The effect of cavity geometry on heat transfer in building wall materials

As known well, majority of the heat losses of buildings occur at walls which are made of a few layers such as plaster, well bricks, insulation material etc. It is expected that the wall brick building have low overall heat transfer coefficient to reduce heat losses through buildings in order to increase building heating performance. . In order to achieve this expectation, the wall bricks are produced with materials which have low thermal conductivity and cavity (hole) which weakens thermal transport mechanism. In this study, it is aimed to decrease the overall heat transfer coefficient of wall brick models with various cavities which affect the natural convection mechanism. For this purpose, some changes are made in the internal cavity geometry of a single cell of the hollow wall brick model and the heat transfer analysis of the proposed geometries was experimentally repeated under three different (7, 9, 12 W) heat flux conditions. The building is simulated as an insulated chamber made of styrofoam with dimensions of 300 mm x 300 mm x 300 mm. The wall brick models are produced from PVC (Decota) material in dimensions of 160 mm x 160 mm x 50 mm and mounted on a wall of the insulated chamber. The experiments are carried out on the brick models having the cavity geometries of regular symmetrical I profile and asymmetrical profiles. The temperatures are measured at six points on the sides of the brick models. The results of the study are presented as the change of the overall coefficient of heat power of the wall materials according to the heat transfer. In the proposed internal geometry, it was observed that the overall heat transfer coefficient decreased from 3.7% to 11.5% for three different heat input values compared to the I profile wall material. Findings include analysis of experimental results.