Thermal–physical properties of selected geomaterials: coal, sandstone and concrete based on basic series and parallel models

Abstract

Thermal diffusivity and thermal conductivity of three types of selected geomaterials: coking coal, sandstone and foamed concrete, are presented in this paper via water absorbability and thermal–physical property measurements. Experimental results show that the relationships among different thermal–physical properties of composite–porous geomaterials are consistent with the theoretical prediction and the previous experimental data. Based on the hypotheses of basic series and parallel heat propagation patterns, the harmonic approach between series and parallel thermal resistance models is performed. Under the combination of water-saturated and oven-drying conditions, this hypothetical model can be used to inversely calculate the effective/equivalent thermal conductivity (ETC) of the solid matrix with the acceptable accuracy compared with five other ETC prediction models based on mixing laws, especially for saturated samples. In addition, the rationality of the respective proportions of series and parallel heat propagation forms is also examined due to the acceptable accuracy of solid matrix inversely calculated ETC. Further validation on solid skeleton ETC of selected geomaterials indicates that the difference between two solid matrix ETC computational methods: namely the forward calculation using the XRD mineralogical composition data and inverse computation using the block sample ETC experimental results, is significant. Compared with the inverse calculation (overall relative uncertainty of 4.26%), the forward calculation results obtained using XRD data are not accurate enough (relative uncertainty is approximately 7.6–11.4%), which requires a large database for validation and further researches.