LATTICE BOLTZMANN SIMULATION OF HEAT TRANSFER ENHANCEMENT IN AN ASYMMETRICALLY HEATED CHANNEL FILLED WITH RANDOM POROUS MEDIA

In this paper, numerical simulation of fluid flow and heat transfer in a 2D planar channel, partially and full filled with random fibrous porous media, is performed using the lattice Boltzmann method (LBM). The fibrous media is constructed of a random matrix of solid fibers, modeled as square obstacles and located in a cross flow. The thermal asymmetry is imposed on the system, such that one wall is isothermal and the other wall is insulated. Nonlocal thermal equilibrium conditions combined with pore level simulation are applied to the solid phase. Criterion for enhancement of heat transfer due to the presence of porous medium is the average Nusselt number on the isothermal wall. The effects of geometrical parameters such as porosity, blockage ratio, and porous block eccentricity, as well as some thermophysical parameters such as Reynolds and Prandtl numbers, are studied. The obtained results indicated that the position and the width of the random porous block has significant influence on the thermal performance of the channel. Furthermore, it was found that channels partially filled with porous medium are more efficient than the fully filled ones. Also, decreasing the porosity or using smaller fibers at a constant porosity can enhance the rate of heat transfer.