Numerical Investigations of Molten Salt Pump Journal Bearings Under Hydrodynamic Lubrication Conditions for FHRs

Abstract

Fluoride salt-cooled, High-temperature Reactors (FHRs), featuring particle fuel, graphite moderator, and molten fluoride salt coolant, are used for electricity generation and process heat applications. The primary loop of an FHR is a closed loop that operates slightly above the atmospheric pressure with the fluoride salt temperature over 600°C. Reliable high-temperature molten salt pumps are critical to the successful deployment of FHRs. To stabilize rotating shafts and reduce the associated friction coefficients, well-designed bearings are required for molten salt pumps. Therefore, it is necessary to investigate the detailed hydrodynamic performance of bearings under high-temperature molten salt conditions. In this study, a computational fluid dynamics software package, i.e., STAR-CCM+, was used to predict the performance of fluoride salt–lubricated bearings. The numerical models were verified and validated respectively based on an analytical solution derived from the Reynolds equation and experimental data published in the literature. Good agreement was observed between the simulation results and the analytical solution and experimental data with a maximum relative discrepancy of less than 5%. The validated numerical model was then employed to predict the pressure distributions, applied static loads, and power losses of high-temperature fluoride salt–lubricated bearings with various Sommerfeld numbers. In addition, a parametric analysis was performed to investigate the influence of the axial and helical grooves of bearings on applied static load and power loss. It is found that under the same salt lubrication conditions, the bearings with helical grooves and axial grooves respectively yield 20% off and 14% off power loss compared with the bearing without grooves.

Keywords:

• Molten salt pump
• journal bearing
• computational fluid dynamics
• FHR

Acknowledgments

The authors would like to thank Xiaodong Sun of the University of Michigan, Scott Svendsen and William Dentler of Flowserve, and Henry Korellis of Kairos Power for their invaluable support of the project.

Disclosure Statement

This material is based upon work supported by the U.S. Department of Energy Office of Nuclear Energy’s Nuclear Energy University Program under award number DENE0008977.

Additional information

Funding

This work was supported by the Nuclear Energy University Program [DE-NE0008977].