CFD assessment of heat transfer and frictional pressure loss correlations for molten salt reactors with non-condensable gases
MSU Affiliation
James Worth Bagley College of Engineering; Michael W. Hall School of Mechanical Engineering
Creation Date
2026-10-30
Abstract
Non-condensable gas (NCG) bubbles generated by fission products, radiolysis, helium sparging, and external contamination can significantly affect the thermal-hydraulic performance of molten salt reactors (MSRs). Although modern MSR system analysis codes incorporate gas-transport capabilities, many heat transfer and pressure loss closure relationships are derived from conventional fluids and have received limited validation for molten salt–gas systems. This study evaluates existing two-phase heat transfer and frictional pressure loss correlations for bubbly molten salt flows using computational fluid dynamics (CFD). A two-dimensional axisymmetric model was developed in ANSYS Fluent using the mixture model with an algebraic slip formulation and the SST turbulence model. Simulations were performed for FLiNaK–helium, FLiBe–helium, and KCl-MgCl₂–helium flows at liquid velocities of 3–5 m/s and gas void fractions of 0–10%. The numerical framework was assessed against air–water two-phase correlations and further evaluated using single-phase molten salt heat-transfer correlations. At constant bulk velocity, increasing void fraction reduced the convective heat transfer coefficient because of changes in mixture thermophysical properties and Reynolds number, while increasing velocity enhanced heat transfer through stronger turbulent transport. Frictional pressure loss decreased with void fraction at constant velocity because of reduced mixture density,viscosity, and Reynolds number. Among the evaluated correlations, Aggour provided the best overall agreement for heat transfer for fluoride-based salts, while Martin & Sims was best for the chloride salt. Müller-Steinhagen and Heck provided the most accurate frictional pressure loss predictions in all cases. These results support selected conventional correlations as practical interim closure relationships while highlighting the need for direct molten salt–gas experimental validation for future MSR system-level thermal-hydraulic modeling under representative reactor bubbly-flow conditions.
Keywords
molten salt reactors, non-condensable gases, heat transfer correlations, frictional pressure loss correlations, computational field dynamics
Publication Date
9-24-2026
Publication Title
Nuclear Engineering and Design
Publisher
Elsevier
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Rights
© 2026 The Authors
Recommended Citation
Buchanan, A. F., & Liu, Q. (2026). CFD assessment of heat transfer and frictional pressure loss correlations for molten salt reactors with non-condensable gases. Nuclear Engineering and Design, 459, 115216. https://doi.org/10.1016/j.nucengdes.2026.115216
