Simplified Calculation Method for Determining Smoke Downdrag Due to a Sprinkler Spray

Li, K. Y.; Spearpoint, Michael

doi:10.1007/s10694-010-0194-5

Cited by 19 publications

(10 citation statements)

References 8 publications

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“…This theory is adopted also in recent publications, e.g. [3][4]6]. However, we explain in the present paper how this theory must be revised, starting from first principles.…”

Section: Figure1 Schematic Of Instability Criterion From Bullen Theorymentioning

confidence: 94%

“…Both effects lead to "smoke logging", a downward displacement of the smoke layer affected by water droplets [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

“…When discharging water droplets, smoke logging is observed in real fires and experimental studies [2][3][4][5]. The downward displacement of smoke layer can pose a great risk for occupants, since the effect of reduced visibility delays escape and increases the duration of exposure of the occupants of a building to the products of combustion.…”

Section: Introductionmentioning

confidence: 99%

“…In the literature, many studies are found on the topic of interaction of water droplets with fire smoke layer [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The cooling effect and drag force produced by water droplets are considered generally to yield smoke logging [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…The cooling effect and drag force produced by water droplets are considered generally to yield smoke logging [1][2][3][4][5][6][7][8]. Bullen [2] presented a theory, leading to an instability criterion of smoke layer under water spray conditions.…”

Section: Introductionmentioning

confidence: 99%

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Description and application of an analytical model to quantify downward smoke displacement caused by a water spray

Tao

Vierendeels

Fang

et al. 2013

Fire Safety Journal

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An analytical model is developed from basic principles to quantify the downward smoke displacement as caused by a water spray from e.g. a sprinkler head. The underlying assumptions are identified and the global balance is described between downward drag force, potentially downward buoyancy due to a cooling effect within the water spray envelope in the smoke layer, and the upward buoyant force in the ambient air below the smoke layer. From this balance, the downward smoke displacement is quantified. It is explained that the classical Bullen theory to define a criterion for smoke layer stability is in general not valid. There is always downward smoke displacement, although potentially small, depending on the circumstances. The tracking of individual water droplets leads to the evolution of the spray envelope radius and provides the total downward drag force on the smoke. An extensive sensitivity study is presented, varying the water spray angle at the nozzle, the water droplet diameter, the smoke layer temperature, and inclusion or not of the cooling effect by water and air entrainment in the downward smoke displacement. It is highlighted that the downward smoke displacement is more pronounced for smaller droplets (for fixed water mass flow rate), and for lower smoke layer temperatures. For larger water spray angle at the nozzle, the downward displacement also increases monotonically with initial smoke layer thickness. A smaller spray angle at the nozzle leads to stronger 2 downward smoke displacement and the variation of downward smoke displacement with initial smoke layer thickness is non-monotonic: stronger descent of smoke for thinner smoke layer, but beyond a critical smoke layer thickness also again a stronger descent with increasing smoke layer thickness. The accuracy of the model as presented is illustrated by means of an experimental data set. Keywords:

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“…This theory is adopted also in recent publications, e.g. [3][4]6]. However, we explain in the present paper how this theory must be revised, starting from first principles.…”

Section: Figure1 Schematic Of Instability Criterion From Bullen Theorymentioning

confidence: 94%

“…Both effects lead to "smoke logging", a downward displacement of the smoke layer affected by water droplets [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Description and application of an analytical model to quantify downward smoke displacement caused by a water spray

Tao

Vierendeels

Fang

et al. 2013

Fire Safety Journal

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Experimental and numerical study of water spray system for a fire event in a confined and mechanically ventilated compartment

2019

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Summary The present work addresses the application of a water spray system in case of a fire event in large‐scale experiments for nuclear safety issues. It focuses on the interaction between a water spray system and a stratified smoke layer due to a pool fire in a mechanically ventilated enclosure. This study is supported by a set of four large‐scale tests and one numerical simulation with a 3D CFD software, named CALIF3S/ISIS, and developed by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The modelling used in this paper is based on an Eulerian‐Lagrangian approach. The fire tests are performed in a 165 −m3 mechanically ventilated single room. The fire is a lubricant oil pool fire of about 400 kW. The ventilation flow rate is 2550 m3.h−1 and corresponds to a renewal rate of 15.5 h−1. The spray nozzles are deluge and sprinkler type. The test parameters are the water flow rate, the time of activation, and the duration of activation. Based on the large‐scale experiments and the numerical simulation, four typical physical mechanisms have been enlightened. The first one corresponds to the cooling of the gas phase that is the straightforward consequence of the heat transfer exchange between the water droplets and the surrounding gas. The second effect is the process of gas mixing and homogenization induced by the water spraying system. The gas concentrations (O2, CO2) in the upper and lower parts of the room tend to the same level. The third effect is the significant increase of the fire heat release rate (HRR), up to 25 %, when the water spray is activated. Then, the last noteworthy effect is the occurrence of gas pressure peaks when the water spray is activated or shut off, consequence of the sudden change of the gas temperature. The processes of gas cooling and fire HRR increase are showed to be the main causes of these variations of gas pressure.

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An Experimental Study on the Smoke-Logging Phenomenon Using Sprinkler for Performance-Based Evacuation Safety Design

Seo

Yoon

Koo

et al. 2016

Fire Science and Technology 2015

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Simplified Calculation Method for Determining Smoke Downdrag Due to a Sprinkler Spray

Cited by 19 publications

References 8 publications

Description and application of an analytical model to quantify downward smoke displacement caused by a water spray

Description and application of an analytical model to quantify downward smoke displacement caused by a water spray

Experimental and numerical study of water spray system for a fire event in a confined and mechanically ventilated compartment

An Experimental Study on the Smoke-Logging Phenomenon Using Sprinkler for Performance-Based Evacuation Safety Design

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