NUMERICAL ANALYSIS OF FLUID FLOW AND HEAT TRANSFER IN A CHANNEL WITH POROUS BAFFLES

In the present study, analysis of fluid flow and heat transfer in the entrance and the periodically fully developed region of a channel with porous baffles in a staggered arrangement, is numerically studied. The Navier-stokes and Brinkman-Forchheimer equations are used to model fluid flow in open and porous regions. The flow is assumed to be laminar. A finite volume based method, in conjunction with the SIMPLE algorithm, is used to solve the equations. The local thermal equilibrium model is adopted in the energy equation to evaluate solid and fluid temperatures. The effect of parameters, such as baffle height, baffle spacing, Reynolds number and thermal conductivity ratio between the porous baffles and the fluid, on the flow field and local heat transfer rate is analyzed at two values of Darcy number. Considering the effect of geometrical and physical characteristics of the porous baffles and flow parameters on the developing velocity profile and the local Nusselt number, it can be concluded that the developing length, as well as the value of fully developed Nusselt number, are affected by these parameters, while, in the case of conventional thermally developed duct flow, the Nusselt number is independent of these parameters. The results indicate that the local heat transfer coefficient significantly depends on the formation and variation of the recirculation caused by the porous baffles, so that, in cases where use of porous baffles leads to a recirculation zone, the local Nusselt number in the entrance region is less than that of the fully developed region. It is also shown that the heat transfer performance ratio is significantly improved for high Prandtl number fluids.