AHU HVAC.ppt Air Distribution Systems, HVAC

This PPT gives details about Air Handing Unit used in Heating, Ventilation and Air Conditioning

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
(An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Department of Mechanical Engineering
Subject:-Heating, Ventilation and Air
Conditioning (ME 411)
B.Tech.Mechanical
PurushottamW. Ingle
Assistant Professor

2. •Airhandlingunit
•Airhandlingunit,FanCoilUnits&Freshairhandlingunits,typesof
fansusedairconditioningapplications,fanlaws,filters,supplyand
returngrills,sensors(humidity,temperature,smoke).TypesofAir
TerminalDevice,SelectionAndSizingofAirTerminalDevice
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

3. Air Handling Unit (AHU)
•Anairhandlingunit,commonlycalledanAHU,isthecompositionof
elementsmountedinlarge,accessiblebox-shapedunitscalled
modules,whichhousetheappropriateventilationrequirementsfor
purifying,air-conditioningorrenewingtheindoorairinabuildingor
premises.
•Theyareusuallyinstalledontheroofofbuildingsand,throughducts,
theairiscirculatedtoreacheachoftheroomsinthebuilding.
•
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

4. MainfunctionsofanAHU
•Inadditiontomanagingtheproperventilationoftheinteriorwith
outsideair,theAHUperformsotherfunctions:
•Filtrationandcontrolofthequalityoftheairthatwillreachthe
interior,byusingairpurificationfilters,anddependingonthe
retentionofthesefilters,theairwillbeclean.
•Controloftheairtemperaturethatregulatestheairconditioning
systemincoldorhot,sothatthethermalsensationintheinterioris
thedesiredone.
•Relativehumiditymonitoringforgreaterindoorcomfort.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

5. •Foritspart,theplacesforwhichtheAHUisintendedarethosein
whichtheflowofpeopleisverylargeandaccumulatesmanypeople
atthesametimeandwhosenaturalventilationislimited:hotel
diningrooms,functionrooms,restaurants,conventionhalls...Itis
alsoasuitableoptionforthosespaceswithveryhighhygiene
requirements:laboratories,cleanroomsoroperatingtheatres,among
others.
•AnAHUcanalsobeusedtoventilateplaceswhereairconditioningis
providedbyradiatorsorunderfloorheating,forexample.
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8. AHU Components
•Airintake:airhandlingunitscollectairfromoutside,whichistreated
anddistributedthroughouttherooms;and/orindoorairthatis
"recycled".
•Filter:dependingontheairpurityrequirements,thefilterappliedwill
haveahigherorlowerparticle,viruses,bacteria,odours,andother
airpollutantsretention.
•Fan:thisisanelectromechanicalsystemthatpowerstheairtoexpel
itfromtheAHUtotheductsthatdistributetheairthroughoutthe
rooms.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

9. •Heatexchangers:devicesthattransfertemperaturebetweentwo
fluids,inthiscase,coolantandair,separatedbyasolidbarrier.
•Coolingcoil:theairpassingthroughthismoduleiscooled.Inthis
process,waterdropletscanbegenerated,whicharecollectedina
condensatetraythankstothebuilt-indropletseparator.
•Silencer:coatingsthatconsiderablyreducethesoundlevelofthe
installation.
•Plenums:emptyspacesinwhichtheairflowishomogenised.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

10. Fan Coil Unit
•Afancoilunit(FCU),orverticalfancoilunit(VFC),isadevicethat
usesacoilandafantoheatorcoolaroomwithoutductwork.
•Afancoilunit(FCU)isadeviceusedtoheatorcoolaroomwithout
theneedforductwork.
•Itconsistsofanindoorcoil,afanandanoutdoorcondensingunit.
Thefanforcesairthroughtheindoorcoil,whichisfilledwith
refrigerant,eithercoolingorheatingitdependingonthedesired
temperatureintheroom.
•Thiscooledorheatedairisthensentintotheroomtomaintaina
comfortableenvironment.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

11. •FCUsareoftenfoundinofficesandothercommercialbuildingsas
wellassomehomes.
•Therearetwomaintypes:verticalfancoils(VFCs)andhorizontalfan
coils(HFCs).VFCsaretypicallyusedforsmallerspacessincetheycan
bemountedverticallyonwallsorceilings,whileHFCsaremore
suitableforlargerareasastheycanbeinstalledhorizontallyonthe
floororceiling.
•Fancoilunitsarestandalonesystemsthatcirculatetheexistingairin
aspace.TheycanalsobepartofalargeHVACsystemwhileair
handlingunits(AHU)areapartofanHVACsystemthatcoolsand
redistributesairintoyourhomeviaducts.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

12. •Yes,fancoilunitsuserefrigeranttocoolorheattheairinaroom.
RefrigerantisplacedinsidetheindoorcoilofanFCUandwhenthe
fanisturnedon,itforcesairthroughthiscoilwhicheitherheatsor
coolsitdependingonthedesiredtemperature.Thecooledorheated
airisthensentintotheroomtomaintainacomfortableenvironment
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

13. •Fan Coil Components
•Fancoilsareverysimplecomparedtootherpiecesofequipment.The
fancoilcontainsafilter,fan,coil,andadrainpanto
catchcondensatefromthecoolingcoil.Thesourceoftheheatingand
coolingisusuallyprovidedbyaChillerandBoilerlocatedina
mechanicalroom,oroutsideontheroof.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

14. •TheseFanCoilsuseChilledwaterorHeatingHotWatertoprovidethe
roomwithcoolingorheating.Acentralventilationunitwillprovide
temperedairthroughamainducttoallthefancoils.
•Thisistheprimaryairsuppliedtotheinletofthefancoiltoprovide
therequiredventilationair(outsideair)inaccordancewithASHRAE
62.1.
•Thefancoilsreducetheamountofductworkneededbythecentral
system,becausemostoftheheattransferisdoneusingwaterinstead
ofair,byusingChilledWaterorHeatingHotWater.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

15. •Airentersthebackofthefancoilandpassesoverfiltersbefore
passingovertheheatingandcoolingcoils.Thefancanbearrangedin
eitherablow-throughordraw-throughconfiguration.Withablow
through,thefanisbeforethecoils,inadraw-through,thefanisafter
thecoils.
•Thefiltersprovideameansofkeepingtheairfreeofdustand
particles,whilepreventingthecoilsfrombecomingclogged.Thefilter
canbeinafiltertrackattachedatthebackofthefancoilora
separatereturnairfiltergrillcouldbeprovidedintheceilingsuchas
iscommoninsomehotelroomstyleinstallationsusinghorizontalfan
coils.
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17. Vertical Fan Coils
•JustliketheverticalstackedHeatPumpsusedinhotels,therearealso
VerticalStackedFanCoils.Theseverticallystackedfancoilscanbe
eitheratwo-pipeorfour-pipesystem.Usinga4-pipesystem,there
willbeachilledwaterandheatinghotwatersupplyandreturn
piping,andofcourseafifthpipeforcondensate.
•Theseverticalfancoilscomewithriserpipingattachedforeasily
stackingthemoneontoptheotherfromfloortofloor.Thesearebest
usedinhigh-risebuildingsuchashotels,condominiums,apartments,
dormitoriesorsimilarhigh-rises.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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19. •FreshAirHandlingUnit(FAHU)isanexcellentsolutionforregulating
andcirculatingfreshairaspartofanHVACsystemanditensuresa
constantflowoffreshcleanairandaverywell-conditioned
environment.
•WhileanAHUcanhandlebothfreshoutsideairandrecirculatedair
fromwithinthebuilding,aFAHUisspecificallydesignedtohandle
onlyfreshoutsideair.
•AfreshairAHUprovidesoneofthemosteconomicalwaysof
addressingtheneedforcleanfreshairinenclosedareaslikekitchens,
restaurantsandcateringfacilities.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

20. •AFAHUsystemconsistsofafan,afilter,aheatexchanger,anda
damper.Thefandrawsintheoutdoorairandpassesitthroughthe
filtertoremovedustandpollutants.Theheatexchangertransfers
heatorcoldbetweentheoutdoorairandtheindoorair,depending
ontheseasonandthedesiredtemperature.
•Afreshairhandingunitbasicallyregulatesandcirculatesthefreshair
intodifferentchambers.ThisHVACunitcollectsthefreshairfrom
outsideandconditionsitinthemixingchamber.Afterconditioning
theair,itcirculatestheairtovariouschambersthroughductworks.
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22. FAN
•Fansarenecessarytodistributeairthroughductstospacesthatare
tobeconditioned.
•TypesofFans
•Fansaremainlyclassifiedintotwogroups,namelycentrifugaland
axialfans.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

23. Centrifugal Fan
•Inacentrifugalfan,airispulledalongthefanshaftandthenblown
radiallyoutwardsfromtheshaft.
•Theairisusuallycollectedbyascrollcasingandconcentratedinone
direction.
•Centrifugalfansmaybesubclassifiedintoforwardcurved,radial,
backwardcurvedandbackwardinclinedtypes.Thesedifferinthe
shapeoftheirimpellerbladesasshowninFigure
•Inaddition,backwardcurvedbladeswithadouble-thicknessblade
arecalledairfoilblades.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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25. •Axialfans
•Inanaxialflowfan,airispulledalongthefanshaftandthenblown
alongtheaxisoftheshaft.
•Propeller,tubeaxial,andvaneaxialtypes(Figure10.21)areavailable
inaxialfans.
•Thepropellerfanconsistsofapropeller-typewheelmountedona
ringorplate.Thetubeaxialfanhasavanedwheelmountedina
cylinder.
•Thevaneaxialfanissimilartothetubeaxialtypes,exceptthatitalso
hasguidevanesbehindthefanbladeswhichimprovethedirectionof
airflowthroughthefan.
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27. Fan Laws
•Thereareanumberofrelationshipsamongfanperformance
characteristicsforagivenfanoperatingatchangedconditions,orfor
differentsizefansofsimilarconstruction;thesearecalledfanlaws.
Theserelationshipsareusefulforpredictingperformanceif
conditionsarechanged.Wewillpresentsomeoftheserelationships
andtheirpossibleuses:
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29. filters
•Aircleanerscanbeclassifiedinanumberofwayssuchas(1)typesofmedia,
(2)permanentordisposable,(3)stationaryorremovable,and(4)electronic
aircleaners.
•Viscousimpingementfilters
•Thedustparticlesintheairstreamstrikethefiltermediaandaretherefore
stopped.Theviscousimpingementairfilterhasamediaofcoarsefibres(glass
fibresandmetalscreens)thatarecoatedwithaviscousadhesive.Air
velocitiesrangefrom90-180mpm.Thistypeoffilterwillremovelargerdust
particlessatisfactorilybutnotthesmallerparticles.Itislowincost.Referto
Figure(a).
•Instrainingtypeairfilters[Figure10.15(b)],thedustparticlesarelargerthan
thespacebetweenadjacentfibresandthereforearetrappedthere.
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31. Dry-type filters
•Theseuseuncoatedfibremats(glassfibresandpaper)asshownin
Figure.Themediacanbeconstructedofeitherlooselypackedcoarse
fibresordenselypackedfinefibres.
•Byvaryingdensity,dry-typeairfiltersaremanufacturedthathave
goodefficiencyonlyonlargerparticles,aswiththeviscous
impingementtype,orarealsoavailablewithmediumorhigh
efficiencyforremovingverysmallparticles.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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33. •HEPA(HighEfficiencyParticulateAir)filterItisaveryhighefficiency
dry-typefilterforremovingextremelysmallparticles.
•Forexample,itistheonlytypeoffilterthatwilleffectivelyremove
virusesassmallas0.05micron.
•AirfacevelocitiesthroughHEPAfiltersareverylow(about15mpm).
•Themediainairfilterscanbearrangedintheformofrandomfibre
mats,screensorcorrugatedsinuousstrips.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

34. •Permanentanddisposableairfilters
•Onecandevelopdisposabletypeairfilterssothattheycanbe
discarded.
•Onecanhavepermanenttypetoo,whichwhensaturatedwithdust,
canbecleanedandreused.
•Permanenttypeshavemetalmediathatwillwithstandrepeated
washings,butcostmorethandisposabletypes.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

35. •Stationaryairfiltersaremanufacturedinrectangularpanels.The
panelscanberemovedandeitherreplacedorcleanedwhendirty.
Renewabletypeairfiltersconsistofarollmountedonaspoolthat
movesacrosstheairstreamasshowninFigure.
•Thefabriciswoundonatake-upspool,drivenbyamotor.Theclean
fabriciscontinuouslybroughtinfrontoftheairstreambyrotating
theshaft.Renewableairfiltersareconsiderablymoreexpensivethan
thestationarytypes,butmaintenancecostsaregreatlydecreased.
Eitherfibrousmaterialsormetalscreensareusedasmedia.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
Stationary and renewable air filters

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37. Electronic Air Cleaners
•Dustparticlesaregivenahighvoltagechargebyanelectricgrid(bank
ofchargingplates)showninFigure.
•Aseriesofparallelplatesaregiventheoppositeelectriccharge.As
thedustladenairstreampassesbetweentheplates,theparticlesare
attractedtotheplates.
•Theplatesmaybecoatedwithaviscousmaterialtoholdthedust.
Afteranintervaloftime,theaircleanermustberemovedfromthe
servicetocleantheplatesandremovethedirt.
•Electronicaircleanersareexpensive,butareveryefficientfor
removingbothlargeandverysmallparticles.
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39. supply and return grills
•Areturnairgrillconnectstoductworkthatallowsairtoreturntoany
coolingorheatingsystem.Theopeningsthatconnecttoductsand
otherspacesforthereturningairarenormallycoveredwithgrillwork.
•Everycoolingorheatingsystemwillhaveairbeingpushedthough
intoroomsandspacesthroughasystemofducts.
•Thisincreasestheairpressureintheconditionedareaandatsome
timewillacttoevenpreventanyfurtherairfromenteringunlessa
circulatingsystemissetuptorelievethepressure.
•Thisisdonenormallythroughreturnductswhichallowtheairtobe
recirculatedorcompletelyventedtotheoutsideincertaincases.A
returnairgrillwillcoversuchducts,andcanalsoacttoregulatethe
flowofair.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

40. •Theyalsoacttocloseofftheductsfromview.Areturnairgrillalso
hasafiltermountedonittotrapparticulatematterandthusensure
thattherecirculatedairismorepure.Thiscanalsointhelongrun
reducetheamountofcleaningrequiredforducts.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

41. •Supply Grille
•Supply grilles will typically be deflected so that you are able to direct
the airflow needed to a specific area. For instance, you would want to
put supply grilles for air conditioning somewhere higher, as cold air
falls, and vice versa for for heating –those supply grilles should be
placed lower on the wall, as heat rises.
•Return Grilles
•For return grilles, the degree of deflection is not necessarily
important unless you are trying to conceal what is in the vent behind
the grille. Most commercial applications utilize light shields that affix
behind the grille, or a double deflected grille, so that the view is
relatively obscured.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

42. •Itisessentialthatyourreturnairventsarenotblocked.MostHVAC
systemsrequireconstantairflowtoworkproperly,andablockedvent
couldcauseyoursystemtoeitherloseefficiencyorfailearlierthanit
should.Someofthemostcommonblockagesincludeplacingacouch
orotherfurnitureinfrontofthevent,aswellascurtains,whichcan
getsuckedinandinhibitairflow.
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45. •Airterminalunits(ATU)arezone-levelairdistributiondevicesthat
regulateairflowformaximumoccupantcomfort.TheATUcontrols
thezonespacetemperaturetomaintainadesiredoccupiedspace
temperature.Invariableairvolume(VAV)systems,theflowofairis
suppliedbyasingleairhandlingunit.
•Airvolumeandvelocityarethekeyselectionfactorsalongsidethe
aestheticappearanceofairterminaldevicessuchasgrilles,diffusers
andlouvres.
12/27/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

46. •Theseterminaldevicesareoftenmissselectedandthendon’t
performcorrectlywheninstalledinanHVACsystem.Differences
oftenoccurinthedesigncriteriaforasupplyorextractdeviceasthe
patternandbehaviouroftheairenteringorexitingneedstobe
different.
•Otherpointstoconsiderincludethethrow,diffusionandequalisation
ofairflow,systembalanceandnoise.
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