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Abstract

A dimpled surface, used as a turbulence promoter, was combined with jet impingement to investigate the potential for heat transfer enhancement. An eight-by-eight jet array was used to impinge a staggered dimple surface, both on the dimples themselves and on the flat portions adjacent to the dimples. The heat transfer coefficient was measured using the transient wide-band liquid crystal method. The jet-to-plate spacing (H/D) studied was 2, 4 and 8. Two dimple geometries were tested: hemispherical concavities and cusped elliptical shapes. All the results were normalized by those from a flat plate. The results varied depending on the H/D spacing and the flow scheme for the exit (one-way, two-way and four-way exits); the effect of geometry variation (hemispherical or cusp shapes) was secondary. The maximum exit flow scheme (four-way exit) achieved the highest enhancement of heat transfer. The combination of dimples and impingement can lead to significant enhancement, but careful optimization of the location of impingement would be required.

Keywords

jet impingement dimple transient heat transfer liquid crystals

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