Abstract
Sodium-cooled fast reactor (SFR) which is one of the most promising candidates to meet the Generation IV International Forum (GIF) declare has drawn a lot of attentions. Turbulent heat transfer in the liquid sodium which is one of those low Prandtl fluids is an extremely complex phenomenon. The limitations of the commonly used eddy diffusivity approach have become more evident for low-Prandtl fluids. The current study focuses on the assessment and optimization of the existing modeling closure for single-phase turbulence in liquid sodium based on the reference results provided by LES method. In this paper, a wall-resolved Large-Eddy Simulation was performed to simulate the flow and heat transfer properties in a turbulent channel at low Prandtl number. The simulation results are firstly compared with the DNS results obtained from literature. A good agreement demonstrated the capability of the employed numerical approach to predict the turbulent and heat transfer properties in a low Prandtl number fluid. Consequently, new reference results were obtained for typical Prandtl number and wall heat flux of SFR. A time-averaged process has been employed to evaluate temperature profile quantitatively as well as turbulent heat flux. Their dependency was also evaluated based on a systematic CFD simulation which covers the typical Reynolds numbers of SFR. Based on the obtained reference results, the coefficients employed in the algebraic turbulent heat flux model (AFM) are calibrated. The optimized coefficients provide a better prediction accuracy of heat transfer properties for typical flow conditions of SFR if comparing with the existing models found in the literature.
Highlights
The sodium-cooled fast reactor (SFR), which is one of the new generation of nuclear power plant designs, has been considered to be one of the most promising candidates for meeting the goal declared by the Generation IV International Forum (GIF) (Sun, 2012)
The simulation results obtained in section LES Simulations of Turbulent Channel Flow at Pr = 0.005 are employed to calibrate the parameters used in the algebraic turbulent heat flux model (AFM), which is derived from the full second moment transport equation for the turbulent heat flux under the hypothesis of local equilibrium between production and dissipation (Dol et al, 1997)
A systematic CFD simulation covering the typical range of Reynolds numbers for SFRs was performed at very low Prandtl number: Pr = 0.005, which corresponds to liquid sodium
Summary
The sodium-cooled fast reactor (SFR), which is one of the new generation of nuclear power plant designs, has been considered to be one of the most promising candidates for meeting the goal declared by the Generation IV International Forum (GIF) (Sun, 2012). In order to circumvent the drawbacks of the eddy diffusivity approach, the transport equation of the turbulent heat flux is carefully analyzed based on the assumption of fully developed flow and local equilibrium, and the algebraic heat flux model (AFM) is obtained This model is believed to be suitable for anisotropic and buoyant flows and adapted to liquid metal convection (Grotzbach, 2013). In the past few decades, different models have been proposed to estimate its value based on different assumptions, such as the Simple Gradient Diffusion Hypothesis (SGDH) model and the General Gradient Diffusion Hypothesis (GGDH) model (Xiong and Cheng, 2014) In these two models, turbulent heat flux is proportional to the turbulent viscosity or Reynolds stress without considering the influence of energy equilibrium. The resulting algebraic expression has the following form (Kenjereš and Hanjalic, 2000): uiθ
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