Characterization of MgCl₂·6H₂O-Based Eutectic/Expanded Perlite Composite Phase Change Material with Low Thermal Conductivity.

The melting points of the phase change materials (PCMs) incorporated into the walls of buildings should be within the human thermal comfort temperature range. In this paper, 15 wt.% of MgCl₂·6H₂O was mixed with CaCl₂·6H₂O to obtain the eutectic with a melting point of 23.9 °C. SrCl₂·6H₂O suppresses the supecooling of the eutectic. The combination with expanded perlite (EP) via the impregnation method overcomes the phase separation and liquid leakage of the CaCl₂∙6H₂O-MgCl₂∙6H₂O mixture. The composite PCM is form-stable with the maximum loading mass fraction up to 50 wt.% and latent heat of 73.55 J/g. EP also significantly reduces the thermal conductivity of the CaCl₂∙6H₂O-MgCl₂∙6H₂O from 0.732 to 0.144 W/(m·K). The heating-cooling cycling test reveals that the composite PCM is thermally stable. The cheap eutectic salt hydrate, with little supercooling, no phase separation and liquid leakage, low thermal conductivity and good thermal reliability, show great potential as envelope materials to save energy consumption in buildings.