Fire Dynamics I - Carleton University
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Transcript Fire Dynamics I - Carleton University
Fire Dynamics II
Lecture # 9
Room-fire Dynamics
Jim Mehaffey
82.583
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
1
Room-fire Dynamics
Outline
• Introduction
• Fire development: experimental findings
• Impact of ventilation, boundary type and fuel load
• Fire growth: combustible linings
• Characterize flashover: Transition from burning of
one or a few objects to full room involvement
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Introduction
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
3
Upper Layer Temperature During an Enclosure Fire
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Contribution of Room Linings to Fire Growth
• First item ignited may be combustible room linings
rather than contents
• Fire spreads up the wall (or corner) and spreads along
upper part of walls (and under the ceiling if also
combustible): wind-aided spread
• A hot upper layer is generated which radiates energy
to portions of the upper wall not yet burning
• Opposed flow flame-spread increases rate of heat
release and temperature of upper layer which, in turn,
causes faster flame spread
• Upper layer may become hot enough for flashover
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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•
•
•
•
Flashover
Transition from burning of one or a few objects to full
room involvement
Statistics
In non-sprinklered residential buildings 22 - 25% of
fires proceed to flashover
Room Size
For small rooms (~100 m3) important to determine
when (if) flashover occurs (life safety)
For large rooms (~1,000 m3) time to flashover can be
long, but a localized pre-flashover fire may be
sufficiently severe to cause local structural damage
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Flashover Criteria
• Flashover has been defined as occurring when:
1. Fire appears (visually) to undergo rapid transition
from localised burning to full-room involvement
2. Crumbled paper placed on floor is ignited
3. Flames emerge from the opening
4. Hot layer temperature reaches 500-600°C
5. Radiant heat flux at floor reaches 20 kW m-2
• Experimental studies have employed criteria 1 to 5
• Theoretical studies employ criteria 4 & 5
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Experiments: Mehaffey & Harmathy, 1985
• 32 room fire experiments
– Fuel: wooden cribs
– Fuel load: simulated hotel & office rooms
• Room Dimensions
– Floor: 2.4 m x 3.6 m
– Ceiling height: 2.4 m
• Ventilation opening
– Open throughout test
• Purpose of experiments
– Assess thermal response of room boundaries exposed
to post-flashover fires
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Impact of boundary (thermal properties)
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Impact of boundary (thermal properties)
• Fuel: wooden cribs: 15 kg m-2 (hotel)
• Window: area = 9% area of floor
– b =0.7 m; h =1.2 m; A h = 0.92 m5/2
• Post-flashover fire: ventilation controlled
– rate of heat release = 970 kW ~ 1 MW
• . . . . “Standard fire” CAN4-S101 (ASTM E119)
Room
1
2
kc (J m-2 s-1/2 K-1)
868
334
2
-4
-1
-2
kc (kJ m s K )
0.753
0.112
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Impact of size of openings
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Impact of size of openings
• Fuel: wooden cribs: 27 kg m-2 (office)
• Thermal inertia of room boundaries
–
kc = 666 J m-2 s-1/2 K-1
– kc = 0.444 kJ2 m-4 s-1 K-2
• Post-flashover fire: ventilation controlled
• . . . . “Standard fire” CAN4-S101 (ASTM E119)
5/2
Room
b (m)
h (m)
A h (m )
3
4
5
0.7
0.7
0.7
1.2
1.6
2.1
0.92
1.42
2.13
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
Q (kW)
970
1,490
2,240
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Experimental Results: Post-flashover Fires
(SFPE Handbook)
Fire
load
(kg)
877
877
1744
1744
1744
•
•
•
•
Window
area
2
(m )
11.2
5.6
11.2
5.6
2.6
Rate heat
released
(kW)
7,950
7,950
13,400
9,600
6,700
Heat lost
exitting gas
(%)
65
52
61
53
47
Heat lost to
boundaries
(%)
15
26
15
26
30
Heat lost
to fuel
(%)
11
11
11
12
16
Radiant heat
lost window
(%)
9
11
13
9
7
Floor area = 29 m2
Fuel load: wooden cribs
First two tests: Fuel-surface controlled
Last three tests: Ventilation controlled
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Experimental Results: Post-flashover Fires (1)
V
Q CONV rate of heat loss by convection thru vent
– Largest single loss: Note % lost as vent area
B
B
Q CONV Q RAD total rate of heat transfer to boundaries & fuel
– Significant loss: Note % lost as vent area
V
Q RAD rate of radiative heat transfer thru vent
– Small loss: Note % lost as vent area
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
14
Pitt Meadows, B.C. - Video
October 19-24, 1996
• 1-storey wood-frame apartment building to be
demolished
• Local fire departments & IAAI plan full-scale fire
tests & training program
• UBC / Forintek invited to monitor tests
• Video - visual display of flashover
- role of ventilation in flashover
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Maximum Possible Heat Release Rate
Q 1500 A h (kW)
• One pane open: b = 0.6 m and h = 1.33 m
Q 1,380 kW
• Window broken: b = 2.7 m and h = 1.33 m
Q 6,200 kW
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Pitt Meadows, B.C. - Video
October 19-24, 1996
• One window pane open at beginning of test
• Appears flashover will not occur as not enough
ventilation (air supply)
• Firefighters break rest of window glazing
• Flashover occurs quickly thereafter
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Temperature Profile in Living Room
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Temperature Profile in Bedroom
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Dynamics II, Winter 2003, Lecture #
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Room Fire Test - Apparatus
• ISO 9705 “Fire tests: Full scale room fire tests for
surface products”
• Contribution of room linings to fire growth (flashover)
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Room Fire Test - Procedure
• Line walls and ceiling with product
• Burner in back corner
– First 10 min: Q = 100 kW (large wastepaper basket)
– Last 10 min: Q = 300 kW (small upholstered chair)
• Observe time to flashover
• Room experiences flashover when Q 1,000 kW
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Room Fire Test - Results
Wall Lining
Gypsum board
Douglas fir plywood
Douglas fir plywood
Polyurethane foam
Ceiling Lining
Gypsum board
Gypsum board
Douglas fir plywood
Polyurethane foam
Time to Flashover
(min:sec)
~ 7:30
~ 3:00
~ 0:13
Results for CAN/ULC-S102
Gypsum board
Douglas fir plywood
Polyurethane foam
FSR ~ 15
FSR ~ 135
FSR ~ 500
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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CAN/ULC- S102: Red Oak and Plywood
• At (red oak) = 43.0 m min FSR (red oak) = 100
• At (plywood) = 47.2 m min FSR (plywood) = 135
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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CAN/ULC-S102: Gypsum Board
• At (gypsum board) = A1 + A2 = 8.0 m min
FSR (gypsum board) = 15
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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CAN/ULC- S102: Polyurethane Foam Insulation
• FSR (PU foam insulation) = 427 (d/t) or 74 (At)
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Room Fire Test - Video
• Test follows ISO 9705
• Walls & ceiling: wooden panelling
• Time to flashover 3:00 min
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
28
Simulation of Rhode Island Fire
• NFSA = National Fire Sprinkler Association
• Simulate the stage area
– dimensions and layout approximately replicated
• Foamed plastic acoustic insulation glued to plywood
on wall and ceiling
– propylene oxide polyol (not PU foam insulation?)
– thickness = 75 mm (3”)
– density = 16 - 20 kg m-3 (1-1.25 lb ft-3)
• Ignition simulated ignition from pyrotechnics
• Would sprinklers have helped?
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Simulation of Rhode Island Fire - Video
• Demonstrates rapid ignition and flame spread over
exposed foamed plastic insulation
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Kemano: Fire in Basement Recreation Room
• Room dimensions: 3.25 m x 3.44 m x 2.2 m (height)
• Walls: 2 gypsum board // 2 (6 mm) wood panelling
• Ceiling: gypsum board
• Floor: carpet over concrete
• Furnishings: couch / coffee table / TV on wood desk
• Ventilation: no window / hollow-core wood door closed
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Temperatures in Basement Fire
• Temperature predictions from Lecture 3 for leaky
enclosures (based on oxygen depletion):
• For a heat loss fraction 1= 0.9,
Tg,lim = 120 K
• For a heat loss fraction 1= 0.6,
Tg,lim = 480 K
• 1 = 0.6 appropriate for spaces with smooth ceilings &
large ceiling area to height ratios
• 1 = 0.9 appropriate for spaces with irregular ceiling
shapes, small ceiling area to height ratios & where
fires are located against walls
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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900
800
Temperature (°C)
700
600
500
400
300
200
100
0
0
5
10
15
20
25
30
40
35
Time (minutes)
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Suppression
At what rate (litre/min) must water be applied to
absorb the heat being released by a fire?
• Assume water starts as liquid droplets at 20°C.
• Account for the energy required to heat the droplets to
100°C and then vaporize them to steam at 100°C.
• Assume density of water is 1000 kg/m3, specific heat
in the range 20-100°C is 4.182 x 103 J/(kg °C) and
heat of vaporization is 2.26 x 106 J/kg.
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Suppression
• Heat absorbed as 1 kg of water heated from 20C
100C steam is
H = 4.182 x 103 J / (kg C) x 80C + 2.26 x 106 J/kg
H = 2.595 x 103 kJ kg-1
• Density of water is 1,000 kg m-3 = 1 kg / litre
H = 2.595 x 103 kJ litre-1
• Define rate of heat release of fire = Q (kW)
• Define efficiency of application of water to fire as < 1
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Suppression
• Divide heat release rate by times heat absorbed per
kg of water that is vaporized to arrive at rate water
must be applied in units of kg s-1
Q
• Required rate of application of water
H
(litre s-1)
• Assume = 1/2 and remember 60 s = 1 min
120
Q
• Required rate of application
(litre min-1)
H
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Suppression
• For 1,000 kW fire, rate water must be applied is
120 x 1,000 / 2.595 x 103 = 46 litre min-1
• For 6,200 kW fire, rate water must be applied is
120 x 6,200 / 2.595 x 103 = 285 litre min-1
1 US gal = 3.785 litres
or
1 litre = 0.264 US gal
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Factors Contributing to Fire Growth
(Pre-flashover Fires)
• Flammability of room contents: Rate of heat release
• Distribution of combustibles (room contents)
• Flammability of room linings: propensity for flame
spread / rate of heat release
• Thermal properties of room linings
• Supply of air: size and status of potential openings
• Size and shape of room
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
38
Factors Contributing to Fire Severity
(Post-flashover Fires)
• Flammability: contents & linings: Rate of heat release
• Quantity of combustibles
• Thermal properties of room linings
• Supply of air: size of unprotected openings
• Size and shape of room
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
39
Pre-flashover Fires
Threats: * life safety in room (& elsewhere) threatened
by toxicity, heat & reduced visibility
* property in room (& elsewhere) threatened
by smoke deposition (corrosivity) & heat
* localised structural damage
Design Strategies:
* inhibit early fire growth
* delay or prevent flashover
* foster evacuation from room / building
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
40
Pre-flashover Fires
Design Options:
* limit flammability of contents & linings
* limit supply of fresh air
* provide early automatic suppression
* provide early detection & alarm
* limit travel distances & provide adequate
exits from room / building
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
41
Post-flashover Fires
Threats: * life safety in rest of building threatened by
toxicity, heat & reduced visibility
* property in rest of building threatened by
smoke deposition (corrosivity) & heat
* fire spread to other rooms or buildings
* structural damage
Design Strategies:
* delay or prevent fire spread
* delay or prevent structural damage
* foster evacuation from building
* control movement of smoke
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
42
Post-flashover Fires
Design Options:
* provide compartmentation
* ensure adequate spatial separations
* ensure structural sufficiency
* limit quantity of combustibles
* provide automatic suppression
* provide adequate means of egress
* provide adequate smoke control
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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Relative roles of contents and linings
in fire dynamics as reflected in
fire loss statistics
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
44
Fire Loss Statistics (1)
1982-1996
Annual Fire Loss Record for American Single-Family Dwellings
Item First Ignited
Fires
Rubbish or Trash
Cooking Material
Structural Member
Electrical Wiring
Mattress or Bedding
Unclassified Material
Interior Wall Covering
Fuel
Exterior Siding
Upholstered Furniture
49,620
42,380
29,960
27,140
20,080
18,830
16,050
15,630
12,190
10,440
Deaths
72
89
226
120
390
72
199
142
17
534
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
Injuries
307
2,011
532
482
1,501
377
480
849
102
965
Damage
$86,331,500
$126,400,300
$433,684,600
$168,927,700
$167,299,300
$102,704,100
$215,122,600
$102,704,100
$103,120,100
$133,440,000
45
Upholstered Furniture: Fire Loss Statistics
1982-1996 (1)
Another Look at the Annual Fire Loss Record for American Single-Family Dwellings
Item First Ignited
Deaths per 100 Fires Injuries per 100 Fires Damage per Fire
Rubbish or Trash
Cooking Material
Structural Member
Electrical Wiring
Mattress or Bedding
Unclassified Material
Interior Wall Covering
Fuel
Exterior Siding
Upholstered Furniture
0.15
0.21
0.75
0.44
1.94
0.38
1.24
0.91
0.14
5.11
0.62
4.75
1.78
1.78
7.48
2.00
2.99
5.43
0.84
9.24
$1,740
$2,983
$14,475
$6,224
$8,332
$5,454
$13,403
$6,571
$8,459
$12,782
Total (all items)
0.81
3.30
$7,518
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
46
Fire Loss Statistics
Upholstered Furniture
1982-1996 (1)
Number of Civilian Deaths per 100 Fires (USA)
Building Type All Fires Upholstered Furniture Mattress or Bedding
Single-Family
Two-Family
1-4 Storey Apt
5+ Storey Apt
0.81
1.16
0.94
0.72
5.11
5.32
4.15
5.60
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
1.94
1.74
2.16
2.27
47
Fire Loss Statistics
Upholstered Furniture
1982-1996 (1)
Number of Civilian Injuries per 100 Fires (USA)
Building Type
All Fires
Single-Family
Two-Family
1-4 Storey Apt
5+ Storey Apt
3.30
5.60
6.53
7.20
Upholstered Furniture Mattress or Bedding
9.24
12.81
15.73
24.40
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
7.48
9.18
12.21
12.50
48
References
1. K.D. Rohr, “Custom Analysis: Examining Fires in Selected
Residential Properties”, National Fire Protection Association, Quincy,
MA, August 1998.
Carleton University, 82.583, Fire
Dynamics II, Winter 2003, Lecture #
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