Phase change behavior of latent heat storage media based on calcium chloride hexahydrate composites containing strontium chloride hexahydrate and oxidation expandable graphite

Calcium chloride hexahydrate (CaCl2·6H2O) composites PCMs containing strontium chloride hexahydrate (SrCl2·6H2O) and oxidation expandable graphite (EGO) were prepared and phase change behavior of CaCl2·6H2O/EGO/SrCl2·6H2O composite PCMs, including supercooling degree, phase change temperature, latent heat, density, thermal conductivity and thermal stability were systematically studied. Results demonstrate that thermal conductivity, heat transfer and the latent capacities of the CaCl2·6H2O/SrCl2·6H2O/EGO composite PCMs are significantly enhanced, supercooling of CaCl2·6H2O/SrCl2·6H2O/EGO composite PCMs are suppressed, mainly ascribe to that the EGO are homogenously dispersed in PCMs due to the existence of oxygen-containing functional groups in EGO, meanwhile, the well-dispersed EGO serving as nuclei to promote the heterogeneous nucleation and crystallization process of CaCl2·6H2O. Moreover, a fifty-run-cycling test verifies that the CaCl2·6H2O/SrCl2·6H2O/EGO composites PCMs contained with 3 wt% SrCl2·6H2O, and 1.0 wt% EGO possesses enhanced thermal behavior with no phase segregation observed; the latent heat was calculated to be 172.26 J/g.