Prediction of the thermal properties of porous building materials based on the pore structure.

Porous building blocks are increasingly gaining interest, thanks to their suitable compromise of structural and thermal properties, and their potential as high-end solution for upcycling waste materials. Having a low thermal conductivity is one of their key performance indicators with respect to their market viability. The present work studies the relation between the pore structure and the effective thermal conductivity of these materials. A numerical framework is implemented to simulate the heat transfer at the pore scale, in order to predict the macroscopic effective thermal conductivity. Simulations are performed on 3D voxel images of the pore structure acquired via micro computed tomography or virtual generation techniques. The thesis first focusses on conventional building blocks with granular and cellular pore structure types, and characteristic pore sizes in the micrometre and millimetre range. A comparison with measurements on real materials validates the framework’s performance. Subsequently, the model is applied to perform a parameter study on the impact of several pore scale parameters. In the second part of the thesis, the framework is extended towards materials with pore sizes down to the nanometre scale. To account for the Knudsen effect on gaseous conduction a novel simplified method is presented, based on the equivalence with thermal radiation. The model’s performance is verified using experimental findings on nanocellular foams provided in the literature, showing good agreement. The parameter study on conventional porous building blocks is finally extended to investigate the potential benefits of such novel pore structures on the resulting effective thermal conductivity.