h-accmcx-qa

7/29/2019 H-ACCMCX-QA

http://slidepdf.com/reader/full/h-accmcx-qa 1/8

H-ACCMCX-QA April2011

Q&A:Air-CooledCondenserwithMicrochannelCoilTechnology

CONTENTS

MicrochannelCoilTechnology .....................................................................................................pages2-6

VSECMotors.................... .................... ................... .................... ................... .................... .................... ..... page7



Q&A:MicrochannelAir-CooledCondenser

Q1. Whatismicrochannelcoiltechnology?

Q2. HowisthemicrochannelcoilbetterthananRTPFcoil?

Microchannelcoilshavesignicantlyimprovedperformanceovertraditionalcopper/aluminumRTPFcoilsina

numberofareas:

1.ImprovedHeatTransferPerformance

Microchannelcoils’heattransferperformanceis20-30%higherthanstandardRTPFcoilsofthesamesize,enabling

comparablecapacitytobeachievedwithasmallercoil.

Thehigherheattransferperformanceisobtainedbytheattubes,whichmaximizeairsideheattransfer,and

microchannelswithinthetubes.Themicrochannelsmaximizerefrigerantsideheattransferviamultipletiny refrigerantchannelswhichprovideincreasedprimarysurfacearea.Additionally,themetallurgicaln-tubebond

resultingfromthebrazeoperationmaximizessurfacecontactandincreasestheheattransfersurfacearea,further

improvingtheheattransferperformanceofthecoil.

2.ReducedRefrigerantCharge

Microchannelcoilshaveasmallervolume,loweringcondenserrefrigerantchargebymorethan

70%.Assuch,theuseofmicrochannelcoilsprovidesamoreenvironmentallyfriendlysolutionforrefrigeration

systemstohelpreduceozonedepletionandglobalwarming.

3.ImprovedCorrosionProtection

MicrochannelcoilshavebeenproventolastsignicantlylongerthanstandardRTPFcoilsinextendedtests.

Thecorrosionpotentialwiththeallaluminummicrochannelcoilsissignicantlylowerthanincopper/aluminum (bi-metal)RTPFcoilsastherearenodissimilarmetalstoinitiategalvaniccorrosion.Thismakesmicrochannelcoilsan

inherentlybettersolutionforcoastalinstallations,oranyapplicationwherecorrosionmaybeaconcern.

PleaserefertoQuestion7formoredetailsonhowmicrochannelcoilsperforminacorrosiveenvironment.

™MicrochannelCoilTechnology

DEFINITIONS

RTPF – Traditional Cu/Al round tube, plate n coil

E-coat – Generic term for a coil coating that is either electro-deposited or a baked epoxy

Tubes

Fins

Manifold

Microchannels

©2011HeatcraftRefrigerationProducts,LL

Microchannelcondensercoilsareallaluminumcoils

withmultipleattubescontainingsmallchannels

(microchannels)throughwhichrefrigerantows.

Heattransferismaximizedbytheinsertionof

angledandlouvered

nsin-betweentheattubes.Thesecomponents

arejoinedwithtworefrigerantmanifoldsusingan

aluminum-zincalloybrazingmaterialina

nitrogen-chargedbrazefurnacetomakethe

completedmicrochannelcoil.

Coilcircuitingisaccomplishedbyplacingbaesin

thedistributionmanifoldstofeedtherefrigerantthroughtheattubes.




4.Durability&ReducedLeaks

Microchannelcoilsrequireonlyonebrazeoperationversus100-250manuallybrazedjointsforRTPF,

signicantlyreducingthelikelihoodforleaks.Additionally,theattubesserveasanguardtohelpprotectthens

fromdamage.

5.EaseofService&Repair

Microchannelcoilsareeasilycleanedandcanbeeldrepairedusingatwo-partepoxyprocess.

Microchannelcoilsareaboutoneinchthickallowingforeasyremovalofanydebristhatmaybecaughtwithin

thecoil.ThisisnotsowithRTPFcoils,whichareoften2to5inchesthickwithstaggeredtubepatternsusing

corrugatednswhichmakedebrisremovaldicult,ifnotimpossible,insomecircumstances.Thedurabilityof

microchannelcoilsalsoallowsforpressurewashing(usingabroadspraypattern),whichisnotrecommendedwith

RTPFcoils.

Coilleaks,whileunlikely,canalsobeeasilyrepairedintheeldusingasimpleprocess.

PleaserefertoQuestion6formoredetailsoneldrepairofleaksinmicrochannelcoils.

Q3. Whereelsehavemicrochannelheatexchangersbeenused,andwhy?

Microchannelcoilshavebeenusedintheautomotiveindustryforovertwodecadesandarenowanindustry

standard.MicrochannelcoilshavereplacedRTPFcoilsinallmainstreamautomotiveairconditioningcondenser,

radiatorandoilcoolerapplications.

Theswitchtomicrochannelcoilsenabledtheautomotiveindustrytoavoidincreasingtheweightoftheirvehicles

andcomplywithregulationsrequiringaphaseoutofR-12tothemoreenvironmentallyfriendlyR-134a.

MicrochannelcoilsallowedtheindustrytomaintainthesamecapacitywithR-134aastheyhadobservedwithR-12.

Microchannelcoilshavealsobeeninstalledinour1/2-6HPCondensingUnitswithverygoodresultsandreliability.

Q4. Ifmicrochannelheatexchangersaresuchgreattechnology,whyhasn’titbeenadoptedbyotherindustries?Microchannelheatexchangershavebeenaroundsincethe1980’sintheautomotiveindustry.Whilethemeritsofthe

technologyhavebeenknownfordecades,applicationofmicrochannelheatexchangerstonon-automotiveindustry

applicationswerecostprohibitiveduetothelowervolumes.Ithasonlybeenrecentlythatthemanufacturing

advancesinmicrochannelheatexchangehaveenabledthetechnologytobepricedcompetitivelywithtraditional

RTPFcoilsintheHVACRindustry.However,manymicrochannelcoilsuppliersarestillnotcostcompetitivefor

refrigerationvolumes.

Q5. Thislookslikeprettytightnspacing.Won’tthiscoilclogupfasterthanourcurrentcoils?

Atrstglance,thetightnspacingofthemicrochannelcoildoeslooklikeitmightposeaproblem.Inapplication,it

islesslikelytoclogthantraditionalRTPFcoils.

Uponcloserinspectionofthemicrochannelcoilyouwillseethatthecoilisonly1.06”thick,vs.2.5”to5.2”thickfortypicalRTPFcoils.TheRTPFcoil’scorrugatednpatterncoupledwithitsthicknessandthestaggeredtubepattern

providemoreopportunityforcloggingthanthemicrochannelcoil.

Asaresult,themicrochannelcoilislesslikelytoclogandiseasiertoclean.




Q6. Whatcanbedoneaboutleaks?Ithasbeensaidrepairingleaksinanaluminumcoilisclosetoimpossible.

Sincetherearenomanuallybrazedjointsinmicrochannelcoils,andtheunitsaredesignedwitharigidstructure,the

likelihoodofleaksisdramaticallyreduced.However,ifrepairtohorizontaltubesisnecessary,asimpleprocessusingan

epoxybasedsealant(suchasRedEpoxy),acleaningsolution,avacuumpump,afewsimpletools,andahotairgunis

allthatisrequired.

2. Clean the area

3. Enlarge the leak area

4. Pull a vacuum

5. Apply a two-part,

heat cured epoxy

6. Cure

StepstoRepairMicrochannelCoils

1. Locate the leak




Q7. Howdomicrochannelcoilsperforminacorrosiveenvironment?

Theall-aluminummicrochannelcoilswithzinccladdingperformverywellinacorrosiveenvironment.A

coastalcorrosiontestwasperformedtocomparethecorrosionresistanceofCu/AlRTPFcoilsandall-aluminum

microchannelcoils.Afteroneyear,bothcoilsweretestedtomeasurecurrentperformanceagainstbaseline

performance.Thechartbelowshowsanimperceptiblechangeinthemicrochannelperformanceandapproximately

an8%reductionincapacityfortheCu/AlRTPF.

Inadditiontotheperformancetesting,beforeandafterphotographsofthecoilsshowamarkeddierencein the

twocoiltypes.

Microchannel - Start

Microchannel- After 1 Year

RTPF -After1 Year

Source:ModineManufacturingCompany

Figure2–RTPFCoilwith1YearofExposure

Figure4–Finswith1YearofExposure

Figure1–RTPFCoilwithNoExposure

Figure3–FinswithNoExposure

RTPF

MicrochannelCoils

Source:ModineManufacturingCompany




Q8. Howwillthealuminumcoilbejoinedtothecoppertubingintheunit?

Themicrochannelcoilwillhaveastainlesssteeltransitionjointbrazedontothealuminumheaderconnection.Oneend

ofthistransitionjointwillhavecopperplatingwheretheunittubingattaches.Becausethecopperandaluminumdonot

touch,thereisnochanceforgalvaniccorrosion.

Q9. Thechannelsareverysmall,won’ttheseplugup?Intwoseparateteststoevaluatesituationsthatcouldleadtocloggingofthechannels,HeatcraftRefrigerationProducts

didnotobserveanychangeinperformanceorinternalcoilplugging.Thersttestusingmultipleunitswithmicrochanne

coilshadthecompressorsgothroughaslowburnouttoobtainaworst-caseburnoutsituation.Inthesecondtest,

miscellaneousdebris(copper,ux,moisture,dust)wasaddedtotherefrigerant.Inbothcasestherewasnochange

observedinperformanceorinternalcoilplugging.

Oursupplierperformedasimilartesttosimulatecompressorburnoutwiththesameresults;nodegradationof

performanceorindicationofinternalcoilplugging.

Q10. HowmuchrefrigerantchargereductionwillIbeabletoachievewithmicrochannelcoils?

Theamountofrefrigerantchargerequiredbythecondenserisreducedbymorethan70%.Thetotalsystemchargewill

dependonthesystemarrangements,connectionmanifoldingandthelengthoftheliquidline.

Q12. IsthereamaximumdesignTDfortheseunits?

Theseunitsareoptimizedforoperationatorbelow15°T.D.Operationabove15°T.D.mayresultinexcessivepressuredrop.

Q11. Canthesecoilsbereplacedifdamaged?

Wecananticipatethatthestructuralrigidityofthecoilscoupledwiththeeliminationofmanually

brazedjointsandimprovedcorrosionresistancewillsignicantlyreducethelikelihoodofcoilfailure.

However,ifacoilmustbereplaced,theseunitshavebeendesignedtofacilitateaveryeasyreplacement

process.ReplacementmicrochannelcoilswillbeavailablethroughInterlink™Parts.Interlink™Partscan

bereachedat(800)686-7278orwww.heatcraftrpd.com

Note:Attimeoforiginalinstallation,customershouldallowsucientroomtoaccessandreplacecoil.




VariableSpeedECMotors(VSEC)

Q1. WhatisanECmotor?HowisthisbetterthanastandardPSCmotor?

Electroniccommutation(EC)andsometimesreferredtoasbrushlessdirectcurrent(BLDC),allowsformoreecient

controloverthespeedofthemotor.ThemotorspeedofanACmotorisdeterminedbythenumberofpolesin

themotorwinding;increasingthenumberofpoleswilldecreasethemotorspeed.InanACmotor,thatspeedisdeterminedbythefrequencyofthealternatingcurrent.Ofcourse,anACmotorisnotlimitedtojustonespeed,but

itdoesmeanthatACmotorsaredesignedtooperateataparticularspeed.TheeciencyofanACmotor(suchasa

PSCmotor)dropssignicantlyasthemotorRPMdeviatesawayfromthedesignmotorspeed.

Q2. WhatistheVariableSpeedECMotor?

ThespeedofanECmotorisgovernedbytheswitchingofelectronics.Thismeansthattheabilitytocontrolspeed

isautomaticinanECmotor.ItalsomeansthatanECmotorrunsatnearfulleciencywhetheritisatstart-up,full

speedoranyspeedinbetween.AnECmotoroersupto50%greatereciencythanashaded-polemotor,andup

to35%greatereciencythanaPSCmotor.Thisisnotthecaseformotorscontrolledbyvariablevoltagecontrols,

inverters,orwavechoppers,especiallyathtelowspeedrange.

Overall,avariablespeedECsystemprovidesamorestablesystem,improvesproductintegrity,improvescompressordurabilityandreducesenergyconsumption.



Since product improvement is a continuing eort,

we reserve the right to make changes in specifcations without notice.

The name behind the brands you trust.™

ABrandofHeatcraftRefrigerationProducts,LLC

2175WestParkPlaceBlvd.•StoneMountain,GA•30087

800.848.9889

www.Heatcraftrpd.com

h-accmcx-qa

Documents