Analysis of Heat Transfer in the Structures with Regularly Arranged Gas Cavities

In the work, the effective thermal conductivity (ETC) of anisotropic composite material (well-conducting media with regular cavities of the air) is studied by numerical modelling. The authors examine the influence of orientation and size of the cavities on the ETC of material structure and the role of thermal conduction, convection and radiation in the heat transfer processes. For modelling, Keraterm type material was chosen. It has been proved numerically that the ETC of similar structures is lower in the case when the cavities are oriented perpendicularly to the heat flux direction as compared with parallel orientation. According to the analysis performed, the radiation heat exchange in such cavities dominates over the convective heat transfer in the observed temperature range. In the calculations of ETC in structures of the kind, convection inside the cavities can be omitted. The proposed approach allows optimisation of the arrangement and size of the cavities in similar building materials.