Abstract
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.
Highlights
A greater thermal mass and better thermal insulation of building envelopes provides improved thermal comfort, reducing the heating/cooling load
Unless the problems of high thermal conductivity, high supercooling degree and phase separation can be solved, the CaCl2 ·6H2 O-MgCl2 ·6H2 O eutectic cannot be integrated into building envelopes for energy saving efforts
It was found that the increase in mass fraction of MgCl2 ·6H2 O leads to reductions eutectic mixtures
Summary
A greater thermal mass and better thermal insulation of building envelopes provides improved thermal comfort, reducing the heating/cooling load. Unless the problems of high thermal conductivity, high supercooling degree and phase separation can be solved, the CaCl2 ·6H2 O-MgCl2 ·6H2 O eutectic cannot be integrated into building envelopes for energy saving efforts. Nucleating agents such as SrCl2 ·6H2 O have been found effective to reduce the supercooling degree of CaCl2 ·6H2 O and its eutectics [14]. If CaCl2 ·6H2 O-MgCl2 ·6H2 O is composited with SrCl2 ·6H2 O and a porous matrix with low thermal conductivity, the problems that hinder its application in building envelopes will be solved simultaneously. The aim of this paper is to prepare a composite PCM with good thermo-physical properties for building envelopes
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