Investigation of impingement surface geometry effects on heat transfer in a laminar confined impinging slot jet

We investigated the laminar heat transfer characteristics of a milli-scale confined slot jet impinging on concave and convex surfaces at a uniform wall temperature. The flow at the nozzle exit had a fully developed velocity profile. The effects of Reynolds number, dimensionless nozzle-to-surface distance, and target surface geometry on heat transfer were investigated. The results revealed that the axial distributions of local Nusselt numbers exhibited a peak at the stagnation point and decreased monotonically in the wall jet region for all values of Re and NIB tested. The local Nusselt numbers for the concave surface were, at maximum, 47% larger than those for the convex surface in the region corresponding to x/B <= 2.0. This is due to the larger unsteady lateral distortions and earlier flapping motion of the jet column for the convex surface than for the concave surface, resulting in a larger heat transfer reduction for the convex surface. (C) 2017 Elsevier Ltd. All rights reserved.