Numerical Investigation on an Obliquely Impinging Circular Air Jet on a Heated Flat Plate at Small Jet Plate Spacing

Jet impingement cooling has been studied extensively as this finds applications in the areas of reactor safety, electronic cooling etc. In practical applications, orthogonal jet impingement is a very ideal situation and the jet may hit the surface at some angle causing local uneven Nusselt number distribution over the surface. In this numerical study, 3-D simulations are carried out in Fluent 14.0 to investigate the effect of Reynolds number, distance between nozzle exit and the plate on the heat transfer characteristics. Standard k-epsilon with standard wall functions and enhanced wall functions, SST k-omega, Standard k-omega, V2F turbulence models have been studied for orthogonal jet impingement in this work. This study has been extended to inclined jet impingement. At jet plate spacing of Z/d <= 0.5, SST k-omega turbulence model predicts Nusselt number variation satisfactorily while for Z/d >= 0.5 V2F turbulence model is best suited. In this work, jet plate spacing of Z/d = 2, Reynolds number of 28000 and 40000 has been studied. At small jet plate spacing and inclined jet impingement, the flow behavior over the plate changes. Profile of constant Nusselt number elongates along the downhill side of the plate. Contours of high Nusselt number compresses towards uphill side of the plate. Maximum heat transfer rate is from the downhill side of the plate and location of point of maximum heat transfer shifts towards "uphill" side of the plate. This shift in point of maximum heat transfer depends on "angle of jet impingement".