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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Fire Dynamics II
Lecture # 1Introduction / Enclosure Phenomena
Jim Mehaffey
82.583 or CVG****
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Fire Dynamics II82.583 or CVG****
• Lectures: Wednesdays 5:30 - 8:30 p.m.• Location: Room 404, Southam Hall• Lecturer: Dr. Jim Mehaffey, Forintek
Tel: (613) 523-0927Fax: (613) [email protected]
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Recommended Text Books• Dougal Drysdale, An Introduction to Fire Dynamics,
Wiley, 1999• Björn Karlsson and James G. Quintiere, Enclosure
Fire Dynamics, CRC Press, 2000• SFPE Handbook of Fire Protection Engineering, 3rd
Ed., 2002
Lecture Noteshttp://www.carleton.ca/~ghadjiso/
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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82.575 Fire Dynamics I• Introduction to basic chemistry & physics of fire• Simple mathematical models describing fires
developing in the open
82.583 Fire Dynamics II• How are basic chemistry & physics altered
when fire develops within an enclosure• Simple mathematical models describing fires
developing in enclosures
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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82.579 Introduction to Fire Protection Engineering (1998, 1999 & 2000)
• 82.579 = Fire Dynamics I + Fire Dynamics II, but delivered in one term, not two terms
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Fire Dynamics II - Course DescriptionCourse addresses the dynamics of fires in buildings. Phenomena that govern ignition, fire growth and severity, temperature and pressure development, toxicity and visibility are investigated. Fire Dynamics IIbuilds on basic concepts presented in Fire Dynamics I. The way containment modifies fire processes is highlighted. Particular emphasis is placed on the reaction of people, buildings and building components to exposure by fire. This basic background provides a foundation for beginning the process of designing a fire safe building.
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Enclosure Fire Dynamics• Fires develop differently in an enclosure than in
the open • Limited supply rate of oxygen causes a
reduction in the rate of burning• Trapping of heat in the enclosure causes an
increase in the rate of burning • Enclosure fire dynamics is a competition
between these two effects
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Proposed Course Outline
• Lecture 1: Introduction / Enclosure Phenomena
• Lecture 2: Ceiling Jets & Ceiling Flames
• Lecture 3: Accumulation or Smoke Filling
• Lecture 4: Vent Flows
• Lecture 5: Chemistry of Room Fire Combustion
• Lecture 6: Smoke and Heat Venting
Winter Break: February 17-23
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Proposed Course Outline (continued)
• Lecture 7: Heat Flow Calculations
• Lecture 8: Flame Spread & Burning Rates
• Lecture 9: Room-fire Dynamics
• Lecture 10: Pre-flashover Fire
• Lecture 11: Post-flashover Fire
• Lecture 12: Backdrafts & Explosions
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Grading– Problem Sets: 60% – Final Exam: 40%
Problem Sets– Number 1: Distributed during Lecture 3 – Number 2: Distributed during Lecture 6 – Number 3: Distributed during Lecture 8 – Number 4: Distributed during Lecture 10
Final ExamFor evaluation purposes only. Not returned to students.
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Introduction / Enclosure PhenomenaOutline
• How does confinement impact fire dynamics?• What types of models, in addition to those we
have seen for fires burning in the open (in Fire Dynamics I) will be needed to describe building fires?
• We’ll look at the details of these new models in subsequent lectures.
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Consider an Unconfined Fire Plume (1)
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Unconfined Fire Plume• Properties of an unconfined fire plume depend on
– Rate of heat release– Diameter of fire base
• Models are available (Fire Dynamics I) to predict– Flame length– Axial temperature as a function of height– Upward axial velocity as a function of height– Virtual point source (of buoyant plume)– Radius (of buoyant plume)– Total upward mass flow (of buoyant plume)– Concentration of CO & soot (in buoyant plume)
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Consider a Fire Plume Confined by a Ceiling
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Unconfined Ceiling Jet• Need to model ceiling jet in order to predict time to
activation of sprinklers or heat detectors• Properties of ceiling jet depend on
– Rate of heat release– Diameter of fire base– Height of ceiling
• Models are available (Fire Dynamics I) to predict– Max. temperature as a function of radial distance– Maximum velocity as a function of radial distance– Time to activation of sprinklers or heat detectors if
they are subjected to max. temp & velocity
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 2: Ceiling Jets & Ceiling Flames• Take a deeper look at unconfined ceiling jets
– review various models for ceiling jets– what do temperature and velocity profiles below the
ceiling look like (will the sprinkler be located where maxima in temperature & velocity occur)?
– what happens if the rate of heat release is strongly time-dependent?
– what if the ceiling jet is immersed within a hot upper layer?
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Consider a Ceiling Flame
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 2: Ceiling Jets & Ceiling Flames• For ceiling flames
– model flame extension under the ceiling– investigate the impact of flame extension under a
ceiling on radiant heat transfer to (and rate of burning of) the burning object
****************************************************************• For flames above a burning object located against
a wall or in a corner– investigate the effect of asymmetric and reduced
entrainment of air on flame dynamics
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Development of a Hot Smoke Layer
Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Development of a Hot Smoke Layer• Ceiling jet eventually reaches enclosure walls• Hot gas is forced downward along wall• Hot gas is buoyant so flow turns upward• Layer of hot gas forms under ceiling
Lecture 3: Accumulation or Smoke Filling• Models for rate of descent of the hot layer• Properties of hot layer (temperature, gas & soot
concentrations)
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Interaction with Openings• If there is an opening to an adjacent room or to
the outdoors, the hot layer flows out of the opening when it descends to top of opening
• Heat in enclosure break windows and thereby create an opening as fire develops
• Hot gas exits from upper part of opening and fresh air enters through lower part
Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Lecture 4: Vents Flows• Models for rate of exit of hot gas from enclosure
through an opening• Models for rate of entry of air into enclosure
through an opening• Model for maximum possible rate of heat
release for a ventilation-controlled fire
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Rate of Ventilation of Fire• Fires burning in the open are well-ventilated. Air can
readily approach a fire from all sides.• Fires burning within enclosures often burn in poorly-
ventilated conditions.
Lecture 5: Chemistry of Room Fire Combustion• Models to predict impact of reduced ventilation on:
– effective heat of combustion– yields of combustion products (CO, CO2, soot)
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 6: Smoke and Heat Venting• In an enclosure fire, smoke and heat in the hot upper
layer are dangerous for occupants, fire fighters, expensive equipment and / or stored goods
• For these reasons either natural or mechanical venting is sometimes employed to keep the upper layer above a predetermined height
• Models to predict size of openings required or rate of mechanical venting needed to meet design objectives
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 7: Heat Flow Calculations
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 8: Flame Spread & Burning Rates• Models for predicting how thermal radiation
from hot upper layer can– Increase rate of flame spread across combustibles– Increase rate of burning of combustibles
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 9: Room-fire Dynamics
Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Lecture 9: Room-fire Dynamics• Flashover: Transition from burning of one or a
few objects to full room involvement
• Fire development: experimental findings• Impact of ventilation and boundary types
• Fire growth: combustible linings
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Lecture 10: Pre-flashover Fire• Models for rate of heat release required for
flashover to occur
• Models for time to flashover
• Models for temperature in hot smoky layer
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 11: Post-flashover Fire• Models for rate of heat release
• Models for hot gas temperature in enclosure
• Models for response of structural elements and enclosure boundaries
• Rational requirements for fire resistance
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 12: Backdrafts & Explosions• Explosions:
– Fuel and air premixed– Following ignition rapid combustion– Deflagration (flame propagates through mixture)– Large pressure rise– Enclosure walls & ceiling may not be able to
withstand pressure → explosion– Explosion venting
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 12: Backdrafts & Explosions• Backdrafts:
– Limited ventilation → large quantity of unburnt “gas”– When opening suddenly introduced, inflowing air
mixes with “gas” creating flammable mixture– Ignition source ignites flammable mixture, resulting
in an extremely rapid burning– Expansion due to heat released expels burning
“gas” through opening & causes fireball outside enclosure
– Draftdrafts can be extremely hazardous
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Lecture 12: Backdrafts & Explosions• BLEVE: Boiling Liquid Expanding Vapour Explosion
– Propane is a liquid under atmospheric conditions– Liquified by application of pressure & stored in tank – In tank, liquid & vapour at equilibrium, with vapour
at high pressure– If tank immersed in fire, heat causes evaporation of
liquid and higher vapour pressure– Activates relief valve (turbulent jet flame)– Pressure may still rise and fire may weaken metal
casing.– Tank ruptures → BLEVE
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Kemano Public Safey Initiative
• Remote company town closed: July 2000
• Firefighter training & fire research
• Forintek invited to participate
• Partners: National Research Council Weyerhaeuser
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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• 6 fire experiments were conducted in one-and two-family houses
• Fires allowed to grow and challenge houses’ wood-frame structures
• No (or delayed) fire suppression
• Temperatures measured at 50 locations in rooms and assemblies
The Fire Test Program
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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• First item ignited: plastic waste-paper basket filled with polyurethane chips and shredded paper
• Waste-paper basket in contact with upholstered furniture or mattress
• Intent: quickly establish a large fire that challenges the wood-frame structure
Ignition Source
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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The Ignition Source
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Rate of Heat Release: Ignition Source
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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• Living room fully furnished
• Walls: wood studs protected by regular gypsum board
• Ceiling: wood joists protected by regular gypsum board
• Doors covered / windows partially open
Fire Test # 1
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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• Same as Fire Test # 1 except:
Walls and ceiling protected by fire-rated gypsum board
Fire Test # 2
Carleton University, 82.583 (CVG****), Fire Dynamics II,
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Purposes:
• Compare abilities of wood-frame walls and ceilings protected by regular & fire-rated gypsum board to contain fire in room of origin
• Generate data to validate computer models predicting thermal response of fire-rated wood-frame assemblies
Fire Tests # 1 & 2
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Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Fire Test 2
Video Clip
Carleton University, 82.583 (CVG****), Fire Dynamics II,
Winter 2003 Lecture # 1
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Fire Exposures
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Living Room Fires - Duplex
ASTM E 119 & CAN/ULC-S101