Experimental Determination of the Thermal Diffusivity of Granular Materials Allowing for Convective Heat Transfer

ABSTRACT Heat transfer within granular materials is a complex multiphase process, often consisting of solid, gaseous, and potentially liquid phases. Conventional methods to determine heat transfer properties typically involve small‐scale testing on a finely ground sample, which has the potential to introduce sample bias into the outcomes. This study presents a method to determine the thermal properties of granular materials from laboratory‐scale experimental measurements, through the determination of the thermal diffusivity and the convective heat transfer coefficient (which is closely related to the Biot number) of the system. A series of experiments was conducted, and they were analyzed using the proposed method. It was shown that these properties can be accurately obtained by a two‐stage process in which values are first estimated, assuming that only the lowest decaying mode dominates (as it does for long times), before fitting the complete analytic solution against the measured curves. The results show that this method gives a very accurate estimate of the diffusivity and Biot number, which may subsequently be used to determine key properties such as thermal conductivity and the convective heat transfer coefficient. This method is experimentally validated using sand as a proof‐of‐concept.