Forced convection heat transfer of molten Salts: A review

Molten salts are used in a wide range of engineering platforms, with particular niche involving high-temperature thermo-fluidic applications. Molten salts are employed as industrial working fluids for several high temperature processing applications, including: as a catalytic medium for fuel production, for synthesis of exotic ceramic materials, and pyrolysis of waste products. Molten salts are of particular interest as materials for energy related applications, such as in the fields of Concentrated Solar Power (CSP), enhanced oil recovery, advanced nuclear reactors and nuclear fuel cycles. Industry wide applications include molten salt eutectics as materials for Thermal Energy Storage (TES) and as Heat Transfer Fluids (HTF), typically for enhancing the commercial grid-scale reliability of utilities that utilize CSP. Molten salts offer unique advantages such as low vapor pressure, extended operating temperature ranges, safe operation, minimal environmental footprint and moderate cost (compared to conventional heat transfer oils and ionic liquids). The scope of this literature review is limited to forced convective heat transfer data for a variety of molten salt formulations. The motivation of this study is guided by the promising role of molten salts in energy related applications, since the knowledge of the range of forced-convective heat transfer coefficients accruing from leveraging this class of working fluids are going to be crucial for determining (as well designing) the size and performance of the thermal devices. This review reveals that there is still a need for characterizing the heat transfer performance for various commercial molten salt eutectics and the available heat transfer data can be predicted reasonably well with available standard correlations. In addition, the goal of this review is to analyze the available literature data for the purpose of identifying the future research directions on this topic. © 2020 Elsevier B.V.