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Enclosure Fire Dynamics
Chapter 1: Introduction Chapter 2: Qualitative description of enclosure fires Chapter 3: Energy release rates Chapter 4: Plumes and flames Chapter 5: Pressure and vent flows Chapter 6: Gas temperatures (Chapter 7: Heat transfer) Chapter 8: Smoke filling (Chapter 9: Products of combustion) Chapter 10: Computer modeling Each course unit represents breaking down the problem into individual pieces
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Goals and expectations
Account for: How size, geometry, openings and buildning material affects an enclosure fire Typical fire development Different ways to characterise an enclosure fire
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Ignition
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Spread to additional fuel
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Free burn Lv is the smoke visibility distance in meters (or cm)
Phi is the equivalence ratio, with a value > 1.0 indicating unburned fuel
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Fire growth CO concentrations are now hazardous
Only 3 times more air available for combustions
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Flashover Unburned fuel in upper layer is able to burn once it mixes with oxygen outside the doorway. Insufficient air now available for combustion
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Temperature history during the course of a compartment fire
Not all fires follow this ideal history It is very difficult to predict early growth during an immediately after ignition Usually assume burning starts with HRR=50kW.
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Definition of flashover
20 kW/m2 Heat flux to floor Sufficient to ignite common combustibles Smoke layer temperature of oC Flames out through opening t.ex. Few regulations for carpeting because it does not usually become involved until closer to flashover
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Influence of oxygen depletion
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Similar fires in compartments of a different size
Larger room in able to dissipate more of the heat, resulting in a lower flux for flame spread
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Ignition - little influence from the compartment
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Spread to second fuel package
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Real differences evident
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Insufficient oxygen in smaller compartment
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Lack of oxygen
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Lack of oxygen
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Lack of oxygen
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Questions? Next unit: fire growth/design fires
Release of pentane from a large spherical storage vessel Is this a premixed flame?
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