辐射槽面喷雾冷却传热特性试验

Experiment on Heat Transfer Characteristics of Radial Groove Surface Spray Cooling

针对表面结构强化喷雾传热机理不明确的现状,在辐射槽道结构表面上,以蒸馏水为工质,研究了喷雾流量、槽道深度对传热特性的影响;通过测定液体离开待冷却表面温度、喷雾液体相变量,结合试验照片,探讨喷雾冷却传热机理。研究发现,热流密度随喷雾流量和表面温度的增大而增加;辐射槽面相比光滑表面具有更好的传热性能,槽道深度越大,效果越好,特别是在喷雾冷却的沸腾区。试验现象和曲线证明快速运动的薄液膜是决定喷雾冷却非沸腾区传热的关键;但在沸腾区,汽泡破裂与液滴对接触壁面的冲击更为重要。当槽道深度超过液膜厚度时,再增加槽道深度对提升非沸腾区传热不利,但深槽面能提供更多的汽化核心,有利于沸腾区传热强化。槽结构影响研究、相变量测定以及传热机理探讨丰富了喷雾冷却理论,为进一步完善模型奠定了基础。

At present, the mechanism of spray cooling enhanced by surface structure spray cooling heat transfer is not clear. With distilled water as the working fluid, experiments are conducted to study the effects of flow rate, groove depth and surface temperature on heat transfer characteristics of spray cooling on radial groove surfaces and flat surface. Heat transfer mechanism of spray cooling is discussed according to the final temperature of cooling fluid, the liquid phase change capacity and experimental photos. Experimental results indicate that the heat flux and surface temperature increase with the increasing of spray flow rate. Radial groove surfaces obtain the better transfer performance in comparison to the flat surface, and when the groove depth increase, heat flux of radial groove surfaces increase, especially in boiling region. The key factors which determine heat transfer in non-boiling region is fast moving liquid film, but in boiling region, bubble rupture and droplet impact on the contact wall are more important. When the radical groove depth exceeds the thickness of the liquid film, increasing the channel depth is unfavorable to the heat transfer in the non-boiling region, but the deeper groove can provide more vaporization cores, which is beneficial to the enhancement of the heat transfer in the boiling region. The research on the influence of groove structure, the determination of phase change and the mechanism discussion enrich the theory of spray cooling, which lays the groundwork for further perfecting the spray cooling model.