Dimensionless Analysis for Predicting High Temperature Alloys Corrosion in Molten Salt Systems for Concentrated Solar Power Systems
A multi-physics corrosion model that include the main corrosion mechanism of Cr oxidation along with diffusion-limited corrosion as the limiting step allow to predict corrosion rates (i.e., current density) and corrosion potentials. Also, a CFD model has shown that temperatures and fluid flows can be accurately predicted in molten salt heat transfer systems including coupons. The CFD predictions allow to characterize natural convection flows in the reactor by analyzing engineering parameters such as Rayleigh number, Nutssel number, and Grashof number, etc. As the temperature and mass transports are coupled in the natural convection system, the analysis of these dimensionless numbers helps to correlate different physics to understand the system better and to reduce complication to solve the problem. These dimensionless numbers around coupons incorporated into the corrosion model allow to predict mass transfer coefficients and boundary layer thickness that determine corrosion rates (i.e., current density).
The model predictions and experiment results suggest that the use of thicker materials to improve the lifetime may not be a good strategy in molten salt systems due to the localized nature of the corrosion.
The authors gratefully acknowledge the support for this work by the DOE EERE SunShot Initiative under a subcontract from SRNL to the University of Alabama and to the University of South Carolina.
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