Pressure drop characteristics of typical stairshafts in high-rise buildings

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Pressure drop characteristics of typical stairshafts in high-rise

buildings

Achakji, G. Y.; Tamura, G. T.

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Pressure Drop Characteristics of Typical

Stairshafts in High-Rise Buildings

by

G.Y. Achakji and G.T. Tamura

A N A L Y Z E D

Reprinted from

ASHRAE Transactions 1988

Volume 94, Pt. 1

p. 1223

-

1237

(IRC Paper No. 1599)

NRCC 30424

Canada

11 n9existe guhe d'information sur les chutes de pression

dans les cages d'escaliers des immeubles ClevCs. C'est

pourquoi on a effectuC des essais en vraie grandeur afin

d'obtenir des donnCes concernant la resistance

fi

1'Ccoulement de l'air qui pennettraient de concevoir

un

s y s t b e de limitation de la propagation de la fmCe dans les

cages d'escaliers grace fi la technique de la mise en pression.

Des donnees ont CtC Ctablies pour les escaliers sans et avec

contremarches, en prCsence et en absence de personnes.

L'Ctude a r6vdlC que la dsistance B 1'6coulement de l'air dans

la cage d'escaliers p u t etre deux fois plus grande lorsque

des personnes s'y trouvent. On a aussi mis au point un

mod$le physique simple servant B matfialiser l'effet de la

prksence de personnes sur la rksistance fi1'6coulement de

a i r Les auteurs dCcrivent dans cet expos6 le modkle

anal ytique, 1'6 tude experimentale et les donnees obtenues

concernant la rdsistance fi 1'Ccoulement de l'air pour les

diverses configurations d'escaliers.

PRESSURE DROP CHARACTERISTICS

OF TYPICAL STAIRSHAFTS

IN HIGH-RISE BUILDINGS

G.Y. Achakji, P.E.

G.T. Tamura, RE.

ASHRAE Fellow

ABSTRACT

L i t t l e i n f o r m a t i o n e x i s t s on t h e p r e s s u r e d r o p c h a r a c t e r i s t i c s of s t a i r s h a f t s i n t a l l b u i l d i n g s . F u l l - s c a l e t e s t s w e r e c o n d u c t e d , t h e r e f o r e , t o d e v e l o p d a t a on t h e a i r f l o w

r e s i s t a n c e r e q u i r e d f o r d e s i g n i n g a smoke c o n t r o l s y s t e m f o r s t a i r s h a f t s by t h e p r e s s u r i z a t i o n t e c h n i q u e . Data were o b t a i n e d f o r open and c l o s e d t r e a d s t a i r s h a f t s , w i t h and w i t h o u t p e o p l e i n s i d e them. The s t u d y r e v e a l e d t h a t t h e f l o w r e s i s t a n c e i n s i d e t h e s t a i r s h a f t w i t h p e o p l e c a n be d o u b l e t h a t w i t h o u t p e o p l e . A l s o , a s i m p l e p h y s i c a l model t o s i m u l a t e t h e e f f e c t of p e o p l e on t h e f l o w r e s i s t a n c e was d e v e l o p e d . T h i s p a p e r d e s c r i b e s t h e a n a l y t i c a l model, t h e e x p e r i m e n t a l s t u d y , and t h e d a t a o b t a i n e d on t h e a i r f l o w r e s i s t a n c e f o r t h e v a r i o u s s t a i r c o n f i g u r a t i o n s . INTRODUCTION Smoke s p r e a d s r a p i d l y from t h e f i r e r e g i o n t o o t h e r a r e a s i n t h e b u i l d i n g t h r o u g h l e a k a g e o p e n i n g s i n t h e f l o o r c o n s t r ~ l c t i o n and v e r t i c a l s h a f t s . The s t a i r w e l l s a r e t h e p r i n c i p l e means of e s c a p e from a b u i l d i n g and s h o u l d be p r o t e c t e d e f f e c t i v e l y t o p e r m i t s a f e e v a c u a t i o n d u r i n g a f i r e . One c o n c e p t o f t e n u s e d f o r p r o t e c t i n g t h e s t a i r w e l l s i s t h e p r e s s u r i z a t i o n t e c h n i q u e which i n v o l v e s i n c r e a s i n g t h e p r e s s u r e i n s i d e t h e s h a f t above t h o s e of i m m e d i a t e l y s u r r o u n d i n g f l o o r s p a c e s by i n j e c t i n g o u t d o o r a i r w i t h a s u p p l y f a n . A knowledge of t h e a i r f l o w r e s i s t a n c e i n s i d e t h e s t a i r w e l l , which h a s a s i g n i f i c a n t i m p a c t on t h e p r e s s u r e d i s t r i b u t i o n , is r e q u i r e d f o r a n a l y s i s of a i r f l o w network and p r e d i c t i o n of smoke movement by computer models.

The d a t a on a i r f l o w r e s i s t a n c e a v a i l a b l e i n t h e l i t e r a t u r e ( C r e s c i 1973; Tamura 1974; Shaw 1976; M a r s h a l l 1985) do n o t c o n s i d e r t h e e f f e c t of v a r i o u s s t a i r c o n f i g u r a t i o n , f l o o r h e i g h t , and more s i g n i f i c a n t l y , t h e e f f e c t of p e o p l e on t h e p r e s s u r e l o s s , which c o u l d s e r i o u s l y a f f e c t t h e p e r f o r m a n c e of a p r e s s u r i z a t i o n system. I n t h i s s t u d y , t h e s e f a c t o r s were i n v e s t i g a t e d and new d a t a on a i r f l o w r e s i s t a n c e have been d e v e l o p e d .

ANALYTICAL MODEL

I n t h e model f o r a i r f l o w and p r e s s u r e i n s i d e a s t a i r w e l l ( F i g u r e l ) , i t i s assumed t h a t a l l l e a k a g e o p e n i n g s i n t h e w a l l s of t h e s h a f t can be r e p r e s e n t e d by an o r i f i c e l o c a t e d i n t h e s h a f t w a l l a t mid-height of e a c h f l o o r . The p r e s s u r e d i f f e r e n c e between t h e i t h and i + l t h f l o o r s i s

G.Y. A c h a k j i , S e n i o r A d v i s o r , C o n t r o l Systems Technology, N a t i o n a l T r a n s p o r t a t i o n Agency of Canada; f o r m e r l y , R e s e a r c h O f f i c e r , I n s t i t u t e f o r Research i n Const n ~ c t i o n , K a t i o n a l R e s e a r c h Counci 1 Canada.

G.T. Tamura, R e s e a r c h O f f i c e r , I n s t i t ~ ~ t e f o r Resenrch i n C o n s t r u c t i o n , i ' a t i o n a l Kesenrch C o u n c i l Canada.

The f i r s t , s e c o n d , and t h i r d t e r m s on t h e r i g h t s i d e of E q u a t i o n 1 r e p r e s e n t p r e s s u r e d i f f e r e n c e s due t o column w e i g h t of a i r , momentum p r e s s u r e l o s s due t o a i r l e a k a g e , and f r i c t i o n a l p r e s s u r e l o s s ( b a s e d on D a r c y ' s e q u a t i o n f o r a i r d u c t s ) , r e s p e c t i v e l y . The mass f l o w r a t e a t t h e l e v e l of t h e i t h f l o o r i s

where t h e l e a k a g e f l o w i s :

I f t h e s h a f t is s e a l e d , w i t h no a i r l e a k a g e t h r o u g h t h e w a l l s , t h e n t h e momentum change t e r m i n E q u a t i o n 1 c a n be n e g l e c t e d . T h e r e f o r e , by m e a s u r i n g t h e p r e s s u r e s i n t h e s e a l e d s h a f t f o r two s u c c e s s i v e f l o o r s and a c c o u n t i n g f o r t h e column w e i g h t of a i r between them, t h e f r i c t i o n p r e s s u r e l o s s , A P f ( i ) , c a n be measured and t h e v a l u e of p r e s s u r e l o s s c o e f f i c i e n t , K , c a n be c a l c u l a t e d :

For t h e purpose of computer modeling of b u i l d i n g a i r f l o w network and smoke c o n c e n t r a t i o n s d u r i n g f i r e , A P f ( % ) c a n be r e p r e s e n t e d by a p r e s s u r e l o s s a c r o s s an o r i f i c e l o c a t e d between f l o o r s of a f r i c t i o n l e s s s h a f t .

F o r d e s i g n p u r p o s e s , t h e f l o w r e s i s t a n c e c a n be r e p r e s e n t e d by a r a t i o of t h e e q u i v a l e n t o r i f i c e a r e a t o s h a f t a r e a , Ao/As. From E q u a t i o n s

4

and 5:

EXPERIMENTAL DETAILS

The tests were c o n d u c t e d t o e s t a b l i s h t h e v a l u e of K f o r v a r i o u s s t a i r c o n f i g u r a t i o n s s o t h a t v a l u e s of A, i n E q u a t i o n 6 c a n be d e t e r m i n e d and a p p l i e d t o computer models f o r

i n v e s t i g a t i n g t h e performance of v a r i o u s p r e s s u r i z a t i o n s y s t e m s . The f u l l - s c a l e e x p e r i m e n t s were d e s i g n e d t o i n v e s t i g a t e m a j o r f a c t o r s i n f l u e n c i n g t h e f l o w r e s i s t a n c e i n c l u d i n g open and c l o s e d t r e a d , f l o o r h e i g h t s of 2.6 m and 3.6 m (8.5 f t and 12.0 f t ) , w i t h and w i t h o u t p e o p l e i n t h e s t a i r s , and w i t h p r e s s u r i z a t i o n by e i t h e r bottom o r t o p i n j e c t i o n . T e s t F a c i l i t y A l l t e s t s were c o n d u c t e d i n t h e s t a i r w e l l of t h e 1 0 - s t o r y e x p e r i m e n t a l f i r e tower a t t h e N a t i o n a l F i r e L a b o r a t o r y of t h e N a t i o n a l R e s e a r c h C o u n c i l of Canada. The s t a i r w e l l ( F i g u r e 2 ) i s a c o n v e n t i o n a l t y p e w i t h o p e n - t r e a d m e t a l s t a i r s t h a t c a n b e m o d i f i e d t o c l o s e d - t r e a d c o n f i g u r a t i o n . The s h a f t h a s a c r o s s - s e c t i o n a l a r e a of 12.5 m 2 ( 1 3 4 f t 2 ) and a t o t a l h e i g h t of 28 m ( 9 2 f t ) ; t h e f i r s t and second f l o o r s a r e 3.6 m (12.0 f t ) h i g h and t h e r e m a i n d e r a r e 2.6 m ( 8 . 5 f t ) h i g h . The s t a i r w a y s l o p e and s t a i r t r e a d s a r e i d e n t i c a l f o r a l l f l o o r s . A

d e t a i l e d d e s c r i p t i o n of t h e t e s t f a c i l i t y , i n c l u d i n g a i r f l o w m o n i t o r i n g s y s t e m s , i n s t r u m e n t a t i o n , c a l i b r a t i o n , and measuring t e c h n i q u e s , i s g i v e n i n A c h a k j i ( 1 9 8 7 ) .

T e s t Method

The e f f e c t of t h e a i r l e a k a g e f l o w on t h e p r e s s u r e g r a d i e n t i n s i d e t h e s h a f t was minimized and made i n s i g n i f i c a n t by s e a l i n g a l l o p e n i n g s and l e a k a g e c r a c k s of t h e s h a f t , i n c l u d i n g a l l s t a i r d o o r s . With bottom i n j e c t i o n , o u t d o o r a i r was s u p p l i e d a t t h e bottom and a l l o w e d t o f l o w up and o u t t h r o u g h t h e open s t a i r d o o r and open o u t s i d e w a l l v e n t s a t t h e t o p f l o o r . With t o p i n j e c t i o n , a i r was s u p p l i e d a t t h e t o p and a l l o w e d t o f l o w down and o u t t h r o u g h t h e open e x i t d o o r a t t h e bottom. V a r i o u s f l o w r a t e s were u s e d f o r each c o n f i g u r a t i o n r a n g i n g from 5 t o 10 m 3 / s ( 1 0 , 6 0 0 t o 21,200 cfm) (0.9 x l o 5

<

Re

<

1.8 x l o 5 ) . The t e s t program i s summarized i n T a b l e s 1 and 2.

The p r e s s u r e d i f f e r e n c e s between f l o o r s i n s i d e t h e s t a i r w e l l were measured u s i n g a t o t a l of 20 p r e s s u r e t a p s (two f o r e a c h f l o o r ) , which were l o c a t e d a s shown i n F i g u r e 2 and c o n n e c t e d t o two p r e s s u r e s w i t c h u n i t s l o c a t e d on t h e ground f l o o r ; e a c h u n i t i s c o n n e c t e d t o a p r e s s u r e t r a n s d u c e r whose o u t p u t s were r e c o r d e d on a c h a r t r e c o r d e r . The a i r f l o w r a t e s were measured u s i n g a c a l i b r a t e d a i r - m o n i t o r i n g system.

S i m u l a t i o n of Occupants and E v a c u a t i o n C o n d i t i o n

An i d e a l a p p r o a c h t o i n v e s t i g a t e t h e a i r f l o w r e s i s t a n c e d u r i n g e v a c u a t i o n i s by t e s t i n g w i t h a l a r g e number of p e o p l e i n s i d e t h e s t a i r s h a f t . I f n o t p o s s i b l e , a s i m p l e p h y s i c a l model based on t h e volume of a human body can b e u s e d . The model u s e d was made of a c y l i n d r i c a l t u b e ( c o m m e r c i a l l y a v a i l a b l e ) , 0.31 m ( 1 . 0 f t ) O.D. and 1.8 m (5.9 f t ) h i g h , t o g i v e , r e s p e c t i v e l y , t h e f r o n t a l a r e a and h e i g h t of an a v e r a g e s i z e d a d u l t .

The e v a c u a t i o n of p e o p l e was s i m u l a t e d by p l a c i n g a g i v e n number o f e i t h e r p e o p l e o r t u b e s o n and between F l o o r s 7 and 8 ( F i g u r e 2 ) . From t h e l i m i t e d d a t a f o r h i g h - d e n s i t y crowd movement down s t a i r s d u r i n g e v a c u a t i o n , t h e v a l u e s of 2.0 and 1.0 p e r s o n / m 2 (0.18 and 0.09 p e r s o n / f t 2 ) were assumed f o r h i g h and medium-density, r e s p e c t i v e l y ( P a u l s and J o n e s 1980). The l o c a t i o n and d i s t r i b u t i o n of p e o p l e a r e shown i n F i g u r e 3.

RESULTS AND DISCUSSIONS

The r e s u l t s a r e summarized i n T a b l e s 1 and 2 f o r f l o o r h e i g h t s of 2.6 m and 3 . 6 m ( 8 . 5 f t and 12.0 f t ) , r e s p e c t i v e l y . The i n t e r n a l f l o w r e s i s t a n c e i s e x p r e s s e d a s p r e s s u r e l o s s

c o e f f i c i e n t ( K ) and t h e r a t i o of e q u i v a l e n t o r i f i c e a r e a t o s t a i r w e l l c r o s s - s e c t i o n a l a r e a (Ao/As) f o r v a r i o u s s t a i r c o n f i g u r a t i o n s and e v a c u a t i o n c o n d i t i o n s . The p r e s s u r e d r o p v a l u e s between two a d j a c e n t f l o o r s a r e a l s o p r e s e n t e d i n T a b l e 1 w i t h t h e i r c o r r e s p o n d i n g a i r f l o w r a t e s .

E f f e c t s of Open and C l o s e d S t a i r T r e a d s

T a b l e 1 shows t h a t t h e t o p and t h e bottom a i r i n j e c t i o n s h a v e s i m i l a r p r e s s u r e d r o p c h a r a c t e r i s t i c s f o r b o t h t h e open and c l o s e d t r e a d s t a i r s . P r e s s u r e d r o p p r o f i l e s i n F i g u r e 4 show a marked change i n s l o p e a t 7.2 m ( 2 4 f t ) s e p a r a t i n g t h e two p r e s s u r e d r o p z o n e s ; t h e f i r s t r e p r e s e n t s t h e p r e s s u r e d r o p s of t h e f i r s t and second f l o o r s and t h e second r e p r e s e n t s t h o s e of t h e r e m a i n i n g f l o o r s . The l a r g e r p r e s s u r e d r o p f o r t h e s e c o n d zone i s m a i n l y due t o t h e l a r g e r l a n d i n g a r e a of t h i s zone, which c a u s e s g r e a t e r o b s t r u c t i o n t o t h e a i r f l o w i n t h e h o r i z o n t a l p l a n e . The r e s u l t s i n d i c a t e t n a t , a t a g i v e n a i r f l o w r a t e , t h e p r e s s u r e l o s s v a r i e s l i n e a r l y w i t h t h e h e i g h t of t h e s t a i r w e l l .

The r e s u l t s ( T a b l e 1 ) i n d i c a t e t h a t t h e o p e n - t r e a d s t a i r s p r e s e n t l e s s r e s i s t a n c e t o f l o w t h a n t h e c l o s e d - t r e a d s t a i r s due t o t h e a d d i t i o n a l f l o w p a s s a g e s provided between t r e a d s f o r t h e f o r m e r . The e f f e c t s of open and c l o s e d t r e a d s become more s i g n i f i c a n t when t h e r e a r e p e o p l e i n t h e s t a i r s . A s shown i n F i g u r e 5, w i t h o u t o c c u p a n t s i n s i d e t h e s t a i r s , t h e

I

I d i f f e r e n c e s i n t h e p r e s s u r e d r o p between open and c l o s e d t r e a d a r e w i t h i n 8%. With o c c u p a n t s

i

i n s i d e t h e s h a f t ( a t h i g h d e n s i t y ) , t h e r e s i s t a n c e of t h e c l o s e d t r e a d was i n c r e a s e d

s i g n i f i c a n t l y o v e r t h a t of open t r e a d , by 62%. These e f f e c t s a r e f u r t h e r d i s c u s s e d i n t h e

E f f e c t s of Occupants i n S t a i r s

T h i s e f f e c t was i n v e s t i g a t e d u s i n g a p h y s i c a l model t o s i m u l a t e p e o p l e . The t e s t s w i t h p e o p l e were a l s o performed b u t o n l y f o r t h e c l o s e d t r e a d s t a i r c o n f i g u r a t i o n .

Model E f f e c t . The p r e s s u r e d r o p d i s t r i b u t i o n s i n s i d e t h e s h a f t w i t h and w i t h o u t

s i m u l a t e d o c c u p a n t s ( F l o o r s 7 and 8 ) a r e shown i n F i g u r e 6 f o r t h e c l o s e d - t r e a d s t a i r s .

-

A t an a i r f l o w r a t e o i 10 m 3 / s ( 2 2 , 0 0 0 cfm)

,

a s shown i n F i g u r e 5 , t h e p r e s s u r e d r o p s between F l o o r s 7 and 8 w i t h o u t o c c u p a n t s a r e 18 and 20 Pa (0.07 and 0.08 i n of w a t e r ) f o r t h e open and t h e c l o s e d - t r e a d s t a i r s , r e s p e c t i v e l y . These v a l u e s a r e i n c r e a s e d w i t h o c c u p a n t s i n s i d e t h e s h a f t t o 32 and 52.5 Pa (0.13 and 0.21 i n of w a t e r ) , r e s p e c t i v e l y . T h i s e f f e c t was d u p l i c a t e d w i t h o t h e r a i r f l o w r a t e s . I n t e r m s of f l o w r e s i s t a n c e ( F i g u r e 7 ) , t h e a v e r a g e v a l u e s of t h e c o e f f i c i e n t K w i t h no o c c u p a n t s a r e 62 f o r t h e open t r e a d and 67 f o r t h e c l o s e d t r e a d . These c o e f f i c i e n t s a r e i n c r e a s e d s i g n i f i c a n t l y w i t h s i m u l a t e d o c c u p a n t s a t h i g h d e n s i t y t o 103 f o r t h e open-tread s t a i r s and 163 f o r t h e c l o s e d - t r e a d s t a i r s . C o r r e s p o n d i n g l y , t h e o v e r a l l e q u i v a l e n t o r i f i c e a r e a w i t h o u t o c c u p a n t s f o r b o t h open and c l o s e d t r e a d i s a b o u t 23% of t h e s h a f t c r o s s - s e c t i o n a l a r e a ; w i t h o c c u p a n t s a t h i g h d e n s i t y , t h i s v a l u e i s d e c r e a s e d t o 18% f o r t h e open t r e a d s t a i r s and 14.5% f o r t h e c l o s e d - t r e a d s t a i r s .

P e o p l e E f f e c t . T e s t s 8.1 and 8.2 were conducted w i t h r e a l p e o p l e a t h i g h and medium o c c u p a n t d e n s i t i e s . The r e s u l t s i n d i c a t e d s i g n i f i c a n t i n c r e a s e i n t h e p r e s s u r e d r o p s i m i l a r t o t h o s e of t h e p h y s i c a l model. With p e o p l e a t h i g h d e n s i t y , t h e p r e s s u r e d r o p i n c r e a s e d by f a c t o r s of 3.0 and 2.5 a t medium and low a i r f l o w r a t e s , r e s p e c t i v e l y ; a t medium d e n s i t y , t h e y were 2.0 and 1.9. The d a t a c l e a r l y i n d i c a t e t h a t K depends on o c c u p a n t d e n s i t y ( F i g u r e 8 ) .

V a l i d a t i o n of t h e S i m u l a t i o n Method. To v a l i d a t e t h e s i m u l a t i o n method u s e d , T e s t s 9.1 and 9.2 were conducted w i t h t h e models p l a c e d i n t h e same l o c a t i o n s a s i n t h e t e s t s w i t h

p e o p l e . The r e s u l t s i n F i g u r e 9 i n d i c a t e a good agreement w i t h t h o s e o b t a i n e d w i t h p e o p l e ; i n t e r m s of K, t h e s i m u l a t i o n method i s w i t h i n 4% f o r medium o c c u p a n t d e n s i t y and 11% f o r h i g h o c c u p a n t d e n s i t y . T e s t s 10 and 11 were conducted u s i n g t h e same number of o c c u p a n t s f o r h i g h d e n s i t y b u t d i s t r i b u t e d on t h r e e f l o o r s ( 6 , 7 , and 8 ) i n s t e a d of two t o r e p r e s e n t a medium o c c u p a n t d e n s i t y on e a c h of t h e s e f l o o r s . A s e x p e c t e d , t h e r e s u l t s were a p p r o x i m a t e l y t h e same f o r b o t h c o n f i g u r a t i o n s , ( i . e . , o c c u p a n t s on 2 and on 3 f l o o r s w i t h medium o c c u p a n t d e n s i t y ) .

E f f e c t of F l o o r H e i g h t s .

I n t a l l b u i l d i n g s , t h e f l o o r h e i g h t v a r i e s from one b u i l d i n g t o a n o t h e r ; g e n e r a l l y i t i s between 2.6 m and 3.6 m (8.5 f t and 12.0 f t ) . However, i n a t y p i c a l s t a i r w e l l , t h e c r o s s - s e c t i o n a l a r e a of t h e s h a f t and t h e s t a i r w a y s l o p e , r i s e l s t e p , a r e u s u a l l y c o n s t a n t r e g a r d l e s s of h e i g h t . I n t h i s s t u d y , t h e two bounding h e i g h t s were i n v e s t i g a t e d .

The p r e s s u r e l o s s c o e f f i c i e n t s f o r t h e f l o o r h e i g h t of 2.6 m ( 8 . 5 f t ) a r e g i v e n i n I

T a b l e 1 and f o r t h o s e of 3.6 m (12.0 f t ) a r e g i v e n i n T a b l e 2. The a v e r a g e p r e s s u r e l o s s I c o e f f i c i e n t s , K , f o r t h e c l o s e d - t r e a d s t a i r s a r e 32 and 67 and f o r t h e o p e n - t r e a d s t a i r s

₁

a r e 29 and 62 f o r h e i g h t s of 3.6 m and 2.6 m ( 1 2 f t and 8.5 f t ) , r e s p e c t i v e l y . The l a r g e r K v a l u e s f o r t h e f l o o r h e i g h t of 2.6 m (8.5 f t ) t h a n of 3.6 m (12.0 f t ) a r e due p r o b a b l y t o t h e l a r g e r l a n d i n g a r e a f o r t h e f o r m e r f o r t h e same s t a i r s l o p e . F i e l d t e s t measurements o b t a i n e d by Tamura and Shaw 1976 i n m u l t i - s t o r y b u i l d i n g s from 1 1 t o 28 s t o r y s w i t h f l o o r h e i g h t s between 3.04 m and 3.6 m ( 1 0 f t and 12 f t ) i n d i c a t e d t h a t t h e a v e r a g e v a l u e of K was 35.

i

CONCLUSIONS

1. The f r i c t i o n p r e s s u r e d r o p was found t o be l i n e a r w i t h h e i g h t and v a r i e d d i r e c t l y w i t h t h e s q u a r e of t h e s u p p l y a i r r a t e s . The p r e s s u r e l o s s c o e f f i c i e n t , K , was i n d e p e n d e n t of Reynolds number f o r t h e r a n g e of f l o w r a t e s used f o r s t a i r w e l l p r e s s u r i z a t i o n . 2. The open-tread s t a i r s p r e s e n t e d l e s s r e s i s t a n c e t o f l o w t h a n t h e c l o s e d - t r e a d s t a i r s ;

3. The p r e s s u r e l o s s c o e f f i c i e n t s were g r e a t l y a f f e c t e d by t h e o c c u p a n t d e n s i t y i n t h e s t a i r w e l l ; a t h i g h o c c u p a n t d e n s i t y a b o u t t h r e e t i m e s and a t medium o c c u p a n t d e n s i t y a b o u t two t i m e s t h o s e w i t h o u t o c c u p a n t s .

4. F o r f l o o r h e i g h t s of 2.6 m and 3.6 q (8.5 f t and 12 f t ) , which a f f e c t t h e a r e a of l a n d i n g s f o r s t a i r s w i t h t h e same s l o p e and c r o s s - s e c t i o n a l a r e a of s h a f t , t h e p r e s s u r e l o s s c o e f f i c i e n t of t h e f o r m e r was t w i c e t h a t of t h e l a t t e r .

5. The s i m u l a t i o n method u s i n g s i m p l e p h y s i c a l models was v e r i f i e d by t e s t s w i t h r e a l p e o p l e . The r e s u l t s i n d i c a t e d good agreement; t h e a c c u r a c y i n t e r m s of K was w i t h i n 4% and 11% f o r medium and h i g h o c c u p a n t d e n s i t i e s , r e s p e c t i v e l y . T h i s method can b e u s e d i n f u t u r e t e s t i n g of s t a i r w e l l p r e s s u r i z a t i o n s y s t e m s , p a r t i c u l a r l y u n d e r f i r e c o n d i t i o n s . 6. The t e s t s i n v o l v e d s i n g l e i n j e c t i o n e i t h e r a t t h e t o p o r b o t t o m of t h e s t a i r w e l l . F u r t h e r tests are r e q u i r e d t o i n v e s t i g a t e t h e e f f e c t of m u l t i p l e a i r i n j e c t i o n on t h e p r e s s u r e d i s t r i b u t i o n i n s i d e s t a i r w e l l s w i t h and w i t h o u t o c c u p a n t s . NOMENCLATURE A = C r o s s - s e c t i o n a l a r e a , m 2 ( f t 2 ) C = C o e f f i c i e n t of d i s c h a r g e (0.6 f o r t u r b u l e n t f l o w ) d 4 A .- D = E q u i v a l e n t d i a m e t e r , m ( f t ) De =

[*I,

where p = p e r i m e t e r of t h e e s h a f t g = A c c e l e r a t i o n due t o g r a v i t y , m / s 2 ( f t / s 2 ) h = H e i g h t of f l o o r , m ( f t ) K = F r i c t i o n p r e s s u r e l o s s c o e f f i c i e n t N = Number of f l o o r s s e r v e d by t h e s t a i r w e l l i n a b u i l d i n g P = S t a t i c p r e s s u r e , Pa ( i n of w a t e r ) Q = V o l u m e t r i c f l o w r a t e , m 3 / s ( c f m ) P = A i r d e n s i t y , kg/m ( l b / f t 3, S u b s c r i p t s f = f l o o r ; i = l o c a t i o n ( i t h f l o o r ) ; 1 = ground f l o o r ; 2 = l e a k a g e ; s = s h a f t REFERENCES

A c h a k j i , G.Y. 1987. "NRC e x p e r i m e n t a l f i r e tower f o r s t u d i e s on smoke movement and smoke c o n t r o l i n t a l l b u i l d i n g s . " I n s t i t u t e f o r Research i n C o n s t r u c t i o n , N a t i o n a l R e s e a r c h C o u n c i l Canada, I n t e r n a l R e p o r t No. 512.

C r e s c i , R . J . 1973. "Smoke and f i r e c o n t r o l i n h i g h - r i s e o f f i c e b u i l d i n g s , P a r t 11." ASHRAE Symposium " E x p e r i e n c e and A p p l i c a t i o n s on Smoke and F i r e C o n t r o l , " L o u i s v i l l e , Kentucky, June.

M a r s h a l l , N.R. 1985. "The b e h a v i o u r of h o t g a s e s f l o w i n g w i t h i n a s t a i r c a s e . " F i r e S a f e t y J o u r n a l , Vol. 9 , pp 245-255.

P a u l s , J.L., and J o n e s , B.K. 1980. " B u i l d i n g e v a c u a t i o n . " F i r e s and Human B e h a v i o u r , C h a p t e r s 13 and 14 John Wiley and Sons Ltd.

Shaw, C.Y., and Tamura, G.T. 1976. "Design of a s t a i r s h a f t p r e s s u r i z a t i o n s y s t e m f o r t a l l b u i l d i n g s . " ASHRAE J o u r n a l , F e b r u a r y , pp 29-33.

Tamura, G.T. 1974. " E x p e r i m e n t a l s t u d i e s on p r e s s u r i z e d e s c a p e r o u t e s . " ASHRAE T r a n s a c t i o n s ,

Tamura, G.T., and Shaw, C.Y. 1976. " A i r l e a k a g e d a t a f o r t h e d e s i g n of e l e v a t o r and s t a i r s h a f t p r e s s u r i z a t i o n systems." Vol. 8 2 , P a r t 2 , pp 179-190.

ACKNOWLEDGEMENTS

The a u t h o r s wish t o acknowledge t h e c o n t r i b u t i o n of R.C. Biggs d u r i n g d i s c u s s i o n and review of t h e p r o j e c t . The a u t h o r s a l s o w i s h t o acknowledge t h e c o o p e r a t i o n and a s s i s t a n c e of

R.A. MacDonald and members of t h e N a t i o n a l F i r e Laboratory i n t h e p r e p a r a t i o n and c o n d u c t i o n of t e s t s .

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TABLE 2

Flow R e s i s t a n c e of Conventional S t a i r w e l l , T y p i c a l F l o o r Height: 3 . 6 m ( 1 2 f t )

Note: The v a l u e s i n t h i s t a b l e a r e t h e a v e r a g e d a t a of bottom and t o p a i r i n j e c t i o n s a t d i f f e r e n t flow r a t e s of 5 t o 10 m 3 / s (10,600 t o 21,200 cfm). A A p e r f l o o r o/ s 0.30 0.28 P r e s s u r e l o s s C o e f f i c i e n t

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NOTES:

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HIGH OCCUPANT DENSITY INCLUDES ALL POSITIONS SHOWN

-

MEDIUM OCCUPANT DENSITY INCLUDES ONLY THE

DARK POSITIONS

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5

Pressure drop between floors

7

and 8: effect of open and

closed

treads, with and without occupant simulation, bottom

injection

200

175

-

WITH OCCUPANTS

₃

1 0 m

Is

WITHOUT OCCUPANTS

150

-

(II 0,

*

TEST5a

~

125

-

+

TEST 5b

03

-

+

TEST5c

0

-

*

TEST 6a

W

-t

TEST6b

3

u

i

7.5

m

Is

3

*

TEST 6c

cn

75

-

V)

W

[r

a

50

-

₃

5 m

Is

I

0

5

10

15

20

25

3 0

BUILDING HEIGHT,

m

Figure 6 Pressure drop distribution: with or without occupant simulation (closed treads, bottom injection)

*

4 /

-

CLOSED WITH OCCUPANTS

/

\

_\

-

*

OPEN NO

-

,

CLOSED OCCUPANTS -,OPEN

-

TEST 1 TEST 2 TEST 5 TEST 6 W

1

5 0.5 1

.O

1.5 2.0 2.5 3.0 x10

REYNOLDS NUMBER, Re

Figure

7

Flow resistance: effect of open and closed treads, with

and

without occupant simulation, (bottom injection)

W

2oo

1

+ TEST 8.2 PEOPLE

---

(HIGH DENSITY)

tn

I

~

150 PEOPLE

2

(MEDIUM DENSITY) 100 3 e WITHOUT 50 PEOPLE W

REYNOLDS NUMBER, Re

Figure 8 Flow resistance: effect of people at high and medium occupant densities (closed treads, bottom injection)

u-

u

HlGH DENSITY

/

0 MEDIUM

\/

/ SIMULAT~ON DENSITY \

-

2

150

\

PEOPLE -1 SIMULATION u I I I I 0.0 0.5 1 .O 1.5 2.0

REYNOLDS NUMBER, Re

Figure 9 Validation of the simulation method by comparison with people tests (closed treads, bottcm injection)

Discussion

R. PITZER, Jim Grigsby, P.E., Corpus Christi,

TX:

In response to the problems of door leakage,

our experience has shown door leakage and general construction materials and practices can be

significant. A 10-story residential building with exterior stairwells had two propeller fans (one in

the basement and one on the fifth floor) with relief at the roof. The initial pressurization test

produced readings of 0.02" W.C. Weatherstripping the doors and caulking conduit and similar

penetrations yielded readings of 0.06" W.C., still falling short of the required 0.15"

W.C.

Two coats

of latex paint on the cinderblock walls resulted in final test pressures of 0.18" W.C.

G.Y.

ACHAKJI: The designers of pressurization systems must account for the air leakage in the

shaft before sizing the capacities of the fans. Some shafts produce more leakage than others,

depending on the quality of workmanship and the construction materials used. An air leakage test

can be conducted to check that. Much information exists on air leakage; data are available in the

literature (Tamura and Shaw 1976).

I must point out, however, that the emphasis in this paper is on determining the effect of various

stair configurations and floor height and the effect of occupants on the pressure loss, which were

not known or available before.

This paper is being distributed in reprint form by the Institute for

Research in Construction. A list of building practice and research

publications available from the Institute may be obtained

by

writing to

the Publications Section, Institute for Research in Construction,

National Research Council of Canada, Ottawa, Ontario, KIA 0R6.

Ce document est distribue sous forme de tire-&-part par l'institut de

recherche en construction. On peut obtenir une liste des publications de

1'Institut portant sur

les techniques ou les recherches en matibre de

bitiment en krivant

&

la

Section des publications, Institut de recherche

en construction, Conseil national de recherches du Canada, Ottawa

(Ontario), KIA 0R6.