Numerical analysis of conjugate convection-conduction heat transfer in an air-filled cavity with a rhombus conducting block subjected to subdivision: Cooperating and opposing roles

Abstract

Two-dimensional numerical simulations are conducted to study natural convection flows and heat transfer characteristics in a square cavity confining conducting solid blocks. The initial solid block, of rhombus shape, is placed at the center of the cavity and subdivided following the mathematical formulae N=4l (l = 0, 1, 2 and 3). The solid blocks resulting from the subdivision of the initial block are uniformly distributed within the cavity to maintain unchanged the volume occupied by the fluid. The flow and temperature solutions are obtained using the Lattice Boltzmann method with the multi-relaxation time collision scheme and Finite Volume method, respectively. The effect of the fragmentation of the initial solid block and its thermal conductivity on fluid flow and heat transfer inside the cavity is examined. The results obtained show that the subdivision of the initial block leads to heat transfer reduction between the thermally active walls of the cavity with negligible, moderate and important rates depending on the number of the blocks and the value of Rayleigh number. It is also shown that the thermal conductivity of the blocks may affect heat transfer positively (cooperating role of conduction) or negatively (opposing role of conduction) depending on whether heat transfer is dominated by natural convection or not.