Numerical analysis of conjugate conduction-natural convection in a hollow building block

Abstract

The Heat transfer through a hollow building block takes place by a combination of all the three basic modes namely conduction, convection and radiation. This study represents the interaction between these modes rather than individual or two of them reported in the open literature. This is believed to provide more accurate estimation of the heat transfer rate across the walls. The goal of the study was to reduce the heat transfer improving the design of the hollow brick. Initially this was achieved by dividing a single cavity into multiple cavities by introducing partitions. Conduction heat transfer in the block material and natural convection and radiation in the cavity were considered. In addition, comparisons between the heat transfer results by including and neglecting the radiative heat transfer were carried out to determine the importance of radiative heat transfer in the study. It was found that increasing the number of cavities for the same block width decreases the heat flux significantly in both the cases. The results show that increasing the number of cavities can be effective in reducing the heat flux without compromising the building blocks strength. Nevertheless, a considerable reduction in the heat flux or increase in the R-value can be achieved through changing the layout of the cavities within the wall and by changing the emissivity of the block material. The combination of these techniques to compensate and remove the insulation layer in the cavity used to increase the wall thermal resistance is presented in this study.