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

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.