Abstract
Due to their interesting thermal properties, liquid metals are widely studied for heat transfer applications where large heat fluxes occur. In the framework of the Reynolds-Averaged Navier–Stokes (RANS) approach, the Simple Gradient Diffusion Hypothesis (SGDH) and the Reynolds Analogy are almost universally invoked for the closure of the turbulent heat flux. Even though these assumptions can represent a reasonable compromise in a wide range of applications, they are not reliable when considering low Prandtl number fluids and/or buoyant flows. More advanced closure models for the turbulent heat flux are required to improve the accuracy of the RANS models dealing with low Prandtl number fluids. In this work, we propose an anisotropic four-parameter turbulence model. The closure of the Reynolds stress tensor and turbulent heat flux is gained through nonlinear models. Particular attention is given to the modeling of dynamical and thermal time scales. Numerical simulations of low Prandtl number fluids have been performed over the plane channel and backward-facing step configurations.
Highlights
Liquid metals with their low Prandtl number have gained increasing attention in recent years
We presented a new anisotropic four-parameter turbulence model (A4P) that derives from the four-parameter turbulence model (4P) widely studied in [4,13,14,15,16] within the framework of heat transfer modeling for low-Prandtl number fluids
An Explicit Algebraic Stress Model (EASM) and an Explicit Algebraic Heat Flux Model (EAHMF) was proposed for the closure of the Reynolds stresses and turbulent heat flux instead of firstorder closure relations used in the isotropic version of the model
Summary
Liquid metals with their low Prandtl number have gained increasing attention in recent years. Since the possibilities for detailed measurement of local flow parameters in liquid metal cooled reactor components are challenging [7], numerical simulations of flow configurations are more important for low Prandtl number fluids than in usual cases. In this respect, Computational Fluid Dynamics (CFD) is regarded as a valuable tool to analyze the thermal-hydraulics behavior of nuclear systems. The more challenging aspects of the thermal-hydraulics of these systems are the low Prandtl number of liquid metals at operating conditions, the non-negligible buoyancy effects in the flow, and the significant turbulence anisotropy [8] For these reasons, very sophisticated models are required to accurately simulate turbulent liquid metals flow and heat transfer
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