Promoting fountain behaviors with cone surface structures under impinging jets

Abstract

Increased heat generation in newer generations of electronic devices necessitates increasingly aggressive thermal management techniques. In automotive applications, jet impingement is particularly attractive for the cooling of power electronics, as integration in the radiator flow loop requires few added components. Arrays of impinging jets are effective at cooling heated surfaces to relatively uniform temperatures, as increased heat transfer is achieved both under and between jets. Under the jets, fluid motion naturally limits the thermal boundary layer, while interactions between jets create a plume or fountain of fluid that departs the surface. To maximize utility of this approach, fountain development must be promoted and spent fluid must be effectively managed. In this study, an angled confining wall and conical surface modifications under each water jet were analyzed. When using an angled wall, crossflow effects on the downstream jets were significantly reduced, suggesting improved performance, particularly for larger arrays. The cone modifications were able to promote fountain and secondary fountain behaviors, improving performance across the surface. In particular, the secondary fountain was seen to reduce a hot spot on the surface. Under a flat confining wall, average surface temperature rises were reduced by 3.5 to 7.5%, despite the area only being increased by 1 to 3%, indicating that 60 to 78% of the thermal improvement is caused by enhanced heat transfer coefficients. The results suggest that the modifications could be effective in hot spot applications and in achieving a uniform surface temperature, potentially improving device performance and increasing lifespan.