Phase change materials (PCMs) are substances that absorb or release latent heat during changes in physical state. PCM is typically introduced in a heat exchanger inside a waste heat recovery system to enhance energy conversion efficiency. Molten salts consisting of multiple components are widely used as a PCM due to their high heat capacity. However, modulating the physical properties of PCMs via experimental trial-and-error is not economically feasible when dealing with complex systems. In this study, we designed six potential nitrates as PCMs via a combinatorial approach with the CALculation of PHAse Diagrams (CALPHAD) method, the Kissinger model, and experimental validations, among the KNO3-NaNO3-LiNO3 ternary system. The measured thermodynamics properties, including the solidus and liquidus temperatures, and enthalpy changes, were in agreement with the predicted values. A promising PCM that exhibited a lower melting activation energy (917.3 kJ/mol) and a higher change in enthalpy (136.4 J/g) than those of the commercial HITEC salt (1135.3 kJ/mol and 86 J/g). The designed PCM also showed a good thermal stability with the 316 stainless steel, which is a typical container material, at temperatures of 150°C and 300°C, respectively, for up to 1 month. The designed PCM is considered promising for waste heat recovery applications in terms of its high heat storage capacity, high heat exchange efficiency, and high thermal stability.
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