A volume averaging approach is applied to derive governing equations for purely viscous homogeneous flows in porous media. Additional terms appear in the volume averaged governing equations related to porosity, tortuosity, shear factor, dispersion coefficient and macroscopic viscosity. Flow in porous media is non-linear in nature in that the shear factor, the dispersion coefficient and the macroscopic viscosity are functions of flow velocity. A shear factor model is proposed based on now through orifice plates and the macroscopic viscosity is defined for purely viscous flows. The predictions of flow velocity profile and pressure drop using the proposed model agree well with published experimental results.