Development of Evaluation Method for Cold Trap in Fast Breeder Reactor: Part 1 — Numerical Analysis of Impurity Precipitation on Mesh Wire

2017 ◽  
Author(s):  
Akinori Tamura ◽  
Shiro Takahashi ◽  
Hiroyuki Nakata ◽  
Akio Takota
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Evaluation Method ◽  
Low Reynolds Number ◽  
Cold Trap ◽  
Precipitation Model ◽  
Low Reynolds ◽  
Boltzmann Method

A cold trap is one of the important components in the Fast Breeder Reactor (FBR) to control oxygen and hydrogen concentration of liquid sodium. For more accurate evaluation of the cold trap performance, we have started a research program to develop the evaluation method based on the 3D numerical analysis. Our evaluation method consists of two steps: one is a numerical analysis of sodium compound deposition on the mesh wires; the other is a numerical analysis of the sodium flow in the cold trap where the effect of the sodium compound deposition is considered as local pressure loss increment. In this study, we have focused on the development of the numerical analysis method of the sodium compound deposition on the mesh wires of the cold trap. As a numerical method, we have adopted the lattice Boltzmann method which is known to be useful for the flow simulation around the complex geometry like the mesh wires. In order to apply the lattice Boltzmann method to the sodium compound deposition simulation around the mesh wire, we proposed a low Reynolds number model and an impurity precipitation model for the conventional lattice Boltzmann method. The low Reynolds number model was validated by a comparison with a theoretical solution of the two-dimensional channel flow. To validate the impurity precipitation model, we conducted a precipitation experiment by using the supersaturated sucrose in the water instead of the liquid sodium with the oxygen and the hydrogen. The comparison between the experiment and the simulation showed good agreement regarding the pressure loss increment. From these results, we confirmed the accuracy of the low Reynolds number model and the impurity precipitation model. The accuracy of our models in the sodium condition will be confirmed in the future study.

Determining Flow Mixing Characteristics in Low Reynolds Numbers Micro Wavy Channels by the Lattice-Boltzmann Method

2010 ◽  
Author(s):  
Amador M. Guzma´n ◽  
Mari´a Gabriela Quezada ◽  
Luis E. Sanhueza ◽  
Andre´s J. Di´az
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Low Reynolds Number ◽  
Mixing Enhancement ◽  
Flow Mixing ◽  
Mixing Characteristics ◽  
Low Reynolds ◽  
Wavy Channels ◽  
Boltzmann Method

The Eulerian and Lagrangian flow mixing characteristics in a two-dimensional (2D) micro wavy channels for low Reynolds number have been investigated using the Lattice-Boltzmann method (LBM) for solving the governing Boltzmann Transport Equation (BTE). Numerical simulations of a Newtonian compressible flow for Reynolds number flow regimes lower than Re = 0.505 are performed using a computational model of a symmetric wavy channel with many cavities and a geometrical aspect ratio of r = a/(2L) = 0.375, where a is the amplitude of the sinusoidal wall, and L is the cavity periodic length. The Eulerian flow characteristics are determined for different Knudsen numbers with the objective of characterizing time dependent velocity and flow patterns. Then, the Lagrangian characteristics are obtained by integrating the Eulerian velocity field. Thousands of massless fluid particles are used for determining fluid particle Lagrangian trajectories, stretching fields and Lagrangian Lyapunov exponents associated to possible evidences of flow mixing enhancement in different regions of the micro channel. The numerical results demonstrate that low Reynolds number compressible flows in micro wavy channels develop Lagrangian characteristics and stretching field that can lead later to flow mixing enhancement characteristics in an electroosmotic flow in microchannels with wavy, grooved and/or any other surface pattering on the channels walls.

A Numerical Analysis Method of Impurity Precipitation on Mesh Wire of Cold Trap in Fast Breeder Reactor

2018 ◽  
Vol 4 (3) ◽  
Author(s):  
Akinori Tamura ◽  
Shiro Takahashi ◽  
Hiroyuki Nakata ◽  
Akio Takota
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Low Reynolds Number ◽  
Cold Trap ◽  
Fast Breeder Reactor ◽  
Analysis Method ◽  
Numerical Analysis Method ◽  
Precipitation Model ◽  
Low Reynolds ◽  
Precipitation Phenomena

Abstract A fast breeder reactor (FBR) is considered as the promising technology in terms of load reduction on the environment, because the FBR has capability to improve usage efficiency of uranium resources and can reduce high-level radioactive waste which needs to be managed for millions of years. A cold trap is one of the important components in the FBR to control the impurity concentration of the liquid sodium. For accurate evaluation of the cold trap performance, we have been proposing the three-dimensional (3D) numerical analysis method of the cold trap. In this method, the evaluation of the impurity precipitation phenomena on the surface of the mesh wire of the cold trap is the key. For this, the numerical analysis method which is based on the lattice kinetic scheme (LKS) has been proposed. In order to apply the LKS to the impurity precipitation simulation of the cold trap, two models (the low Reynolds number model and the impurity precipitation model) have been developed. In this paper, we focused on the validation of these models. To confirm the validity of the low Reynolds number model, the Chapman–Enskog analysis was applied to the low Reynolds number model. As a result, it has been theoretically confirmed that the low Reynolds number model can recover the correct macroscopic equations (incompressible Navier–Stokes equations) with small error. The low Reynolds number model was also validated by the numerical simulation of two-dimensional (2D) channel flow problem with the low Reynolds number conditions which correspond to the actual cold trap conditions. These results have confirmed that the error of the low Reynolds number model is ten times smaller than that of the original LKS. The validity of the impurity precipitation model was investigated by the comparison to the precipitation experiments. In this comparison, the mesh convergence study was also conducted. These results have confirmed that the proposed impurity precipitation model can simulate the impurity precipitation phenomena on the surface of the mesh wire. It has been also confirmed that the proposed impurity precipitation model can simulate the impurity precipitation phenomenon regardless of the cell size which were tested in this investigation.

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