EFFECT OF THERMAL STRATIFICATION ON FREE-CONVECTION IN A FLUID-SATURATED POROUS ENCLOSURE

Natural convection heat transfer from an isothermal vertical surface i n a fluid-saturated porous medium under the influence of thermal strat ification has been numerically analyzed using the finite element metho d. The combined effect of Rayleigh number and thermal stratification o n the global heat flux in porous cavities of varying aspect ratios has been analyzed. It is observed that the global heat flux (1) decreases with increasing values of the thermal stratification b and (2) increa ses with increasing values of Rayleigh number Ra. However, the cumulat ive heat flux along the midsegment of the vertical wall increases with increasing It and decreases with Ra. With increasing b, a reduction i n the convection zone with a downward drift is noticed. Global heat fl ux can be boosted by reducing the width L of the cavity by a factor of similar to 8 or more. The flow field and the heat transfer results ar e presented through the streamlines, isotherms, and global heat flux p lots.