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Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis,...
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Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis, 2nd Edition

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Mathematical and Computational Fluid Mechanics".

Deadline for manuscript submissions: closed (15 December 2023) | Viewed by 8433

Special Issue Editor

Dr. T. Hoehne

E-Mail Website
Guest Editor
Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328 Dresden, Germany
Interests: fluid mechanics; computational fluid dynamics; numerical simulation; numerical modeling; CFD simulation; multiphase flow; engineering thermodynamics; thermal engineering; mechanical engineering; turbulence; heat transfer; CFD coding; turbulence modeling; convection; thermodynamics; large eddy simulation; nuclear engineering; mass transfer
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Over the last two decades, three-dimensional CFD codes have increasingly been used for the prediction of single-phase and multiphase flows under stationary or unsteady conditions in nuclear reactor applications. The motivation for this is that several important thermohydraulic phenomena cannot be predicted with sufficient accuracy and spatial resolution using traditional system analysis codes.

However, CFD codes contain empirical models to simulate turbulence, heat transfer, multiphase interaction, and chemical reactions. Such models must be validated before they can be confidently used in nuclear reactor applications. The necessary validation can only be performed by comparing model predictions with reliable data.

Submissions of papers that focus on single-phase and multi-phase CFD simulations, with a focus on validation in areas such as single-phase and multi-phase heat transfer, free-surface flows, direct contact condensation, and turbulent mixing are welcomed. These simulations should relate to nuclear reactor safety issues, such as pressurized thermal shock, critical heat flux, pool heat exchangers, boron dilution, hydrogen distribution in containments, thermal striping and fatigue, etc. The use of systematic error quantification and the application of best practice guidelines (BPGs) are strongly encouraged.

Experiments that provide suitable data for CFD or CMFD validation are also welcome. These should include local measurements using multi-sensor probes, laser-based techniques (LDV, PIV, or LIF), hot-film/wire anemometry, imaging, or other advanced measuring techniques. Papers should include a discussion of measurement uncertainties.

Dr. Thomas Höhne
Guest Editor

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Keywords

  • single-phase and multi-phase heat transfer
  • free-surface flows
  • direct contact condensation
  • turbulent mixing
  • pressurized thermal shock
  • critical heat flux
  • pool heat exchangers
  • boron dilution
  • hydrogen distribution in containments
  • thermal striping and fatigue
  • error quantification
  • application of best practice guidelines (BPGs)

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Published Papers (4 papers)

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13 pages, 8630 KiB  
Article
CFD Modeling of Heat Exchanger with Small Bent Radius Coils Using Porous Media Model
by Sergey Dmitriev, Andrey Kurkin, Aleksandr Dobrov, Denis Doronkov, Aleksey Pronin and Dmitry Solntsev
Fluids 2023, 8(5), 141; https://doi.org/10.3390/fluids8050141 - 28 Apr 2023
Cited by 3 | Viewed by 1844
Abstract
The efficiency of heat transfer in air-cooled heat exchangers of various industrial facilities depends on the flow rate of the coolant, its inlet temperature and ambient temperature. These parameters are transient and depend both on the features of the technological process and on [...] Read more.
The efficiency of heat transfer in air-cooled heat exchangers of various industrial facilities depends on the flow rate of the coolant, its inlet temperature and ambient temperature. These parameters are transient and depend both on the features of the technological process and on weather conditions. One option for a compact design of heat exchangers is the use of close-packed coils with a small bending radius. In this case, heat transfer in the complex geometry of the annular space cannot be described by simple one-dimensional dependencies. To solve this problem, it is necessary to consider the three-dimensional spatial structure of the heat exchange surface. Since the size of the grid elements will be several orders of magnitude less than the size of the facility, the size of the computational grids for CFD modeling full-scale heat exchangers will be billions of finite volumes, and even on powerful supercomputers, the solution time will be about a month. One way to reduce computational costs is to use reduced order models, in which the computational domain is not modeled directly; instead, simplified models, such as a porous medium model, are used to describe it. However, such models require additional closing relations and coefficients that characterize the actual channel geometry. This paper presents a technique for creating a digital twin of a heat exchanger with small bend radius coils based on a porous medium model. The values of heat transfer coefficients and hydraulic resistance depend on the speed of air movement in the space between the coils. The calculated value of the thermal power obtained using the strengthened model was 529 kW, which corresponds to the passport data of 500 kW, with less than 6% deviation for the heat exchanger under study. This confirms the correctness of the calculation with accepted simplifications. The calculation time in this case was only a few minutes when using a personal computer. The developed numerical model allows for the resolution of performance characteristics based on the temperature of the cooled medium at the inlet, air temperature, and fan speed. Analyzing the different modes of turning on the cooling fans made it possible to determine the values of the thermal power when turning off the fans or reducing the number of revolutions. Full article
(This article belongs to the Special Issue Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis, 2nd Edition)
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23 pages, 53102 KiB  
Article
CFD Study of Thermal Stratification in a Scaled-Down, Toroidal Suppression Pool of Fukushima Daiichi Type BWR
by Sampath Bharadwaj Kota, Seik Mansoor Ali and Sreenivas Jayanti
Fluids 2023, 8(1), 20; https://doi.org/10.3390/fluids8010020 - 4 Jan 2023
Viewed by 1793
Abstract
During the 2011 nuclear catastrophe at Fukushima Daiichi, Unit 3 had a sharper increase in containment pressure than Unit 2, with thermal stratification of the suppression pool cited as one of the contributing factors. In the present work, the buoyancy-induced circulation consequent to [...] Read more.
During the 2011 nuclear catastrophe at Fukushima Daiichi, Unit 3 had a sharper increase in containment pressure than Unit 2, with thermal stratification of the suppression pool cited as one of the contributing factors. In the present work, the buoyancy-induced circulation consequent to steam condensation in a large, toroidal pool of water is studied using computational fluid dynamics (CFD) simulations with a view to understanding the role of important design parameters of the suppression pool system. The tunnelling phenomenon observed in the development of the thermal stratification process is delineated in terms of the establishment of a thermocline. The effects of the number of steam injection points and the cross-section of the pool on thermal stratification characteristics have been investigated through a number of case studies. In all the cases, the surface temperature, which is responsible for over-pressurization of the containment, is found to be significantly higher than the bulk pool temperature. Multiple injection points with the same overall steam flow rate are found to lead to higher surface temperatures due to a shortened circulation path. For the same volume of pool water, the simulations show that a deeper and narrower pool gives rise to significantly higher temperatures than a wider and shallower pool. This is attributed to the relatively deeper penetration of the buoyancy-induced circulation into the pool. Full article
(This article belongs to the Special Issue Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis, 2nd Edition)
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22 pages, 13991 KiB  
Article
Numerical Analysis Related to the ROCOM Pressurized Thermal Shock Benchmark
by Thomas Höhne and Sören Kliem
Fluids 2023, 8(1), 4; https://doi.org/10.3390/fluids8010004 - 22 Dec 2022
Cited by 3 | Viewed by 2296
Abstract
The development, verification, and validation of Computational Fluid Dynamics (CFD) codes in reference to nuclear power plant (NPP) safety has been a focus of many research organizations over the last few decades. Therefore, a collection of Rossendorf Coolant Mixing Test Facility (ROCOM) CFD-grade [...] Read more.
The development, verification, and validation of Computational Fluid Dynamics (CFD) codes in reference to nuclear power plant (NPP) safety has been a focus of many research organizations over the last few decades. Therefore, a collection of Rossendorf Coolant Mixing Test Facility (ROCOM) CFD-grade experiments was made obtainable to line up a global International Atomic Energy Agency (IAEA) benchmark regarding Pressurized Thermal Shock (PTS) situations. The benchmark experiment describes the complicated flow structures in mixed convection zones of the RPV during PTS events. The experiments were utilized to validate CFD codes. Additionally, an experiment with no buoyancy forces was elite to point out the influence of density variations. Compared to earlier studies, the turbulence models of the CFD code improved a lot. The turbulence modeling approach shows a respectable agreement with the experimental data. Full article
(This article belongs to the Special Issue Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis, 2nd Edition)
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18 pages, 1742 KiB  
Article
Estimation of Flow Field in Natural Convection with Density Stratification by Local Ensemble Transform Kalman Filter
by Masahiro Ishigaki, Yoshiyasu Hirose, Satoshi Abe, Toru Nagai and Tadashi Watanabe
Fluids 2022, 7(7), 237; https://doi.org/10.3390/fluids7070237 - 12 Jul 2022
Cited by 1 | Viewed by 1621
Abstract
For estimating thermal flow in a nuclear reactor during an accident accurately, it is important to improve the accuracy of computational fluid dynamics simulations. The temperature and flow velocity are not homogeneous and have large variations in a reactor containment vessel because of [...] Read more.
For estimating thermal flow in a nuclear reactor during an accident accurately, it is important to improve the accuracy of computational fluid dynamics simulations. The temperature and flow velocity are not homogeneous and have large variations in a reactor containment vessel because of its very large volume. In addition, Kelm’s work pointed out that the influence of variations of initial and boundary conditions was important. Therefore, it is necessary to set the initial and boundary conditions taking into account the variations of these physical quantities. However, it is a difficult subject to set such complicated initial and boundary conditions. Then, we can obtain realistic initial and boundary conditions and an accurate flow field by data assimilation, and we can improve the accuracy of the simulation result. In this study, we applied data assimilation by a local ensemble transform Kalman filter to a simulation of natural convection behavior in density stratification, and we performed a twin model experiment. We succeeded in estimating the flow fields and improving the simulation accuracy by the data assimilation, even if we applied the boundary condition with error for the true condition. Full article
(This article belongs to the Special Issue Application of Computational Fluid Dynamics in Nuclear Reactor Safety Analysis, 2nd Edition)
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