St. Lawrence Burns: ventilation rate measurements

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St. Lawrence Burns: ventilation rate measurements

NATIONAL RESEARCII COUNCIL

CANADA

DIVISION OF BUILDING

RESEARCH

ST. LIlWRENCE

BURNS

VENTILATION

RATE MEASUREl\IEIlTS

by

J. H. McGuire

Report No.

154

of

the

Division of Building Research

OTTAWA

PREFACE

The circumstances t h ~ h l e d t o t h e c a r r y i n g out of f i r e t e s t s on e i g h t buildings

i n

t h e p r o j e c t known a s t h e

S t . Lawrence B u r n s , and t h e o b j e c t i v e s and t h e ways

i n

which t h e s e were achieved a r e f u l l y described i n a general r e p o r t ,

It c o n s t i t u t e s t h e complete record of t h e planning and execution of t h e experiments, t o g e t h e r with a l l general information, The d e t a i l s on each kind of measurement made, i n c l u d i n g t h e r e s u l t s obtained, a r e contained i n s e p a r a t e companion r e p o r t s of which t h i s i s one. A l l t h e r e s u l t s a r e combined and a r e discussed and f i n a l concl-usions drawn i n a summary r e p o r t .

Duplication has been avoided a s f a r a s p o s s i b l e , and

it

w i l l be necessary t o r e f e r t o t h e general r e p o r t i n reading any of t h e o t h e r r e p o r t s including t h i s one f o r any information which i s p e r t i n e n t t o more than one of them. A l i s t i n g of a l l r e p o r t s on t h e p r o j e c t follows t h i s preface,

The p a r t i c i p a t i o n of t h e B r i t i s h J o i n t P i r e Research Organization i n t h e experiment, t h e i n t e r e s t and support of t h e Federal C i v i l Defence a u t h o r i t i e s , t h e a s s i s t a n c e of t h e Ontario F i r e Marshal and h i s s t a f f , and f i n a l l y t h e complete co-operation and very considerable a s s i s t a n c e extended by t h e Hydro-Electric Power Commission of Ontario a r e a l l g r a t e f u l l y achowledged. It i s a pleasure a l s o t o be able t o record t h e s p e c i a l c o n t r i b u t i o n made by members of t h e s t a f f of t h e P i r e Section who worked long hours, o f t e n under t r y i n g f i e l d condi- t i o n s and a t g r e a t personal inconvenience, t o meet t h e many deadlines and t o complete t h e p r o j e c t i n a most s a t i s f a c t o r y manner.

The au.-t-hor of t h i s r e p o r t i s M r . J. H. McGuire, now r e s e a r c h o f f i c e r with t h e F i r e Sec-tion of t h i s Division, who a s a member of t h e s t a f f of t h e B r i t i s l l J o i ~ l % F i r e Research Organization planned and supervised t h e meas~zrements made

w i t h t h e radiometers, anernorneters and r e s i s t a n c e theraometers.

Ottawa

NO.

-

REPORTS ON

--

THE

ST. LA'V'JREIJCE BURNS

_---

SUB-TITLES

General Report

Smoke and Sound Measurements Temperature Measurements Radiometer Measurements

V e n t i l a t i o n Rate Measurements Resistance Thermometer

RAeasurements

Radiant Temperature o f Openings Gas A n a l y s i s Summary Report G. W. S h o r t e r G . Williams-Leir G. l?Jilliams-Leir J . H. McGuire J.

H.

McGuire J , H. FBcGuire D. G. Stephenson J . R . J u t r a s G .

W.

S h o r t e r and J . H. McGuire

ST

.

L4l03RETJCE BURNS

VENT1 LATION RrlTTt: YIZASUREDIIENTS by

J. H. LlcGuire

V e n t i l a t i o n i s a n important f a c t o r i n f l u e n c i n g t h e r a t e of burning i n b u i l d i n g f i r e s . A s very l i t t l e information has been a v a i l a b l e on t h i s s u b j e c t ,

it

was decided t o t a k e measurements d u r i n g t h e course of t h e S-t. Lawrence experimental b u i l d i n g f i r e s c a r r i e d out

a t

A u l t s v i l l e , Ontario, by t h e F i r e S e c t i o n of t h e Division of Building Research, National Research Council. I n l e t a i r speed

w a s

measured and t h e scope of t h i s note i s

confined t o a t h e o r e t i c a l i n v e s t i g a t i o n of t h e a i r speeds t o be expected, instrumenta-tion, and a stat-ement of r e s u l t s . THEORETICAL

By adopting c e r t a i n s i m p l i f y i n g a s s ~ u n p t i o n s , e s t i m a t e s of t h e speed of a i r e n t e r i n g a burning b u i l d i n g can be obtained. If f r i c t i o n a l r e s i s t a n c e i s neglected and t h e r a t i o of t h e i n l e t a r e a t o t h e h o r i z o n t a l c r o s s -

s e c t i o n a l a r e a of t h e b u i l d i n g i s s m a l l , so t h a t t h e gases w i t h i n t h e b u i l d i n g can be considered s t a g n a n t , t h e speed

of t h e i n l e t a i r can be shown ( s e e Appendix A ) t o be:

where

To

= ambient temperature ( a b s . )

T; = a b s o l u t e tempera-ture of gases w i t h i n b u i l d i n g

I

8 _{= temperature r i s e , above ambient, of}

gases w i t h i n b u i l d i n g

R = h e i g h t between i n l e t and o u t l e t

Al = i n l e t a r e a

A2 = o u t l e t a r e a

The above e x p r e s s i o n was u s e d t o a s s e s s t h e r a n g e s of wind c p c e d f o r v!llicil a s u i t a b l - e i n s tnrnent; s h o u l d be desi{;ned. 11 vnl~rc-2 o f 1000°C was assumed f o r

o ' ,

Table I

lis-ts

v a r i o u s p o s s i b l e c o n d i t i o n s . During

t h e e a r l y s t a z e s o f a f i r e t h e i n l e t a i r s p e e d s would be s u b s t a n t i a l l y l e s s -than ti~o:;e -ivr?n by equa-tion (1) and T a b l e I , and it v v a s d e c i d e d t h z t t h e rninin~un

air

s p e e d

which a s u i t a b l e instnj-rncnt s h o u l d be c a p a b l e o f r e , e ; i s - t e r i n g was

1 . 5

mph.

Tne e s t i n a t e s of maximlam a i r s p e e d g i v e n by T a b l e

I c a n be e x p e c t e d t o be h i g h , p r i n c i p a l l y b e c a u s e they

r e l a t e t o the c o n d i t i o n s ob-Laini-ng a f t e r t h e r o o f h;-~il c o l l a p s e d , vihen i n f a c t l o w r mean g a s t e m p e r a t u r e s [night have been e x p e c t e d . For t h i s r e a s o n and b e c a u s e i n t e r e s i s

was f o c u s e d p r i m a r i l y on t h e i n i t i a l s t a t y e s o f t-he f i r e s p r i o r t o t h e c o l l a p s e of t h e r o o f , it was n o t c o n s i d e r e d e s s e n t i a l t h a t t i l e anemometer s h o u l d r e s p o n d t o a i r s p e e d s h i g h e r t h a n 1 5 mph,

-

ESTIPiIATES OF 1NL:ET A I R SPEED

S e p a r a t i o n

I

C o n d i t i o n r e p r e s e n t e d

I

i n l e t - o u t l e t I House, r o o f i n t a c t

I

1 0 House, r o o f open Comnunity H a l l , r o o f i n t a c t I n l e t A i r Speed mph

To measure induced v e n t i l a t r i o l i r a t e s umcler t h e c o n d i t i o n s which prevail-ed d u r i n g t h e S t . LavJrence e x p e r i - ments it was n e c e s s a r y f o r a n anemometer t o o p e r a t e o v e r a wide range of t e m p e r a t u r e s ; a t t h e s t a r t of a t e s t t h e anemometer t e m p e r a t u r e might have been -20°P, w h i l e a t a l a t e r s t a g e it migh-t have r i s e n s e v e r a l h-uncired d e g r e e s c e n t i g r a d e .

To meet t h i s requirement and t o

ensure

s i m p l i c i t y and p o r t a b i l i t y , a d e f l e c t i o n t y p e was chosen, tile f i n a l d e s i g n b e i n g i l l u s t r a t e d i n F i g .

9.

The c a l i b r a - t i o n of t h e i n s t r u m e n t can be a l t e r e d by clnanging %be d i s - t a n c e b e - t l ~ e e n

m

t h e vane and t h e p i v o t . .ihe movement i.s c j a ~ p e d e l e c t r o m a g n e t i c - a l l y a s a r e s u l t of eddy c u r r e n t s induced i n t h e copper p l a t e when it moves i n t h e f i e l d c r e a t e d by t h e permanent magnets.

It was n o t p r a c t i c a l t o atternpt t o r e a d t h e s c a l e of each i n s t ~ m n e n t d i r e c t l y because of t h e i n t e n s e h e a t and t h e d a n g e r o f p e r s o n a l i n j u r y from f a l l i n g d e b r i s . Telescopes which allowed r e a d i n e s

tcr

_{be t a k e n a t a range of 50 f t were} t h e r e f o r e used.

9 i o i d e n t i c a l anemometers were c o n s t r u c t e d and t h e c a l i b r a t i o n of one of them i s g i v e n i n Pig. 10. SITING AND RECOVERY OF AN.Ff'IOli4ETERS

Anemometers were p l a c e d on t h e s i l l s of t h e ground f l o o r windoiris, wllich were of t h e s a s h t y p e and were opened a t t h e bottom t o l e a v e a b o u t a t h i r d of t h e window a r e a uncovered. The p r e c i s e l o c a t i o n s i n t h e v a r i o u s t e s t s a r e i l l u s t r a t e d i n Figs. 1,

6

and 8. I n o r d e r t o r e c o v e r t h e a n e m m e t e r s when it became a p p a r e n t t h a t t h e y were l i k e l y t o be damaged by f a l l i n g d e b r i s o r by o v e r h e a t i n g , each w a s a t t a c h e d t o a c o n t i n u o u s w i r e p a s s i n g t h r o u g h a n e y e - b o l t f i x e d t o t h e w a l l above t h e window. It was t h u s p o s s i b l e t o withdraw a n i n s t r u m e n t s a f e l y f r o m a d i s t a n c e of a b o u t 50 f t .

RESULTS

The r e s u l t s a r e shown i n P i g s . 11 t o

1 4 .

During t h e f i r e i n house No. 1 t h e o u t d o o r wind speed ranged from z e r o t o 6 mph, and s i n c e t h e a i r speeds g i v e n i n Fig. 11 a r e small compared w i t h this v a l u e it cannot be s a i d whether t h e y r e p r e s e n t v a r i a t i o n s i n t h e o u t d o o r wind c o n d i t i o n s o r induced v e n t i l a t i o n a i r speeds. I n t h e l i s h t o f t h i s

e x p e r i e n c e no f u r t i l e r mea surernent s were a t t e m p t e d d u r i n g subsequent house b u r n i n s experiments.

In

t h e c a s e of -Lho commvnity ha1.3

,

t h e anemor,,eter on t h e leeljvarci s i d e nl!xa?;s gave nefi9t-j.ve readirl2:j nrlcl ii;

appeared t h a t no

air

~ : . n t e r e d t h e b u i l d i n g fl.olit t h a t s i d e .

On t h e vrindnrarcl s i d e t h e i n l e t a i r speed i n c r e a s e d from a b o u t 4.5 rnph a t t h e s t a r t of t h e t e s t t o 6 mph,

at

which tirne it was t h o u g h t pr.udent, t o withdraw t h e an.er:?orrlei;er. The outdoor win(] speed at- t h e t i ~ ~ - : e

was

6 t o 8 mp1.i.

&wing t h e s c h o o l burn t h e outdoor wind speed was l e s s t h a n 1 rnph, which war; rr~uch l e s s t-k~an t-ha-t which

occurred d u r i n g any o f t h e p r e v i o u s e x y e r i n e n t s . A t t h e

window

i n

t h e main body of t h e b u i l d i n g a n a i r speed of

7.4

rnph was recorded.

The fact; - t h a t t h e i n l e - t a i r speed a t th.e wirldow i n t h e s u b s i d i a r y r e a r hal.1 eqnal-led, i f nol; exceeded, t h i s v a l u e a t a t i m e when t h e f i r e was confined t o .the main hal.1 was unexpected. The connection betv~ecrl th e tvro c.ompar tments was b:r a s i n g l e open cloor aboul; 6 ft- G in. h i & by

3

f t $vide.

A p o s s i b l e e x p l a n a t i o n can be offerecl: s i n c e t h e c o n n e c t i o n between t h e r e a r h . a l l and t h e main b u i l . d i n g was a n open

doorway, t h e p o s i t i o n of t h e r e a r h a l l window had no s i g - n i f i c a n t e f f e c t on t h e induced

air

speed. The a i r cou.ld be regarded a s e n t e r i n g $he main b u r n i n g compartment.

However, t h e a c t u a l i n l e t a r e a

wa:;

l e s s , and ec1ua.tir.ir.l (1) su-ggests t h a t t h i s ~011.15 t e n d t o i n c r e a s e -the valixe of cvr.

Yrior t o th.e s c h o o l burn it h a d been f o ~ m i l n e c e s s a r y

t o withdraw t h e anemometers some t i m e b e f o r e t h e r o o f s collapsecl and i t was assumed t h a t t h i s would be t h e c a s e d u r i n g t h e b u n l i n e of t h e scEiool. The ~ a n g e adjustment was

t h e r e f o r e s e t t o g i v e t h e b e s t accura.cy a t 1-ow a i r specd.s.

This proved t o be a wise p o l i c y s o f a r a s t h e anemometer i n t h e rnain b i l i l d i n g was concerned 'owl; n o t f o r t h e one associ.at;ed w i t h tile aru1e:c. 21:orn t h e recortl of t h e o b s e r - v a t i o n s it h a s been fomc'l. that- -the t i m e at- which t h i s l a - t t e r anemometer went o f f s c a l e corresponds v e r y cl.osely t o t h e t i n e a-b which large openings began t o a p p e a r i n t h e r o o f of

m a i ~ b u i l d i n g . A s d i s c u s s e d p r e v i o u s l y t h e open window axea i n t h e annex c o n s t i t u t e d . an i n l e t a r e a t o t h e main b u i l d i n g . I n t h e l i e h t of t h i s f i n d i n g it can be expected t h a t t h e i n l e t a i r speeds would be h i g h a f t e r t h e r o o f i n t h e main b u i l d i n g c o l l a p s e d . A s soon a s t h e annex became f u l l j r

involved i n t h e f i r e ( a f t e r

45

minutes) rn0L-e 1vindo1:~s

fractu.r.ed and th.e v e n t i l a t i o n c o n d i t i o n s were no l o n g e r s o c1osel.y a s s o c i a t e d wikh t h e f i r e i n tile rnain bv.ildirlc. A s

shovm i n Fig.

1 4

t h e i n l e t a i r s;:eed.s t h a n d r o p ~ e d t o v:jlu.es t o be expected i n sing1.e-st-or:: b u i l d i r l g T i r e s . A t about- t h . i s p o i n t t h e anemometer had t 0 be ~ ~ ~ i : i t i ~ . d ~ a ! v n .

m i o r t o t h e burn i t h a d been expec t p . 6 t h a - t %kt? armex ~ ~ o u l d become involved at- a r(r:lc7tivel.y e a r l y s . t r ? i ; ~ n71d t h a t % h e

It i s of i n t e r e s t t o compare t h e r e s u l t s obtained during t h e school burn with values estimated from expres- s i o n (1). A t t h e time when t h e measurements i n t h e main b u i l d i n g had t o be discontj-nued

all

t h e u p s t a i r s and. most of t h e dolvnstairs windows had f a l l e n out. I n equation (1)

wf should t h e r e f o r e assume A 1 = A 2 . Using t h e value

8 _{= 1 0 0 0 ° C} a s previously gives an e s t i m a t e of

7.8

_mph

which corresponds closel-y with t h e maximum value recorded (about

7

mph). For t h e condition where l a r g e openings had appeared i n t h e roof of t h e main b u i l d i n g t h e p r e d i c t e d maximum a i r speed was 16 mph. I n v i e v of t h e anomalous conditiorls causing t h e i n l e t a i r speed a t t h e window i n t h e annex t o be controll.ed temporarily by conditions i n t h e main b u i l d i n g ,

it

i s not t h e r e f o r e s u r p r i s i n g t h a t t h e anemometer i n t h e annex went o f f s c a l e .

SASH REMOVED BEFORE FIRE

GROUND FLOOR

r

NOTES .

I , ALL WALLS 8 CEILINGS OF FIBREBOA RO EXCEPT

- IN BEDROOMS, WALLS 8 CEILINGS OF PLASTER

- IN KITCHEN, WLIINSCOT OF WOOD

2 lNSTRUM£NTA NON I N BASEMENT WEST CORNER LEGEND 4 THERMOCOUPL E S % RESISTANCE THERMOMETER

(3

RAOIOME T E R S

@ THERMOPILE RAOIOME TER

A

SMOKE M E T € - R S

0 7 10

t - 1 1 b 1 3

F E E T

GROUND FLOOR FIRST FLOOR .? 0 r\l NOTES :

I . ALL WALLS B CEILINGS OF FIBREBOARD BEDROOM I 2. INSTRUMENTATION IN BASEMENT WEST CORNER

L

2 6 Z O " ~ ~ ~ ~ LEGEND .' --a THERMOCOUPLES

-& RESISTANCE TNERMOME TER

0

RADIOMETERS @ TNERMOPILE RADIOMETER GAS COLLECTORS SMOKE METERS O U F E E T

\ COVEREO WITH PLASTERBOARD L - - LOWER XI TCHEN -2 14'- 6 " x 8'- 8" T SASH REMOVED DINING ROOM 1 4 ' - 1 0 " ~ 15'- 5 " L I VING ROOM 11'-2'; 1 4 ' - 9 " GROUND FLOOR

-

_i -7 D CLOSED BEDROOM NOTES :

I ALL WALLS B CEILINGS OF P L A S T E R

2 .

INS TRUMEN TA Noh' IN BASEMENT SOUTH CORNER LEGEND.' --o THERMOCOUPLES RESISTANCE THERMOMETER

0

RADIOMETERS

@ THERMOPILE RADIOME TEU GAS COLLECTORS SMOKE METERS

O U

F E E T

FIGURE 4

-

BUILDING NO. 4 - TWO

-

STOREY WOOD FRAME DWELLING WITH CLAPBOARD EXTERIOR AND BRICK INFILLING

DOOQ l EFT OPEN

NOTES :

1 ALL WALLS B CEILINGS OF PRESSED PAPERBOARD 2. INSTRUMEN TATION IN BASEMENT LEGEND : --o THERMOCOUPLES -% RESISTANCE THERMOMETER

0

RADIOMETERS @ THERMOPILE RADIOMETER GAS COLLECTORS SMOKE METERS 10 F E E T FIRST FL OOR

FIGURE 5 - B U I L D I N G NO. 5 - T W O

-

S T O R E Y WOOD F R A M E D W E L L I N G W I T H CLAPBOARD E X T E R I O R

NOTE :

CEILING B WAINSCOT OF WOOD WALLS OF PLASTER

-

THERMOCOUPLES

A RESISTANCE THERMOME TERS ANEMOMETERS

0

RADIOMETERS @ THERMOPILE RADIOMETER GROUND FLOOR 0

-

5 10 FEET

F I G U R E 6

-

BUILDING NO. 6

-

T W O

-

S T O R E Y SOLID B R I C K

GROUND FLOOR

d

F I R S T F L O O R

N O T E S :

I . ALL WALLS d CEILINGS OF PLASTER

2.

INS TRUYEN TA TION /N BASEMENT SOUTH CORNER

LEGEND :

-

rHERMOCOUPLES

& RESISTANCE THERYOME TER

0

RAD/OME TERS @ THERMOPILE RADIOMETER GAS COLLECTORS SMOKE METERS 0 5 L m s * - -. d 10 F E E T

NOTE :

WALLS OF PLASTER CEIL IMG OF WOOD

LEGEND :

5

RESISTANCE THERMOMETERS ANEMOMETERS

0

_RADIOMETERS THERMOPILE RADIOMETER GROUND FLOOR 0

-

5 10 FEET

F I G U R E

8

-

B,UILDING

NO.

8

-

T W O

-

S T O R E Y S O L I D B R I C K

0 ii'

THE SPEED OF A I R ENTERING R BURITIIJG BUILDING

--- a---

-~ 3 o m

a corsiderat-ion of conservation of mass flow

at the inlet and outlet,

where

z,

A,

p

and v are over-all fuel/air ratio,

area, density, and air speed respectively.

The significance of the sub- and super-scripts is inaicated

in

Fig.

15.

Neglecting frictional resistance and assuming that

the gas speed within the building is low (i.e. that the

inlet and outlet areas are small compared with the horizontal

cross-sectional area of the building), energy considerations

at the inlet, following Bernoulli, give

where

p

represents pressure.

Similar considerations,

at the outlet, assuming

that combustion

is

completed within the enclosure, give

Adding

equations (2) and

( 3 )

Since the gases within and outside the building

may be considered stagnant, the left side of equation

(4)

is given by the difference in weights of the inside and

outside gases. Therefore

The e f f e c t of p r e s s u r e changes on d e n s i t y i s i n t h i s case n e g l i g i b l e , s o t h a t

where

QA

i s t h e temperature r i s e , above ambient, of t h e gases w i t h i n t h e b u i l d i n g a t a h e i g h t h.

F r o m equations ( I ) , ( 6 ) and

( 7 )

I

I f Qh i s c o n s t a n t t h e n

A maxim~m e s t i m a t e of t h e i n l e t a i r speed may be obtained by n e g l e c t i n g t h e c o n t r i b u t i o n of t h e f u e l t o t h e mass flow. For a f u e l / a i r r a t i o of s t o i c h i o m e t r i c p r o p o r t i o n s t h e e r r o r i n n e g l e c t i n g z i s l e s s t h a n 20 p e r c e n t .

I n

t h e e a r l y s t a g e s of t h e f i r e t h e f u e l / a i r r a t i o i s much l e s s and