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Twin Wheel system– humidity control and energy saving
The Twin Wheel might not be as important to humanity as the wheel. But within the air treatment business we still consider this system a landmark innovation, and it creates a high indoor air quality as well as energy savings for the benefit of our common environment.
•The outer rotor pre-cools supply air.Thesystemtherebylowerstherequirementsonbothcoolingcoilandchiller.
•The outer hygroscopic rotor also transfers humidity from supply to exhaust air flows.Thisleaveslessmoisturetoremoveforthecoolingprocess,whichmakesitpossibletodownsizecoilsandchillersevenfurther.
•Need for heater dramatically reduced.Theinnerrotorrecoversenoughheatfromtheexhaustairflow–heatingforfreeformostoftheyear!
•The Twin Wheel is a perfect match for chilled beams and fan coils.Itlowerstheriskforcondensationonthechilledbeamthroughanenergyefficientmechanism.Chilledbeamsarethemselvesefficientpartsofacirculatingliquid-basedflow,thatbesidesenergysavingsalsolowersnoise,amountofduct-workandrequiredcapacityofmainAirhandlingunit.
This makes the Twin Wheel such a good idea:
Air quality
Todaywedemandacomfortableenviron-mentwheninsideabuilding.Oneimportantparameterforagoodindoorenvironmentistheairquality.Goodindoorairqualityinturnisacombinationoffactorslikeoxygenlevel,humidity,absenceofodorandpollution-andobviouslytherighttemperature.
Energy costs
Coolingandheatingprocessestypicallydemandhighlevelsofenergysupply.Inmodernbuildingsairtreatmentisoftenthebiggestconsumerofpower.Thisfact,togetherwithconstantlyincreasingglobalenergyprices,callforsystemsoptimizedforbestoverallefficiency.AtFläktWoodswecombineourexperiencewithadvancedtechnologyto
achieveintelligentsystemsolutions.Theyaresoundinvestmentswithshortbreak-evenanddramaticsavingsinthelongrun.
Environment
Theenvironmentisalsoawinnerwithoursolutions.Fornature,regardlessofenergysource,theleastharmfulkilowattofenergyistheonesavedandneverproduced.
Controlled humidity
Controloverthehumiditycontentoftheairisonefactortoreachgoodindoorairquality.Humiditycontrolisalsoessentialforuseof‘chilledbeams’,anaircoolingtechniquewithgoodefficiencyandhighlevelsofcomfort.
How does the Twin Wheel system work?
Fläkt Woods has designed the Twin Wheel system to improve on cooling and humidity control versus other solutions on the market. The purpose is to produce cool and dry air while lowering the cost for these processes compared to conventional systems.
The components of a Twin Wheel system
Rotary heat exchanger
Rotaryheatexhangersareusedforheatingandcoolingrecoveryinairhandlingsystemsandtypicallyenhancestheirefficiency.Therotaryheatexchangersmaincompo-nentistherotor,whichismadeofeitherthinfoldedsheetaluminiumormicro-glass,formedastriangularpipes.
Sensible rotor
Whenspinning,therotortransfersheatorcoldbetweensupplyandexhaustairstreams.Inthiscase,wheretheexchangeisrestrictedtotemperaturetransfer,itiscalleda‘sensible’rotor.Hygroscopic rotor
Throughsurfacetreatmenttherotorcanalsobegivenmoist-transferringabilities.Itisthencalleda‘hygroscopic’rotor.Thistypeofrotorcanalsorecoverenergyfromwatervapor,
whichmeansthatitcanrecoverbothsensibleandlatentenergy.Thetransferprincipleisthesameforbothmoistandtemperature.
FläktWoodsamericanSEMCO-unithasdevelopedahygroscopicrotorwithapro-prietarysurfacetreatmentof3Å(angstrom).
Thisrotorismoreefficientthantraditionaltypesinabsorbingmoist.Themoleculargridof3Åpermitswatervaportobetransferredwhilepollutions,whichtypicallyhavelargermolecules,arenotcarriedover.
Cooling recovery
TheTwinWheelcontrolleroperatesthetworotorsinsequence,resultinginloweredrequirementeffectonthecoolingcoil.
Cooling coil
Thepurposeofthecoolingcoilistocooland/ordehumidifyair.Coolingisachievedwhenwarmairpassesthroughthecoolingcoil,whichconsistsofparallelpipes.Whenthereisalsoademandforde-humidification,thetemperatureofthebatteryislowereduntilthepassingairreachesitsdewpoint.Thecondensatedmoististhenextractedbyadripseparator.Theoutcomeofthispro-cessisairwithlowertemperatureandlowerhumidity.
Controls
TheTwinWheelisequippedwithapre-programmedin-tegratedcontrolsystem,specificallydevelopedtomeettherequirementsforcosteffectiveness,userfriendliness,reliabilityandenergyef-ficiency.ThecontrolsystemisbasedonapowerfuldigitalcontrollerwithModbuscommunicationandanintegratedwebserverasstandard.Theuserinterfacein-cludesanoperatorpanel,withaneasytouse“pushandpull”navigationthroughalogicalmenustructure.ThecontrolsystemisautomaticallyselectedandconfiguredinACONandtherebysimplifiesthedesignprocessreducestimeandmoneyspentonengineeringanddocumentation.
Humidity control
TheTwinWheelcontrolleroperatesthehygroscopicrotorandcoolingcoilinsequencetoadewset-pointvalue,therebylimitingthesupplyairhumiditylevel.Duringthecauseoftheyear,thesystemwilllimitindoorhumidity.
The traditional system
Inaconventionalsystem,coolinganddryingisachievedbycondensatingawayexcessmoistureonacoolingcoil.Inthenextsteptheairisre-heatedinaheatingcoiltoreachthedesiredtemperature.Bothcoolingandheatingtypicallyrequireconsiderableamountsofenergy,leavingroomforimprovementinbothcostandenviron-mentalaspects.
Whenoutdoorairiswarmerthantheexhaustairflowthereisaneedforcooling.Thehygroscopicrotorthenreducestemperatureoftheincomingair.Simultaneouslyittransfersmoisturefromthein-boundtotheoutboundairflows(incaseswhereabsolutehumi-dityishigheroutdoors)
Afterpassingthroughthehygro-scopicrotortheairpassesthroughthecoolingcoil,wherethetemp-eratureisreducedfurtherandmoistureiscondensateddowntorequiredlevels.Sincetheairhasalreadybeencooledbythehygroscopicrotor,thedemandforcoolingislowered.Thesavingcanbeupto50%ofthenominalrequiredcoolingeffect,whileatthesametimetheneedforafollowingre-heatingbatteryinmostcasesdisappear.
Thenowdehumidifiedandcoo-ledaircontinuestothesensiblerotor,whereheatfromexhaustairisrecoveredandusedtore-heatit.Theairthenissuppliedtothebuilding,whithcontrolledlevelsonbothtemperatureandhumidity.Notethatthetemperatureexchangeinthesensiblerotor,whereexhaustairiscooled,furtherimprovesthecoolingrecoveryofexhaustairinthehygroscopicrotor!
Twin Wheel advantages in overviewThe Twin Wheel system contains three main parts; the hygroscopic rotor, a cooling coil and a sensible rotor.
1 2 3
Exhaust air
Outdoor air Supply air
Hygroscopic rotor
Sensible rotor
Cooling coil
0·03090 80 70 60 50 40 30 20
140135130
Relative moisture content, x/xs 1)
Dry-bulb temperature, °C
Enthalpy per kg dry air, kJ/kg, kcal/kg
125120
0·029
30
25
20
15
10
5
0
-5
-10
0·75
0·80
0·85
Specific volume, m3/kg
Wet-bu
ld tem
perat
ure, °C
0·90
0·028
0·027
0·026
0·025
0·024
0·023
0·022
0·021
0·020
0·019
0·018
0·017
0·016
0·015
0·014
0·013
0·012
0·011
0·010
0·009
0·008
0·007
0·006
0·005
0·004
0·003
0·002
0·001
0·000605550454035302520151050-5-10
-10 -5 0 5 10 1520 25 30 35 40
45 50 55 60 65
7075
8085
9095
100
105
110
115
120
125
130
135
140
-10
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
9510
010
511
011
5
Enth
alpy p
er kg
dry
air
kJ/k
g (1
kJ/k
g) =
0. 2
39 /
kcal/
kg
Moisture content per kg dr y air x, kg/kg
Airflowrate5m3/s•Outdoorcondition:29°Cdrybulb,50%relativehumidity
Requiredsupplyaircondition:20°Cwith8g/kgabsolutehumidity
Exhaustairdesigncondition:23°Cwith9g/kgabsolutehumidity
Thetotalcoolingdemandis184.4kWandthereheatdemandis56.5kW.
Withthetwinwheelsystemthefirstrotaryheatexchanger(green)recovers
100kWofcoolingleavingjust84.4kWforthecoolingcoil.Thereheatdemand
isfurnishedbythesecondrotaryheatexchanger(red)andthesupplyfan.
Laboratory testedTheTwinWheelsystemhasbeentestedinourlaboratory
underdefinedandaccuratelymeasuredconditions.
Count on savingsNow let’s see what the Twin Wheel system can achieve in real life! The situation is a typical setup where there are specific demands on both temperature and humidity to maintain a good indoor climate.
27.311.3
16.19.5
23.09.5
29.012.5
18.010.5
12.08.0
18.98.0
20.08.0
Dry bulbhumidity
5.0 m3/s
5.0 m3/sC / g/kg
Extract
Supply
Fan coilsFancoilsaremostcommonlyusedinareaswhereindividualroomcontrolisessential,suchashotels,privateandpublicofficebuildings,hospitalsandschools.FläktWoodscanofferclassic,cassetteandsatellitefan-coils.
ControlsFläktWoodsoffersawiderangeofintegratedcontrolsolutionsforairhand-lingandindoorclimatesystems.Factorymountedanpre-wiredcontrolswillreduceinstallationtimeandsimplifyon-sitelogistics.PreprogrammedandfactorytestedcontrolapplicationsbasedonFläktWoodsextensiveexpe-riencealsomeansafastcommissioningprocessandwillsecureareliableandenergyefficientoperationofthesystem.Basedonsupportforopenstandardcommunicationprotocols,integrationtoabuildingmanagementsystemcaneasilybecarriedoutbyanindependentsystemintegrator.
With our broad range of products and century-old experience, one thing is obvious to us; You have to look at the big picture. It is by carefully combining products into systems, utilizing smart controls, one can achieve the best energy solutions.
When the pieces fit, you get the big picture
Air handling unitsOurcomprehensiveAirHandlingUnitofferingallowsustodeliveroptimisedsolutionsforanycustomer.OurR&Dworkfocusesonreducingenergyconsumptionandcreatingfactorycompleteairhandlingsystemsolutionswithcontrols.Ourexperienceinthemarine,off-shore,pharma-ceuticalandhospitalmarketsmakesustheperfectpartnerforsuchapplications.
e3 – Fläkt Woods
Integrated advantages
FollowingtheKyotoprotocoltheEuropeanUnionhassetatargettoreduceenergyconsumption.Forbuildingsthetargetissetata22%reductionby2010.It’scalledtheEPBDdirective.
ToaddresstheneedscreatedbytheEPBDdirec-tive,FläktWoodshaspouredalotofeffortintocreatingthee3Concept.Oursolutionisabroadapproachleavingnostoneunturnedtoachieveoptimumresults.
High-performingcomponentsareanobviousstartout.Butitisbycombiningproductsintoasystem,utilizingsmartcontrol,onecanachievethebestenergysolutions.
Thee3logoisusedtohighlightproductsandsystemsthatdeliversavingsonbothEnergy,EconomyandEnvironment.
Chilled beamsInsystemswithChilledBeams,theindoorairiscooledbymeansofcoldwater.Chilledbeamscreateastableandcomfortableenvironmentbysupplyingdraughtfreecooling.ByusingChilledBeamsupto75%ofthetotalcoolingcapacitywillbehandledbythewater.Apartfromtheenergysavingitalsomeanslessductworkforair,smallerairhandlingunitsandlowernoise.
ChillersTheFläktWoodsrangeofchillersaredesignedtominimisetheoverallannualenergyconsumptioninalltypesofbuildings.FläktWoods’heatandcoolingrecoverysystems(e.g.Econet)allowforthedeploymentofsmallerchillersthanwouldotherwisebethecase.Thisleadstosignificantlyreducedinvestmentsandoperationalcost.
KaunasAKROPOLISwillbethebiggestshoppingcentreinKaunasandincentralLithuania,withawideselectionofnationalandinternationalstores.
TheAKROPOLISshoppingcentreincentralLithuaniawillattractcustomersfromalloverLithuaniaandneighbouringcountries.TheAkropolisshoppingcentreinKaunas,Lithuaniaincludesanicerink.Toavoidfogintheareaaroundtherinkitisnecessarytosupplyairatatemperatureof16°Candanabsolutehumidityof8g/kg.Theoutdoordesignconditionis27°Cand55%relativehumidity(12.3g/kg).
TwoEUairhandlingunitseachequippedwithtworotaryheatexchangerssupplyatotalof15.4m3/s.Thetotalcoolingdemandis448kWandthereheatdemandis53kW.Bymeansofthetwinrotorsystemthecoolingdemandonthechillerisreducedbyonethirdto300kWandthereheatdemandiseliminated.Notonlyistherunningcostreducedbutalsothesizeofthechillerplant.
References
FACTS AbOuT KAunAS AKROpOLIS
• 73,063 m2 total area
• Supermarket ”hyper-Maxima” - 6,778 m2
• More than 220 operators
• More than 2,500 fast food and
restaurant seats
• Over 2,759 parking spaces
• 9 million visitors a year are expected
• Multiplex cinema – 7 screens, more than
1,418 seats
Akropolis shopping center Kaunas, Lithuania
”By means of the twin rotor system the cooling demand on the chiller is reduced by one third to 300kW and the reheat demand is eliminated.
John Dalton building Manchester, England
FourTwinWheelsystemsweresuppliedtotheJohnDaltonBuildingatManchesterMetropolitanUniversity.ThisbuildingisfortheDepartmentofComputingandMathematicswhichhousestheirownteachingandresearchlaboratoriesofferingperson-centredworkingandlearningenvironmentforstaffandstudents.Researchiscarriedoutincomputerscience,intelligentsystems,computationalfluiddynamics,informationsystemsandmathematicalmodelling.
EnergyefficiencyandindoorqualitycontrolwereavitalfactorforthisProjectandtheconsultantRMJMdesignedasystemforthelaboratoriesincorporatingchilledbeamsanTwinWheelairhandlingunits,theairhandlingunitsprovidingfreshairtothechilledbeams.Wewereabletoshowtheclientthroughourdevelopmentacalculationmethodtoenableperformanceofthetwinwheelunitstobepredicted,alongwithenergyusageatallconditionstoenablepaybackperiodstobecalculated.TheTwinWheelsystemshowedamarkedefficiencyimprovementinthesummercyclereducingchillersizingbyupto50%andalsobetterinthewintercyclethanmostsystemswithheatrecovery.
FACTS AbOuT JOHn DALTOn buILDIng
• Assembly hall lecture theatre with the
capacity of 234
• Tiered Lecture theatres with the capacity
of 60–234
• Meeting rooms with the capacity of 20–60
• Computer training suites with the capacity
of 20-40
Further referencesUnilever, Kingston, UK
Manchester Metropolitan University,
UK Fitzrovia, London, UK
M W Kellog, London, UK
227 Tottenham Court Road, London, UK
Bidborough House, London, UK
Greenwich Peninsula, London, UK
We Bring Air to Life
Fläkt Woods group SA18, avenue Louis Casaï, CH-1209 Geneva, SwitzerlandTel. +41 22 309 3800email [email protected] www.flaktwoods.com
See global website for international sales offices www.flaktwoods.com
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Fläkt Woods is a globalleader in air management.We specialise in the design and manufacture of a wide range of air climate and airmovement solutions. And our collective experience is unrivalled.
Our constant aim is toprovide systems thatprecisely deliver requiredfunction and performance, as well as maximise energy efficiency.
Air Handling units (AHus)
Modular,compactandsmallAHUunits.Designedtoensureoptimisa-tionofindoorairquality,operationalperformanceandservicelife.
Air Terminal Devices and Ducts
Supplyandexhaustdiffusersandvalvesforinstallationonwalls,ceilingorfloorareallincludedinourlargerangeandfitalltypesofapplications.
Chilled beams
Activeinductionbeamsforventilation,coolingandheating,andpassiveconvectionbeamsforcooling.Forsuspendedorflush-mountedceilinginstallation–andmulti-serviceconfig-uration.WithuniqueComfortControlandFlowPatternControlfeatures.
Residential ventilation
Acompleterangeofproductsforresidentialventilation.Consistsofventilationunits,exhaustairfansandcookerhoodsdesignedtooptimiseindoorcomfortandsaveenergy.
Energy recoveryDessicant-basedproductandsystemsthatrecoverenergy,increaseventilationandcontrolhumidity.
Fans
Advancedaxial,centrifugalandboxedfansforgeneralandspecialistapplications.ComprehensiverangeincludinghightemperatureandATEXcompliantoptions.Engineeredforenergyefficiencyandminimisedlifecyclecost.
Chillers
Air-cooledandwater-cooledchillerswithcoolingcapacityupto1800kW.Designedtominimiseannualenergyconsumptioninalltypesofbuildings.
Controls and drives
Variablespeeddrivesandcontrolsystems,alltestedtoensuretotalcompatibilitywithourproducts.Specialistteamcanadviseonenergysavingandoverallsystemintegration.
Acoustical products
Acompletelineofsoundattenuatingproducts,includingrectangularandroundsilencers,MediaFreesilencers,customsilencersandacousticenclosurepanels.
Solutions for all your air climate and air movement needsFläktWoodsisprovidingsolutionsforventilationandairclimateforbuildingsaswellasfansolutionsforIndustryandInfrastructure.