(758f) Thermophysical Property Estimations of Molten Salts

Projection of molten salt performance in thermal storage systems, whether based on sensible heat or latent heat, is highly dependent on the predictions of thermophysical properties.  In the absence of experimental data, heat transfer properties rely on theoretical estimations.  This work focuses on thermodynamic predictions of mixture properties for molten salts supportive of ongoing advanced heat transfer fluid research at the Sandia National Laboratories.*  Thus far, the candidate mixtures  studied experimentally and theoretically at Sandia are made up of either ternary or quaternary nitrate and mixed nitrate/nitrite salts of various compositions. Experimentally, mixture properties such as heat capacity, melting points, and heat of fusion are obtained by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).  Classical thermodynamics are applied to resolve phase transitions of molten salt mixtures as well as mixture properties.  Classical thermodynamics assumes a continuous mathematical form for the equation of state and expediently extrapolates pure/binary properties to multicomponent mixtures.  The Wilson equation, developed originally for organic mixtures, is used to study phase boundaries of molten salts in this work.  Molecular thermodynamics where atomistic simulation forms the basis for constructing the equation of state are conducted where our fundamental understanding and experimental knowledge are lacking.  Mixture properties involving calcium nitrate are calculated using MD simulations.

*Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin company, for the United States Department of Energy under contract DE-AC04-94AL85000.