Numerical Investigation of Laminar Impinging Jet Cooling of a Protruded Heat Source

Abstract

Thermofluid dynamics of an unconfined steady two-dimensional laminar jet impinging on an isothermal protruded heater is numerically studied for low jet inlet Reynolds number (Re) between 50 and 250. Results are shown for a range of impingement distances (h/W) between 1 and 10 for Prandtl numbers (Pr) 0.71 and 7.56. The volumetric entrainment increases with increasing h/w and decreasing Re. The reattachment distance of the wall jet appears to increase with Re and shows discernible deviation from the backward-facing step flow prediction for Re>150. Correlations are presented for average heater surface and sidewall Nusselt numbers as functions of Re and h/w for Pr=0.71 and Pr=7.56. In an overall convection dominant heat transfer, a relatively warmer and diffusion-dominated recirculation zone is identified adjacent to the sidewall with a low Nusselt number, which enhances significantly at Pr=7.56 when Re is increased above 100. At a low impingement distance, integrated kinetic energy flux shows greater magnitude in the impingement region but with a higher rate of decay. The integrated heat flux is greatly influenced by Re, and the effect is more pronounced at Pr=0.71. Self-similar behavior is observed for the velocity and heat flux profiles throughout the length in the developed region and for the temperature distribution over the heater surface. Both high Re and high h/w seem to adversely affect the self-similar behavior owing to a slower wall jet development.