Heat transfer in block walls

Combined conduction-convection-radiation heat transfer in concrete block walls with one or two cavities is simulated using the CFD code “FIDAP”. It is shown that the resistance of the block itself depends on the temperature difference between the external and internal parts. The heat flux is shown to vary appreciably, approximately 30 %, between the upper and the lower parts of the block. Assuming spatially cyclic boundary conditions, ie heat transfer to the lower part of the block equal to heat transfer from its upper part, results in a vertical heat flux upwards which can be of the order of 20-30 % of the heat flux across the block.