Evaluation of the Thermal Properties of Ternary Mixtures of Fatty Acids for Green Thermal Energy Storage Application

In the present study, experimental and thermodynamic aspects of solid-liquid equilibrium were evaluated for ten ternary fatty acid mixtures formed by capric, undecylenic, pentadecylic, margaric, and stearic acids, as potential phase change materials (PCMs). The latent heat and melting temperature of ternary fatty acids mixtures were obtained from differential scanning calorimetry (DSC). Furthermore, the coefficients of the non-random two-liquid (NRTL) thermodynamic model were calculated using a quasi-binary mixing rule to correlate the liquidus line of solid-liquid equilibrium for the studied ternary mixtures. The comparison between the results of the proposed thermodynamic model and the experimental data showed average absolute deviations lower than 1%, validating the correlated thermodynamic model. The melting temperatures of the ternary mixtures of the studied fatty acids were in the range of 281-315 K, and their melting enthalpies ranged between 26.09 and 45.74 kJ mol-1, indicating that the studied mixtures had good potential to be utilized as low-temperature thermal energy storage materials.