A numerical investigation of electronic cooling enhancement is carried out in this study in order to determine how the operating temperature can be maintained under the allowable level. A new technique based on use of porous or foam material inserted between the components on a horizontal board is studied. One energy equation model has been adopted to analyse the thermal ®eld. The control volume method based on ®nite differences with appropriate averaging for diffusion coef®cients is used to solve the coupling between solid,¯uid and porous regions. The effect of parameters such as Reynolds number, Darcy number and thermal conductivity ratio are considered in order to look for the most appropriate properties of the foam or porous substrate that allow optimal cooling. The results show that for high thermal conductivity of the porous substrate, substantial enhancement is obtained compared to the¯uid case even if the permeability is low. In the mixed convection case, the insertion of the foam between the blocks leads to a temperature reduction of 50%. List of symbolsA binary function b source term B binary function c height of the blocks, m C dimensionless height of the blocks C c=H c E Ergun constant c p¯u id speci®c heat, J/kg Á K Da Darcy number e thickness of the porous matrix, m E dimensionless thickness of the porous matrix E e=H H channel height, m k thermal conductivity, W/m Á K K permeability of the porous material, m 2 l channel length, m L dimensionless channel length L l=H l 1 entrance length, m l 2 length after the last block, m Nu Nusselt number p pressure, N/m 2 P dimensionless pressure Pr¯uid Prandtl number q local heat dissipation, W/m 3 Q heat dissipation per unit length in each block, W/m Re Reynolds number R k thermal conductivity ratio R m viscosity ratio s spacing between the blocks, m S dimensionless spacing between the blocks S s=H T temperature, K u axial velocity, m/s U dimensionless axial velocity U u=u 0 v transverse velocity, m/s V dimensionless transverse velocity V v=u 0 w block width, m W dimensionless block width W w=H x axial co-ordinate, m X dimensionless axial co-ordinate X x=H y transverse co-ordinate, m Y dimensionless transverse co-ordinate Y y=H Greek symbols a thermal diffusivity of the¯uid b thermal expansion coef®cient of the¯uid, 1=K e porosity k inertial coef®cient l dynamic viscosity, kg/m Á s m kinematic viscosity of the¯uid h dimensionless temperature q¯uid density, kg/m 3 w stream function, m 2 /s