Effect of combining with thermally expanded graphite on thermal conductivities of the lanthanum sulfate hydrate types of chemical heat storage material

Abstract

In the present work, the apparent thermal conductivities (TCs) parallel to the compaction direction of disk-like pelletized composites consisting of lanthanum sulfate hydrate (La2(SO4)3·xH2O (x ≤ 9) and β-La2(SO4)3·xH2O (x ≤ 1)) and thermally expanded graphite (TEG) were investigated to accumulate the fundamental thermophysical properties required to design a chemical heat-storage process that could recycle relatively low-temperature exhaust heat. The apparent TCs of both La2(SO4)3·xH2O/TEG and β-La2(SO4)3·xH2O/TEG were increased with increases in the content of TEG. Moreover, the apparent TCs were linearly increased with increases in the density regardless of the content of La2(SO4)3·9H2O at 50, 60 and 90 wt%. This density effect was possibly caused by a decrease in the interfacial thermal resistance between the interfaces of La2(SO4)3·9H2O - La2(SO4)3·9H2O, TEG - TEG and La2(SO4)3·9H2O - TEG grain pairs when the crimping force was enhanced due to increase in the density.