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

A numerical analysis was carried out to study the laminar natural convectio n in an enclosure induced by a heated backward step. The effects of the Ray leigh number Ra, the Prandtl number Pr, and geometrical size of the enclosu re on the flow structure and heat transfer characteristics are investigated in detail. Results reveal that the presence of the backward step can enhan ce the heat transfer coefficient about 32% for Ra = 10(7) and Pr = 0.71. Th e extent of heat transfer enhancement increases with the decrease in Ra. Th e influence of the dimensionless distance between the heated backward step and cooled plate L-2 on the average Nusselt number (Nu) over bar is more si gnificant for the system with a smaller Ra. A larger dimensionless height o f the insulated vertical plate H-2 results in a higher (Nu) over bar. For H -2 = L-1 = L-2 = 1, Pr = 0.71, and 10(3) less than or equal to Ra less than or equal to 10(7), the average Nusselt number can be correlated as (Nu) ov er bar = 0.353Ra(0.256). (C) 2001 Elsevier Science Ltd. All rights reserved .