Experimental study and thermodynamic modeling of solid-liquid equilibrium of binary systems: Dodecane-tetradedcane and tridecane-pentadecane for cryogenic thermal energy storage

In the present work, the equilibrium phase behaviors and thermal characteristics (phase diagrams, enthalpies, melting/freezing temperatures) of the binary systems dodecane-tetradedcane (C₁₂H₂₆-C₁₄H₃₀) and tridecane-pentadecane (C₁₃H₂₈-C₁₅H₃₂) were experimentally investigated to employ the potential PCMs for cryogenic applications. In addition, the phase diagrams were theoretically obtained by using both the ideal and non-ideal thermodynamic models. Results show that the compositions of eutectic points appear at 18 wt% C₁₄ for the C₁₂-C₁₄ system and 10 wt% C₁₅ for the C₁₃-C₁₅ system. The specific eutectic compositions of these two systems have satisfied enthalpies (158.0 J/g for C₁₂-C₁₄ and 143.1 J/g for C₁₃-C₁₅ in the melting process), slight supercooling (0.3 °C for C₁₂-C₁₄ and 0.4 °C for C₁₃-C₁₅), minor hysteresis (3.9 °C for C₁₂-C₁₄ and 2.2 °C for C₁₃-C₁₅) and superior thermal stability. Therefore, they are very attractive as the candidate PCMs in cryogenic energy storage systems. Moreover, the melting temperatures calculated by the theoretical models agree well with the experimental data. Especially for the non-ideal solubility model, the mean relative deviations are only 4% for the C₁₂-C₁₄ system and 8% for the C₁₃-C₁₅ system, respectively.