• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.14-20
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• 2017

A numerical study was conducted to identify the predictive performance for the bare-bead thermocouple (TC) using FDS (Fire Dynamics Simulator) in simulated thermal environments of fire. A relative prediction bias of TC temperature calculated from reverse-radiation correction by FDS was evaluated with the comparison of previous experimental data. As a result, it was identified that the TC temperatures predicted by FDS were lower than the temperatures measured by bare-bead TC for the ranges of heat flux and gas temperature considered. The relative prediction bias of TC temperature by FDS was gradually increased with the increase in radiative heat flux and also significantly increased with the decrease in the gas temperature. Quantitatively, at the gas temperature of $20^{\circ}C$, the TC temperature predicted by FDS had the relative bias of approximately -20% with the radiative heat flux of $20kW/m^2$ corresponding to thermal radiation level of the flashover. It is predicted from the present study that more accurate validation of fire modeling will be possible with the quantitative prediction bias occurred in the process of reverse-radiation correction of temperature predicted by FDS.

• Steel and Composite Structures
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• v.10 no.2
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• pp.129-149
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• 2010

The objective of this study is to formulate a general 3D material-structural analysis framework for the thermomechanical behavior of steel-concrete structures in a fire environment. The proposed analysis framework consists of three sequential modeling parts: fire dynamics simulation, heat transfer analysis, and a thermomechanical stress analysis of the structure. The first modeling part consists of applying the NIST (National Institute of Standards and Technology) Fire Dynamics Simulator (FDS) where coupled CFD (Computational Fluid Dynamics) with thermodynamics are combined to realistically model the fire progression within the steel-concrete structure. The goal is to generate the spatial-temporal (ST) solution variables (temperature, heat flux) on the surfaces of the structure. The FDS-ST solutions are generated in a discrete form. Continuous FDS-ST approximations are then developed to represent the temperature or heat-flux at any given time or point within the structure. An extensive numerical study is carried out to examine the best ST approximation functions that strike a balance between accuracy and simplicity. The second modeling part consists of a finite-element (FE) transient heat analysis of the structure using the continuous FDS-ST surface variables as prescribed thermal boundary conditions. The third modeling part is a thermomechanical FE structural analysis using both nonlinear material and geometry. The temperature history from the second modeling part is used at all nodal points. The ABAQUS (2003) FE code is used with external user subroutines for the second and third simulation parts in order to describe the specific heat temperature nonlinear dependency that drastically affects the transient thermal solution especially for concrete materials. User subroutines are also developed to apply the continuous FDS-ST surface nodal boundary conditions in the transient heat FE analysis. The proposed modeling framework is applied to predict the temperature and deflection of the well-documented third Cardington fire test.

• Journal of the Korea Safety Management & Science
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• v.11 no.2
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• pp.77-85
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• 2009

Considering heat insulation and beautiful sight of construction, making use of exterior panels is increasing. Recently the exterior panels now are weak very much, and so in consequence of the weakness fire spreads rapidly. Compared with internal fire, external vertical fire spread rate goes rapidly and it is extensive in spread range, therefore it is dangerous very much. Accordingly, under present condition of poor standard of exterior panels, it is required to take measure to meet the appropriate situation. In this study, by making use of FDS(Fire Dynamic Simulation) program about external vertical fire of high rise building, fire behavior is searched by computer. It is important that realizing by computer fire modeling about external vertical fire must be included certainly in procedure of fire performance design in the future. In modeling program, FDS version 5 is available, and aluminium composite panel is applied in external panels. In this study, for realizing of actual fire condition, FDS is applied by details of fire scenarios considering influence of wind.

• Fire Science and Engineering
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• v.26 no.2
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• pp.40-52
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• 2012

This paper presents the uncertainty analysis results of fire modeling input parameters for motor control center in switchgear room of nuclear power plants. FDS (Fire Dynamics simulator) 5.5 was used to simulate the fire scenario and Latin Hyper Cube Monte Carlo simulations were employed to generate random samples for FDS input parameters. The uncertainty analysis results of input parameters are compared with those of the model uncertainty analysis and sensitivity analysis approaches of NUREG-1934. The study results show that the input parameter uncertainty analysis approach may lead to more conservative results than the uncertainty analysis and sensitivity analysis methods of NUREG-1934.

• Fire Science and Engineering
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• v.27 no.2
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• pp.31-39
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• 2013

The Fire Dynamics Simulator (FDS) has been applied to simulate a full-scale pool fire in well-confined and mechanically ventilated multi-compartments representative of nuclear power plant. The predictive performance of FDS was evaluated through a comparison of the numerical data with experimental data obtained by the OECD/NEA PRISME project. To identify clearly the FDS results regarding to the user-dependence in the process of FDS implementation except for the intrinsic limitation of FDS such as simple combustion model, only the over-ventilated fire condition was chosen. In particular, the importance of accurate boundary conditions (B.C.) in mechanically ventilated system were discussed in details. It was known from FDS results that the B.C. on inlet and outlet vents did significantly affect the thermal and chemical characteristics inside the compartments. Finally, it was confirmed that the FDS imposed an accurate ventilation B.C. provided qualitatively good agreement with temperatures, heat fluxes and concentrations measured inside the nuclear-type multi-compartments.

• Fire Science and Engineering
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• v.21 no.2 s.66
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• pp.98-104
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• 2007

This study is related with the fire risk assessment for fire area at nuclear power plant by use of FDS (Fire Dynamics Simulator) that is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The major purpose of this research is to analyze the sensitivity of the fire modeling when the heat release rate that is an important input variable is changed as well as when the grid size that is a critical factor of the fire model is modified. The result is presented at the conclusion with some comments for CFD model application.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.93-98
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• 2008

On this study, The combustion properties in 3 kinds of sandwich panels based on ISO 13784-1(Room Corner Test for Sandwich panel building systems) using FDS Version 5 modeling method were tested and analyzed. Comparative analysis for those two results between FDS and real tests were made mainly concentrating on heat release rate.

• Fire Science and Engineering
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• v.27 no.2
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• pp.80-88
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• 2013

The validation of Fire Dynamics Simulator (FDS) was conducted for the under-ventilated fire in well-confined multi-compartments representative of nuclear power plant. Numerical results were compared with experimental data obtained by the OECD/NEA PRISME project. The effects of the numerical boundary conditions (B.C.) in ventilated system and the flame suppression model applied within FDS on the thermal and chemical environments inside the compartment were discussed in details. It was found that numerical B.C. on the vent flow resulting from over-pressure at ignition and under-pressure at extinction should be considered carefully in order to predict accurately the species concentrations rather than temperatures and heat fluxes inside the multi-compartment. The default information of suppression model applied within FDS resulted in artificial phenomena such as flame extinction and re-ignition, and thus the FDS results on the under-ventilated fire showed good agreement with the experimental results as the modified suppression criteria of the fuel used was adopted.

• Fire Science and Engineering
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• v.20 no.4 s.64
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• pp.13-18
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• 2006

The fire protection regulation for the nuclear power plants is based on the qualitative fire hazard assessment and the quantitative fire risk analysis, and the fire risk is managed by the fire protection plan with the appropriate balance among the fire prevention, fire suppression and the minimization of the fire effect. In these days, the zone model or the field model is generally used for the detail evaluation for the fire risk. At this paper, with consideration of the present trend, we evaluate whether the quantitative fire risk analysis and the assessment of fire result for fire areas at nuclear power plants can be possible by use of Fire Dynamics Simulator (FDS) that is the state-of-the-art fire modeling tool. Consequently, it is expected that the quantitative fire risk evaluation propelled by the fire modeling can be available as an applicable tool to improve the core damage frequency as well as the quantitative fire risk analysis.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.25-32
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• 2016

A sensitivity analysis of FDS(Fire Dynamics Simulator) results for the input uncertainty of heat release rate (Q) which might be the most influencing parameter to fire behaviors was performed. The calculated results were compared with experimental data obtained by the OECD/NEA PRISME project. The sensitivity of FDS results with the change in Q was also compared with the empirical correlations suggested in previous literature. As a result, the change in the specified Q led to the different dependence of major quantities such as temperature and species concentrations for the over- and under-ventilated fire conditions, respectively. It was also found that the sensitivity of major quantities to uncertain value of Q showed the significant difference in results obtained using the previous empirical correlations.