Abstract. Hollow blocks or bricks are widely used due to the good thermal insulation, lightweight, and acoustic insulation etc. In this paper, we present a numerical study of heat transfers coupled by natural convection and radiation conduction through a hollow block with three cavities used for the construction of ceilings of buildings. This hollow block is subjected to an incident solar flux and exchanging heat with the air ambient. The governing equations of the mathematical model used for the simulation are discretized by the finite volume method and solved by the SIMPLE algorithm. The main objective of this simulation is to study, in steady state, the effect of the thermal conductivity of the solid partitions on heat flux through this hollow block. The results are presented in terms of streamlines, the isotherms, temperature profiles on the actives surfaces and the obtained global heat flux.

This work examines numerically, the heat transfer coupled by conduction, natural convection and radiation through hollow block subjected to real boundary conditions. A hollow block of this type is usually used for the construction of ceilings in buildings. The top horizontal face of this hollow block is exposed to an solar irradiance and exchange heat with the air ambient with a thermal transfer coefficient. While the lower face exchange heat with the indoor air with another thermal transfer coefficient. And an adiabatic vertical side is assumed. The discretization of partial differential equations governing and boundary conditions was done using the finite differences method and the SIMPLE algorithm. The effects of the solar irradiance and the emissivity of the internal cavity surfaces on the flow structures were examined. The results showed that the emissivity affect the heat transfer through the hollow block considerably. The solar flux alters significantly the flow structure and the thermal fields through the studied structure.

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