A numerical investigation of heat transfer and entropy generation during jet impingement cooling of protruding heat sources without and with porous medium

In the present study, fluid flow and thermal characteristics associated with forced convection cooling of an array of discrete protruding heat sources mounted on impingement plate of channel by an impinging laminar jet is investigated for various Reynolds number (Re) and channel height (H/L). It is observed that, the magnitude of average Nusselt number for all heat sources increases with increasing Re and decreasing H/L, except the regions of heat sources covered by recirculation bubbles which may be due to accumulation of heat resulting in hot spots. In order to eliminate these hot spots, a porous layer is attached to the impingement plate. A parametric study is conducted to predict the performance of porous layer on fluid flow pattern, heat transfer and entropy generation for various values of Darcy number (Da), Reynolds number (Re), channel height (H/L), porosity (∊) and porous layer thickness (h/H). For the purpose, equations governing two-dimensional, time-dependent, incompressible and laminar flow are solved in a Cartesian framework by using Streamline Upwind Petrov-Galerkin (SUPG) Finite Element (FE) method. The generalized Darcy-Forchheimer-Brinkman model is adopted to model the flow in porous medium. The recirculation bubbles on heat sources are completely eliminated with the inclusion of porous layer at Darcy number, Da=10-2. The magnitude of overall Nusselt number and global entropy generation due to heat transfer (Sθ,Ω‾) and fluid friction (Sψ,Ω‾) increases with increasing Da,Re,h/H and decreasing ∊ and H/L. The optimum configuration for maximum heat transfer and minimum entropy generation is observed at Da=10-2,Re=1000,H/L=1.0,h/H=0.75 and ∊=0.5.