Thermal properties and application of a novel CaCl₂·6H₂O/expanded graphite shape-stabilized composite phase change material for electric radiant heating

In recent years, electric heating has been popularized and applied as a heating form of clean energy. In order to realize the peak shifting and valley filling of heating electricity to reduce heating cost and improve energy efficiency, phase-change heat storage electric heating system has become a hot topic of research and application. In this paper, using CaCl₂·6H₂O as phase change material (PCM), SrCl₂·6H₂O as nucleating agent and expanded graphite (EG) as porous supporting carrier, a novel shape-stabilized composite PCM was prepared by melt blending method. The thermal physical properties of shape-stabilized composite PCM with different prepared proportions were studied through experiments. The experimental results showed that 88%CaCl₂·6H₂O + 2%SrCl₂·6H₂O + 10%EG (50 mesh to 100 mesh) is the optimal prepared proportion of the shape-stabilized composite PCM. The composite PCM with a latent heat of 172.92 kJ/kg, a thermal conductivity of 3.85 W/m·K and a super-cooling degree less than 2 °C, has good shape stability and thermal reliability. A kind of novel electric heating module was fabricated with prepared composite PCM and carbon fiber heating wire. The heat storage and release characteristics of the module were studied through experiments, and the effects of different electric heating power, EG particle size and module size on its thermal performance were also studied. The experimental results showed that the internal temperature of the module was uniform and the module can maintain stable heat dissipation for a long time. The temperature fluctuation of the module surface is relatively small. In summary, the module can meet the heating requirements of buildings when applied to electric radiant heating in the building, and the CaCl₂·6H₂O/EG shape-stabilized composite PCM shows great promise in building energy saving.