Transient Natural Convection in a Square Porous Cavity Submitted to Different Time-Dependent Heating Modes

Natural convection induced in a square porous enclosure with its horizontal sides insulated and its vertical sides submitted to various periodic heating modes is studied numerically using the Darcy model. Parameters of the problem are the Rayleigh number (100 ≤ R ≤ 500), the amplitude of the variable temperatures) (0 ≤ a ≤ 1) and its (their) period (0.001 ≤ τ ≤ 1.2). The effect of the heating modes on the flow field and heat transfer is studied. It is found that the flow becomes multicellular and the heat transfer can be significantly improved for all the variable heating modes considered. The best improvement. is obtained when the active wall temperatures vary in opposition of phase. The resonance phenomenon is also observed when the period of the imposed temperature(s) is varied.