Abstract
Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.
Highlights
The topic of jet impingement heat transfer has been widely researched, and details of such investigations can be found in [1,2,3]
Array jet impingement was studied for inline and staggered configurations under maximum crossflow condition, where correlations were provided for jet mass flux distribution, crossflow mass flux distribution in impingement channel, and row-wise averaged Nusselt number in reference to the row closest to the blocked end
The authors concluded that impingement with effusion had higher thermal-hydraulic performance compared to three other crossflow exit schemes, indicating that effusion holes efficiently remove the spent air from the impingement channel when effusion holes were arranged in a staggered form relative to the jet footprint
Summary
The topic of jet impingement heat transfer has been widely researched, and details of such investigations can be found in [1,2,3]. The entrainment effects were identified on a free jet, and it was observed that local jet recovery temperature provided a better nondimensional profile of heat transfer. Impingement heat transfer simulation is an active area of thermal research, and researchers are exploring performance and quality improvements by different mathematical models even on simple round jets with smooth target surfaces. Katti et al [41] provided experimental measurement of single free jet heat transfer, and Jeffers et al [42] studied the stagnation zone with a single confined and submerged jet. They used a long tube to develop flow at the jet exit. They found an overall cooling effectiveness and it was biased towards better impingement cooling
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