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 center dot 6H(2)O was mixed with CaCl2 center dot 6H(2)O to obtain the eutectic with a melting point of 23.9 degrees C. SrCl2 center dot 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 CaCl2 center dot 6H(2)O-MgCl2 center dot 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 CaCl2 center dot 6H(2)O-MgCl2 center dot 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.