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.