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論文

Experimental investigation of natural convection and gas mixing behaviors driven by outer surface cooling with and without density stratification consisting of an air-helium gas mixture in a large-scale enclosed vessel

安部 諭; Hamdani, A.; 石垣 将宏*; 柴本 泰照

Annals of Nuclear Energy, 166, p.108791_1 - 108791_18, 2022/02

This paper describes an experimental investigation of natural convection driven by outer surface cooling in the presence of density stratification consisting of an air-helium gas mixture (as mimic gas of hydrogen) in an enclosed vessel. The unique cooling system of the Containment InteGral effects Measurement Apparatus (whose test vessel is a cylinder with 2.5-m diameter and 11-m height) is used, and findings reveal that the cooling location relative to the stratification plays an important role in determining the interaction behavior of the heat and mass transfer in the enclosed vessel. When the cooling region is narrower than the stratification thickness, the density-stratified region expands to the lower part while decreasing in concentration (stratification dissolution). When the cooling region is wider than the stratification thickness, the stratification is gradually eroded from the bottom with decreasing layer thickness (stratification breakup). This knowledge is useful for understanding the interaction behavior of heat and mass transfer during severe accidents in nuclear power plants.

論文

Unsteady natural convection in a cylindrical containment vessel (CIGMA) with external wall cooling; Numerical CFD simulation

Hamdani, A.; 安部 諭; 石垣 将宏; 柴本 泰照; 与能本 泰介

Energies (Internet), 13(14), p.3652_1 - 3652_22, 2020/07

 被引用回数:0 パーセンタイル:0(Energy & Fuels)

In the case of a severe accident, natural convection plays an important role in the atmosphere mixing of nuclear reactor containments. In this case, the natural convection might not in the steady-state condition. Hence, instead of steady-state simulation, the transient simulation should be performed to understand natural convection in the accident scenario within a nuclear reactor containment. The present study, therefore, was aimed at the transient 3-D numerical simulations of natural convection of air around a cylindrical containment with unsteady thermal boundary conditions (BCs) at the vessel wall. For this purpose, the experiment series was done in the CIGMA facility at Japan Atomic Energy Agency (JAEA). A 3-D model was simulated with OpenFOAM, applying the unsteady Reynolds-averaged Navier-Stokes equations (URANS) model. Different turbulence models were studied, such as the standard k-$$varepsilon$$, standard k-$$omega$$, k-$$omega$$ shear stress transport (SST), and low-Reynolds-k-$$varepsilon$$ Launder-Sharma. The results of the four turbulence models were compared versus the results of experimental data.

論文

CFD analysis of the CIGMA experiments on the heated JET injection into containment vessel with external surface cooling

Hamdani, A.; 安部 諭; 石垣 将宏; 柴本 泰照; 与能本 泰介

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.5463 - 5479, 2019/08

The present study introduces thermal mixing and stratification produced by heated air jet located at the bottom level of the containment vessel. The investigation was carried out experimentally and numerically in the large containment vessel called CIGMA (Containment InteGral effects Measurement Apparatus). The experiments were conducted with external surface cooling and various air jet inlet temperatures. The containment cooling was done by flooding the water on the external side of half-upper of a vessel. To identify their influence on the thermal mixing and stratification phenomena, the investigation focuses on mixing convection which occurred in the cooled region of a containment vessel. Temperature distribution and jet velocity were measured by thermocouple and Particle Image Velocimetry (PIV) respectively. Numerical simulation was performed using Computational Fluid Dynamics (CFD) code OpenFOAM to investigate the detail effects of external cooling on the fluid flow and thermal characteristics in the test vessel. CFD results showed a good agreement with experimental data on both temperature and velocity. Both temperature and velocity of hot air jet decayed rapidly downstream jet nozzle. Thermal stratification was observed by visualization of temperature contour maps over a cross-section in the containment vessel. Vigorous mixing was also noticed in the upper region of the containment vessel. Effect of external cooling on mixing and the thermal stratification were presented and discussed.

口頭

Numerical simulation of a buoyant heated air jet in large containment vessel CIGMA with outer surface cooling

Hamdani, A.; 安部 諭; 石垣 将宏; 柴本 泰照; 与能本 泰介

no journal, , 

Gas density stratification build-up and its propagation/erosion, which is regarded as a benchmark of hydrogen behavior in a severe accident, were experimentally and numerically studied by using buoyant jet in the containment vessel. The experiments were conducted with external surface cooling and high-temperature air-jet inlet up to 435 degrees Celcius. The CFD simulation was also performed, and the data on temperature and velocity profile were used for the validation.

口頭

大型格納容器内における自然対流による密度成層浸食挙動のRANS解析

石垣 将宏; 安部 諭; Hamdani, A.; 柴本 泰照

no journal, , 

シビアアクシデント時の格納容器内の熱流動を解析する上でCFD解析の高度化は重要な課題である。また、CFD解析に対して初期・境界条件の不確かさの影響の重要性が指摘されている。本研究では、大型格納容器実験装置CIGMAを用いた外面冷却実験をCFD解析し、実験の初期条件および境界条件の影響を評価した。実験では、ヘリウムおよび空気による密度成層を容器頂部に形成し、容器外面冷却により自然対流を発生させて成層の混合挙動を観察した。本過程に対してRANSモデルを用いた数値解析を行った結果、比較的小規模な構造物においてもその熱容量が無視できないことが示され、構造物温度境界条件が自然循環挙動に大きな影響を及ぼすことが明らかになった。

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