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Computer Modeling of Fire Smoke Movement in Multizone Structure Using Two Open Source Platforms
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Casualty of garment factory workers from factory fire in Bangladesh is a recurring tragedy. Smoke, which is more fatal than fire itself, often propagates through different pathways from lower to upper floors during building fire. Among the toxic gases produced from a building fire, carbon monoxide (CO) can be deadly, even in small amounts. This paper models the propagation and transportation of fire induced smoke (CO) that resulted from the burning of synthetic polyester fibers using two open source platforms, CONTAM and Fire Dynamics Simulator (FDS). Smoke migration in a generic multistoried garment factory building in Bangladeshis has been modeled using CONTAM where each floor is compartmentalized by different zones. The elevator and stairway shafts are modeled by phantom zones to simulate contaminant (CO) transport from one floor to upper floors. In this study, constant coefficient model of source and sink is used to find the extreme condition of fire and smoke propagation. It is kind of impossible to check the simulation project practically as it would involve testing full-scale fire in a garment facility. For this reason, two generic building structure resulting outputs are considered and comparative analysis and study is performed. Simulation method is operated based on “transient” contaminant flow, air flow. Transient integration method is performed based on Implicit Euler. FDS analysis involves burning of two different stacks of polyester jacket of six feet height and with a maximum heat release rate per unit area of 1500kw/m2 over a storage area 50m2and 150m2, respectively. The resulting CO generation and removal rates from FDS are used in CONTAM to predict fire-borne CO propagation in different zones of the garment building. “SFPE Handbook” is used as reference for the input values of fuel. Smokeview (SMV) is a support program used with Fire Dynamics Simulator to visually illustrate the code written in FDS. Real-time smoke propagation with time and space is displayed using SMV. In our study, two different types of fuel is used – Polyester and Cotton. For these fuels peak heat removal rate per unit area (HRRPUA), time of peak, smoke generation and removal rate are studied over a defined time period. For measuring smoke generation and removal rate, temperature of the room two separate devices is set within the smoke pathway. Findings of the study exhibit that the contaminant flow rate is a strong function of the position of building geometry, location of initiation of fire, amount of burnt material, presence of AHU and contaminant generation and removal rate of CO from the source location etc. In this study, source’s generation rate, removal rate, storage area of cloths, AHU supply and return rate, floor position are taken as variables. Varying these parameters smoke propagation in a multistory building is analyzed. The transport of fire-smoke in the building Hallways, stairways and lifts are also investigated in detail to examine the safe operation of the occupants in case of fire. Because using hallways smoke propagates from source room to other rooms of the floor and using phantom zone (stairways, lifts) smoke propagates to other floor of the building. That is why analysis of smoke propagation in hallways and phantom zone is given utmost importance in this study.
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CONTAM is a multizone building airflow and contaminant transport computer program often used for ventilation and indoor air quality analysis. The program was recently enhanced to incorporate CFD capabilities for both outdoor and indoor environmental analysis. This paper introduces the CFD features implemented within the most recent version, CONTAM 3.0. The outdoor or external CFD link predicts wind pressure coefficients and contaminant concentrations for airflow paths at the building surface. A converter computer program translates the wind pressure coefficients to the CONTAM data format. This external CFD link is useful for parametric studies of the impact of outdoor air quality on indoor environment when considering different wind directions or contaminant locations, especially simulations under transient conditions. The ability to embed a single CFD zone in a CONTAM network model has also been implemented. This enables the detailed modeling of a zone when the well-mixed multizone assumption is not appropriate and then uses the multizone approach for the rest of a building, thus capturing the local distribution of air and contaminant properties in a zone and their impacts on other zones of a building. CFD capabilities are demonstrated using a generic residential house model to show how these two new CFD features enhance the existing CONTAM capabilities for both indoor and outdoor air quality analysis.
Revised and significantly expanded, the fifth edition of this classic work offers both new and substantially updated information. As the definitive reference on fire protection engineering, this book provides thorough treatment of the current best practices in fire protection engineering and performance-based fire safety. Over 130 eminent fire engineers andresearchers contributed chapters to the book, representing universities and professional organizations around the world. It remains the indispensible source for reliable coverage of fire safety engineering fundamentals, fire dynamics, hazard calculations, fire risk analysis, modeling and more. With seventeen new chapters and over 1,800 figures, the this new editioncontains: • Step-by-step equations that explain engineering calculations • Comprehensive revision of the coverage of human behavior in fire, including several new chapters on egress system design, occupant evacuation scenarios, combustion toxicity and data for human behavior analysis • Revised fundamental chapters for a stronger sense of context • Added chapters on fire protection system selection and design, including selection of fire safety systems, system activation and controls and CO2 extinguishing systems • Recent advances in fire resistance design • Addition of new chapters on industrial fire protection, including vapor clouds, effects of thermal radiation on people, BLEVEs, dust explosions and gas and vapor explosions • New chapters on fire load density, curtain walls, wildland fires and vehicle tunnels • Essential reference appendices on conversion factors, thermophysical property data, fuel properties and combustion data, configuration factors and piping properties.
The advantage of utilizing modeling to study fire performance of textiles is the ability to conduct detailed studies of the effect of fabric characteristics on flame spread. First, two textile materials are chosen for modeling that exhibit two limit cases: complete flame spread (nylon 6,6/cotton fiber fabric) and self-extinguish (flame retardant rayon/nylon 6,6/para-aramid fiber fabric) in the standard vertical flame test (ASTM D6413). Parameter estimation for unknown model parameters is performed for these samples followed by a sensitivity analysis. Then a new sample is modeled—flame retardant cotton fiber fabric, flame retardant cotton. This modeling exercise shows that computational fluid dynamics modeling is capable of capturing the fire characteristics of different fabric samples in the vertical flame test only when the parameters are carefully estimated considering the modeling assumptions and approaches. Additionally, several areas for further investigation are proposed to improve simulation capability when conducting vertical flame test modeling with textile samples.
The velocity divergence (rate of fluid volumetric expansion) is a flow field quantity of fundamental importance in low-Mach flows. It directly affects the local mass density and therefore the local temperature through the equation of state. In this paper, starting from the conservative form of the sensible enthalpy transport equation, we derive a discrete divergence constraint for use in large-eddy simulation (LES) of low-Mach flows. The result accounts for numerical transport of mass and energy, which is difficult to eliminate in relatively coarse, engineering LES calculations when total variation diminishing (TVD) scalar transport schemes are employed. Without the correction terms derived here, unresolved (numerical) mixing of gas species with different heat capacities or molecular weights may lead to erroneous mixture temperatures and ultimately to an imbalance in the energy budget. The new formulation is implemented in a publicly available LES code called the Fire Dynamics Simulator (FDS). Accuracy of the flow solver for transport is demonstrated using the method of manufactured solutions. The conservation properties of the present scheme are demonstrated on two simple energy budget test cases, one involving a small fire in a compartment with natural ventilation and another involving mixing of two gases with different thermal properties.
A comprehensive methodology has been developed for obtaining and using smoke toxicity data for fire hazard analysis. This description of the methodology comprises (1) determination that the post-flashover fire is the proper focus of smoke inhalation deaths; criteria for a useful bench-scale toxic potency (LC50) measurement method; (2) a method which meets these criteria, especially validation against real-scale fires; (3) a computational procedure for correcting the results from the bench-scale test for the CO levels observed in real-scale post-flashover fires; (4) procedures for reducing the usage of animals and broadening the applicability of data by interpreting gas measurement data using the N-Gas Model; and (5) a procedure for identifying whether a product produces smoke within the ordinary range of toxic potency for postflashover fires.
Two different numerical simulation tools, Fire Dynamic Simulator (FDS) and ThermaKin, are investigated with respect to their capability to predict the mass loss rate of polymer materials exposed to different fires. For validation, gasification apparatus and cone calorimeter tests are conducted. The main focus is on the influence of residue formation. Therefore, poly (butylene terephthalate) (PBT) and PBT reinforced with glass fibres (PBT-GF) are investigated and compared. PBT decomposes almost completely, while PBT-GF forms residue. The materials are characterised in order to provide suitable input parameters. Additionally the total incident heat flux to the sample is measured. With accurate input parameters, FDS and ThermaKin predicted the pyrolysis behaviour of PBT very well. Only some limitations are identified regarding the residue-forming PBT-GF. Both numerical simulation tools demonstrate a high value regarding the assessment of parameters’ relative impacts and thus the evaluation of optimisation routes in polymer and composite development.
Current multizone airflow network models assume air momentum effects, contaminant concentrations, and air temperatures are uniformly and homogeneously distributed in a zone of a building. These assumptions can cause errors for zones where air and/or contaminant are not well mixed. A coupled multizone-CFD program has been developed to improve the multizone model by applying a CFD model to those poorly mixed zones and the multizone model to the remaining zones. This paper validates the coupled multizone-CFD program by using experimental data obtained in a four-zone facility with nonuniform distributions of air momentum effects, contaminant concentrations, and air temperatures. The calculated results by the coupled program generally agreed with the experimental data although discrepancies exist in some cases. The coupled multizone-CFD simulations used less computing time than the CFD simulations for the whole flow domain.