Scale Model Reconstruction Of Fire In An Atrium
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Publicado: 8 de noviembre de 2012
Scale Model Reconstruction of Fire in an Atrium
James G. Quintiere and Michael E. Dillon
Abstract Scaling principles are derived and explained for the simulation of smoke movement in building fires. The scaling is primarily based on representing transient inviscid flows characteristic of large Reynolds number. This form of scaling is sometimes called Froude number scaling since the momentum andbuoyancy effects are modeled. A technique is used to compensate for the neglect of Reynolds number effects at solid boundaries. The scaling technique was applied to clarify the performance of a smoke control system which operated in an actual fire incident in a department store atrium. The scale model results confirmed a design flaw in the smoke control system. The high velocity inlet air was shownto be responsible for mixing and destratifying the hot smoke in the atrium and dispersing it throughout the department store. It is believed this the first time a scale model in fire was used as evidence in civil litigation case. Keywords Fire · scale modeling · smoke control system
Nomenclature
c D g k L p Q t T v ˙ V Specific heat Diameter Gravitational force per unit mass Thermal conductivityLength Pressure Energy release rate Time Temperature Velocity Volumetric flow rate
J.G. Quintiere Department of Fire Protection Engineering, University of Maryland, College Park, MD e-mail: jimq@umd.edu K. Saito (ed.), Progress in Scale Modeling, C Springer Science+Business Media B.V. 2008 109
110
J.G. Quintiere, M.E. Dillon
x,y,z α ρ ν
Position Thermal diffusivity, k/ c DensityKinematic viscosity
Subscript
fan F m o w Fan Full-scale Small-scale model Initial or reference Solid wall boundary
Superscript
(˙ ) (∧ ) Per unit time Dimensionless
Introduction
Many aspects of fire phenomena can be scaled using geometrically similar models. In general all of the variables cannot be completely scaled since too many dimensionless groups appear. However, usually the mostrelevant significant dimensionless groups can be preserved in a scale model study. This is referred to as partial scaling. A review of scaling techniques successfully used in fire problems has been described by Quintiere [1]. In particular, smoke flow scaling studies have been performed by Heskestad [2] and Quintiere et al. [3]. These two studies used reduced scale fires in a geometrically scaledenclosure representing building components. An analog technique using a water and salt-water system to simulate the buoyancy difference caused by hot smoke and cold air has been successfully used to describe fire induced flows in series of rooms [4]. A11 of these studies are based on a scaling principle which maintains a balance between the buoyancy and convective “forces”, while ignoring viscous and heatconduction effects. Based on the success of these studies, a scale modeling approach was used to study the motion of smoke in an actual atrium due to a fire. In this actual fire, a smoke control system was activated which extracted smoke from the roof of the atrium. However, in this incident an issue arose concerning the operation of the smoke control system and on the distribution of smokethroughout the building housing the atrium. The issue concerned whether the smoke control system was responsible for the improper dispersal of smoke. Since this problem was very similar to the dynamic features of the smoke movement in buildings previously studied [2–4],
Scale Model Reconstruction of Fire in an Atrium
111
similar scaling techniques were used in developing a scale model study.These scale model results would ultimately be used in the litigation of the smoke control design issue. Because the scale model was used in litigation, there are not extensive results to demonstrate its complete characteristics. However, the video results were especially graphic in resolving the issue. A description of this fire will be described along with the atrium geometry and design features...
James G. Quintiere and Michael E. Dillon
Abstract Scaling principles are derived and explained for the simulation of smoke movement in building fires. The scaling is primarily based on representing transient inviscid flows characteristic of large Reynolds number. This form of scaling is sometimes called Froude number scaling since the momentum andbuoyancy effects are modeled. A technique is used to compensate for the neglect of Reynolds number effects at solid boundaries. The scaling technique was applied to clarify the performance of a smoke control system which operated in an actual fire incident in a department store atrium. The scale model results confirmed a design flaw in the smoke control system. The high velocity inlet air was shownto be responsible for mixing and destratifying the hot smoke in the atrium and dispersing it throughout the department store. It is believed this the first time a scale model in fire was used as evidence in civil litigation case. Keywords Fire · scale modeling · smoke control system
Nomenclature
c D g k L p Q t T v ˙ V Specific heat Diameter Gravitational force per unit mass Thermal conductivityLength Pressure Energy release rate Time Temperature Velocity Volumetric flow rate
J.G. Quintiere Department of Fire Protection Engineering, University of Maryland, College Park, MD e-mail: jimq@umd.edu K. Saito (ed.), Progress in Scale Modeling, C Springer Science+Business Media B.V. 2008 109
110
J.G. Quintiere, M.E. Dillon
x,y,z α ρ ν
Position Thermal diffusivity, k/ c DensityKinematic viscosity
Subscript
fan F m o w Fan Full-scale Small-scale model Initial or reference Solid wall boundary
Superscript
(˙ ) (∧ ) Per unit time Dimensionless
Introduction
Many aspects of fire phenomena can be scaled using geometrically similar models. In general all of the variables cannot be completely scaled since too many dimensionless groups appear. However, usually the mostrelevant significant dimensionless groups can be preserved in a scale model study. This is referred to as partial scaling. A review of scaling techniques successfully used in fire problems has been described by Quintiere [1]. In particular, smoke flow scaling studies have been performed by Heskestad [2] and Quintiere et al. [3]. These two studies used reduced scale fires in a geometrically scaledenclosure representing building components. An analog technique using a water and salt-water system to simulate the buoyancy difference caused by hot smoke and cold air has been successfully used to describe fire induced flows in series of rooms [4]. A11 of these studies are based on a scaling principle which maintains a balance between the buoyancy and convective “forces”, while ignoring viscous and heatconduction effects. Based on the success of these studies, a scale modeling approach was used to study the motion of smoke in an actual atrium due to a fire. In this actual fire, a smoke control system was activated which extracted smoke from the roof of the atrium. However, in this incident an issue arose concerning the operation of the smoke control system and on the distribution of smokethroughout the building housing the atrium. The issue concerned whether the smoke control system was responsible for the improper dispersal of smoke. Since this problem was very similar to the dynamic features of the smoke movement in buildings previously studied [2–4],
Scale Model Reconstruction of Fire in an Atrium
111
similar scaling techniques were used in developing a scale model study.These scale model results would ultimately be used in the litigation of the smoke control design issue. Because the scale model was used in litigation, there are not extensive results to demonstrate its complete characteristics. However, the video results were especially graphic in resolving the issue. A description of this fire will be described along with the atrium geometry and design features...
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