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Characterization of calcium chloride tetrahydrate as a phase change material and thermodynamic analysis of the results

Ushak, Svetlana, Suárez, Miriam, Véliz, Sussy, Fernández, Angel G., Flores, Elsa, Galleguillos, Héctor R.
Renewable energy 2016 v.95 pp. 213-224
calcium, calcium chloride, differential scanning calorimetry, energy, heat, ions, lithium chloride, melting point, phase transition, potassium chloride, renewable energy sources, sodium chloride, temperature, thermodynamic models, viscosity
To study the feasibility of calcium chloride tetrahydrate as a phase-change material, we determined its melting point and heat of fusion using differential scanning calorimetry (DSC) in the temperature range of 0 °C-60 °C. We also determined the density and viscosity of molten calcium chloride tetrahydrate in the temperature range of 40 °C-65 °C and studied the effect of adding small quantities of LiCl, NaCl and KCl (1 mass %) on the resulting thermal and physical properties. Based on the determination of the thermophysical properties, the energy storage density was evaluated for the different systems. The CaCl2·4H2O + 1 mass % of LiCl exhibited higher values (174 J/cm³) than pure CaCl2·4H2O (156 J/cm³), and the CaCl2·4H2O + 1 mass % of NaCl (151 J/cm³).Some of the results were interpreted using thermodynamic models and functions, indicating that the addition of alkaline chlorides contributes to releasing water molecules from the hydration layer of Ca⁺² ions, which appears to have a determining effect on the behavior of molten CaCl2·4H2O.