Heat transfer mechanism and performance optimization scheme of refractory oxide solid heat storage materials.

Clean energy advances can drive solid heat storage technology. Because of their high-temperature, corrosion, and excellent thermal shock resistance properties, refractory oxides are widely used as solid heat storage materials. However, their applications are limited owing to their poor heat-transfer performance resulting from their multicomponent, multiphase, and complex nature and thus understanding their heat-transfer mechanism will be crucial for their performance optimization. In this study, the thermal properties and mechanisms of corundum, high-alumina, and magnesia bricks were characterized using heat-transfer theories and models. Macroscopic analysis of the bricks revealed that they are all "internal porosity" materials. By comparing the weighting parameter j , the multiphase high-alumina brick shows poor heat-transfer path patency and the measured thermal conductivity is the lowest at 3.55 W m−1 K−1. Microscopic analysis found that in contrast to the thermal conductivity of other materials, the thermal conductivity of high-alumina bricks was significantly affected by phonon intrinsic scattering. Moreover, corundum and magnesia bricks exhibited a wider range of ultimate heat-transfer performance than the high-alumina brick. Hence, the heat-transfer performance of refractory oxide can be enhanced by increasing their particle contact, reducing the negative effects of microcracks, phases, and impurities, and by reducing the number of defects on phonon heat transfer, thereby providing an optimization scheme for improving the heat-transfer performance of the materials. [ABSTRACT FROM AUTHOR]