Natural convection heat transfer in an enclosure with a heated backward step

A numerical analysis was carried out to study the laminar natural convection in an enclosure induced by a heated backward step. The effects of the Rayleigh number Ra, the Prandtl number Pr, and geometrical size of the enclosure on the flow structure and heat transfer characteristics are investigated in detail. Results reveal that the presence of the backward step can enhance the heat transfer coefficient about 32% for Ra=107 and Pr=0.71. The extent of heat transfer enhancement increases with the decrease in Ra. The influence of the dimensionless distance between the heated backward step and cooled plate L2 on the average Nusselt number Nu is more significant for the system with a smaller Ra. A larger dimensionless height of the insulated vertical plate H2 results in a higher Nu. For H2=L1=L2=1, Pr=0.71, and 103⩽Ra⩽107, the average Nusselt number can be correlated as Nu=0.353Ra0.256.