Thermal conductivity in porous materials

Abstract

This study investigates how pore size and shape affect the thermal conductivity of concrete employing three-dimensional computational simulations. It focuses on the thermal and heat distribution of a concrete cube containing cylindrical pores filled with air distributed throughout the cube. The cube is subject to a temperature difference across the opposing faces of it while all the remaining surfaces are adiabatic. The research aims to answer whether it is the number of pores or the size of pore geometries that affects thermal conductivity more significantly at the same porosity levels. The simulations were produced through COMSOL Multiphysics using steady-state heat transfer simulation, under idealized conditions.

The results reported a more significant drop in effective thermal conductivity in the cases where smaller but more numerous pores were used. This was consistent throughout and observed during all levels of porosity. Therefore, heat is transferred less effectively when the material has more and smaller pores rather than bigger and less pores (at the same porosity level). Moreover, this dissertation supports the importance of the geometric pore size and organization in thermal optimizing for porous construction materials.

The study contributes, in practice, to energy conscious building design implications for thermal insulating strategies using porous concrete and theoretical implications of design through understanding pore geometry and thermal transfer at physics of calculations. Limitations to this study would be consideration to moisture content, force or irregular pores shapes. Future consideration of follow-up studies could incorporate these considerations for experimental validation of results from this research.