Enclosure Fires Research Articles

Behaviour of Double Glazing in Corner Fires

The results of fifteen experiments in which a double glazing assembly was exposed to enclosure fires of increasing severity are presented. The glazing assembly was exposed to the typical two zone or one zone fire enclosure environment with consistency and repeatability within each set of three experiments conducted at each severity level, evident from the enclosure gas temperature profiles. The results presented include; enclosure local gas temperatures, local exposed glass surface temperatures, local shaded glass temperatures, total incident fluxes, convective and radiative fluxes, incident flux distributions at time of first cracking and inner and outer pane behaviours. A simple lumped model approach is developed to predict the response of the glazing to thermal insult. Total loss of glazing integrity is related graphically to the time of first crack.

COMPUTATIONAL STUDY ON TOXIC GASES RELEASED FROM COMPARTMENT FIRES SUPPRESSED WITH HALOGENATED AGENTS

The evolution of toxic gases in the hot layer of an enclosure fire is simulated by a batch perfectly stirred reactor model using the SENKIN program from the CHEMKIN distribution package. The initial species composition was obtained from experimental data both for slightly underventilated and highly underventilated conditions. The formation rates of toxic gases were studied using a comprehensive kinetic mechanism, including the GRI 3.0 submechanism representing hydrocarbon oxidation, the National Institute of Standards and Technology (NIST) hydrofluorocarbon mechanism, and the NIST CBrF3 and CF3I inhibition mechanisms for the initial mole fractions of CBrF3 and CF3I ranging from 0.5 to 5.0%. An analysis of modeling results, including the prediction of the equilibrium concentration, provided important insight into the effects of adding CBrF3 and CF3I on the formation of toxic gases in the hot layer. Sensitivity analysis was performed under the highly underventilated conditions, leading to the identification of the chemical reactions that have the most significant influence on the formation of toxic products.

DYNAMIC AND RADIATIVE ASPECTS OF FIRE–WATER MIST INTERACTIONS

A two-phase multiclass model is developed to describe the interaction between a compartment fire and a water mist. Turbulent combustion is modeled using the EBU-Ar coupled with the renormalization group k–ϵ turbulence model. A multiphase radiative transfer equation including the contributions of soot particles, combustion products and water droplets is used to model radiation. The model is applied first to a two-dimensional enclosure fire. A parametric study of the influence of water spray flow rate and water droplet diameter on fire mitigation is presented. Gas-phase cooling is found to be the main fire suppression mechanism. The influence of water spray on radiation is studied with special emphasis on the contribution of each radiative phenomenon. Results demonstrated that the attenuation of radiation by the water spray is two-fold: the radiant energy emitted by the flame is reduced and this energy is attenuated by water droplets. The role of droplet scattering in the attenuation of thermal radiation in fire–water mist interactions is clearly demonstrated. For the droplet diameters considered, it is found that there are two distinct regimes: a fire extinction regime and a fire enhanced regime. This finding is consistent with previous experiments. Applied to a three-dimensional fire-sprinkler scenario, the model predictions are in good agreement with experimental data.

Characterization of room environments in growing enclosure fires

Experimental studies of growing enclosure fires were conducted to test previously derived scaling relationships for characterizing room environments including temperature and combustion product distributions. The scaling laws were derived based upon similarity relationships of steady ceiling flow, and extended to growing fires with consideration of a characteristic convective flow time. To examine the scaling hypothesis, well-defined growing enclosure fires were established, and transient temperatures and species concentrations were measured at different locations below the ceiling. The experimental results show that the nondimensional temperatures and species concentrations correlate well with respect to normalized time and space coordinates, which demonstrated the applicability of the scaling relationships as a means to predict room environments for growing enclosure fires.

Mass pyrolysis rates and excess pyrolysate in fully developed enclosure fires

Several critical aspects of fully developed enclosure fires need significant investigation and understanding of the underlying physics. Fire resistance of wall, ceiling and floor building elements depends on the maximum heat fluxes and the heat flux history from a fire and on the structural and thermal properties of the building elements of an enclosure. Maximum heat fluxes usually occur after the enclosure is fully involved in fire. In this regime, called post-flashover, combustion can be fuel (well-ventilated fires) or ventilation controlled (under-ventilated fires). For ventilation-controlled fires, the gas temperature is determined from the consumption of the incoming air into the enclosure and the energy exchanges of the combustion products with the enclosure boundaries. Although heat losses to the walls affect the development of gas temperature, quasi-steady-state conditions can be reached wherein conduction heat losses are small in comparison with the heat release rate in the enclosure. This situation applies for thick walls. In contrast for thin walls, steady-state conditions are developed early while radiation and convection heat losses are significant. This work deals with the late stages of fully involved fires in enclosures. The enclosure geometry (rectangular (cubic-like) and corridor), the fuel area and the opening size affect the air inflow, the burning rate and the excess pyrolysate issuing out of the enclosure. The excess pyrolysate, burns outside forming a fire plume on the external façade wall. For larger openings, the air inflow increases, the excess pyrolysate decreases and the burning rate reaches a maximum value that depends on the stoichiometric air to fuel ratio by mass. Further increase in the size of the opening leads to well-ventilated fire and finally, to free burning fire behaviour. The present analysis and results for these phenomena also explain Kawagoe's equation of mass loss rate m ̇ T =0.1 A o H o (kg/s) for pyrolysis in under-ventilated fires.

Technical Note: A Technique for Conducting Small-Plot Burn Treatments

An experimental design required burn treatments for 10-m2 circular plots. We constructed a fire enclosure for the plots using sheetmetal, electrical conduit, and other commonly available materials. We field tested the enclosure in sagebrush-grass ecosystems in central Nevada and central Utah, and evaluated peak fire temperatures using small metal tags striped with temperature sensitive paint. We obtained average peak surface temperatures of 310, 307, and 381 C in bare ground, under grass, and under shrub microsites, respectively, for the Nevada sites and 253, 299, and 337 C for the same microsites, respectively, in Utah. Subsurface (2-cm depth) temperatures rarely exceeded 79 C, the lowest temperature detectable by our method. The enclosure contained the fire and did not permit escape of any embers or firebrands. The fire enclosure, burn technique and temperature monitoring method used are inexpensive, easily deployed, and desirable for experiments where larger-scale burns are impractical. DOI:10.2458/azu_jrm_v56i3_korfmacher

Characterization of the fire environments in central offices of the telecommunications industry

AbstractEight free burning and two sprinklered fire tests were performed with electrical cable trays and live digital switch racks in a large enclosure to simulate telecommunications central office (TCO) fires started by electrical overheating. Very‐slow‐growing (non‐flaming), slower‐growing (partially flaming) and low‐intensity‐faster‐growing (flaming) fires releasing gray‐white, gray, and black smoke, respectively, were observed in the tests. Under quiescent conditions present in the unvented enclosure fire tests for cables, very‐slow‐growing fires were detected in about 1452 s, whereas the slower‐growing fires were detected in about 222 s by commercial fire detectors. Under ventilation conditions typical of TCOs, detection times were very similar for the five types of commercial TCOs fire detectors used in the tests. The average detection times for slower‐growing fires (cable fires) and low‐intensity‐faster‐growing fires (digital switch rack fires) were 242±17% and 249±11%s respectively.The TCO procedures to reduce smoke damage from fires (on fire detection, inlet ventilation flow is turned off and exhaust flow is turned on) were found to be beneficial. The extent of smoke damage decreased significantly with an increase in the exhaust flow rate. The chloride ion mass deposition suggested that equipment recovery would be possible in the smoke environment if the cable vapor concentration could be reduced below about 3 g/m3.The metal corrosion rate was found proportional to the 0.6th power of the smoke concentration, similar to that found for the corrosion of metal surfaces exposed to aqueous solutions of HCl and HNO3 and for acid rain with no protective layer at the surface. Sprinkler water was found to wash down the smoke deposits on the surfaces with little indication of corrosion enhancement. Copyright © 2003 John Wiley & Sons, Ltd.

Effects of Surface Flame Spread of Plywood Lining on Enclosure Fire in a Modified ISO Room

Surface burning areas of plywood lining installed at walls and ceiling of a modified ISO room enclosure were estimated using surface temperatures measured in the full-scale enclosure fire tests. Based on the surface burning areas, the development of surface flame spread at the lining surface has been assessed experimentally. The correlation of the resulting surface flame spread at different burning times was attempted with other important experimental data associated with the enclosure fire growth, including heat release, room temperatures, heat fluxes imposed on the floor, the interface height of the hot and cold gas layer etc. Results showed that for the plywood lining used the surface burning area was a critical factor that significantly influenced the enclosure fire growth and could be reasonably well correlated to many other parameters of the enclosure fire. The study not only investigated the effect of surface flame spread of the lining on the enclosure fire growth in-depth but also produced useful experimental data and analyses for the further development of numerical modeling for enclosure fires lined with combustible materials.

Technical note: a technique for conducting small-plot burn treatments

An experimental design required burn treatments for 10-m2 circular plots. We constructed a fire enclosure for the plots using sheetmetal, electrical conduit, and other commonly available materials. We field tested the enclosure in sagebrush-grass ecosystems in central Nevada and central Utah, and evaluated peak fire temperatures using small metal tags striped with temperature sensitive paint. We obtained average peak surface temperatures of 310, 307, and 381 degrees C in bare ground, under grass, and under shrub microsites, respectively, for the Nevada sites and 253, 299, and 337 degrees C for the same microsites, respectively, in Utah. Subsurface (2-cm depth) temperatures rarely exceeded 79 degrees C, the lowest temperature detectable by our method. The enclosure contained the fire and did not permit escape of any embers or firebrands. The fire enclosure, burn technique and temperature monitoring method used are inexpensive, easily deployed, and desirable for experiments where larger-scale burns are impractical.

Fully Involved Enclosure Fires: Effects Of Fuel Type, Fuel Area And Geometry

For the design of fire safety systems, evacuation analysis structural response and external façade performance, the heat release rate history is a primary factor regarding the development of building fires starting from the room of fire origin. This work examines the steady state heat release rate period in enclosures that occurs after the initial growth period ends because either fire has spread to all fuel available or ventilation- controlled conditions have been established. It extends previous important work by identifying how fuel type (e.g. stoichiometric ratio), fuel surface area, room geometry and opening affect the rate of burning. Using recent well-designed experiments in cubic like enclosures and in corridors together with a simple theory, correlations are developed for the rate of pyrolysis, of incoming air flow and of excess pyrolysate. In the course of the analysis, critical areas of research are suggested concerning combustion efficiency, heat fluxes, and effective fuel area involved in pyrolysis

On numerical comparison of enclosure fire in a multi-compartment building

This paper reports a validation study of a CFD simulation for an enclosure fire in a single level multi-room building. Model predictions are compared against measured data of Luo and Beck (Fire Safety J 23 (1994) 413). The CFD-based fire model focuses on the use of laminar flamelet approach to account for the combustion of fire. Global radiation in the multi-compartment building is evaluated though the discrete ordinates method (Combust. Sci. Technol. 59 (1988) 321). Soot model proposed by Syed et al. (Proceedings of the 23rd Symposium on Combustion, The Combustion Institute, 1990. p. 1533) that accounts for the essential physical processes of nucleation, coagulation, surface growth and oxidation is utilised to predict the soot formation and burnout. The presence of soot augmenting the global radiative heat exchange was considered. Overall, our results are in good agreement with the experimental data of Luo and Beck's and also consistent with their numerical results.

Performance of a single glazing assembly exposed to a fire in the centre of an enclosure

AbstractThe result of 14 experiments in which a single glazing assembly was exposed to fires of increasing severity in the centre of an enclosure are presented. The glazing assembly was exposed to a two zone fire enclosure environment with consistency and repeatability within each set of three experiments conducted at each fire severity level evident from the enclosure gas temperature profiles. The results presented include heat release rates, enclosure and local gas temperature, heat flux distribution, glass surface temperatures, shaded glass temperatures, thermally induced strains, crack bifurcation patterns and loss of integrity of the glazing assembly. Limits regarding the maximum incident heat fluxes required to cause catastrophic failure of the glazing assembly are suggested. Copyright © 2002 John Wiley & Sons, Ltd.

Prediction of carbon monoxide in fires by conditional moment closure

Carbon monoxide is the chief killer in fires. Dangerous levels of CO can occur when reacting combustion gases are quenched by heat transfer, or by mixing of the fire plume in a cooled under- or overventilated upper layer. In this paper, carbon monoxide predictions for enclosure fires are modeled by the conditional moment closure (CMC) method and are compared with laboratory data. The modeled fire situation is a buoyant, turbulent, diffusion flame burning under a hood. The fire plume entrains fresh air, and the postflame gases are cooled considerably under the hood by conduction and radiation, emulating conditions which occur in enclosure fires and lead to the freezing of CO burnout. Predictions of CO in the cooled layer are presented in the context of a complete computational fluid dynamics solution of velocity, temperature, and major species concentrations. A range of underhood equivalence ratios, from rich to lean, are investigated. The CMC method predicts CO in very good agreement with data. In particular, CMC is able to correctly predict CO concentrations in lean cooled gases, showing its capability in conditions where reaction rates change considerably.

Enclosure smoke filling and management with mechanical ventilation

Enclosure smoke filling and management are addressed from the standpoint of the volumetric flow rates commonly used for mechanical ventilation system design. In this context, fire-induced gas expansion is treated as a volumetric source term. A two-layer analysis developed previously for enclosure smoke filling without mechanical ventilation is extended to consider the impact of mechanical ventilation on smoke layer descent rates and conditions within the smoke layer. A spreadsheet-based model of enclosure smoke filling developed in conjunction with the previous unventilated analysis is also extended to consider both mechanical extraction and injection systems. Some implications of mechanical ventilation on the development and descent of a smoke layer in an enclosure fire are discussed.

Application of Inverse Analysis to Thermal Contact Resistance between very Rough Nonconforming Surfaces

A method to determine the contact conductance at the interface between steel and concrete under high temperature conditions, typical of enclosure fires, using experimental measurements and inverse heat conduction analysis is presented. This method is adopted because the interface under investigation is formed by very rough non-conforming surfaces and there are no data or mathematical models capable of describing such an interface. A specimen representing a square steel tube filled with concrete is heated in a modified electrical furnace to temperatures comparable to those observed in structural elements exposed to fire, and temperature-time histories in two-second increments are recorded at ten locations. The results are used to obtain a correlation representing averaged contact conductance for the steel-concrete interface of square steel tube filled with non-reinforced concrete as a function of temperature.

The Characteristic Analysis of Oil Pool Fires Phenomena for Fire Safety Design in Engine Room (Part 1) An Experimental Study on Thermal Properties and States during Oil Burning

Many fire accidents in engine rooms of ships and marine structures come into existence in the world, and the unexpected burning of hydrocarbon liquid, such as fuel oil and lubrication oil, tends to be a good half of those primary cause. For the preventive design of oil burning fire in engine rooms, it is necessary to be grasped entirely the oil pool fires phenomena by an analysis taking thoroughly account of the governing factors and the characteristics of flammability liquid fireIn order to investigate the distinctive factors of fire spread and extinguishing by some numerical simulations of fire accident in an engine room, the basic experiments on oil burning are executed in the condition of (1)oxygen rich atmosphere, and (2)oxygen lean atmosphere. Furthermore, the oil burning phenomena in enclosed-compartment is estimated qualitatively using a simplified mathematical model with a principle feature of enclosure fire. From the results of these experiments, it can be clarified as for threshold conditions of fire spreading, thermal properties and states of oil pool fires.

Performance of a single glazing assembly exposed to enclosure corner fires of increasing severity

AbstractThe results of 19 experiments in which a single pane glazing assembly was exposed to enclosure corner fires of increasing severity are presented. The glazing assembly was exposed to a two zone fire enclosure environment, with consistency and repeatability within each set of three experiments conducted at each fire severity level, evident from the enclosure gas temperature profiles. The results presented include heat release rates, enclosure and local gas temperatures, heat flux distributions, glass surface temperatures, shaded glass temperatures thermally induced stains, crack bifurcation patterns and loss of integrity of the glazing assembly. The results and observations obtained are presented in the form of a toolkit for the estimation of the occurrence of cracking and failure of single glazing in enclosure fires. Copyright © 2001 John Wiley & Sons, Ltd.

Comparison of different combustion models in enclosure fire simulation

In this study, three combustion models, the volumetric heat source (VHS) model, the eddy break-up model and the presumed probability density function (prePDF) model, are examined in enclosure fire simulation. The combustion models are compared and evaluated for their performance in predicting three typical enclosure fires, a room fire, a shopping mall fire and a tunnel fire. High Reynolds number turbulence k– ε model with buoyancy modification and the discrete transfer radiation model (DTRM) are used in the simulation. Corresponding experimental data from the literature are adopted for validation. The results show satisfactory prediction in flow patterns and features in the complex enclosure fires. However, it is shown that these combustion models are not able to show consistent performance over the different locations and enclosure fires. The needs for adequate turbulent combustion models in enclosure fires are discussed.

Review of: Enclosure Fire Dynamics

Abstract Understandably, one of the prilnary requirements for all individuals involved in any aspect of modern fire safety and fire protection engineering, including fire scene investigation and reconstruction, is to understand how a fire behaves in an enclosed space. Enclosure Fire Dynamics addresses, in a clear and logical manner, physical changes in such an environment. The book is a collaboration of two internationally renowned experts in the field of fire protection engineering and presents the reader with an academic understanding of the dominating mechanisms influencing fires in compxtments, or enclosures.

A Kinetic Study on the Production of Toxic Compounds in Enclosure Fires Under Suppression by Halon Replacement Extinguishing Agents

AbstractThis paper presents the results of a theoretical investigation designed to characterise the mechanism of formation of those toxic compounds which are produced when halon replacement extinguishing agents are released in the hot upper‐layer of typical enclosure fires. The present work was primarily motivated by the fact that in many building fires the extinguishing agent may not be directly applied to the flame but released in the hot layer. For this purpose, detailed chemical kinetic modelling techniques were used to predict the generation of combustion products and toxic byproducts within the hot layer. This can be justified based on the fact that recent studies in this field have shown that the production of major combustion products in the upper‐layer is kinetically controlled. Effects of the mixing phenomenon were investigated by considering two possible extremes using infinitely fast and infinitely slow mixing models. The heat loss variation was also studied under isothermal and adiabatic conditions. Calculations presented here show that the concentration of toxic compounds originated from halon replacement extinguishing agents are much higher than those of halons mainly because for such agents, due to the lack of significant chemical reaction inhibition, higher extinguishing concentration are required.