從火災科學看消防工程Smoke control planning Building smoke control Area Uses-high fire load, occupant assembly, no opening, fire source, command center Vertical-stairwell,

從火災科學看消防工程

中央警察大學消防系主任

沈子勝教授

課程目標

了解火災在建築物中發展情形。

消防安全工程之內容。

介紹消防安全工程一些技術。

消防工程之目標

人命安全

財物保護

營運不中斷

文化資產的保護

對環境的保護

火災科學(compartment fire)

觀念:

1.區劃空間:

2. 火災:

Plan

Flame - Heat Smoke - Gas

觀念:

4.火災成長:

• Ignition (IG)

• Established Burning (EB)

• Full Room Involvement (FRI)

• Growing Fire

• Fully Developed Fire

• Fire Prevention

Rate

of

Hea

t R

elea

se (

Q)

or

Tem

per

atu

re (

T)

IG

Time

EB

Growing

Fire

Fully

Developed

Fire

FRI

區劃空間火災各個階段(Compartment Fire) 起燃(Ignition)

火羽流(Fire Plume)

天花板下方熱氣流(Ceiling Jet)

兩區域上方煙層(Smoke Layer)

閃燃(Flashover)

全盛期燃燒(Fully Developed)

衰退(Decay)

熱釋放率的重要性

區劃空間火災的動力

性能式消防安全工程設計的基礎

區劃空間內容物品

可動式內容物品

upholstered furniture, boxes, book shelves, rack-storage, electronic equipment, Christmas trees, flammable/combustible pools, etc.

固定式內容物品

wall coverings, wall to wall carpet, paneling, wooden doors, wooden trim/molding, etc.

熱釋放率的量測

3MJ/kgair or 13.1MJ/kgO2的重要性

由消耗的空氣量推測熱釋放率


Source: SFPE Handbook of Fire Protection Engineering, Fig. 3-1.1



Red Chair HRR

0

500

1000

1500

2000

2500

0 50 100 150 200 250 300 350

Time (sec)

HR

R (

kW

)

Green Chair HRR

0

500

1000

1500

2000

2500

0 50 100 150 200 250 300 350 400 450 500

Time (sec)

HR

R (

kW

)

Large Leaf Plant HRR

0

100

200

300

400

500

600

700

0 20 40 60 80 100 120 140 160 180 200 220

Time (sec)

HR

R (

kW

)

Small Leaf Plant HRR

0

200

400

600

800

1000

1200

0 20 40 60 80 100 120 140 160 180 200 220

Time (sec)

HR

R (

kW

)

Cribs and Pallet Stacks


Geometry of cribs and pallets

Pallet Stack HRR


Upholstered Furniture HRR


Upholstered Furniture HRR


Wardrode

Source: SFPE Handbook of Fire Protection Engineering , Fig. 3-1.12

Wardrobe HRR


簡化的熱釋放率曲線 HRR

Time

Square-Wave

bt

maxQ

Pool fires, crib fires, wastebaskets, in-depth burning, etc.

簡化的熱釋放率曲線

maxQ

maxQ

Time Time

HRR HRR

bt bt

Furniture, Christmas Trees, Wall Linings, etc.

Triangle


Time

HRR

vt

2t


2

vttQ kWQst ,

22

1055

skW

tg

gt Time to 1055 kW


NFPA 72 (1996), Appendix B

Fast

Medium

Slow

stg 149

sts g 399150

stg 400


2

2

2

skW 00659.0 slow

skW 0.006630.0469 medium

skW 0475.0 fast



簡化的熱釋放率曲線 When you construct a heat release rate curve, make

sure that the area under the curve equals the available

energy (combustible mass )

mHcEnergy

bo

ig

t

t

dttQEnergy

bo

ig

t

t

c dttQmH

Smoke toxicity

Temperature of smoke layer

Smoke layer height

Fire Protection Engineering

Fire Protection Engineering

Fire Dynamics (Compartment fire)

Detection system

Suppression system

Smoke control

Human behavior(Evacuation)

Agent application (Fire fighting)

Barriers

Structure

Detection and fire dynamics

FPE 553 Class 9 Lecture Overheads OvrHd 9-9

FLAME

FUEL

Ceiling Jet Correlations

for Unconfined Ceilings

H CEIL

Bouyant

Plume

z

Air Entrainment

Ceiling Jet

To u =

0 Q(t)

for T = T ( Q, r, z, H )

and u = u ( Q, r, z, H )

ceil

ceil

g g .

.

.

r

Lump response actuation model

Response Time

of Spot Type Smoke Detectors

Co= mass concentration

of smoke outside detector

Let C = mass concentration inside detector,

d C i

i

d t =

(C - C ) o i

where (L/v) = time “constant”

L = characteristic length of detector

v = velocity of smoke flowing by detector


Suppression system and fire

dynamics


RADIATION FL

A

ME

Radiation


Sprinkler Actuation Models

Objective- Calculate sprinkler actuation time and corresponding heat release rate;

model input should include sprinkler properties, fire heat release rate

history, and sprinkler location on ceiling

HEAT BALANCE

Rate of Thermal Energy Increase of Sprinkler Link=

Rate of Convective Heating by Ceiling Jet + Rate of Radiant Heating by

Flame/Plume/Jet

- Rate of Conduction to sprinkler frame and piping

FPE 553 Class 9 Lecture Overheads OvrHd 9-4-1

Sprinkler Actuation Model

Neglecting Radiative Heating and Conduction Cooling

q = h (T - T ) g L conv •

= (T - T ) g L mc hA dT

dt L

= (T - T )/ g L

= mc hA

FPE 553 Class 9 Lecture Overheads OvrHd 9-4-2

Sprinkler Actuation Model (Continued)

Convective Heat Transfer Correlation for Forced Convection Over Cylinders and Spheres

2/1

2/12/12/1

][u

RTIu

AkB

vmCL

]Re[ 2/1BL

kNu

L

kh

2/12/1

2/1

vL

kBu

h 47.0Re

40 < Re < 4,000


}e){1T - (T T T t/

ogO L

Solution for Constant and Constant T g

t t r

T L T LA

T g

o T

To solve for t when T = T r L LA

)(

)(1/

Og

OLt

TT

TTe

])(

)(1ln[

Og

OLAr

TT

TTt

])(

)(1ln[

2/1

Og

OLA

r

TT

TT

t

u

RTI


Plunge Test Tunnel

hinged cover

test sprinkler Heated Air

u = 2.6 m/s

Re-circulation Wind Tunnel (convective heat transfer only limit T .) g

T >> T air LA

)](1ln[

u t- RTI

1/2

r

Og

OL

TT

TT

measure .T , T , T know gOL

*RTI accounts for heat of fusion

as well as heat capacity.

* However, H << mc fusion )T(T OLA



Measured RTI Values

Type of Sprinkler (ft-sec) (m-sec)

Fast Response (ESFR,

Residential, etc.)

Conventional Response

Fast response devices can be either thin

links or bulbs.

40-50 22-28

130-600 72-360


FLAME

FUEL


for Unconfined Ceilings

H CEIL

Bouyant

Plume

z

Air Entrainment

Ceiling Jet

Q(t)

for T = T ( Q, r, z, H )

and u = u ( Q, r, z, H )

ceil

ceil

g g .

.

.

r



Author Year Actuation Code Sprinkler

1972 Alpert

Heskestad & Delichetsios 1978

Motevalli & Marks 1990

Cooper 1990

Kung et al 1984

DETACT

LAVENT

TDISX SPRINK 1.0


Conduction Cooling of Sprinkler Link

WATERWAY

Sprinkler Frame

Link

Assume: 1. Conduction Cooling FL TT

2. Frame remains at initial temperature

because: a) it is more massive than link, b) cooled by

water in pipe.

OF TT

)T-(Tc-)T-(TA h td

T d mc OLLg

L

conductive cooling term c is constant Let

)()()(

mc

hA

dt

T d000

L TThA

cmcTTTT LLg

OLL TTT OGG TTT


Sprinkler Convective Heating with

Conduction Heat Loss to Sprinkler Frame and

Water

inertia parameter = (mc/hA)u1/2 = const for sprinkler

If Tg & u are constant ( = const)

]T)uC/ (1 -T[RTI

u

dt

TdL g

L

)}]C/u 1(RTI

tu{ exp1[

)C/u (1

T T 1/2

1/2

1/2

g

L

ceiling jet temperature

rise conduction

parameter convective heating and link

thermal

Q

)uC(1

TTlim

2/1

gL

t



FMRC 0N0J5.RU/0N1J6.RU


T g

t

T L C = 0

C = 1

T

T LA1

LA2


C Factor Measurements for 27 sprinkler heads (from

FMRC Report by Bill + Heskestad)

Cmin = 0.52 (m/s)1/2

Cmax = 1.60 (m/s)1/2

typical C approximately equal to:

1.0 (m/s)1/2 for conventional response link

0.60 (m/s)1/2 for fast-response link


Let TLA = link actuation temperature rise above To

tr = response time at which TL = TLA

From solution for constant Tg + u

Comparing to solution for C=0, would get some result with a virtual RTI,

RTIV, given by

RTIV = RTI/(1+C/u1/2)

and TLA,virtual = TLA (1 + C/u1/2)

}T

)C/u(1T - 1{ln

)C/u1(u

RTI- t

g

1/2LA

1/21/2r


Fire Size at Sprinkler Actuation

QðtÞ ¼ Qacte

0:023Δt

Impact

Equation by Madrzykowski and Vittori

Q

where Q(t) :Heat release rate at time t (kW)

Qact : Heat release rate at activation time (kW)

Δt :Time after sprinkler activation (s)

t : Time (s)

Smoke control

Smoke production-air entrainment

Smoke contents

Narcotic gas, irritant gas

Soot

Volume

Density

temperature

Smoke toxicity

Temperature of smoke layer

Smoke layer height

Smoke control planning

Building smoke control

Area

Uses-high fire load, occupant assembly, no opening, fire source, command center

Vertical-stairwell, elevator, escalator,

Vertical penetration (pipe or shaft)

Smoke control in

Particular structures High-rise building

Atrium

Tunnel

Subway system

Hospital

Historical building

Nuclear facility

Semi-conductor fab

Fire dynamics and life safety

Life safety criteria

Temperature

Radiation (heat flux)

Visibility

Combustion products concentrations (CO, CO2, HCN,…)

Oxygen depletion

Smoke layer height

Evacuation

B route: 避難安全驗證法

Structure evaluation


Calculation temperature of post-flashover fire temperature:

Method of Magnusson and Thelandersson • Considering fuel load density, opening factors

and building types

• Construct the temperature curve

Other methods: • Babrauskas and williamson

• EUROCODE


Thermal exposure of structure components

Structure performance under load-bearing and heat impact (temperature rise):

Deformation

collapse

Structural elements

Non-load-bearing surfaces--- ceiling, partitions

Deck--- roof, floor

Horizontal supports--- beams, girders

Vertical supports--- columns, load-bearing walls

Evaluation of fire performance

Fire resistance testing methods: International standard- ISO 834

North America- ASTM E119 • 3 criteria: structural stability, integrity,

temperature rise on the unexposed face.

Calculation methods Use numerical method or simplified formulas

Determine the temp. of deformation and its strength during exposure to fire

Documents

從火災科學看消防工程Smoke control planning Building smoke control Area Uses-high fire load, occupant assembly, no opening, fire source, command center Vertical-stairwell,