Heat Transfer From Novel Target Surface Structures to a Normally Impinging, Submerged and Confined Water Jet

Contemporary electronic systems generate high component-level heat fluxes. Impingement cooling is an effective way to induce high heat transfer coefficients in order to meet thermal constraints. The objective of this paper is to experimentally investigate the heat transfer from five novel target surface structures to a normally impinging, submerged, and confined water jet. The five target structures were: 90 deg vane, a $2×2$ pin fin array, and three geometries, which turn the flow away from, and back towards, the surface to be cooled to create an annular jet. The experiments were conducted for inlet Reynolds numbers of $500≤Re≤22,000$⁠, based on the mean velocity and jet tube diameter. The confined impinging jet was geometrically constrained to a round 8.5 mm diameter, square edged nozzle at a jet exit-to-target surface spacing of $H/D=0.5$⁠. The heat transfer characteristics of the five target surfaces were nondimensionally compared to a flat surface, and surface effectiveness of up to 2.2 was recorded. Enhancements of up to 45% were noted when the wetted surface area of the target surface structures was considered. The pressure drop attributed to the target surfaces is also considered. The findings of the paper are of practical relevance to the design of primary heat exchangers for high-flux thermal management applications, where the boundaries of cooling requirements continue to be tested.