1-Room Air Distribution

8/9/2019 1-Room Air Distribution

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MSYS 4480

Air-Conditioning SystemsWinter 2015

1Satwinder Singh2/5/15


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Air Distrib tion System

! r"ose# $o %reate the "ro"er%ombination o& tem"erat re' h midityand air (e)o%ity in the o%% "ied *oneo& the %onditioned room+

, & not "ro"er)y designed' the air distrib tionsystem has the "otentia) to %om"romise the

%om&ort %onditions it was designed tomaintain+.

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$wo asi% )es

Coo)ing# Di ser se)e%tion sho )d bebased on the ratio o& the di ser sthrow to the )ength o& the areas "")ied to a%hie(e high AD!,minimi*e dra&t.3eating# Di ser-to-room t sho )d not

e %eed 1567 to minimi*estrati %ation ,minimi*e strati %ation.



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Com&ort Criteria

For Occupied zone: Air tem" maintained between :9-::67 3 maintained between 25-;0< Ma im m air motion in the o%% "ied *one

50 &"m %oo)ing 25 &"m heating

Ma im m tem"erat re gradient 1-26 %oo)ing 46 heating



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=%% "ied >one



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oom Air Distrib tionMethods

Dis")a%ement ?enti)ation @o%a)i*ed ?enti)ation

Mi ing Systems

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Con(entiona) Mi ingSystems

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$y"es o& Air !rimary Air#

$he %onditioned air dis%harged by the s "")y o t)et+ $his air "ro(ides the moti(e &or%e &or room air motion+

$ota) Air# $he mi t re o& "rimary air and entrained room air

whi%h is nder the in en%e o& s "")y o t)et%onditions+

$his is %ommon)y %onsidered to be the air within an

en(e)o"e o& 50 &"m B0+25 m/s ,or greater. (e)o%ity+ $he tem"erat re di eren%e between the tota) air andthe room air %reates b oyant e e%ts whi%h %a se %o)ds "")y air to dro" and warm air to rise+



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$hrow / Dro"

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$hrow / Dro"


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$hrow and $ermina) ?e)o%ity

$3 =W# $hrow is the distan%e &rom the %enter o& the o t)et &a%e to a "ointwhere the (e)o%ity o& the air stream is red %ed to a s"e%i ed (e)o%ity+Es a))y 150 &"m B0+:5 m/s 100 &"m B0+50 m/s 50 &"m B0+25 m/s

$hese (e)o%ities are re&erred to as termina) (e)o%ity and there&oreindi%ated as $150 B$0+:5 ' $100 B$0+50 ' $50 B$0+25 res"e%ti(e)y+

$hrow is "rimari)y a & n%tion o& mass ow and o t)et (e)o%ity andthere&ore %an be red %ed by de%reasing either o& these (a) es+



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$hrow and $ermina) ?e)o%ity



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S"read $he di(ergen%e o& the airstream in

hori*onta) or (erti%a) ")ane a&ter it)ea(es the o )et+



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$ermino)ogy = t)et/ n)et $ermina)s

Fri))e egister Di ser



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= t)et C)assi %ation

Fro " A+ = t)ets mo nted in or near the %ei)ingthat dis%harge air hori*onta))y+Fro " + = t)ets mo nted in or near the oorthat dis%harge air (erti%a))y in a non- s"reading Get+Fro " C+ = t)ets mo nted in or near the oorthat dis%harge air (erti%a))y in a s"reading Get+Fro " D+ = t)ets mo nted in or near the oor that

dis%harge air hori*onta))y+Fro " H+ = t)ets mo nted in or near the %ei)ingthat "roGe%t "rimary air (erti%a))y+

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Fro " A = t)ets

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AD! Dra&t is de ned as a )o%a)i*ed &ee)ing o&

Coo)ing or Warmth+ Dra&t is meas red abo(e or be)ow the room

tem"erat re and an air (e)o%ity o& 90 &t/min,0+15 m/s. esear%h indi%ates that a high "er%entage o&

"eo")e are %om&ortab)e when the e e%ti(edra&t tem"erat re di eren%e is between -967 B-2 6C and I2 67 BI1 6C and the air(e)o%ity is )ess than :0 &"m B0+9; m/s +



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AD! H e%ti(e Dra&t $em"erat re

HD$ = , t x - t r . J a+, V x - V r .

t x

K @o%a) Air Stream $em"erat re ,7.t

r K A(erage oom $em"erat re ,7.

V x

K )o%a) (e)o%ity ,&t/min.V

r K )o%a) (e)o%ity ,&t/min.

a K 0+0: ,7+min/&t.



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AD!ADPI is de ned as the "er%entage o& )o%ations in the o%% "ieds"a%e whi%h meet the %om&ort %riteria based on (e)o%ity andtem"erat re meas rements taLen at a gi(en n mber o& ni&orm)ydistrib ted "oints+



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7a%tors a e%ting AD!

1+ ?e)o%ity o& air at the in)et to the s "")yair di sers , oise Criteria.

2+ S "")y to oom $em"erat re Di eren%e9+ Feometry and !osition o& air s "")y

o t)et4+ !osition o& et rn Air = t)et

5+ oom Feometry;+ oom S r&a%e $em"erat re:+ nterna) 3eat So r%es



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Chara%teristi% )ength &or (ario sdi ser ty"es



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Di ser Se)e%tion1+ Determine the air ow

reN irements and room si*e2+ Se)e%t ty"e o& di ser9+ Determine oom Chara%teristi%

)ength

4+ Se)e%tion $/@ ratio &rom these)e%tion g ide tab)e

5+ Ca)% )ate the $hrow ,$.;+ Se)e%t the di ser &rom

%ata)og e that mat%hestermina) (e)o%ity o& 50&"m,0+25 m/s.

:+ Hns re other %riteria are met, oise' $ota) !ress re et%+.



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=bser(ations on AD!1+ Fenera))y' the higher the room )oad' the more diO% )t it is to a%hie(e a

high AD! +2+ A (a) e o& $/@ K 1+0 genera))y wi)) "rod %e an a%%e"tab)e AD! +9+ Some air o t)ets are better than others at a%hie(ing high AD! (a) es+

7or e am")e' a sidewa)) gri))e has a ma im m AD! (a) e o& 85' whi)e

the %ir% )ar %ei)ing di ser %an a%hie(e an AD! (a) e o& 9+4+ A wide $/@ range a))ows the designer more e ibi)ity in se)e%ting the airo t)et &or o"tim m AD! +

5+ = t)ets with a wide $/@ range are more a"")i%ab)e to ?A? systems asthey %an maintain a high AD! e(en when t rned down to )ow air(o) me+

At 20 t /h/&t2 B;9 W/m2 a %ei)ing s)ot di ser has a t rn-down ratioo& 20< whi)e maintaining an AD! o& greater than 80+ At the same%ondition the high sidewa)) gri))e has a t rn-down ratio o&a""ro imate)y 50


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$ota) !ress re Dro"

S "")y air o t)ets "rod %e# Stati% "ress re )oss

?e)o%ity "ress re )oss+



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Stati% !ress re @oss Stati% "ress re )oss is eN a)

to the di eren%e between thein)et stati% "ress re ,S!i. andthe room "ress re , s a))y

atmos"heri%.+ $he stati% "ress re )oss isde"endent on o t)etgeometry and/or &ree areaand m st be deri(ed by test+

Stati% "ress re )oss is dire%t)y"ro"ortiona) to the (o) me o&air s "")ied thro gh theo t)et+

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?e)o%ity !ress re @oss $he (e)o%ity "ress re )oss is eN a) to the (e)o%ity"ress re at the in)et ,?!i. and the room (e)o%ity"ress re ,*ero.+

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H am")e



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oise Criteria


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Example:A Mode) 520 si*e ; in+ 5 in+ s "")y gri))e o"erating at 150 %&m has beense)e%ted to s "")y a 10 &t 15 &t room as shown+ What is the best de e%tionsetting o& the di ser b)ades i& %onditioned %oo) air is s "")iedP


7or 50 &"m throw#06 de e%tion# 22 +:5K 1:226 de e%tion# 18 +:5K 14456 de e%tion# 11 +

:5K 8

226 de e%tion"ro(ides thebest %o(erage andwo )d bethe o"tim mse)e%tion+

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Ded %tions1+ $he sN are ")aN e and sN are %one di ser are an e %e))ent

%hoi%e &or a%o sti%a))y sensiti(e a"")i%ations or when highair (o) mes "er o t)et are desired+ $his is d e to theaerodynami% %ones and high &ree area+

2+ !er&orated di sers tend to be noisier than other a(ai)ab)emode)s at the same air (o) me+ $his is d e to the restri%ted&ree area o& the "er&orated &a%e and "attern de e%tors inthe air stream+

9+ $here is a &air)y )arge (ariation in generated noise )e(e)s'e(en between (ario s "er&orated di ser ty"es+ $he % r(ed"attern %ontro))ers o& the "er&orated % r(ed di sergenerates )ess so nd than the )ess aerodynami% ne%Lde e%tors o& the "er&orated ne%L de e%tor di ser+

4+ Se)e%ting o t)ets based on ne%L (e)o%ity is a "oor indi%ationo& a%o sti% "er&orman%e+

5+ $o ens re "redi%tab)e so nd )e(e)s it is essentia) tore&eren%e the man &a%t rers %ata)oged so nd )e(e)s &or thes"e%i ed "rod %t+

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1-Room Air Distribution

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