CFD analysis of low Prandtl number fluid with internal heat generation flowing in a rod bundle at low reynolds numbers

CFD analysis of low Prandtl number fluid with internal heat generation flowing in a rod bundle at low reynolds numbers Full article

Journal

Nuclear Engineering and Design
ISSN: 0029-5493

Output data

Year: 2026, Volume: 453, Article number : 114888, Pages count : 17 DOI: 10.1016/j.nucengdes.2026.114888

Tags

Thermal-hydraulics; Fast reactor fuel; Liquid metal fuel; Internal heat generation; Natural circulation

Authors

Arnold Benjamin ¹ , Petrov Victor ^2,1,3 , Sergeenko Konstantin ⁴ , Manera Annalisa ^2,1

Affiliations

1	PSI Center for Nuclear Engineering and Science, Paul Sherrer Institut, 5232 Villigen PSI, Switzerland
2	ETH Zurich, Zurich, Switzerland
3	University of Michigan, Ann Arbor, Michigan, USA
4	MIPT Sobolev Institute of Mathematics, Novosibirsk, Russian Federation

The aim of this study is to evaluate the performance of commonly used RANS turbulence models in the context of heat generating liquids of moderately low Prandtl numbers of 0.1 and 0.2. This situation is of particular interest in the context of novel nuclear reactors using liquid metal fuels, such as the prototypical Dual Fluid Reactor described for example in (Arnold et al., 2025; Sierchuła et al., 2019; Weissbach et al., 2020). This reactor uses a liquid metal coolant (Lead) and a liquid metal fuel (Uranium-Chromium eutectic) in two separate circuits. This concept can be considered as a mixture of a molten salt reactor and a lead cooled fast reactor. The liquid metal fuel and -coolant allow a fast neutron spectrum as well as high operating temperatures. The liquid fuel enables continuous online reprocessing and also offers the possibility to implement passive safety systems such as subcritical drain tanks. The current study investigates fundamental thermal-hydraulics of a triangular-lattice rod bundle arrangement with a pitch-to-diameter ratio of 1.4. The focus lies on the low Reynolds number regime of f lows (Re ≤ 5000), which is of particular interest in case of natural circulation. Since the streamwise- as well as the crossflow direction are widely used and in their nature quite different, both situations are analysed. The study is performed using the Nek5000 DNS code as well as the Ansys Fluent code, which was used for RANS simulations. The investigated Prandtl numbers of 0.1 and 0.2 were selected since they are the highest and lowest Prandtl numbers expected to occur in the liquid fuel of the dual fluid reactor studied in (Arnold et al., 2025). The DNS results are compared with two RANS models, namely the 7-equation Reynolds stress model (RSM BSL) and the 2-equation k-omega-SST model.

Arnold B. , Petrov V. , Sergeenko K. , Manera A.
CFD analysis of low Prandtl number fluid with internal heat generation flowing in a rod bundle at low reynolds numbers
Nuclear Engineering and Design. 2026. V.453. 114888 :1-17. DOI: 10.1016/j.nucengdes.2026.114888 OpenAlex

Submitted:	Oct 14, 2025
Accepted:	Mar 9, 2026
Published online:	Mar 19, 2026

≡ OpenAlex:

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