<p>Impingement provides the highest heat transfer coefficients among the conventional cooling technologies used in gas-turbine. This paper reviews published articles on innovations to enhance impingement and suggests potential growth areas. Some of the notable features that will be explored are: Orifice Shape, Reduction in Crossflow, Target Surface Modification, Impingement Reuse. If space permits, we will discuss pulsating jets as well. One of the unexplored areas is: Insert Surface modification. This paper does not aim to draw conclusive explanation of the heat transfer patterns but provide thought provoking reasoning that will guide the future researchers on enhancing impingement heat transfer with new configurations. Orifice shapes can be round, triangular, racetrack, notched etc. The reduction in crossflow is achieved by larger channels or extraction of the spent coolant. Target surface modification includes, dimples, pins, ribs, and special shapes. Reduction in crossflow also includes converging or diverging channels. Impingement reuse is a technique of collecting the spent jets in a post impingement chamber and re-impinging that to a downstream surface. This reuse is suitable for shroud and downstream of first stage components as the first stage vane usually does not have enough pressure allowance for double impingement. The orifice studies show that it is hard to beat a sharp-edged round orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number with corresponding jet Reynolds number. Some of the target surface modifications require the surface protrusions to be perfectly aligned with the jet, which is difficult to achieve with inserts.</p>

Impingement Heat Transfer Innovations and Enhancements:  a Discussion on Selected Geometrical Features

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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