The thermal dispersion effects on the Darcy-Forchheimer natural, mixed and forced convection heat transfer with viscous dissipation effects over an isothermal vertical flat plate in a fluid saturated porous media are examined numerically. The coefficient of thermal diffusivity has been assumed to be the sum of molecular diffusivity and the dispersion thermal diffusivity due to mechanical dispersion. The non-dimensional governing equations are solved by using finite difference method with a Crank Nicolson implicit numerical technique. The results show that in natural, mixed and forced convection heat transfer, when the modified Darcy number is increased the heat transfer rates are enhanced and when the modified Forchheimer number are increased the Nusselt numbers are decreased. The effect of both viscous dissipation and thermal dispersion was found to increase both velocities and temperatures inside boundary layer and to reduce heat transfer rates.
In this study, the influence of thermal radiation and dispersion on a porous
medium which was filled in a vertical cylinder was numerically solved. A
finite-difference method was used to solve the non-dimensional equations by
applying a Crank-Nicolson implicit numerical technique. Moreover, an
experimental setup has been initially built to investigate the effect of
three different grain sizes of the porous materials on the heat transfer
process. The numerical results indicated that the thermal radiation
increased the momentum and the thickness of the thermal boundary layer
during the natural convection heat transfer process. Whereas, the thermal
dispersion factor decreased the momentum and the thickness of the boundary
layer during the natural convection heat transfer process, which enabled a
steady and transient heat transfer. The experimental results indicated that
the pore size of the medium significantly affected the rate of the heat
transfer process. A smaller pore size showed a greater effect and could be
used in different applications that involve a higher heat transfer rate,
while a larger pore size can potentially be used as an insulating material.
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