1111Two-dimensional simulation of airflow and thermal comfort in a roomAA.pdf

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P a a s s e n [ 9 ]. Y e a r - r o u n d s i m u l a t i o n b y L u t e a n dP a a s s e n [ 1 0 ] h a s s h o w n t h a t r e a s o n a b l e i n d o o rt e m p e r a t u r e s f o r t h e r m a l c o m f o r t c a n b e m a i n t a in e df o r t h e m o d e r a t e D u t c h c l i m a t e w i t h th i s s y s t e m ,b u t t h a t m e c h a n i c a l c o o l i n g w i ll b e n e e d e d f o r aw a r m e r c l i m a t e , h i g h e r i n t e r n a l h e a t o r l i g h t b u i l d i n gs t r u c t u r e s .

H o w e v e r , f o r f u l ly u n d e r s t a n d i n g t h e i n d o o r t h e r -m a l - c o m f o r t a s p e c t s o f n a t u r a l v e n t i l a t io n , a s w e lla s th e p o s s i b l e e n e r g y s a v i n g s in th e s e a s o n s w h e nt h e o u t d o o r a i r c a n b e u s e d f o r f r e e c o o l in g , t h ea i rf lo w p a t t e r n s a n d t e m p e r a t u r e d i s t r i b u t io n s w i t h int h e v e n t i l a t e d r o o m n e e d t o b e f ul l y i n v e s t i g a t e d .A l so , c o m b i n i n g i n d o o r c o o l i n g s y s t e m s s u c h a sc o o l in g r a d i a t o r s w i t h o p e n - w i n d o w v e n t i l a t io n t oi m p r o v e i n d o o r t h e rm a l c o m f o r t n e e d s e s t i m a t io no f t h e e n e r g y p e r f o r m a n c e s c o n c e r n e d . T h e m o s t -w i d e l y - u se d o n e - p o i n t m o d e l f o r c a l c u l a t i o n o f n a t-u r a l v e n t i l a t i o n r a t e i s o b v i o u s l y n o t a d e q u a t e f o rt h e s e p u r p o s e s . F u r t h e r i n v e s t i g a t io n s m a y n e e df u l l - s c a l e i n s i t u m e a s u r e m e n t s o f t h e d e t a i le d f lo wp a r a m e t e r s . O n t h e o t h e r h a n d , t h e d e v e l o p m e n to f c o m p u t a t i o n a l f l ui d d y n a m i c s h a s e n a b l e u s t op e r f o r m ' n u m e r i c a l e x p e r i m e n t s ' a b o u t a i r f lo w de -t a i l s [ 6 , 1 1 , 1 2 ] . T h e r e f o r e , n u m e r i c a l s i m u l a t i o n so f s e v e r a l ty p i c a l o p e n - w i n d o w s i t u a ti o n s w e r e c o n -d u c t e d p r i o r t o f u l l- s c a l e i n s i t u m e a s u r e m e n t s . I nt h is p a p e r , d e t a i ls o f t h e s e p r e l i m i n a r y s i m u l a t i o n sa r e r e p o r t e d .

2 . C a s e s e t - u pT h e s i m u l a t io n r e s e a r c h w a s c o n d u c t e d f o r a n

o f f ic e r o o m a s i l l u s t r a t e d i n F ig . l ( a ) , 4 . 5 m l o n g ,2 . 7 m h i g h a n d 4 m w i d e . T h e f a c a d e h a s a g l a z i n g

a r e a o f a l m o s t t h e w h o l e w i d t h a n d a h e i g h t o f1 .5 m . T h e l o w e r a n d u p p e r p a r t o f t h e g l a z i n g c a nb e o p e n e d s e p a r a t e l y , e a c h w i t h a m a x i m u m o p e n i n go f 0 .5 m i n h e i g h t . T h i s c o n f i g u r a t i o n o f t h e r o o mi s s i m i l a r t o t h e t e s t c e l l r e p o r t e d i n r e f s . 9 a n d1 0 . It i s a s s u m e d t h a t t h e r e a r e t w o o f fi c e w o r k e r sa n d t w o c o m p u t e r t e r m i n a l s p r e s e n t i n t h e r o o m .T a k i n g i n t o a c c o u n t l i g h t i n g a n d s o l a r r a d i a t i o n ,t h e o v e r a l l i n t e r n a l h e a t i n th e p r e s e n t s i t u a t i o n i sa s s u m e d t o b e 4 5 W / m e f l oo r a r e a . F o r s i m p li c i t y ,t h e w h o l e s i t u a t i o n i s s i m p l i f i e d in t o a t w o - d i m e n -s i o n a l i s s u e, a s i l l u s t r a te d i n F i g. l ( b ) . T h e t h e r m a le f f e ct o f t h e o c c u p a n t s a n d e l e c t r ic a p p l i a n c e s a r el u m p e d t o g e t h e r a n d r e p r e s e n t e d b y a r e c t a n g u l a rb l o c k a g e , w i t h 2 0 0 W c o n v e c t i v e h e a t . S in c e t h e2 - D s im p l i f ic a t i on m e a n s t h a t t h e w i d t h c o n s i d e r e di s o n e m e t r e , t h e 2 0 0 W i n t e rn a l h e a t c o r r e s p o n d st o 4 5 W / m e f l o o r a r e a .

S i x d i f f e r e n t s i t u a t i o n s a r e s i m u l a t e d a n d a n a l y z e d .T h e d i f f e r e n c e s b e t w e e n t h e c a s e s a r e t h e o u t d o o rt e m p e r a t u r e s , w i n d o w o p e n i n g s a n d in t e r na l c o o li n gs y s t e m s . C a s e 1 t o c a s e 3 a re i n t e n d e d t o c o m p a r et h e d i f f e r e n c e s a t d i ff e re n t o u t d o o r t e m p e r a t u r e s .C a s e 4 t o c a s e 6 a re i n t e n d e d t o c o m p a r e t h ep e r f o r m a n c e s o f d i f fe r e n t i n d o o r c o o l i n g d e v i c e s a th i g h o u t d o o r t e m p e r a t u r e s . I n c a s e 4 , a c o o l in gr a d i a t o r w i t h a c o o l i n g c a p a c i t y o f 1 0 0 W i s p l a c e db e l o w t h e w i n d o w . I n c a s e 5 a n d c a s e 6 , t h e c e i l in gi s a s s u m e d t o b e c o o l e d o r p a r t l y c o o le d , w i t h ac o o l i n g c a p a c i t y o f 8 0 W a n d 3 7 W r e s p e c t i v e l y .T h e d e t a i l s a r e g i v e n in T a b l e 1 . I n s u m m a r y , t h e s ec a s e s m a y r e p r e s e n t a r o o m w i th m o d e r a t e l y h ig hi n t e r n a l h e a t s i t u a t e d i n a m o d e r a t e c l i m a t e , a n dt h e o u t d o o r a i r t e m p e r a t u r e s c o n s i d e r e d a r e p o s s i b lef o r f r e e c o o l i n g .

1 Lower Opening / //, , - //

(a )~g. 1

(b)Sketch of the simulation cases. (a) Configurations of the room. (b) 2-dimensional simplification.


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TABLE 1. Summary of the simulation cases67

Case no. Case descri ption Opening size (m)Upper Lower

Temperatures (C)Outdoor Wall

Simulation resultsVentilationrate(ach)

Ventilatedheat(w)

Moderate outdoor temperatur e 0.5Low outdoor temperature 0.05High outdoor temperature 0.5With a cooling radiator (100 W) 0.5With a cooling ceiling (80 W) 0.5With a partly cooled ceiling (37 W) 0.5

0.5 20 220.03 15 220.5 25 280.5 25 250.5 25 250.5 25 25

13 2004 170

11 21221 13423 12024 147

3 . M a t h e m a t i c a l f o r m u l a t i o n a n d m e t h o d o fs o l u t i o n

3 . 1 . A i r f l o w m o d e l

3 .1 .1 . T h e t u r b u l e n c e m o d e lNumerical simulation of the airflow and temper-ature dis tribution in the roo m involves the numericalsolution of the mass conservation equation (con-tinuity), momentum transport equations, and theene rgy trans por t eq uation [ 13 [. One special difficultyof the solution of the equations comes from thefact that the flow encoun tered in rooms is turbulent,i.e., the velocity and temperature at a given pointalways fluctuate against time at rat her high fr equency[14, 15]. Therefore, certain turbulence models aredeveloped for the purpose of the numerical solution.In recent years, they have been used for numericalpredictio n of airflows in rooms. Encourag ing results,reviewed by Whittle (1986) and Nielson (1989),have been achieved. Among the models, the standar dk - e turbulen ce model [ 16 ] proves to be economi callyapplicable and acceptable in prediction accuracyfor engineering purposes. It should be mentionedthat T sutsumi [ 17 ] has us ed the large eddy simulation(LES) turbulence model to simulate the naturalconvection through window openings in a room.However, tremendous computer time and memoriesare needed for a simulation. In our study, thestandard k - e turbulence model is used.In this model, two extra transport equations, inaddition to the trans port equations mentioned above,the turbulent kinetic energy (k) equation and theturbulence energy dissipation rate (e) equation willalso be solved. These equations are:

~u i =0 (1)Ox~

~u~ _ 1 ~p ___~ [uj ~x~ p ~x i + ~x j L(Vt+ vl) ~ ] + t~(To- T)gi

(2)-H ~ ~'t +u~ ~x~ ~x j (3)

0 _0 + ul + +

Oui u t ~ ( T - To) -- -e +/ 3 gi (4)Ox j (rH Ox i ( o u I Uyoxy ~XyL\O-2 ~ ~ k ~ ~ ]

~u___ e2 e " t O (T- To) a x j - C 2 - ~ + C 3 ~ [ 3 ~ . - - O x j gy (5)where the turbulent viscosity is given by:,~ = C, k ~/e (6)where the emp~ic~ cons~ts ~e: a~= 1.0, ~,= 1.3,~ = 0.9, C~ = 1.44, C~ = 1.92, C~ = 1.44 ~d C. =0 .0 9.With the st~d~d k - e t~b~ence model, speci~bo ~d ~ conditions have to be specked to t~ e ~toac co st the ~iction effect ~d heat tr~ sf er ~om asolid w~l. In the pro gr ~ PHOENICS, the lo g ~i t ~cw~l ~c t io n is used [16]. It must be noted that theconvection heat transfer thus c~ c~ ate d ~ dependon the dis~ ce of ~e ~s t ~d-n ode f rom the w~,~d ~erefore, the ~s t gid-node dis~nce from thew~l needs to be op t~ ed . Accord~g to Re ~ e t a l .[18], the ~c ti on ~ d heat tr ~s fe r from ~ e wM1 thuspredicted ~e ~ good agee ment ~th meas~ements.For convective heat ~om the ~temM heat so~ce,~e d fl ~ b o~ d~ conditions ~e set for the a~acenta~. It is ~s ~e d that 80 W ~e convected ~t o the


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68a i r f r o m t h e t o p a n d 6 0 W f r o m e a c h o f th e t w ov e r t i c a l s i d e s o f t h e b l o c k .

3 .1 .2 . M o d e l o f t h e o p e n i n g sT h e c a l c u l a t i o n s a r e r e s t r i c t e d t o t h e d o m a i n i n s i d e

t h e r o o m . T h e i n f l u en c e o f t h e o u t d o o r c o n d i t i o n so n t h e i n d o o r c l i m a t e is r e p r e s e n t e d b y a n a p p r o -p r i a te b o u n d a r y c o n d i t i o n a t t h e o p e n i n g s . I n t h ep r e s e n t s i m u l a t io n s , o n l y t h e i n f l u e n c e o f t h e i n d o o ra n d o u t d o o r t e m p e r a t u r e d i f f er e n c e is in v e s t ig a t e d ,t h e r e f o r e t h e b o u n d a r y c o n d i t i o n w il l r e f l e c t t h i sn a t u r e . I t m u s t b e n o t e d t h a t , i n t h e m o m e n t u me q u a t i o n ( e q n . ( 2 ) ) , t h e p r e s s u r e p o n l y s t a n d s f o rt h e r e l a t iv e p r e s s u r e d u e t o t h e n a t u r e o f v e l o c i t yv a r i a t io n , a n d t h a t t h e g r a v i t y e f fe c t i s c o m b i n e di n t h e b u o y a n c y t e r m f l ( T o - T ) g i in t h e s a m e e q u a -t i o n [ 1 9 ]. T h e r e f o r e , t h e o u t s i d e p r e s s u r e s n e a r t h et w o o p e n i n g s a r e a s s u m e d t o b e t h e sa m e a n d e q u a lt o t h e a t m o s p h e r i c p r e s s u r e P o = 0 , i .e ., th e v a r i a t i o no f t h e a b s o l u t e s t a t ic p r e s s u r e d u e t o g r a v i t y a t t h ed i f f e r e n t h e i g h t i s ( a n d m u s t b e ) o m i t t e d f o r th eb o u n d a r y c o n d i t i o n s a t t h e o p e n i n g s . F u r t h e r m o r e ,i n t h e l o w e r o p e n i n g , w h e r e i n f lo w is e x p e c t e d , t h es t a g n a t io n p r e s s u r e o f t h e c o m p u t a t i o n g r i d - n o d e st h e r e is a s s u m e d t o b e e q u a l to t h e a t m o s p h e r i cp r e s s u r e , i . e . ,- - + P i = P 0 ( 7)2a n d t h e t e m p e r a t u r e o f t h e i n f lo w a ir is o u t d o o rt e m p e r a t u r e ; w h i l e t h e s t a ti c p r e s s u r e a t t h e h i g h e ro p e n i n g , w h e r e o u t f lo w is e x p e c t e d , is a s s u m e d t ob e e q u a l t o t h e a t m o s p h e r i c p r e s s u r e P o . T h i s b o u n d -a r y s p e c i f i c a t io n i s b a s e d o n t h e B e r n o u l l i e q u a t i o n ,a n d f r i c t i o n a t t h e o p e n i n g s i s n e g l e c t e d . D e t a i lsa b o u t h o w t h i s is d o n e i n t h e n u m e r i c a l s c h e m e sc a n b e f o u n d i n r e f . 2 0 .3 .2 . N u m e r i c a l s c h e m e s a n d a l g o r i t h m s f o rs o l u t i o n

T h e g o v e r n i n g d i f f e r e n t i a l e q u a t i o n s a r e d i s c r e -t i z e d b y f i n i te - v o l u m e m e t h o d ; u p w a r d d i f f e r e n c i n gi s u s e d t o r e f l e c t t h e p h y s i c a l n a t u r e t h a t c o n v e c t i o nis a n a s y m m e t r i c p h e n o m e n o n [ 1 3, 2 1 ]. T h e st ag -g e r e d g r i d s a r e u s e d t o l o c a t e t h e d i s c r e t i z e d g r id -n o d e s f o r v e l o c i t y c o m p o n e n t s , e n t h a l p y a n d p r e s-s u r e s, w h i c h i s k n o w n a s t h e S I M P L E p r o c e d u r e .I n P H O E N I C S , th e S I M P L E m e t h o d i s e n h a n c e d a n da n e x t r a e q u a t i o n i s s o l v e d f o r th e e v o l u t i o n o fp r e s s u r e [ 2 2 ].3 .3 . M o d e l f o r t h e a n a l y s i s o f t h e r m a l c o m f o r ti n r o o m sT h e r m a l c o m f o r t is d e fi n e d as " t h a t c o n d i t io n o fm i n d i n w h i c h s a t i s fa c t i o n i s e x p r e s s e d w i t h th e

t h e r m a l e n v i r o n m e n t " . T h e r e f o r e , b o t h t h e r m a l e n -v i r o n m e n t a n d p e r s o n a l v a r i a b l e s in f l ue n c e t h e r m a lr e s p o n s e a n d c o m f o r t . In m o d e r n o f fi c es , t h e o c -c u p a n t s t e n d t o b e i n a m o d e r a t e a c t iv i t y l ev e l. Itw a s f o u n d t h a t p e r s o n s w i t h l o w e r a c t i v i t y l e v e l sa r e s e n s i ti v e to d r a u g h t s [ 2 3 [ , a n u n d e s i r e d l o c a lc o o l in g o f t h e h u m a n b o d y c a u s e d b y a ir m o v e m e n t[ 2 4 , 2 5 ] .

F a n g e r e t a l . [ 2 6 ] d e v e l o p e d a m a t h e m a t i c a l m o d e lt o q u a n t i f y t h e d r a u g h t r i s k in t e r m s o f t h e p e r -c e n t a g e o f d i ss a t is f ie d p e o p l e . I n th i s m o d e l , t h ep e r c e n t a g e d i s s a t i s f i e d p e o p l e d u e t o d r a u g h t s ,P D ( % ) , i s c a l c u l a t e d f r o mP D = ( 3 4 - T ~ ) ( V -O . O 5 ) 6 2( 3 .1 4 + O . 37 V I) ( 8 )f o r V < 0 . 0 5 m / s in s e r t V = 0 . 0 5 m / s, a n d f o r P D > 1 0 0l e t P D = 1 0 0 , w h e r e T a i s t h e l o c a l a i r t e m p e r a t u r e( C ), V i s t h e m e a n v e l o c i t y ( m / s ) , a n d I is t h et u r b u l e n c e i n t e n s i t y (% ) , w h i c h i s d e f i n e d a s t h ev e l o c i t y f lu c t u a t i o n o v e r t h e m e a n v e l o c i t y . T h et u r b u l e n t i n t e n s i t y c a n b e c a l c u l a t e d f r o mI = 1 0 0 ( 2 k ) 5 / V ( 9 )T h e v a l u e s o f Ta , V a n d k c a n b e o b t a i n e d f r o mt h e a i r f l o w c a l c u l a t i o n , a n d t h e r e f o r e , t h e P D d i s -t r i b u t i o n c a n b e c a l c u l a t e d .

I n m o s t c a s e s i n b u i l d in g s , t h e a i r t e m p e r a t u r en o r m a l l y i n c r e a s e s w i t h h e i g h t a b o v e t h e f l o o r . I ft h e g r a d i e n t i s s u f f i c i e n t l y l a r g e , l o c a l w a r m d i s-c o m f o r t c a n o c c u r a t t h e h e a d a n d / o r c o l d d i s c o m f o r tc a n o c c u r a t t h e f e et , a l t h o u g h t h e b o d y a s a w h o l ei s t h e r m a l l y ' n e u t r a l ' . T h e f e w e x p e r i m e n t a l i n v e s -t i g a ti o n s t h a t h a v e b e e n c o n d u c t e d t o e x a m i n e t h ei n f l u e n c e o f t h e v e r t i c a l t e m p e r a t u r e d i f f e r e n c e o nh u m a n c o m f o r t a re r e v i e w e d i n t h e A SH R A E h a n d -b o o k [ 2 7] . It w a s f o u n d t h a t p e o p l e a r e m o r es e n s i t iv e t o t h e p o s i ti v e t e m p e r a t u r e d i f f e r e n c e - -h i g h e r a b o v e a n d l o w e r b e l o w - a n d l e ss s e n s i t iv et o th e n e g a t i v e v e r t ic a l t e m p e r a t u r e d i f f e r e n c e s. I nt h e r e s e a r c h c o n d u c t e d b y O l e se n e t a l . [ 2 8 ] , s e a t e ds u b j e c t s in th e i r p r e f e r r e d a v e r a g e t e m p e r a t u r e sw e r e s u b j e c t e d t o v e r t ic a l t e m p e r a t u r e d i f f e re n c e so f d i f f e r e n t m a g n i t u d e . I t w a s f o u n d t h a t w h e n t h et e m p e r a t u r e d i f f er e n c e is la r g e r t h a n 3 C b e t w e e nh e a d ( 1 .1 m a b o v e th e f l o o r ) a n d a n k l e s ( 0 .1 ma b o v e t h e f l o o r ) , t h e p e r c e n t a g e o f d i s sa t is f i ed p e o p l ei n c r e a s e s d r a s t i c a ll y . I n t h e I S O s t a n d a r d [ 2 9 ] , iti s r e c o m m e n d e d t h a t th i s v e r t ic a l t e m p e r a t u r e d if -f e r e n c e b e l e s s t h a n 3 C .

I n t h e p r e s e n t s t u d y , e q n . ( 9 ) w il l b e u s e d t oe v a l u a t e t h e d r a u g h t r i s k s in t h e o p e n - w i n d o w s it -u a t i o n s i n v e s t i g a t e d . S i n c e t h e P D i n d e x d o e s n o tt a k e i n t o a c c o u n t t h e i n fl u e n c e o f t h e t e m p e r a t u r es t r a t i f i c a ti o n , t h e o v e r a l l t h e r m a l c o m f o r t w i ll a l s ob e a n a l y s e d f r o m t h e t e m p e r a t u r e s t r a t i f i c at io n s .


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694 . R e s u l t s a n d d i s c u s s io n s

The simulated ventilation rates and the heat car dedaway by the ventilated air of the six cases are listedin Table 1. The temperature stratifications of allthe cases are illustrated in Fig. 2, in which thetemperatures in the section I-I indicated in Fig. 1are plotted against the height. The graphical formsof velocity vectors, i sotherms (contou rs of tem-perature), turbulent kinetic energies and the per-centage of dissatisfied people due to draught areillustrated in Figs. 3-8.Case 1

Case 1 is to simulate the situation when theoutdoor temperature is moderate . The outdoor airtemperature is assumed to be 20 C. In reality, mostpeople would open their windows to welcome thismild, fresh air. Correspondingly, the simulated re-sults are also promising. With the two windows fullyopen, a ventilation rate as high as 13 ach is achieved.The average air temperature in the occupied zoneis approximately 21 C (Fig. 3(c)), while the tem-peratur e difference between the heights 0.1 m and1.1 m is less than 0.5 C, as illustrated in Fig. 2.In the occupied zone, the air velocities are lowerthan 0.1 m/s (Fig. 3(a)), and the turbulent kineticener gy (k) is lower than 10 -4 J/kg (Fig. 3(b)). Thedraught risk, calculated from eqn. (9) is illustratedin Fig. 3(d), which shows that, in most of the regionin the room , the PD value is nearly zero. It indicatesthat there is little risk of draught.

Looking at the flow patterns illustrated in Fig.3(a), it is clear that the thermal plume formedaround the internal heat source plays a dominantrole. The entrainment of the thermal plume produc es

[ ~- - ?2 . 5 ~ [ ]C a ~ 4 [ ]

[]2 C a s e 5~ []~ ~ [ ]

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1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5Temperature( o C)F ~ . 2 . Y a ~ a t ~ o n s o f ~ e a ~ t e m p e r a t u r e s v s , h e L O t L ~

the recirculation flows in the upper space of theroom. Similar to the flows in a displacement ven-tilation situation [3[, the recirculation flows appearabove a certain height, at which the entrained flowrate is equal to the su pplie d flow rate from below,and this height depends on the supplied flow rate.In this case, it can be seen from Fig. 3(a) that partof the fresh air is entrained into the hot plumedirectly, while the o the r part ten ds to flow downward.The overall flow pattern is thus formed.Case 2

Now that it has been shown that open-windowventilation has a positive effect in every aspectconcerned with comfort when the outdoor tem-perature is moderate, Case 2 is to simulate thesituation of opening the windows at a relativelylower outdoo r temperature, at 15 C in this case.The lower and upper openings are assumed to be30 mm and 50 nun wide slots, respectively.

A ventilation rate of 4 ach is obtained, at whichthe average air temperature in the occupied zoneranges from 20 to 24 C, as illustrated in Fig. 4(c).The temperature difference between the height 0.1m and 1.1 m is as large as 3.2 C, which is greaterthan the rec omm end ed value 3 C [29]. The airvelocity near the lower opening is about 0.3 m/s(Fig. 4(a)), and the generated turbulence is muchhigher than in case 1. The maxi mum value o f k isabou t 2 10 -~ J/kg (Fig. 4Co)). Conseque ntly, itcan be seen from Fig. 4(d) that the local PD dueto draught near the floor is rather high, whichindicates that occupants may feel too cold at theirankles and/or knees.

The flow pat ter n illustrated in Fig. 4(a) showsthat the fresh air comes downward towards the floor

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6/11

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F i g . 3 . S i m u l a t e d f i e l d d i s t r i b u t i o n s o f c a s e 1 . ( a ) V e l o c i t yv e c t o r s . ( b ) C o n t o u r s o f k ( 1 0 - s J / k g ) . ( c ) I s o t h e r r a s ( C ) . ( d )P e r c e n t a g e d i s s a ti s f i ed p e o p l e ( % ) d u e t o d r a u g h t .

2 5

F i g . 4 . S i r a u l a t e d f i e l d d i s t r i b u t i o n s o f c a s e 2 . ( a ) V e l o c i t yv e c t o r s . ( b ) C o n t o u r s o f k ( 1 0 - ~ J / k g ) . ( c ) I s o t h e r m s ( C ) . ( d )P e r c e n t a g e d i s s at i s fi e d p e o p l e ( % ) d u e to d r a u g h t .


7/11

i m m e d i a t e l y a f t e r a d m i t t e d , b e c a u s e o f i ts l o w t e m -p e r a t u r e . T h i s p h e n o m e n o n i s r a t h e r d i f fe r e n t f r o mt h a t i n c a s e 1 (F i g . 3 ( a ) ) . I t i s b e c a u s e o f t h i sc h a r a c t e r i s t i c o f t h e f lo w th a t t h e t e m p e r a t u r e s t r at -i f i c a ti o n is m o r e s e v e r e , a n d w o r s e f r o m t h e p o i n to f v i e w o f t h e r m a l c o m f o r t . T o a v o i d t h is , o n ep o s s i b i l i t y is t o r a i se t h e t e m p e r a t u r e o f t h e o u t d o o ra i r i n o n e w a y o r a n o t h e r b e f o r e i t i s a d m i t t e d i n tot h e o c c u p i e d s p a c e a n d a l s o to i n c r e a s e t h e a i r f l owr a te . T h is m a y i n d i ca t e t h a t t h e m i n i m u m t e m p e r -a t u r e o f th e o u t d o o r a i r t h a t c a n b e u s e d f o r f r e ec o o l i n g s i m p l y t h r o u g h n a t u r a l v e n t i l a t i o n i s l i m i t e db y , a m o n g o t h e r t h in g s , t h e r m a l c o m f o r t re q u i r e -m e n t s .C a s e 3

T h i s c a s e s i m u l a t e s a ' s u m m e r ' s i t ua t i on : t h eo u t d o o r a i r t e m p e r a t u r e i s 2 5 C a n d t h e i n t e r n a lw a l l s u r f a c e t e m p e r a t u r e is a s s u m e d t o b e 2 8 C.C o m p a r e d w i t h c as e 1 , t h e i n d o o r - o u t d o o r t e m -p e r a t u r e d i f f e r e n c e i s 3 K i n s t e a d o f 2 K , w h i l e a l lt h e o t h e r c o n d i t i o n s a r e t h e s a m e . T h e r e f o r e , t h es i m u l a t e d I l o w p a t t e r n , t u r b u l e n t k i n e t i c e n e r g yd i s t r i b u t i o n ( F i g . 5 ( a ) a n d ( b ) ) , a s w e l l a s t h et e m p e r a t u r e s t r a t i f ic a t i o n ( F i g . 2 ) a r e s i m i l a r t ot h o s e i n c a s e 1 , a n d o n l y t h e a v e r a g e t e m p e r a t u r el e v e l is h ig h e r . T h e v e n t i l a t i o n r a t e i s 1 1 a c h , a n dt h e a v e r a g e a i r t e m p e r a t u r e i n t h e o c c u p i e d z o n ei s a b o u t 2 6 . 5 C. T h e t e m p e r a t u r e d i f f e re n c e b e t w e e nt h e h e i g h t s 0 . 1 m a n d 1 .1 m i s l e s s t h a n 0 . 5 C .S i n c e t h e a ir t e m p e r a t u r e i s r a t h e r h i g h , t h e P Dd u e t o d r a u g h t i s v e r y l o w .

H o w e v e r , i t i s p o s s i b l e t h a t i t i s t o o w a r m i n t h er o o m i f t h e r a d i a n t e n v i r o n m e n t i s t a k e n i n to a c -c o u n t . T h e r e f o r e , t h e f o l l o w i n g s i m u l a t i o n c a s e s ,c a s e s 4 - 6 , a r e s e t u p t o i n v e s t i g a te t h e p o s s i b i l i ti e so f a u x i l ia r y i n d o o r c o o l i ng c o m b i n e d w i t h o p e n -w i n d o w v e n t i l a t i o n .C a s e 4

A c o n v e c t i v e c o o l i n g r a d i a t o r w i t h a c o o l i n g c a -p a c i t y o f 1 0 0 W i s p l a c e d b e l o w t h e w i n d o w . T h er a d i a n t e f f e c t o f t h e r a d i a t o r i s t a k e n i n t o c o n s i d -e r a t i o n b y s e t t i n g t h e w a l l i n t e r na l s u r f a c e t e m -p e r a t u r e t o 2 5 C .

T h e f l o w p a t t e r n i s r a t h e r d i f f e r e n t in t h i s e a s e( F i g. 6 ( a ) ) . A s h o r t - c i r c u i t o c c u r s f o r t h e v e n t i l a t e df lo w . A l m o s t a l l th e f r e s h a i r i s e n t r a i n e d i n t o t h eh o t p l u m e d i r e c t l y , a n d t h e n c i r c u l a t e d t o t h e u p p e ro p e n i n g i m m e d i a t e l y . D u e t o t h i s s h o r t - c ir c u i t e f fe c t ,t h e v e n t i l a t i o n r a t e i s r a t h e r h i g h - - 2 1 a e h , a n d1 3 4 W o f h e a t , n e a r l y 7 0 % o f t h e t o t a l i n t e r n a lh e a t , a r e c a r r i e d a w a y b y v e n t i l a t i o n .

T h e l o w e r z o n e o f t h e r o o m i s d o m i n a t e d b y t h er e e i r e u l a t i o n f l o w c a u s e d b y t h e c o o l i n g r a d i a t o r

71

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(d)Fig. 5. Simulated field distributions of case 3. (a) Velocityvectors . (b) Contours o f k(10 -3 J /kg) . (c) I so the rms (C) . (d)Percentage dissatisfied people (%) due to draught.


8/11

7 2

# v v = = v v = ~_ ~ ~ .' : : : : -. . . . ., . . . . . . : > . = , a ~ : : : :~ . . . . . - 4 - - ~ % ~ % ~ , " :" ~ . . . . _ ~ ~ [ % . ~ N % ~ ~ "

. } ~ ~ , - ~/ ~ ~~ ~ ~ ~ /

',~ ~ . ~ . ~ . _ ~ . ~ - ' - ~ ~~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ , ~' : 0 1 2 0 m / s .(a )

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(d )~ . 6 . S ~ a t e d f i e l d ~ b u t i o ~ o f c ~ e 4 . ( a ) g e l o c i Wv e c t o r s . ~ ) e o n t o ~ o f ~ ( I 0 - a J N g ) . ( e ) I s o ~ e ~ ( ~ C) . ( d )P e r e e n ~ g e ~ s a ~ f i e d ~ e o ~ l e ( % ) d u e t o ~ a u ~ t .

a n d i s n o t m u c h a f f e c t e d b y t h e v e n t i la t i o n a ir . D u et o t h e b u o y a n c y e f f e c t, th e c o o l e d a i r f r o m t h ec o o l i n g r a d i a t o r t e n d s t o t l o w in s u c h a w a y t h a ti t s t i c k s t o t h e f l o o r . A s a r e s u lt , r a t h e r s e v e r et e m p e r a t u r e s t r a t i f i c a t i o n e x i s t s : t h e t e m p e r a t u r ed i f f e r e n c e b e t w e e n t h e h e i g h t s 0 .1 m a n d 1 .1 m i sn e a r l y 2 . 5 C ( F i g . 2 ) . T h o u g h t h i s v a l u e is l o w e rt h a n 3 C , t h i s s t r a t i f i c a t i o n w il l b e e n h a n c e d b yt h e r a d i a n t e f f e c t o f t h e r a d i a t o r [ 2 7 , 3 0 ]. T h e r e f o r e ,a c o o l i n g r a d i a t o r l o c a te d b e l o w t h e w i n d o w m a yn o t b e i d e a l f o r t h e r m a l c o m f o r t . I t s h o u l d b e n o t e dt h a t t h e t u r b u l e n t k i n e t i c e n e r g y n e a r t h e f l o o r i sa r o u n d 0 . 6 1 0 - a J /k g ( F ig . 6 ( b ) ) , w h i c h , a c c o r d i n gt o e q n . ( 9 ) , w il l c o n t r i b u t e t o t h e d i s c o m f o r t d u et o d r a u g h t . O n t h e o t h e r h a n d , t h e c o o l in g e n e r g yf r o m t h e c o o l i n g r a d i a t o r i s w e l l p r e s e r v e d i n t h el o w e r p a r t o f th e r o o m , a n d t h e v e n t i l a t io n d o e sn o t c a u s e m u c h l o s s o f t h is e n e r g y . T h e r e f o r e , th ee n e r g y e f f i c i e n c y c a n b e s a t i s fa c t o r i l y h i g h .Case 5

A s a n a l t e r n a t i v e , t h e w h o l e c e i l i n g i s a s s u m e dt o b e ' li g h tl y ' c o o l e d w i t h a c o n v e c t i v e c o o l i n gc a p a c i t y o f a p p r o x i m a t e l y 1 8 W / m 2, w h i c h i s e q u i v -a l e n t t o t h e a s s u m p t i o n t h a t t h e t e m p e r a t u r e d if -f e r e n c e i s a b o u t 5 C a n d t h e c o n v e c t i v e h e a t t r a n s f e rc o e f f i c i e n t a c = 4 W / m 2 K . A s i n c a s e 4 , t h e r a d i a n te f f e c t i s t a k e n i n t o a c c o u n t b y s e t t i n g t h e w a l ls u r f a c e t e m p e r a t u r e t o 2 5 C .

T h e s i m u l a t e d f l o w p a t t e r n i s i l l u st r a t e d i n F ig .7 ( a ) . A s c a n b e s e e n , t w o m a i n r e c i r c u l a t i o n s t r e a m sa r e f o r m e d : o n e is t h e c o o l e d d o w n w a r d s t r e a ma l o n g t h e r e a r w a l l f r o m t h e c e i l in g , w h i c h i s s u b -s e q u e n t l y e n t r a i n e d b y t h e t h e r m a l p l u m e ; t h e o t h e ro n e i s th e v e n t i l a te d a i r s t r ea m . T h e c o n s e q u e n tt e m p e r a t u r e d i s tr i b u ti o n i s r a t h e r u n i f o r m a n d t h et e m p e r a t u r e r a n g e s b e t w e e n 2 5 C a n d 2 5 . 5 C i nt h e o c c u p i e d z o n e ( Fi g. 7 ( c ) ) . T h e t e m p e r a t u r es t r a t if i c a t io n i s s m a l l. T h e r e f o r e , t h e t e m p e r a t u r ed i s t r i b u t i o n i s i d e a l f o r t h e r m a l c o m f o r t . H o w e v e r ,t h e t u r b u l e n t k i n e t i c e n e r g y is r a t h e r h ig h , r a n g i n gf r o m 0 . 1 1 0 - a t o 2 .1 1 0 - a J / k g i n t h e o c c u p i e dz o n e ( F ig . 7 ( b ) ) . T h e P D d u e t o d r a u g h t i s s l ig h t l yh i g h a l o n g t h e r e a r w a l l (F i g . 7 ( d ) ) . T h i s m a y s u g g e s tt h a t t h e c e i li n g s h o u l d b e l i g h t l y c o o l e d t o a v o i ds t r o n g d o w n w a r d c o n v e c t i v e fl ow s .

S t i l l , a h i g h v e n t i l a t i o n r a t e c a n b e m a i n t a i n e d ,a n d t h e v e n t i l a t i o n a i r c a r r i e s a w a y 6 0 % o f t h ei n t e r n a l h e a t . T h e r e i s a f e a r t h a t o p e n i n g t h e w i n d o ww h i l e t h e c e i l i n g is c o o l e d m a y l o s e e n e r g y . I n t h ep r e s e n t s i m u l a t i o n , th i s d o e s n o t o c c u r s in c e t h e r eis a l w a y s a th e r m a l p l u m e i n t h e r o o m . H o w e v e r ,i t c a n b e s e e n t h a t t h e t h e r m a l p l u m e i s s l ig h t l yc o o l e d b y t h e c e il in g b e f o r e b e i n g d i s c h a r g e d ( F ig .7 ( c ) ) . I f t h e i n t e r n a l h e a t s o u r c e i s l o c a t e d f u r t h e r


9/11

7 3

: : : , : . - : :| ] ; : . : . : : : : : : : : : : :~.~ ~ : , . ~ ~ ~ Y x ~ ~ x .~ ~ ' , / ~ ~ ~ N ~ ~ ~~ ~ :, , , / l ~ i . - - ~~' '. . . . ~ / / / ~ 1 ' ~~ ' , ~ " " ' ~ ~ i ~ I ' - ~~., ~ - . . . . . ,~ , . ~~ ' ~ ~ l I ~ ~ ~ / ~ . ~ d~ ~ - _ . , /~ ~ " ~ . ~ ~ . . . . . . I , , ~~ ~ : - - . . , . . . . . . ~ , ~

~ ~ ~ ~ _ ~ ~ ~ ~ ~ ~

. : 0 . 2 0 m / s .(a)

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(d)P i g . 7 . S i m u l a t e d f i e l d d i s t r i b u t i o n s o f e a s e g . ( a ) V e l o e i Wvectors. (b) Contours of k ( l O - a J / k g ) . ( e ) Isotherms (e). (d)Percentage dissatisfied people (%) due to draught.

away from the window, the discharged air wouldbe fur ther cooled. This cooling of the exhau st airis obviously a waste of energy.Case 6

Different from case 5, only the inner half of theceiling is assumed to be cooled, with a coolingcapacity of app rox ima te 16 W/m e (37 W in total).With this small cooling, the temperatures (Fig. 8(c))can still be much lower in comparison with case3. The flow patterns, turbulent kinetic energy (Fig.8(a) and (b)) are about the same as in case 5. ThePD due to the draught from the ceiling is muchreduced (Fig. 8(d)). The temperature stratificationis small (Fig. 2). Most significant is that the co olingenergy needed is much reduced, since nearly 75%of the internal hea t is carried away by the ventilationair.

5 . C o n c l u d i n g r e m a r k sFor the room with a moderately high internal

heat, the lower and up per dual-window configurationcan give a high ventilation rate due to the buoyancyeffect alone. At moderat e o utdoo r temperatures, theresulting temperature distribution in the room isgood for thermal comfort. However, at relativelylow outdoor temperatures, the resulting verticaltempe ratur e difference can be too large for thermalcomfort, though t he average temper ature within theroom is moderate. Therefore, the comfort require-ment may limit the minimum temp eratures at whichfree cooling by natural ventilation through the dualwindow openings can function well. When indoorcooling devices are combined with the dual windowopenings, it is shown that the positio ns of the coolingsurfaces are important both for thermal comfortand for ene rgy efficiency. A cooling radiator situatedbelow the window tends to give a large verticaltempe ratur e difference in the occupied zone, whichis not desirable for thermal comfort. When the ceilingis lightly cooled, the resulting temperature distri-bution in the whole room becomes rather uniform.As far as energy efficiency is concerned, both ofthe cooling systems can be fairly good as long asthe outdoor temperature is not too high.

6 . F u r t h e r s t u d i e sThe results of the preliminary two-dimensional

simulation highlight the possibility of maximizingthe buoya ncy effect by providing dual window open-ings. It may indicate that, even during windless


10/11

(c)

. . . . . :

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. : 0 . 2 0 m / s .O)

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. 5 7 6 . 5

( d )F i g . 8 . S i m u l a t e d f i el d d i s t r i b u t i o n s o f c a s e 6 . ( a ) V e l o c i t yv e c t o r s . ( b ) C o n t o u r s o f k ( 1 0 - 3 J / k g ) . ( c ) I s o t h e r m s ( C ). ( d )P e r c e n t a g e d i s sa t i s fi e d p e o p l e ( % ) d u e t o d r a u g h t .

days, a high ventilation rate can be achieved throug hsuch a window. Though it can be expected thatwind will generally increase the natural ventilationrate, what influence wind will have on the ventilati onthrough the dual window openings will be a pointof further investigations.

N o m e n c l a t u r e

ach

C pC p ~ C I ~C2, C3giHIkPPDPiP oT

Ui, 7ZjVl~X i , X j

Avlv tP~~r~~

air exchange rate per hour in a ventilatedroom, defined as the ventilated airflowrate divided by the room volume (1/hour)specific heat of air (J/kg)empirical constants in the k - e turbulencemodelgravitational acceleration component s inith directio n (m/s e)enthalpy (J/kg)turbulent intensity (%)turbulent kinetic energy (J/kg)relative pressure of air (Pa)percentage dissatisfied people (%)relative pressure at the inlet opening(Pa)relative atmospheric pressure (Pa)temperature of air (K)air temperature (C)reference temperature (K)velocity components in ith and jth di-rections (m/s)mean velocity of air (m/s)velocit y at the inlet opening (m/s)Cartesian coordinates (m)thermal expansion coefficient of air 1/K)dissipation rate of turbulence energy (W/kg)thermal conductivity of air (W/m K)laminar viscosity of air (me/s)turbulent viscosity of airflow (me/s)density of the air (kg/m 3)turbulent Prandtl numberturbulent Schmidt number of kturbulent Schmidt number of e

R e f e r e n c e s

1 A i r c o n t a m i n a n t s , A S H R A E H a n d b o o k - - 19 85 F u n d a -m e n t a l s , C h . 11 , p . 1 1 . 9 .

2 G . W . B r u d r e t t , R e q u i r e m e n t s f o r v e n ti l a ti o n , P r o c . C I B SS y m p o s i u m N a t u r a l V e n t i l a t i o n by D e s i g n, L o n d a n, D e c.1980 , p . 1 - 7 .


11/11

753 P. Kofoed and P. V. Nielson, Thermal plu mes in ventilated

rooms -- An experimental research work, P r o c. 3 r d S e m i n a ro n A p p l i c a t i o n o f F l u i d M e c h a n i c s i n E n v i r o n m e n t a lP r o t e c t i o n 1 9 8 8 , Silesian Technical University, Gliwice, Po-land.

4 E. Skaret and H. Mathisen, Venti lati on efficiency, P r o c . I n t .S y m p o s i u m o n I n d o o r P o l l u t io n , H e a l t h a n d E n e r g y C o n-s e r v a t i o n , Massachusetts, MA, October 13-16, 1981.

5 M. Sandberg, Definition of ventilation efficiency and theefficiency of mechanical ventilation systeros, P r o c . 3 r d A I CC o nf . E n e r g y E f f t c i e n t D o m e s t i c V e n t i l a t i o n S y s t e m s f o rA c h i e v i n g A c c e p t a b l e I n d o o r A i r Q u a l i t y, September20- 23, 1982, UK, pp. 13.1- 13.22 .

6 Q. Chen, J. van der Kooi and A. Meyers, Measurement s andcomputations of ventilation efficiency and temperature ef-ficiency in a ventilated room, E n e r g y B u i l d . , 1 2 (1988)85-99.

7 J. E. Holt, Probl ems in commercial and industrial ventilation,P r o c. C I B S S y m p o s i u m N a t u r a l V e n t i l a t i a n b y D e s i gn ,D e c . , 1 9 8 0 , L o n d o n , pp. 35-44.

8 D. Etherrid ge, Domestic ventilatio n sys tem design -- changesin the wind? W a t s o n H o u s e B u l l. , 4 6 (3) (1982) 12-16.

9 A. H. C. van Paassen, Passive solar energy in intelligentbuildings, A S H R A E T r a n s . , 9 4 (1) (1988) 1289-1297.

10 P. J. Lute and A. H. C. van Paassen, Integrated controlsyst em for low energy buildings, P r oc . A S H R A E S y m p o s i u mB u i l d i n g O p e r a t i o n D y n a m i c s , L o u i s , M i s s ou r i , J u n e 9 -1 3,1990 .

11 P. V. Nielson, Progress and trends in air infiltration andventilation research, P r o c . l O t h A 1 V C C o n f ., C o v e n t r y , M rInfiltration and Ventilation Centre, Warwick, UK, 1989.

12 Q. Chen, C. A. Meyers and J. van der Kooi, Convec tive heattransfer in rooms with mixed convection, P r o c . I n t . S e m i n a ro n A i r F l o w P a t t e r n s i n V e n t i l a t e d S p a c e s , L i e g e , TheNational Fund of Scientific Research in Belgium, pp. 69-82.

13 S. V. Patank ar, C onv ecti on and diffusi on, N u m e r i c a l H e a tT r a n s f e r a n d F l u i d F l o w , McGraw-Hill, 1980, Ch. 5.

14 A. Melikov, H. Hanzawa and P. 0. Fanger, Airflow char-acteristics in the occupied zone of heated spaces withoutmechanical ventilation, A S H R A E T r a n s . , 9 4 (1988) 52-70.

15 H. Hanzawa, A. Melikov and P. 0. Fanger, Airflow char-acteristics in the o ccupied zone of ventilated spaces,ASHRAET r a n s . , 9 3 (1987) 524-539.

16 B. E. Launder and D. B. Spalding, The numerical compu tati onof turbulent flow, C o m p . M e t h o d s A p p l . M e c h . E n g . , 3(1974) 269-289.17 J. Tsutsumi, Numerical simulati on of thermal c onvec tion ina roo~n with natural ventilation caused by buoyancy, P r o c .C IB W 5 7 S y m p o s i u m o n E n e r g y M o i s t u r e a n d C l i m a t ei n B u i l d i n g s , R o t t e r d a m , N e t h e r la v w l s , S e p t ., 1 9 00 .18 U. Renz and U. Terhaag, Pred iction s of air flow patte rn ina room ventilated by an air jet -- the effect of turbulencemodel and wall function formulation, P r o c. R O O M V E N T ' 9 0 ,E ~ u j in e e ri n g A e r o - a n d T h e r m o d y n a m i c s o f V e n t i la t e dR o o m : 2 n d I n t . C o n f ., O s l o , N o r w a y , J u n e 1 3 - 1 5 , 1 9 90 .19 D. J. Tritton, Convec tion , P h y s i c a l F l u i d D y n a m i c s , Clar-endon, Oxford, 1988, 2nd edn., Ch. 14, pp. 163-165.

20 H. I. Ros ten and D. B. Spalding, T h e P H O E N I C S R e f e r e n ceM a n u a l , CHAM TR/200, Oct., 1987, Ch. 6, pp. 6.91-6.92.21 S. V. Patankar, Recent de velo pmen ts in computatio nal heattransfer, T r a n s . A S M E - - J . H e a t T r a n s f e r , 1 1 0 (1988)1037-1045.22 H. I. Rost en and D. B. Spalding , How PHOENICS opera tes,T h e P h o e n i c s B e g i n n e r ' s Guide, CHAM TR/100, Oct., 1987,Ch. 2, pp. 2.10-2.15.23 B. W. Jon es, K. Hsieh and M. Hashinag a, The eff ect of airvelocity on the thermal comfort at moderate activity levels,A S t t R A E T r a n s. , 92 (Part 2B) (1986) 761-769.24 P. O. Fanger and N. Christensen, Percepti on of draught inventilated spaces, E r g o n a m i c s , 2 9 (2) (1986) 215-235.25 D. A. McIntyre, The effect of air movement on thermalcomfort and sensation, in P. O. Fanger and O. Valbjorn(eds.), I n d o o r C l i m a t e , Danish Building Research Institute,Copenhagen, 1979, pp. 541-560.26 P. O. Fanger, A. Melikov, H. Hanzawa and J. Ring, Airturbulence and sensation of draught, E n e r g y B u i l d . , 12(1988) 21-39.27 Physiological principles, comfort, and health, ASHRAEH a n d b o o k - - 1 98 9 F u n d a m e n t a l s , Ch. 8, pp. 8.20-8.22.

28 B. W. Olesen, M. Scholer and P. O. Fanger, Vertical airtemperature differences and cond ort, in P. 0. Fanger andO. Valbjorn (ed s.), I n d o o r C l i m a t e , Danish Building ResearchInstitute, Copenhagen, 1979, pp. 561-579.

29 I n t e r n a t i o n a l S t a n d a r d I S O 7 7 30 , M o d e r a t e t h e r m a l e n -v i r o n m e n t s - - D e t e r m i n a t i o n o f t h e P M V a n d P P D i n d ic e sa n d S p e c i f i c a t i o n o f t he c o n d i t i o n s f o r t h e r m a l c o m f or t ,Ref. No. 7730-1 984( E), August, 1984, p. 5.30 Radiant heating and cooling, A S H R A E H a n d b o o k - - 1 99 1H V A C A p p l i c a t i o n s , SI edition, Ch. 48, pp. 48.4-48.5.

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