Preprint of "NaCl Influence on Heat Capacity for Glycerol-Water Solution: Experimental Measurement and ePC-SAFT Modeling"

The effect of NaCl concentration on the thermophysical properties of an 85 wt% aqueous glycerol solution was examined experimentally and modeled using ePC‑SAFT. Nine solutions containing 1–10 wt% NaCl were prepared and their density, viscosity, and specific heat capacity (Cp) were measured from 278 to 353 K. Density increased linearly with NaCl content, while its temperature dependence remained unchanged. Viscosity rose by roughly 5 % for each 1 wt% increase in NaCl, especially at lower temperatures where glycerol‑based systems are most sensitive. Cp decreased linearly with NaCl concentration; the suppression intensified at higher temperatures, reflecting a salt‑induced disruption of the hydrogen‑bonding network. The density and heat‑capacity data of the glycerol–water–NaCl system were modeled using the electrolyte perturbed‑chain statistical associating fluid theory (ePC‑SAFT) equation of state. To enable a consistent description of both volumetric and caloric properties, a new parameter set for pure glycerol was developed by incorporating heat capacity data into the fitting procedure. For the ternary system, a hierarchical optimization of binary interaction parameters was performed, resulting in a temperature- and NaCl mass fraction-dependent association binary interaction parameter between glycerol and water. The final model reproduces the measured density and heat capacity of the ternary mixture with deviations of 0.32% and 0.14%, respectively, demonstrating that remarkably accurate simultaneous modeling of volumetric and caloric properties of complex glycerol‑based electrolyte systems is achievable with ePC‑SAFT when suitably parametrized. The presented experimental framework and validated thermodynamic model provide a robust foundation for characterizing crude glycerol‑based mixtures and can be extended to related ternary systems relevant to thermal energy storage and glycerol purification applications.