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EvaluAir an
Laura FRATranssolar Enekessling@trans
ABSTRACT
All too oftenplay a signifbuildings. Adevidence thacombined wimechanical sstrategy to “comfort expecompensate f
The non-goveconsumption,paper presentypical classrsystem desigparameters oenvironmentaand the Pred
The design stthermal comtemperature air with full only about 75
INTRODUC
Thermaworks of O. climate regionaturally venPMV model ventilated an
Elevatein mechanicacooling effec
uationnd El
ANKE, Dr. Wergietechnik Gmssolar.com
T
today’s builficant role indaptive comf
at extended oith elevated systems. The a“static” and ectations, it ifor higher tem
ernmental org, technical sy
nts the designroom. A conv
gn in regard of the buildinal parameters
dicted Mean V
tudies helpedmfort: A simp
and dew poinheat recovery5%. Both con
TION
al comfort staFanger, usin
ons systematintilated build
[3]. Adaptivd air conditiod air speed hally controllect of elevated
n of Cevate
Wolfgang KEmbH, Munich, G
ldings requirn this environfort models, operative temair speed coaim of this padeterministic
is about chanmperatures an
ganization BRystems and en strategy, imventional des
to achieved ng are assesss the thermal
Vote for eleva
d to develop aple decentrant. In additionry aiming on ncepts provide
andards e.g. ng the Predicc discrepanciings with theve comfort moned buildingas long been d indoor climair speed usi
omford Air
ESSLING, MGermany
re massive renmental impadeveloped o
mperature anontrolled by aper is to propc HVAC connging environd humidities
RAC is plannenergy dema
mplementationign for air cocomfort, req
sed using thel comfort of thated air speed
a hybrid systeal mechanican, ceiling fan26°C operate the same co
of ASHRAEcted Mean Voies were foune static “commodels, devegs give eviden
used in practmates. With Aing the Stand
rt Con Spee
Martin ENG
esource inputact and the sn the basis d humidity rthe occupan
opose a low-entrol systemsonmental cons.
ning a new unnd the design in buildingonditioning aquired designe dynamical he occupantsd (PMVeas) ac
em comfort deal system prns provide airtive room temomfort in term
E [1] and ISOVote (PMV) asnd, particular
mfort zones” deloped on fience that extentice as well a
ASHRAE Stadard Effective
nceptd in T
GELHARDT
t. The way wsystems and eof field studranges are ants. Adaptiveenergy, hybrids. In this conditions, espe
niversity buildgn team is ing simulation aaccording then of ventilatithermal simu is evaluated
ccording to th
esign which provides the rr movement. Cmperature anms of PMVeas.
O [2] are doms comfort indrly in warmerdefinitions baeld studies innded temperaas in the ASHandard 55-201e Temperature
ts withTropic
T
e define the energy requi
dies in tropicacceptable foe comfort typd system designtext adaptivecially the air
ding in Dhakvestigating aand analysis e static “comfion systems ulation progr
d with the Stanhe ASHRAE S
provides goodroom with teCompared tod 12 g/kg hu.
minated by thdex. Being cr zones, to exased on the sn the tropicsture and hum
HRAE Standa13, Appendixe (SET) is des
h Temcal Cl
Mun SummWOHA Archi
“comfortableired to air cocal and subtror indoor climpically can bgn method as
ve is not abor speed, to c
ka, Bangladesalternative coof thermal c
fort zone” is and energy
ram TRNSYS ndard EffectivStandard 55-2
d fresh air quempered sup conventiona
umidity ratio
he studies anarefully deve
xplain observix comfort ps, as well as
midity ranges ard 55 to offsex G, a procedscribed. The
mperedlimate
m WONG itects, Singapor
e” thermal condition and ropical climamate especiabe achieved s an alternatiout changing create comfo
sh. To reduceomfort strategcomfort conce
compared todemand. The
S 17 3D. Baseve Temperatu2013.
uality and anpply air of 2al concepts of
the energy d
nd heat balaneloped in mid
ved thermal coparameters in s comparing are acceptablet higher temdure for evaluSET can be c
d e
re
conditions cool our
ates, give ally when with less
ive design people’s
rt and to
e resource egies. The epts for a o a hybride thermal ed on six ure (SET)
excellent 20°C air f returned demand is
nce model d-latitude omfort in Fanger’s naturally
le [4]. mperatures uating the calculated
for a wrelative
Tospeed (rtemperaair and used fosimulatiimplemPredicterepresenInternet
Tothermal (-3) and-0.5 < P
THE PR
ThBRAC architectropics.a role mfans to ereinforc
TocomfortambientSingapothat forchange be used
O
RoomA
Hei
operabsides of
oppossides of
Six ce
Figure
wide range of e humidity (RHo evaluate therange: 0.15 ≤ature is calculthe four rem
or comfort evion. To be
mented in a wed Mean Votenting an occut CBE Thermo summarize:l sensation, ded compare wiPMVeas < 0.5,
ROJECT
he non-goveris particularl
cts commissioFor compari
model: Whereelevate air spce natural veno cross checkt with the SETt air temperaore’s summerr the given pair speed). T
d for comfort
Occupancy 23 pupils 1 teacher
geometry Area: 80 m² ight: 3.5 m
Doors ble, on two f the room
Windows site on two f the room
eiling fans
1 left: classro
six environmH), average ee cooling eff≤ v ≤ 3 m/s). Ilated to achie
maining paramvaluation anduseful for th
way that the e for elevatedupant contro
mal Comfort T the implemeefined as follith the analyti, which is equ
rnmental orgaly interested oned are WOson study, thever appropri
peed in the ocntilation by prk the proposeT and PMVeas
ature of 30°Cr period. The parameters thhe survey proevaluation in
oom at SOTA
mental and peelevated air spfect of elevatIn a second seve the same meters the Prd comparisonhe evaluationrequired air
d air speed (Polled fan to inTool developeented procedlows: hot (+3ical comfort uivalent to a s
anization BRin a sustain
OHA, Singapohe School Of iate, the class
ccupied zone. revailing wined design stras a short comC and an airmeasured lo
he environmeovides an add
n the tropics. M
A; right: local
ersonal parampeed (v), clotted air speed step the air spSET as beforredicted Mean [1, Appendn and designspeed to cre
PMVeas) as foncrease air sed at the Univure allows ev), warm (+2)zone model osatisfaction o
RAC is currenable buildingore, who are The Arts (SOsrooms are nThe passive
nd directions. ategy and to
mfort survey wr humidity racal air speedsnt is comfor
ditional confiMentioned w
l air speed and
meters: air tething factor (
d first the SEpeed is replacre. With this aan Vote for edix G and Bn of alternaeate the sam
or the referencspeed as requversity of Calvaluating the), slightly warof Standard 5
of 90% of the
ently planningg concept whexperienced
OTA) in Singnaturally vent
building desiAir conditionfamiliarize th
was made at Satio of 17.5 s are in the rartable (none irmation that
work on adapti
nd comfort me
emperature (T(clo) and metaT is calculateced by still aiadjusted averalevated air spB]. This proctive comfort
me perceived ce case - couluired. An exelifornia Berke different desrm (+1), neut5-2013, chapoccupants wi
g a new univhich creates in the designapore, also detilated and thign and the elned zones arehe design tea
SOTA. The clg/kg. This r
ange of 0.4 toof the occupthe proposedive comfort m
easurements,
(Tair), mean raabolic rate (med for the pair (0.15 m/s) rage air tempepeed (PMVea
cedure was t and climatcomfort - orld be determi
xemplified tooeley [5]. sign strategietral (0), slightpter 5.3.2. Coith the enviro
versity buildibest comfort
n of naturallyesigned by W
hermal comfolevation of the reduced to aam with the slassroom (Figrepresents a o 1.0 m/s (Figpants wanted d design parammodels under
top view pla
adiant tempemet). arameters andand an adjusterature, the aias) is calculatimplementede concepts tr in other wined by the siol including
es with the 7tly cool (-1),
ompliance is aonmental cond
ing in Dhakat in the loca
y ventilated bWOHA Architort is enhancehe classroomsa minimum. strategy evalugure 1) was stypical outdogure 1). The r
to change cmeters SET anlines this con
n of the class
erature (MRT
d the given ated average air speed of stited and can b
d into buildinthe method
words the samimulation codPMVeas is th
-point scale ocool (-2), co
achieved whenditions.
a, Bangladesal context. Thbuildings in thtects, serves aed with ceilins above groun
uating thermsurveyed for aoor climate oresults showe
clothing nor and PMVeas canclusion [4].
sroom [6].
T),
air air ill be ng is
me de he
of ld en
h. he he as ng nd
al an of ed to an
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
1
Table 2.Variants of comfort design for a typical classroom
Plant Shading
InfiltrationClassroomSemi-outdoor
Exhaust Air over Facade
Fans
Tempered Air Supply
CoolingWater
V2: 20/20V3: 22/22
Compared to Singapore, Dhaka’s summer climate differs significantly in terms of humidity ratio and ambient air temperature (Figure 2).
As a consequence, the BRAC University comfort design could rely on natural ventilation for the winter period, but not for the hot and humid summer time.
Thus, based on the original design concept of the SOTA classrooms energy efficient comfort design strategies for a typical classroom of BRAC University have been compared, analyzing the difference between a conventional fully air conditioned and a hybrid system concept for the Dhaka summer period.
IMPLEMENTED BUILDING SIMULATION METHOD
All environmental parameters (room geometry, internal and external loads, occupancy, buildings physics, ventilation, cooling power, etc.) are modelled with the dynamical thermal simulation program TRNSYS 3D on an hourly base. In a second step the thermal comfort is modelled based on the calculated environmental parameters and the control strategy of the fans using the Engineering Equation Solver (EES) where the codes for SET and PMVeas have been implemented according to the ASHRAE Standard 55-2013.
The simulation model
The thermal simulation work was carried out for a typical classroom model of BRAC University in Dhaka with dimensions 9.0*9.0*3.1 m³. The east and west façades are 30% glazed, semi-outdoor hallways affiliate on the outside. The hallways are naturally shaded by façade plants. For a typical university schedule, the classroom’s operation time includes weekdays from 07:00 to 17:00, fully occupied by 40 students. Sedentary activity with 70 W sensible and 65 g/h (40 W) latent load per student as well as adaptive clothing from 0.5 to 1 clo were assumed. In Table 1 the major characteristics of the classroom model are summarized.
Table 1. Simulation settings for the classroom model used in TRNSYS 17 3D
Conventional comfort design with full air conditioning and fan coil cooling
In the tropics, the typical climate concept for offices and public buildings is closed façades combined with full air conditioning. So for the conventional case, a climate concept with conditioned supply air and heat recovery from the returned air combined with fan coil cooling was chosen (Figure 3). Aiming at 26°C operative temperature and 12 g/kg humidity ratio, this system fulfills the conventional “static” PMV comfort standard. For evaluation the following design assumptions are made: Fresh air supply is set to 30 m³/h*pers in order to achieve good air quality for an university environment. Fresh air is
supplied with 20°C and a dew point temperature of 14°C (10 g/kg), the latent and sensible heat recovery is 75%. The fan coil unit is designed to cool the room air to maximum 26°C operative temperature and to keep room air humidity ratio below 12 g/kg. Infiltration is set to 0.2/h. In this system the air conditioning is introducing fresh air, cooling, dehumidification and air circulation (to be distinguished from the air movement in the hybrid system: see next sub-chapter).
Hybrid system comfort design, decoupling cooling from air movement, with tempered air and elevated air speed
For the hybrid system comfort concept fresh air is supplied with also 30 m³/h*pers to the room. The supply air is tempered, meaning cooled to 20°C (resp. 22°C) air temperature and dew point (equal to 14.7 resp. 16.7 g/kg) only. The supplied air is pressurizing the room and spilling over to the hallways, which minimizes infiltration (Figure 4). The condensate from the decentralized supply air units is used for irrigation of the façade plants.
To establish constant comfort, six ceiling fans with controlled air speed are used in addition. Air velocity is automatically elevated in two steps from 0 to 0.7 to 1.2 m/s, if perceived comfort exceeds 0.5 PMVeas. This is set to be in line with recommended limits for air speed of sedentary work (0.7 m/s) and maximal air speed under occupant control (1.2 m/s) according to ASHRAE Standard 55.
For further comparison a design without any mechanical ventilation but natural window ventilation (air change rates, driven by thermal boundary conditions, range from min. 4.8/h to about 10/h) and elevated air speed with ceiling fans has been compared (see next chapter).
RESULTS AND DISCUSSIONS
In Table 2 the four variants of different comfort designs are compared. The first variant V1 stands for the conventional comfort concept of full air conditioning and fan coil cooling. The variants V2 and V3 are based on the comfort design of tempered air and use of fan. V4 represents the fully natural ventilated design with no air tempering but use of fans.
All four variants have been evaluated on the same basis with PMVeas for the purpose of comparing the achieved comfort. Figures 5 and 6 show that for V1, V2 and V3 the achieved PMVeas is in the range of 0.2 to 0.5. Thus, those variants provide excellent comfort. In contrast, V4 provokes uncomfortably warm conditions, even though fans are at high air speed of 1.2 m/s (Figure 8). Its PMVeas increases up to typically 2, in maximum to 3. Thus, V4 is not discussed any further.
Climate Data SWERA Dhaka Time May - Oct Occupants 110 W/PersShading West/East External Operation Day 07:00 - 17:00 Electrical Loads 5 W/m²Classroom Area 81 m² Total Operation Hours 1320 h Artificial Light 10.5 W/m²Classroom Volume 251 m³ Occupants Number 40 Air Supply 30 m³/Pers
Climate, Shading & Geometry Internal Loads & Air SupplyTime Settings & Occupants
Figure 5 PMVeas curves of comfort design variants over Dhaka’s summer period
Figure 6 Sorted PMVeas curves of comfort design variants over Dhaka's summer period
0
0.5
1
1.5
2
2.5
3
0 220 440 660 880 1100 132
PMVeas
Operative Hours
V1 V2 V3 V4
May Jun Jul Aug Sep Oct
Time
0
0.5
1
1.5
2
2.5
3
0 220 440 660 880 1100 1320
PMVeas
Operative Hours
V1 V2 V3 V4
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
5
10
15
20
25
30
5 10 15 20 25 30 35 40
Hum
idity
Rat
io [
g/kg
]
Outdoor Air Temperature [°C]
Pressure: 965.1 hPa
Operation Time 0h - 24h
Figure 2 Psychrometric chart with IWEC Singapore (grey) and SWERA Dhaka (red) summer climate data
Variant Ceiling Fan Coil Heat recoveryFan Unit Tsupply [°C] Tdewpoint [°C] [%]
V1 No Yes 20 14 75V2 Yes No 20 20 -V3 Yes No 22 22 -V4 Yes No - - -
Mechanical Ventilation
Figure 3 Conventional comfort design with full air conditioningand fan coil cooling
Figure 4 Comfort design with tempered air and elevated air speed
Plant Shading
InfiltrationClassroomSemi-outdoor Chilled
Water
Air Conditioning
Heat Recovery:latent + sensible
Fan Coil Unit
20 / 14T / DP
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
2
Figure 7 Dand its m
Design day chmajor parame
V1
V2
V3
hart showing eters for the c
the achievecompared var
pdssctPt
M1
Mrhco
owftpc(
uontrs
sss
(cn
clefb
d PMVeas iants [7]
Figure 7parameters’ idesign days summer situasimulation wcalculation [7the left ordinPMVeas are sthe diagram’s
V1 leadMRT with 2711 g/kg (Figu
In contrMRT values ratio of 16 tohumidities iscomparable Poccupation.
The comof maximal 0warmer and mfor most of ththe same rangprovide the sceiling fans r(Figure 8).
V2 estabusing the lowoperative timnecessary duthird of operrequired. If thsavings would
But as Asedentary actspeed is thesavings are le
The co(Figure 9) givconcepts can no heat (cold)
As roomcompared to latent heat reenergy could full sensible be required.
7 on the left ginteraction foin June we
ation in Dhawere used a7]. Tair, MRTnate. Determishown on thes top indicate ds to average7°C, and to a ure 7, diagramrast, the hybbetween 28°
o 18 g/kg. Ths compensatePMVeas value
mparison of V0.7 m/s is suffmore humid ehe operative tge (Figure 7,same comforrun constantly
blishes good wer fan step
me. With V3e to the reasrative time this would be d be about - 4
ASHRAE 55 tivity in the oe preferred ess with - 25%omparison oves evidence achieve sign) recovery is m air tempeconventiona
covery wouldbe reduced eand latent hr
gives a detaior variant Vere chosen toaka. The resuas input parT and humiditined fan stepe right scale.
the occupante values for reduced ave
m at the top). rid variants °C and 31°C
he impact of hed by elevates in the rang
V2 and V3 shfficient for V2environment itime in order , middle andrt in all variay during the
thermal comof 0.7 m/s
3 a higher ason mentionethe higher fa
acceptable to42% (Figure recommends
occupied zonevariant even
%. f the varianthat substant
ificant energyinstalled.
erature and hal systems add be less effee.g. from 66 reat recovery
led comparis1, V2 and Vo represent ults from therameters for ty ratio are pp as well as Black plotte
ts’ operative Tair with 23rage humidit allow higher
C and higher high temperated air speedge of 0.2 to 0
hows that a f2, whereas thin V3 requireto keep the P
d bottom diagants with fan1320 h of oc
mfort while cat all 1320
average air sed above. Alman step of 1.o the users th9).
s limiting aire, V2 with 0.n though the
nts’ energy tially less mey savings eve
humidities ardditional senective. For V2to 45 kWh/m
y system (75%
son of the V3. Three
a typical e thermal
comfort plotted on
resulting ed bars at time. .5°C and
ty ratio of
r Tair and humidity
atures and d causing 0.4 during
fan speed he slightly es 1.2 m/s PMVeas at gram). To n, the six ccupation
constantly hours of
speeds is most one .2 m/s is he energy
speed for .7 m/s air e energy
demand echanized en though
re higher nsible and 2 cooling
m²a, but a %) would
CONCL
Thwhile pr
Meclassrooevaluatisupply o
Bafresh aisupply toperativtempera
Thinstallatin false costs ofsimplifi
It paramettemperacooling
Wassess h
REFER
[1] ASH[2] ISO
com[3] Ric
http[4] Ric
Com[5] Tyl
Ber[6] Wo
com[7] Lau
Fig
20
40
60
80
100
120
140
160
Cei
ling
fan
[h]
LUSIONS
he paper’s puroviding equaethodology, om in Dhaka,ion for elevaof tempered aased on the reir quality witthe fresh air ve time. Comature and 12 ghe supply airtions for mec ceilings, ver
f the system iied building eis to be noteters configuratures and higrun on low o
While similar bhybrid comfor
RENCES
HRAE StandO 7730:2005.mfort using cachard de p://eetd.lbl.gochard de Deamfort and Preler Hoyt, et rkeley. http://olfgang Kessmmunication.ura Franke. 20
gure 8 Runninaccumulatin
00
00
00
00
00
00
00
00
00
V1
FAN 1.FAN 0.
urpose is to inal comfort coimplementat Bangladesh,
ated air speedair and the usesults, a hybrith 30 m³/h*pat 20°C temp
mpared to the g/kg humidityr systems cahanical roomrtical shafts eitself as well envelope desid that achiev
re in two comgh humidity coperative tempbuilt examplert designs in t
dard 55-2013.. Ergonomicsalculation of tDear. 2011
ov/sites/all/filar, Gail Brageeference. al. 2013. CB
/cbe.berkeleysling and M Transsolar K014. Adaptiv
ng hours of fang to 1320 h o
1320
V2
.2 [m/s]
.7 [m/s]
nvestigate whompared to thtion in build, have been cd proved to bse of ceiling fid system com
pers and exceperatures andconventionaly ratio, energan be install
ms with centraetc. are not ras for the bu
ign and thermved comfort omplete differcompensated
mperatures andes of hybrid tropical clima
. Thermal Envs of the therthe PMV and1. Adaptiveles/dedear-semer, Donna Co
BE Thermal y.edu/comfortMartin EngeKlimaEngineeve HVAC Com
ans of each vof total opera
927
35
393
128
V3 V4
hether a hybrhe conventionding simulatioarried out. Thbe a powerfufans as typicamfort conceptellent thermald dew point. Il concept of cy savings areled decentralal air conditiorequired. The
uilding as lessmal zoning of of the systemrent ways: thby elevated
d low humiditsystems existates. The met
vironmental Crmal environmd PPD indicese Thermal m04feb2011.ooper. 1997.
Comfort Totool/. lhardt. 2014ering. mfort Concep
ariant, tive time
5
rid system conal concept ofon, and anahe implemen
ul tool to expally installed. t with dedical comfort. A In addition, cconditioned ae about 25%. l and operatoning systemse substantialls space is usef the universitms analysed ishe hybrid syair speed, whty without elet, the paper’sthod proved t
Conditions foment — Anas and local th
Comfort, .pdf.
ASHRAE R
ool, Center fo
4. Thermal
pts for a Hot a
Fig
Ele
ctric
al E
nerg
y [k
Wh/
m²a
*]
omfort designf full air condlysis of therted method b
plain thermal
ated fresh air ssimple decen
ceiling fans pair with full h ed per rooms, heat recovey lighter hyb
ed for the air y building. s comparablestem variant
hereas systemevated air mos outcome filto be useful fo
or Human Ocalytical deter
hermal comforBackground
RP-884. Deve
or the Built
comfort stu
and Humid C
ure 9 Electriventilation,
81
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0
20
40
60
80
100
120
V1
n can lead toditioning and rmal conceptbased on ASH comfort ach
supply is proentral mechanprovide accepheat recovery
m in case of ery, insulatedbrid system whandling sys
e, while theirt provides co
ms with full aovement. lls the gap offor these desig
ccupancy. rmination an
ort criteria. d, Simulati
eloping an A
Environmen
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Climate. Mast
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66
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significant efan coil coolits for a typi
HRAE’s SET-hieved with 1
posed which nical system ptable air mov
aiming on 2
f occupation d supply and rwill have lowtems and wil
influencing omfort with hir conditionin
f a missing mgn evaluation
d interpretati
ons, Future
Adaptive Mod
t, University
TA in Singa
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emand of eachdehumidificat
49
71
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CeiliSysteAir tr
energy savinging. ical universi-PMV comfo100% fresh a
provides goois proposedvement durin
26 °C operativ
only. Typicreturn air ducwer investmell allow a mo
environmenthigh operativng and fan co
methodologyns.
ion of therm
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del of Therm
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apore. Priva
TU Munich
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30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
3