The objective of this study is to determine the enhancement of heat transfer using a novel jet plate configuration and compare that to a flat baseline jet orifice plate. Physical mechanisms that lead to an enhancement of heat transfer coefficient when comparing both configurations are discussed. In the presented work, two jet plates with two-dimensional arrays of 20 x 26 circular air jets impinging on a flat wall parallel to the jet orifice plates are studied. The first staggered dimple-protrusion (concave-convex) plate is arranged to have negative Poisson ratio (NPR) properties when microscopically loaded. This plate features jet diameters of 6.88 mm \[0.271 in\] and 14.55 mm \[0.573 in\] for the concave and convex shapes, respectively. The second jet plate is flat-bottomed, which serves as a baseline for the heat transfer study. This plate has a constant jet diameter of 3.49 mm \[0.137 in\] calculated based on the total average open area of the first plate.

Heat transfer characteristics, along with structures of the turbulent flow are investigated over jet-Reynolds numbers of 5,000, 7,000, and 9,000. Jet-to-target plate distance (z/D) is varied among (2.87, 3.25 and 4) jet diameters. The concave-convex shapes yield higher heat transfer coefficients when compared to a flat jet plate configuration. Nusselt number enhancement of up to 55% at the last row location is observed.

A numerical study is also carried out to compare various turbulence models (kε-EB, kε-Lag EB, kε-v^2^ƒ, kω-SST, RST). The best performing turbulence model is selected based on comparison of simulation results against experimental data. Numerical simulations are analyzed in detail to explain the underlying mechanism of heat transfer in such geometries.


Multi-Jet Impingement Heat Transfer With a Dimple-Pimple Patterned Jet Plate

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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