Influence of Buoyancy and Inter-Surface Radiation on Confined Jet Impingement Cooling of a Semi-Cylindrical Concave Plate

Abstract In this article, the confined jet impingement cooling of a semi-cylindrical concave plate is analyzed numerically. The investigation is done for different jet Reynolds numbers (Rej)ranging from 100 to 1000, as the Richardson number (Ri) corresponding to this interval ranges between 0.1 and 10. For any Richardson number, the modified Grashof number (Gr*) is fixed at 105. When analyzing the impact of inter-surface radiation between the target plate and confined surfaces on the overall cooling performance, three emissivity values (ε0.05, 0.5 and 0.9) are taken into consideration. Additionally, simulations are done for the pure convective heat transfer, ignoring inter-surface radiation (ε=0.0). The influence of surface emissivity and the Richardson number on velocity, temperature and pressure distribution in the flow region, local dimensionless temperature (θ) alterations on the target plate and confined walls, alterations in convective (Nuc), radiative (Nur), overall Nusselt numbers (Nuover), pressure coefficient (Cp) and ratio of radiative Nusselt number to overall Nusselt number (Nur/Nuover) on the target plate are highlighted. The findings demonstrate that surface emissivity has significant influence on thermal and hydrodynamic boundary layer formation, buoyancy induced flow and heat transfer, and the proportion of inter-surface radiation in overall heat transfer rises as the Richardson number and surface emissivity increase. At low Richardson numbers, the pressure in the stagnation region is greater than the atmospheric pressure. However, as the buoyancy effect increases, the pressure in the stagnation region falls below the atmospheric pressure and rises towards the exit.