The need on effective heat transfer enhancement has been increasing day by day. Because of that, researchers/engineers who work on heat transfer are required to obtain new techniques to address raising accumulation of heat transfer. Heat transfer can be enhanced by active and passive methods and passive methods are mostly chosen, as no external power input is required. Porous media is one of the most popular passive heat transfer techniques. Porous media can be divided into periodic and stochastic structures. In this thesis, the analysis of heat and fluid flow in 2D periodic structure and 3D aluminum and ceramic foam structures under mixed and forced convection heat transfer are studied. The governing equations are solved at pore scale and volume-averaged transport parameters as permeability, inertia coefficient, interfacial heat transfer coefficient and thermal dispersion are obtained by using volume averaging of the obtained pore scale velocity, pressure and temperature. For the change of periodic structure, the interfacial heat transfer coefficient and thermal dispersion with respect to Reynolds, Richardson and porosity under mixed convection are studied probably for the first time in literature. For foam structure, the changes of permeability, inertia coefficient, interfacial heat transfer coefficient and thermal dispersion with respect to Re are discussed. The determination of thermal dispersion by using tomography method is probably reported for the first time. For 2D periodic structures, the interfacial convective heat transfer coefficient successfully found while for the thermal dispersion conductivity the Volume Averaging Technique fails for high Richardson numbers under mixed convection. Based on good agreement between the computational values of this study and reported correlation in literature, it is observed that the use of micro-tomography technique for determination of volume-averaged transport parameters yield satisfactory results if properly used. The comprehensive methods for inspection, verification and validation of the obtained computational results for 3D digitally generated foam are suggested.