Abstract: 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.

Key words: heat transfer enhancement, liquid temperature, phase change capacity, radial groove surface, spray cooling