buoyancy-driven air flow in a closed half-scale stairwell model- velocity and temperature...

8/4/2019 Buoyancy-driven Air Flow in a Closed Half-scale Stairwell Model- Velocity and Temperature Measurements by Zohrabian Et. Al

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PROGRESS AND T R E ND S I N A T R I N F I L T R A T I O N AN D V E N T I L A T I O N R ES EA R CH10 th A I V C conference, D i p o l i , Finland2 5 -2 8 S e p t e m b e r 1989.

Poster 1 2

BUOYANCY-DRIVEN AIR FLOW IN A CLOSED HALF-SCALE STAIRWELLMODEL: VEL OCIT Y AND TEMPERATURE I~EX XJRE ME NTS

A . S . Z O HR A BI AN , B S c , M S c - P hD R e s e a r c h Studen tM.R.MOKHTARZADEH-DEHGHAN, B S C , M S C , D I C , P h D , M A S M E , A M I M e c h E -

L e c t u r e r ,


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SUMMARY

This paper des cr ibe s an exper ime nta l s tu dy of th e buoyancy-dr ivenf lo w an d t h e a s s o c i a t e d e n er g y t r a n s f e r w i t h i n a c l o s e d , h a l f -s c a l e s t a i r w e l l m odel. It prov ides new da t a on th e ve lo c i t y ,t empera tu re , volume and mass f low ra te s o f the a i r c i r cu la t i ngbetween the upper and lower s to re ys . The r e s u l t s a r e p resen tedf o r v a ri o u s h e a t i n p u t r a t e s f rom t h e h e a t e r , l o c a t ed i n t h e lo werf l o o r . F or m ost o f t h e d a t a p r es e n te d , h e a t t r a n s f e r t o t h esu r round ing atmosphere t ake s p la ce th rough the s i de wa l l s .How ever, t h e c a s e o f i n s u l a t e d s i d e w a l l s i s a l s o i n c l u d e d and t h ee f f e c t s on t h e p a ra m e te rs o f i n t e r e s t a r e d i sc u s se d . Thev e l o c i t i e s were measured us ing hot-wire anemometers of a tempera-tu re compensated ty pe , and t h e tempe ratures were measured usin gplatinum re si s ta n ce thermometers. These measurements weresuppor ted by f low v is u al is a t io n using smoke. The paper a l s op r o vi d e s d a t a on t h e r a t e o f l ea k ag e th ro ug h t h e s t a i r w e l l j o i n t s ,measured using a co nc en tra tio n decay method.


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LIST OF SYMBOLSA Throat area (0.462 m2C I c C o n c e nt ra t io n i n s i d e a nd o u t s i d e s t a i r w e l l (ppm ).

-1 -1c S p e c i f ic h e a t a t c o n st a n t p r e s s u re (J kg K 1 .PDT 7 D i f f e r e n t i a l t e m p e r a t u r e (TH - TC), (C deg .) .g G r a v i t a t i o n a l a c c e l e r a t i o n (m s - ~ ).h One h a l f t h e h e i g h t o f t h e s t a i r w e l l m odel ( m ) .k -1 K-l)Heat conduc t iv i ty (J mmU I md Upflow and downflow mass flow r a t e s (kg s- I ) .

Leakage rate (kg sell .R a te of s u pp ly of h e a t t o t h e s t a i r w e l l (W).

6s Volume f low r a t e through leak age (m3 s-l) .0Tav Average tempera tu re wi th in t he s t a i r w e l l ( C ) .

T ~ ' ~ Mean tem pe ra tu re s of warm upwards-flowing a i r and0col d downwards-flowing a i r , r es pe ct ive ly ( C) .'maxu Maximum v e l o c i t of t h e flow moving up t h e-!s t a i r w e l l (m s 1 .'maxd Maximum ve l o c i t y of t h e f low moving down t h es t a i r w e l l (m s - ~ ) .

3vs St a i r w e l l volume (m ) .'m Ari thme t ic average of t he volume flow ra te s , o ft h e upf low and downf low (m3 s-') , Gm = (


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D I M E N S I O N L E S S G R O U P S

F r Froude n u m b e r -A ( g h ?

G r G r a s h o f n u m b e r - g B D T A hu2

P r P r a n d t l number - "P k

R a R a y l e i g h n u m b e r - G r . rR e R e y n o l d s n u m b e r - vm

V A4

S t S t a n t o n number - 5!P C T A ( g A ) 'P av

D E F I N I T I O N S

T h r o a t area : The area s h o w n by DD' i n Figure 1.

Side w a l l : A r e a def ined by ACDEFDHIA i n F igu r e 1.


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INTRODUCTIONObtaining a b e t t e r understanding of th e mechanism and char ac ter -i s t i c s o f a i r movement w i t h in s t a i r w e l l s , i n p r i v a t e d w e l l i ng s ,ho tels and publ ic b ui ldings such as ho sp i ta ls and undergrounds t a t i o n s , i s impor tant i n re la t i on t o wide ranging problems sucha s f i r e sa fe ty , energy saving and movement of micro-organisms andcontaminants. Improvements i n the ba si c understanding can beobtained by car ry ing out s imple t e s t s on smal l -scale models ,se t t in g up s imple an al yt ic al models o r using high- level computa-t ional models .Fi re s account annual ly fo r thousands of dea ths and m il l io ns ofpounds i n lo ss of pro per ty . Moodie e t al!) have c a r r i e d o u texper iments on a one- thi rd sc al e model of an esc al at or t o inv es t i -gate t he f i r e which occurred i n King's Cross underground s ta t i o ni n 1987. The r e su l t s showed th a t , fo llowing the ign i t i on , th eflame was soon es tab l i she d across th e f u l l wid th o f th e e sc a la to rchannel. The f lame fr o n t then remained low i n th e e sc a la to rchanne l as the f i r e developed and then p rogressed i n the esca la to r .Zohrabian e t a1. ( 2 ) have shown th a t s lop ing the s t a i rw el l ce i l i ngspeeds up th e migra tion of smoke from th e lower t o t he uppercompartment, hence helps i n the spread of f i r e .Most rooms in ho sp i ta ls a re connected by co rr id ors and s t a i rw el ls .The impo rtance of movements of micro-organisms i n a h o s p it a ls ta i r s h a f t has been shown by sev era l workers i n recent years . Themeasurements by Miinch e t a1 . ( 3 ) i n d i c a t e t h a t t r an s p o r t o f m icro-organisms depends on th e temperature d i f fe re n t i a l wi thin t hes t a i r w e l l . The experim ental measurements of Zohrabian e t a l . ( 2 )on a ha lf- sc al e st ai rw el l model showed t h a t the volume f low ra t eof the a i r f low from the lower f l oo r t o the upper was increase d byincre asin g the heat ing load o r changing the s ta i r w el l geometry .Hence micro-organisms, a s we ll a s to xi c ag ents o r contaminantswhich can cause wound inf ec ti on , can be tr an sf er re d t o th e upperf lo or s by way of the s t a i rw el l . Therefore , sp ec ia l ar rangementso r ap p r o p r i a t e s t a i r w e l l d e s ig n i s needed wi th in ho sp i t a l bu i ld ings ,i n or de r t o minimize the f low of unwanted germs o r contaminants t ot h e h ig h e r f l o o r s .A number of o the r usef ul exper imental s tu di es a re repo r ted byBrown and ~olvason(4) haw(^) , Shaw and Whyte ( 6 ), F eu s te l e t a ~ ( ~ )Marshall (819) , Mahajan(l0) , R i ff a t e t a l . ( l l ) and R i f f a t and ~ i d ( l ~ ) .An aly tic al modell in of re le va nt f lows a re reporte d by Reynolds andReynolds e t a l . (13q4 ) , N ev rala a nd ~ r o b e r t15) ~ i d d a r n e n t ( l ~ )App lications of Computational Fluid Dynamics t o f lows rel ev an t t o


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2. EXPERIMENTAL R IG AND INSTRUMENTATIONA schematic d iagram of t he ha l f - sc a le s t a i rw el l model i s shown i nF igure 1. The de t a i l s o f ins t rumenta t ion can be found in Ref . 121.T h er ef o re , o n ly a b r i e f r e f e r en ce t o t h e i n s tr u m en ta t i o n and t h eimprovements of th e o r i g in a l model i s made here.The ve lo c i t i es were measured us ing h o t wi res o f t empera tu recompensated typ e having a t ime c on s ta nt of about Is and accuracyo f l e s s t h a n 1 0 p e r c e n t f o r t h e r an ge o f v e l o c i t i e s measu re dwi thi n th e s t a i r w e l l . The tempera tures were measured us ingplat inum re s i s t an c e thermometers having a t ime cons t an t of 3 minand accuracy of 5 0 . 2 5 ~ ~ . he pro be s were f ix e d t o t h e w a ll s bysp ec ia l l y des igned clamps . The s ig na ls from the se probes weret r an s f e r r ed t o an A pple com pu te r f o r p r o ces s in g , v i a s i g n a lcond i t ion ing e le c t ro n i cs and Analogue- to -Dig ita l con ver te r s .The m o di f ic a t io n s t o t h e r i g d e s c r ib e d i n r e f e r e n c e [2] were:(i) The l i g h t b u lb s u sed a s h ea t s o u r ce were repla ced by ane l e c t r i c r a d i a t o r w i t h s u r f a c e a r e a of 0.57 m x 0.659 m

and wi th a loa din g power of 1 kW.(ii) Both s i d e w al ls were made of Perspex of 10 mm t h i ck n es s(o r i g i na l l y one of th e wa l ls was made of Perspex of 12.5 mm

th ic kn es s and th e o th e r made of wood of 18 mm t h i c k n e s s ) .T h is en s u r ed b e t t e r t h e rm a l s ym metry i n t h e s t a i r w e l l .

3. RESULTS3.1 . F low ch ar ac te r i s t i c s

A two-dimensional v iew of th e f low p at te rn i s shown i n Figu re 2 .The main re ci rc ul at in g f low , re ci rc u la t i on zones , and upward anddownward flows i n th e s t airw ay can be seen. Comparison wi thprevious work [.2] showed th a t , alt ho ug h some changes had beeni nt ro d u ce d i n t o t h e d e s ig n o f t h e r i g a nd c om p le te ly d i f f e r e n ttype of h ea t source was used ( se e se c t io n 2 ) , t h e o v e r a l l c h a ra c t -e r i s t i c s o f t h e f lo w d i d n o t chan ge s i g n i f i c a n t l y . For f u r t h e rd e t a i l s e e r e fe r e nc e [2] .

3.2. V e l o c it y an d t em p e ra tu r e p r o f i l e s i n t h e t h r o a t a r e aFigures 3 and 4 show, r e sp ec t iv e l y , the ve l oc i ty and tempera tu red i s t r i b u t i o n s a t v a ri o u s d i s t a n c e s from t h e s i d e w a ll a nd f o rv a r io u s h e a t in p u t r a t e s . The r e s u l t s i n d i c a t e two d i s t i n c tregions : one asso cia ted with t h e warm upflow; i n the upper p a r to f t he th ro a t a re a , and one wi th t he c o ld downflow, i n the lowerp a r t . The r e s u l t s i n d i ca t e an i n c r e a s e i n v e lo c i t y t o a maximumv er y c l o s e t o t h e c e i l i n g , a f t e r which it d ro ps t o z e r o a t t h e


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i n p u t r a t e .In o rd er t o ob ta in some idea o f th e three-d imensiona l behav iour o ft h e f lo w, t h e a bove r e s u l t s a r e a l s o pr e se n te d i n an a l t e r n a t i v eway. Figures 5 and 6 show, r e s p ec t i v e ly , t h e v e lo c i t y andt em p e ra tu r e p r o f i l e s a t v a r i o u s d i s t a n c e s f rom t h e s i d e w a l l .F igure 5 show s t h a t t h e v e lo c i t y p r o f i l e s c an b e co n s id e r edun ifo rm over abou t two- th i rds o f th e wid th o f th e s t a i rw el l .Therefo re , th e o ve ra l l f lu id f low may be cons idered a s two-dimensional . F igure 6 shows high er tempe ratures fo r h igh er he ati n p u t r a t e s . A l so , t h e t em p e ra tu re p r o f i l e s show h ig h e r d eg r eeo f u n i fo r m i ty , a c r o s s t h e s t a i r w e l l , f o r h i g he r i n p u t r a t e s . T h isun i fo rmi ty i s even more pronounced i n th e upper reg ion of th eth ro at are a . However, it i s i n t e r e s t i n g t o n o te t h a t , a lt ho ug h,a s expec ted , th e lowes t t empera tu res were measured a t po s i t io n w/6,the h igh es t t empera tu res were no t r ecorded a t the mid-wid th o ft h e s t a i r w e l l ( e xc e pt f o r t h e 1 00 W h e a t i n p ut r a t e ) , b u t a t w/3.Th is in d i ca te s complex flow behav iour near the s t a i r s .

3.3. Leakage MeasurementF ig u re 7 show s t h e r e s u l t s o f t h e t r ace r -d ecay t e s t f o r a 1 00 Wh e a t i n p u t r a t e . I t shows var ia t ions o f C02 t r acer gas concen-t r a t i o n ag a in s t t im e . The n eg a t i v e s l o p e o f t h e l i n e i s e q u a l t ot h e a i r ch ange r a t e , g i ve n by

bS/vs = A i r change ratewhere V i s t h e s t a i r w e l l v olu me , and bs i s th e volume f low r a t eSthrough leakage.However, f o r t h e a c t u a l vo l u m e tr i c a i r f l ow r a t e , o r a i r l ea ka ger a t e i n t h i s c a s e , t h e s t a i r w e l l volum e was m u l t i p l i e d by t h e a i rchange ra te . Tab le 1 g i v e s t h e a i r l ea k ag e r a t e s t h ro ug h t h es t a i r w e l l j o i n t s , f o r v a r io u s h e a t i n p u t r a t e s . The r e s u l t si n d i c a t e t h a t t h e l e ak ag e r a t e i n c r e a s e s w i th h e a t i n p u t r a t e . Itshou ld be no ted t h a t the c a l cu la t io n of l eakage mass f low ra t e wasbased on th e ar i th m et ic average T and room tempera ture . Theca l cu l a t i o n of l eak ag e h e a t f l ow ?gte was based on th e dif fe re nc ebetween T an d -t h e room tem pera ture.av

3.4. Maximum v e l o c i t i e s , mean tem pera tures and flow r a t e sTable 2 shows th e maximum v e l o c i t i e s and mean tem pera tures i n t h eupf low and downflow s treams a t va r io us d is t an ce s f rom the s i d ew a l l and f o r v a r io u s h e at i n p u t r a t e s . The r e s u l t s i n d i c a t e t h a tt h e maximum a i r v e lo c i t y v a r i e s s l i g h t l y ac r o s s t h e w idth of t h e


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It was found that n=0.22. This is in agreement with the previousresults [2] and also is generally consistent with the modeldescribed by Reynolds (13) in which the value of 0.25 was suggest-ed.Assuming that the inflow and the outflow through cracks take placein the lower and upper compartment, respectively, one expectsthat $ = & + 6%. The results of table 3 show that the two sidesof above refationship differ by less than 5 per cent. Thepossible reasons for this discrepancy are given in section 4.3.

3.5. Rate of heat loss through the stairwellTable 4 gives the rate of heat loss from the stairwell for variousheat input rates. The results show that the heat losses throughthe several stairwell boundaries vary approximately linearlywith the heat input rate. The results also indicate that over 50per cent of the heat is lost through the stairwell side walls(for further discussion see section 4.4).

3.6. Effect of insulated side walls on the resultsTable 5 shows the rate of heat loss from the stairwell withinsulated side walls. The results show a substantial increase inthe rate of heat transfer through the other walls. For example,the rate of heat transfer through the upper compartment ceilinghas tripled. The results (not given here) also showed thathigher velocities and temperatures resulted, both in the upflowand in the downflow streams.

4. DISCUSSION4.1. Characteristic dimensionless numbers

The characteristic dimensionless numbers relevant to the naturalconvection in stairwell flows are Froude, Stanton, Reynolds andGrashof numbers. Table'6 gives values of the dimensionlessnumbers for the half-scale stairwell geometry. Full discussionof their range for the half-scale model is given by Reynolds eta1 (I4). The corresponding values for full-scale stairwells canbe found using the scaling principles set out by Reynolds(13).These are based effectively on Froude scaling. For example, for aFroude number about 1.4 times the prototype value, requires thatthe ratio of the energy input of the model to the prototype be


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on t h e e q u i v al e n t f u l l s c a l e .It s h o u ld be n o t ed t h a t :(i) The f l u i d p r o p e r t i e s were e v a l u a te d a t t h e a r i t h m e t i c

mean o f th e 45 tempera tu re r ead ings d i s t r i bu te d wi th int h e upper and lower compartments .

(ii) The volume f low ra te s used fo r th e ca lc ul at io n of Reynoldsand Froude numbers were based on th e av erag e of t h e up-flow and downflow volume flow r a t e s .

The f low ch ar ac te r i s t ic s i n t he lower compar tment may be unders toodby re fe re nc e t o th e Rayleigh number. One of th e most common, ands imp les t na tu ra l convec t ion p rob lems occurs when a ve r t i c a l hea tedf l a t p l a t e t ra n s fe r s h e at t o a s t i l l , co ld e r s u r r o u n d in g f l u id .Th is i s ap pr o xim ate ly t h e ca s e c lo s e t o t h e h ea t e r , w he re ,d ep en din g upon f l u id p r o p e r t i e s an d t h e t h e r m a l g r ad i en t , t r an g i -t i o n t o tu rb ul en t f low occ urs when Rayleigh number i s abou t 10 .The Rayleigh number, based on the he at er hei gh t , the di f fe re nc ebetween the su r fac e tempera tu re o f t he he a te r and th a t o f th es ur ro un d in g f l u i d , and t h e f l u i d p r o p e r t i e s e v a l u a te d a t t h ear i th m et ic mean of th e tem peratures measured i n th e lower compar t-ment, was found t o be w ith in th e range 4.361 x lo8 t o 1.763 x 10' ,f o r 1 00 W t o 900 W h e a t i n p u t r a t e s , r e s p e c t iv e l y .

4.2. The v e lo c i t y an d t em p e ra tu re d i s t r i b u t i o n s i n t h e t h r o a t a r eaThe flow was symmetrical with re sp ec t t o th e mid-plane of th est a ir w e ll . Th is was examined by measuring tem pera ture s andv e l o c i t i e s a t t he t h ro a t a re a a t w/2 , w/3 and w/6 d is ta n c e s fromb o th s i d e w a l l s of t h e s t a i r w e l l . T he re was a d is c r ep an cy o f l e s sthan 2 per cen t between th e tempera tu res and le s s than 3 pe r ce n tbetween the v e lo c i t ie s measured from th e two s i de s . The refore , asymmetrical con di t ion was assumed with re sp ec t t o t he mid-planeo f t h e t h r o a t a r e a , and t h e m easu rements were c a r r i e d o u t i n o n lyon e h a l f o f t h e s t a i r w e l l .

4 .3 . Volume and mass f low r a t e s and fa c to rs af fe ct in g th e i r accuracyTable 3 g ives th e f low ra te s i n th e upflow and downflow a t thet h r o a t a r e a f o r v ar i ou s h e a t i n p u t r a t e s . A s mentioned i ns e c t i o n 3.4 , t h e r e s u l t s i n d i c a t e a d is c re p an c y of l e s s t h a n 5 p e r


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4.4. H ea t t r an s f e r r a t e s t hr ou gh t h e s t a i r w e l l w a l l s and j o in t sThe h e a t t r a n s f e r r a t e s t hr ou gh t h e s t a i r w e l l a r e g i ve n i n Ta bl e4. The r e s u l t s i n d i c a t e t h a t more t h an h a l f o f t h e h e a t i n p u t t ot o t h e s t a i r w e l l i s l o s t t hr ou gh t h e s i d e w a l l s . The r e s u l t s a l s oi n d i c a t e t h a t t h e r e i s a d i f f e r e n c e o f l e s s t h an 3 p e r c e n tbetw een t h e m easu red h e a t i n p u t r a t e t o t h e s t a i r w e l l and t h e r a t eo f m easu red h ea t l o s s f rom th e s t a i r w e l l . T h i s e r r o r i n t h e h ea tb a l an c e ca n b e a t t r i b u t e d t o t h e f o l lo w in g f a c t s :(i) The ca l cu la t io n o f the h ea t lo s s was based on the su r fac e

tempera tu res measured a t the mid-p lane o f th e s t a i rw el l ,and were assumed uniform across i t s wid th. However, li m it edmeasurements showed th a t f o r a he at i np ut of 600 W , t h esu rfa ce temp erature var ie d by 0.4C deg.

(ii)The hea t inp u t r a te t o th e r a d i a t o r was de te rmined fromrecord ings of vo l tage and cur ren t . The accuracy o f t heh ea t i n p u t r a t e w as ab o u t 2 p e r c en t .

I n o rd e r t o i n v e s t ig a t e t h e e f f e c t of t h e h e a t tr a n s f e r r a t ethr o ug h t h e s i d e w a l l s on t h e v e lo c i t y an d tem pe ra tu r e p r o f i l e sa t t h e t h r o a t a r e a , t h e s i d e w a l l s of t h e s t a i r w e l l w ere i n s u l at e d .T ab le 5 g i v e s t h e h e a t t r a n s f e r r a t e s f o r t h i s c as e . The r e s u l t s( n o t shown h e r e ) i n d i ca t ed t h a t i n s u l a t i o n o f t h e s i d e w a l l sr e s u l t e d i n a n i n c r ea s e i n t e mp er at ur es i n t h e t h r o a t a r e a o fapp roxim ately 3C deg. f o r 300 W and betw een 5C deg. t o 8C deg .f o r 6 0 0 W h e a t i n p u t r a t e s , r e s p e c t i v e l y . A ls o, t h e v e l o c i t i e sa t t h e t h r o a t a r e a i n c r e a s e d by up t o 1 3 p e r c e n t i n t h e u pflowand up t o 15 pe r c en t i n t he downflow, fo r 300 W and 600 W h e a ti n p u t r a t e s , r e s p e c t i v e ly . The r e s u l t s a l s o i n d i c a te d t h a ti n s u l a t i o n o f t h e s i d e w al l s r e s u l t e d i n a s i g n i f i c a n t i n c r e a s ei n t h e r a t e o f h e a t t r a n s f e r th ro ug h t h e o t h e r w a l ls . Forexample, th e r a t e of h ea t t r an sf er through th e upper-compar tmentce i l i n g i n c r ea s ed by ab o u t 60 p e r c en t f o r b o th 300 W and 600 Whe at inp ut ra te s . Fur thermore, th e Reynolds number inc rea sed by20 p er ce nt , and th e Grashof number by about 6 pe r c en t.

5. CONCLUDING REMARKSThis paper has addres sed a number o f que s t ions l e f t open i n th eau tho rs ' e a r l i e r s tu d i es o f s t a i rw el l f lows . The symmetry o fthe f low, and in f luence s which g ive r i s e t o depar tu res f rom it,have been in ve s t i ga ted . Tracer-gas determ inat io ns of th e leakager a t e from th e n o m in al ly s ea l ed t e s t r i g have b een ca r r i ed o u t ,and t h e r e s u l t s hav e been u s ed t o an a ly s e d i sc r ep an c i e s i n o th e rmeasurements . The inf lue nc e of thermal boundary co nd iti on s has


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ACKNOWLEDGEMENTST h e a u t h o r s w o u l d l i k e t o a c k n o w l e d g e t h e h e l p f u l i n f o r m a t i o nw h i c h t h ey received f r o m t h e A i r I n f i l t r a t i o n and V e n t i l a t i o nC e n t r e ( A I V C ) , and F i r e R e s e a r c h S t a t i o n ( FR S ). T h e y a l s o w i s ht o thank t h e Science and E n g i n e e r i n g R e s e a r c h C o u n c i l f o rf i n a n c i a l suppor t g iven as p a r t of the ' E n e r g y i n B u i l d i n g s 'S p e c i a l l y P r o m o t e d P r o g r a m m e .R E F E R E N C E S1. M O O D I E , K . , J A G G ER , S.F. , B E T T I S , R . J . and B E C m T T , H .

" F i r e a t K i n g ' s C r o s s U n d e r g r o u n d S t a t i o n - Scale m o d e lf i r e g r o w t h t e s t s " .H e a l t h and S af e ty E x e c u t i v e , R e s e a r c h and L a b . Services.H a r p u r H i l l , B u x t o n , D e r b y s h i r e , S K 1 7 9 J N , 1988.

2 . ZOHRABI AN , A. S . , MOKHTARZADEH-DEHGHAN, M.R. , REYNOLD S, A . J .M A R R I O T T , B . S . T ." A n e x p e r i m e n t a l s t u d y of buoyancy-driven f l o w i n a h a l f ;s c a l e s t a i r w e l l m o d e l " .B u i l d i n g E n v i r o n m e n t , V o l . 2 4 , N o . 2 , pp . 141-148, 1989.

3. MUNCH, W, , & D EN , H . , S C H K A L L E , Y . D . and T H I E L E , F." F l o w of m i c r o - o r g a n i s m s i n a h o s p i t a l s t a i r s h a f t - F u l ls ca l e m e a s u r e m e n t s and m a t h e m a t i c a l m o d e l " .E n e r g y and B u i l d i n g s , -, pp. 2 5 3 - 2 6 2 , 1986.

4. BROWN, W.G. and S O L V A S O N , K . R ." N a t u r a l convection through rec tangula r openings i np a r t i t i o n s - V e r t i c a l P a r t i t i o n s " .I n t . J. H e a t M a s s T r a n s f e r , V o 1 . 5 , pp. 859-868, 1962.

5. SHAW, B.H." H e a t and m a s s t r a n s f e r by n a t u r a l convection an d combinedn a t u r a l and forced a i r f l o w through l a rg e r ec t an g u l a ropenings i n a v e r t i c a l p a r t i t i o n " .I n s t n . M e c h . E n g s . , ~ 1 1 7 / 7 1 ,pp.31-39, 1971.

6 . SHAW, B.H. and WHYTE, W." A i r m o v e m e n t through d o o r w a y s - t h e i n f l u e n c e of t e m p e r a t u r eand i t s c o n t r o l by forced a i r f l o w " .B SE . D e c . 1 9 7 4 , V o l . 4 2 , pp. 2 1 0 - 2 1 8 , 1974.

7 . F E U S T E L , H . , Z U E RC H E R , C . H . , D IA M ON D , R . , D I C K I N S O N , B.,G R I M S R U D , D . , and L I P S C H U T Z , R ." T e m p e r a t u r e and w i n d - i n d u c e d a i r f l o w p a t t e r n s i n a s t a i r ca se :


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MARSHALL, N.R." A i r e n t r a i n m e n t i n t o s m o k e and hot gases i n open s h a f t s " .F i r e S a f e t y J o u r n a l , -o, pp. 3 7 - 4 6 , 1986.MAHAJAN, BA L M." M e a s u r e m e n t of i n t e r z ona l h e a t and m a s s t r a n s f e r by n a t u r a lconvection".So l a r E n e r g y , V o l . 3 8 , N o . 6 , p 437-446, 1 9 8 7 .R I F F A T , S . B . , W ALK ER , J. and L I T T L E R , J ." Z o n e t o zone t r a c e r gas m e a s u r e m e n t : Laboratory c a l i b r a t i onand values of a i r f l o w s up and d o w n s t a i r s i n houses".9 t h A I V C C o n f e r e n c e " E F F EC T IV E V EN TI LA TIO N" 12-15 September1988. N o v o t e l , G e n t . , B e l g i u m .R I F F A T , S . B . and E I D , M ." M e a s u r e m e n t of a i r f l o w b e t w e e n t h e f l o o r s of houses u s in ga por tab le SF6 s y s t e m " .E n e r g y and B u i l d i n g s , -2 , pp . 67-75, 1988.R J I Y N O L D S , A . J ." T h e s c a l i n g of f l o w s of energy and m a s s through s t a i r w e l l s " .B u i l d . and E n v i r . , V o l . 2 1 , P a r t 3/4, pp. 149-153, 1986.REYNO LDS, A .J . , MOKHTARZADEH-DEHGHAN, M.R. andZ O H R A B I A N , A . S ." T h e m o d e l l i n g of s t a i r w e l l f l o w s " .B u i l d . and E n v i r . , V o l . 23, N o . 1 , pp . 63-66, 1988.N E V R A L A , D . J . and P R O B E R T , S . D ." M o d e l l i n g of a i r m o v e m e n t i n r o o m s " .J o u r n a l of M e c h . E n g . Science, V o l . 1 9 , N o . 6 , 1977.L IDDAM E NT , M. ." M o d e l l i n g t h e i n f l u e n c e of v e n t i l a t i o n s t r a t eg i e s ond i s t r i b u t i o n and hea t l o s s i n a singl 'e f a m i l y d w e l l i n g " .Proceedings of 2 n d I n t . C o n g r e s s on B u i l d i n g E n e r g yM a n a g e m e n t . 30 M a y - 3 June 1983, I o w a , U SA.ZOHRA BIAN, A .S . , MOKHTARZADEH-DEHGHAN, M.R. , REY NOL DS, A .J ."A nume r i c a l s tu d y of buoyancy-driven f l o w s of m a s s andenergy i n a s t a i r w e l l " .9 t h A I V C C o n f e r e n c e " EF F EC T IV E V E NT IL AT IO N " 12-15 S e p t e m b e r1988. N o v o t e l , G e n t . , B e l g i u m .S I M C O X , S. and SCHOMBERG, M.


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T a b l e 1: R a t e o f l e a k ag e t h r o ug h t h e s t a i r w e l l j o i n t s ,f o r va r i ou s h e a t i n p u t r a t es .

EXTERNALTEMP.

T~(OC)19.521.021.5

HEAT INPUTRATE4(w )100300600

DISTANCE FROMSIDE WALL (m)

w/2

5w/12

w/3

w/4

w/6

w/12

EXTERNALCONCENTRA.

TION(PPM)

150-160150-160

1 8 0

LEAKAGERATEis

(m3 / s )5 .42x10- ~8. 21x10-'8.92x10-'

AIR CEIANGERATE

i s /v sp e r h o ur0.06590.09980.1085

sl! *maxu 'rnaxd T~ T~(w) (m / s (m / s 1 (OC) (OC)100 0.17 0.24 29.7 28 - 3300 0 .28 0 .31 35.4 32.1600 0.36 0.36 43.6 36.8900 0.42 0.54 50.1 41.8100 0 .16 0 .23 29.8 28 O300 0.27 0.27 35.5 31.6600 0 .34 0.36 43.6 37.3900 0 .41 0.54 50.4 41.5100 0.17 0.22 29.7 27 -8300 0.27 0.27 35.5 31.6600 0.34 0.36 43 -4 37.2900 0.46 0.50 50.7 41 .1100 0.17 0.21 29.8 27.3300 0.26 0.23 35 -5 31.1600 0.32 0.32 43.2 37 .O900 0.3 8 0. 47 50.6 42.5100 0.17 0.18 28 .O 26.8300 0.24 0. 21 35 O 30.2600 0.31 0 .31 42 .5 36.2900 0.35 0.47 49.6 41.4100 0.17 0.16 27.6 26 - 0300 0.24 0.18 32.8 28.2

280

LEAKAGERATE

me( kg / s )6 . 4 5 x 1 0 - ~9.69x10-'1 . 0 4 x 1 0 - ~

1 .29x10- ~ ( 1 . 4 9 x l 0 - ~ 1 21.5900 0.1575


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Ta bl e 3: Volume an d m a s s f lo w r a t e s i n t h e u pf lo w an ddownflow ( i n c l u d i n g l e a k a g e ) , a t t h r o a t areaf o r v a r i o us h e a t i n p u t r a t e s .

Tab le 4: R ate o f h e a t l o s s f rom t h e s t a i r w e l l a tv a r i ou s h e a t i n p u t r a t e s ( s e e F i gu r e 1).

CORRESPONDINGWALLACCDDEEFFGGHHI+IA

SIDE WALLSLEAKAGETOTAL LOSS

100(w)15.6

4.73 O6.33.72.55.5

58.60 .6

100.5

300(w)39.917.2

7 .329.4

9.66 .1

16 .8164 O1.1

291.4

600(w)

67 -441.518 .258.71 8 . 112 .133.5

350.41 .8

601.7

900(w)

95.645.523 .183 O26.718 .742 - 8

583.93 -1

922.4


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Table 5: Rate of heat loss from the stairwell, withinsulated side walls (see Figure 1).

TOTAL LOSS

Table 6: Basic performance characteristics ofthe closed-stairwell geometry.

288.4 586.5 I


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Wall mmCD 940DE 1285AC 1155EF 2520~d 0765FG 1136GH 1070

Figure 1. Schematic diagram of, the half-scale stairwell model.


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Figure 4 Temperature distributions at various distancesfrom the side wall, for various heat input rates.(a) w / 2 , (b) 4 3 , ( c ) w/6

0 l OO W, 0 3 0 0 W , A 6 O O W , + 3 O O W .


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buoyancy-driven air flow in a closed half-scale stairwell model- velocity and temperature...

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