verify the effectiveness of heat transfer enhancement on the impacted surface for optimizing cooling performance of two-phase jet cooling, this article studied the effects of different pin-finned surface structures on the flow and heat transfer characteristics of confined array jet cooling combined with high-speed microscopic imaging methods. Two kinds of pin-finned surface morphology were designed:smooth cutting needle rib (0.6 mm×0.6 mm×1.0 mm) and rough needle rib with porous sintered layer (particle size 73~53 μm). In the experiment, jet cooling heat sink with smooth surface was used as the control group, anhydrous ethanol was used as the working medium, and all the inlet temperatures were the same (20℃). When the flow rate is 7.5 mL/s and the heating heat flux increases from 5 W/cm2 to 100 W/cm2, the heat transfer coefficient of the heat sink continues to increase but the increase rate gradually decreases, and no phase change is observed. Under the experimental conditions of changing the fluid flow rate (fluid Reynold number) with fixed heat flux 82.6 W/cm2, 80.5 W/cm2, when the flow rate decreases from 7.5 mL/s to 1.0mL/s, it can be clearly observed that the working fluid in the jet cavity gradually enters bubble flow, slug flow and annular flow from stratified turbulence flow, which correspond to the initial boiling zone, nuclear boiling zone and membrane boiling zone, respectively.