Two Effective Thermal Conductivity Models of Porous Media with Hollow Spherical Agglomerates

Based on the structure feature of xonotlite-type micro-pore calcium silicate, micro-pore calcium silicate is simplified as porous media with hollow spherical agglomerates, and two element models, point-contact empty spherical shell model and area-contact empty cubic model, are developed. Through applied one-dimensional heat conduction in the cell, the models for calculation of the effective thermal conductivity of micro-pore calcium silicate are derived. As compared with the experimental data of calcium silicate, the results show that the calculating results by the models have better agreement with those by experiment, and the models can be used to approximately calculate the effective thermal conductivity of porous media which have similar structure feature with micro-pore calcium silicate. In addition, the effect of temperature and contact parameter on the effective conductivity is analyzed, and it implies that the extent of contact between the hollow spherical agglomerates in xonotlite-type calcium silicate is not very high.