Characterization of MgCl(2)·6H(2)O-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 MgCl(2)·6H(2)O was mixed with CaCl(2)·6H(2)O to obtain the eutectic with a melting point of 23.9 °C. SrCl(2)·6H(2)O 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 CaCl(2)∙6H(2)O-MgCl(2)∙6H(2)O 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 CaCl(2)∙6H(2)O-MgCl(2)∙6H(2)O 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.