暖通空调专业外文翻译

英文文献

AirConditioningSystems

Airconditioninghasrapidlygrownoverthepast50years,fromaIuxurytoastandard

systemincIudedinmostresidentiaIandcommerciaIbuiIdingsoIn1970,36%of

residencesintheUoSowereeitherfullyairconditionedorutiIizedaroomair

conditionerforcooling(BIue,etaIo,1979)oBy1997,thisnumberhadmorethan

doubIedto77%,andthatyearaIsomarkedthefirsttimethatoverhalf(50.9%)of

residencesintheUoSohadcentraIairconditioners(CensusBureau,1999)。An

estimated83%ofaIInew

homesconstructedin1998hadcentraIairconditioners(CensusBureau,1999)。

AirconditioninghasaIsogrownrapidlyincommerciaIbuildings。From1970to1995,

thepercentageofcommerciaIbuiIdingswithairconditioningincreasedfrom54to73%

(JacksonandJohnson,1978,andDOE,1998).

Ai.conditionin.i.buiIding.i.usuaII.accompIishe.wit.th.us.o.mechanica.o.heat-ac

tivate.equipment.I.mos.appIications.th.ai.conditione.mus.provid.bot.cooIin.an.dehu

midificatio.t.maintai.comfor.i.th.buiIding.Ai.conditionin.system,ar.aIs.use.i.othe

.appIications.sue.a.automobiIes.trucks,aircraft.ships.an.industria.faciIities.Howe

ver.th.descriptio.o.equipmen.i.thi.chapte.i.Iimite.t.thos.commonI.use.i.commercia.

an.residentia.buiIdings.

Commercia.buiIding.rang.fro.Iarg.high-ris.offic.buiIding.t.th.corne.convenienc.sto

re.Becaus.o.th.rang,i.siz.an.type.o.buiIding.i.th.commercia.sector.ther.i..wid.var

iet.o.equipmen.appIie.i.thes.buiIdings.Fo.large,buiIdings.th.ai.conditionin.equipm

en.i.par.o..tota.syste.desig.tha.incIude.item.sue.a..pipin.system,ai.distributio.s

ystem.an.coolin.tower.Prope.desig.o.thes.system.require..quaIifie.engineer.Th.resi

dentia.buiIdin,secto.i.dominated

bysinglefamilyhomesandlow-riseapartments/condominiumsoThecooIingequipment

appIiedinthesebuiIdingscomesinstandardapackages"thatareoftenbothsizedand

insta11edbytheairconditioningcontractoro

ThechapterstartswithageneraIdiscussionofthevaporcompressionrefrigeration

eyeIethenmovestorefrigerantsandtheirseIection,followedbypackagedChilled

WaterSystems.

1.1VaporCompressionCycle

Eve.thoug.ther.i..Iarg.rang.i.size.an.variet.o.ai.conditionin.system.use.i.bui

Idings.mos.system,utiIiz.th.vapo.compressio.eyeI.t.produc.th.desire.cooIin.an.dehu

midification.Thi.eyeI.i.aIs.use.fo.refrigeratin.an.freezin.food.an.fo.automotiv.ai

.conditioning.Th.firs.paten,o..mechanicaII.drive.refrigeratio.syste.wa.issue.t.Jac

o.Perkin,i.183.i.London,an.th.firs.viabI.commercia.syste.wa.produce.i.185.b.Jame.H

arriso.an.D。E.Siebe。

Beside.vapo.compression.ther.ar.tw.Ies.commo,method,use.t.produc.cooIin.i.buiIding

s.th.absorptio.eyeI.an.evaporativ.cooling.Thes.ar.describe.Iate.i.th.chapter.Wi1.1

h.vapor

compressioneyeIe,aworkingfluid,whichiscalledtherefrigerant,evaporates

andcondensesatsuitabIepressuresforpracticaIequipmentdesignso

Thefourbasiccomponentsineveryvaporcompressionrefrigerationsystemarethe

compressor,condenser,expansiondevice,andevaporatoroThecompressorraisesthe

pressureoftherefrigerantvaporsothattherefrigerantsaturationtemperatureis

sIightlyabovethetemperatureofthecoolingmediumusedinthecondenseroThetype

ofcompressoruseddependsontheapplicationofthesystem。LargeelectricchiIlers

typicalIyuseacentrifugalcompressorwhilesmaIIresidentiaIequipmentusesa

reciprocatingorscrolIcompressor.

Thecondenserisaheatexchangerusedtorejectheatfromtherefrigeranttoa

cooIingmediumoTherefrigerantentersthecondenserandusuaIlyIeavesasasubcooIed

IiquidoTypicalcooIingmediumsusedincondensersareairandwateroMost

residential-sizedequipmentusesairasthecooIingmediuminthecondenser,whilemany

IargerchiIlersusewateroAfterIeavingthecondenser,theIiquidrefrigerantexpands

toaIowerpressureintheexpansionvaIveo

TheexpansionvaIvecanbeapassivedevice,suchasacapiIIarytubeorshort

tubeorifice,oranactivedevice,suchasathermaIexpansionvaIveoreIectronic

expansionvaIveoThepurposeofthevaIveistoreguIatethefIowofrefrigerantto

theevaporatorsothattherefrigerantissuperheatedwhenitreachesthesuetionof

thecompressoro

A.th.exi.o.th.expansio.vaIve.th.refrigeran.i.a..temperatur.beIo.tha.o.th.mediu

.(ai.o.water,t.b.cooIed.Th.refrigeran.traveI.throug..hea.exchange,caIIe.th.evapora

tor.I.absorb,energ.fro.th.ai.o.wate.circuIate.throug.th.evaporator.I.ai.i.circulat

e.throug.th.evaporator,th.syste.i.caIIe..direc.expansio.system.I.wate.i.circuIate.

throug.th.evaporator,i.i.caIIe..chiIIer.I.eithe.case.th.refrigeran.doe.no.mak.dire

c.contac.wit.th.ai.o.wate.i.th.evaporator.

TherefrigerantisconvertedfromaIowquaIity,two-phasefluidtoasuperheated

vaporundernormaIoperatingconditionsintheevaporatoroThevaporformedmustbe

removedbythecompressoratasufficientratetomaintaintheIowpressureinthe

evaporatorandkeepthecycleoperatingo

AlImechanicaIcoolingresultsintheproductionofheatenergythatmustberejected

throughthecondenseroInmanyinstances,thisheatenergyisrejectedtothe

environmentdirectIytotheairinthecondenserorindirectIytowaterwhereitis

rejectedinacooIingtoweroWithsomeappIications,itispossibIetoutilizethis

wasteheatenergytoprovidesimultaneousheatingtothebuiIdingoRecoveryofthis

wasteheatattemperaturesupto65°C(1500F)canbeusedtoreducecostsforspace

heating.

Capacitie.o.ai.conditionin.ar.ofte.expresse.i.eithe.ton.o.kiIowatt.

(kW.o.cooIing.Th.to.i..uni.o.measur.reIate.t.th.abiIit.o.a.ic.plan.t.freez.on.sho

r.to.(90.kg.o.ic.i.2.hr.It.valu.i.3.5.k.(12,

00.Btu/hr).Th.k.o.therma.cooIin.capacit.produce,b.th.ai.conditione.mus.no.b.confus

e.wit.th.amoun.o.eIectrica.powe.

(aIs.expresse.i.kW.require.t.produc.th.cooIin.effects

2O1RefrigerantsUseandSeIection

U.unti.th.mid-

1980s.refrigeran.seiectio.wa.no.a.issu.i.mos.buiIdin.ai.conditionin.appIication.be

caus.ther.wer.n.reguIation.o.th.us.o.refrigerants.Man.o.th.refrigerant.historicaII

.use.fo.buiIdin.ai.conditionin.appIication.hav.bee.chIorofIuorocarbon.(CFCs.an.hyd

rochIorofIuorocarbon.(HCFCs).Mos.o.thes.refrigerant.ar.nontoxi.an.nonfIammabIe.Ho

wever.recen.UoS.federa.reguIation.(EP.1993a.EP.1993b.an.Internationa,agreement.

(UNEP.1987.hav.pIace.restriction.o.th.productio.an.us.o.CFG.an.HCFCs.HydrofIuoroc

arbon.(HFCs.ar.no.bein.use.i.som.appIication.wher.CFC.an.HCFC.wer.used.Havin.a.und

erstandin.o.refrigerant.ca.heI..buiIdin.owne.o.enginee.mak..mor.informe.decisio.ab

ou.th.bes.choic.o.refrigerant.fo.specifi.appIications.Thi.sectio.discusse.th.diffe

ren.refrigerant.use.i.o.propose,fo.buiIdin.ai.conditionin.appIication.an.th.reguIa

tion.affectin.thei.use.

Th.America.Societ.o.Heating.Refrigeratin.an.Ai.Conditionin.Engineer.

(ASHRAE.ha..standar.numberin.system,fo.identifyin.refrigerant.

(ASHRAE.1992).Man.popuIa.CFC.HCFC.an.HF.refrigerant.ar.i.th.methan.an.ethan.seri

e.o.refrigerants.The.ar.caIe.haIocarbons.o.haIogenate.hydrocarbons,becaus.o.th.pr

esenc.o.haIoge.eIement.sue.a.fIuorin.o.chIorin.(King.1986)

Zeotrope,an.azeotrope.ar.mixture,o.tw.o.mor.differen.refrigerants..zeotropi.mi

xtur.change,saturatio.temperature,a.i.evaporate.

(o.condenses,a.constan.pressure.Th.phenomen.i.caIIe.temperatur.gIide.A.atmospheri

.pressure.R-407.ha..boiIin.(bubble,poin.o.-44°.(-47°F.an..condensatio.

(dew.poin.o.-37.(-35F).whic.give.i..temperatur.gIid.o.7.(12°

F).A.azeotropi.mixtur.behave.Iik..singI.componen.refrigeran.i.tha.th.saturatio.tem

peratur.doe.no.chang.appreciabl.a.i.evaporate.o.condense,a.constan.pressure.R-

410.ha..smaI.enoug.temperatur.glid.(les.tha.5。5°C.10°F.tha.i.i.considere..near一

azeotropi.refrigeran.mixture.

ASHRA.group,refrigerant.b.thei.toxicit.an.fIammabiIit.(ASHRAE.1994)o

Grou.A.i.nonfIammabI.an.Ieas.toxic.whiI.Grou.B.i.fIammabI.an.mos.toxic.Toxicit.i.b

ase.o.th.uppe.safet.Iimi.fo.airborn.exposur.t.th.refrigerant.I.th.refrigeran.i.non

toxi.i.quantitie.les.tha.40.part.pe.miIIion.i.i..Clas..refrigerant.I.exposur.t.les

.tha.40.part.pe.miIIio.i.toxic,the.th.substanc.i.give.th..designation.Th.numerica.

designation.refe.t.th.fIammabiIit.o.th.refrigerant.Th.las.colurn.o.Tabi.4.2o.show,

th.toxicit.an.flammabiIit.ratin.o.commo,refrigerants.

Refrigeran.2.i.a.HCFC.i.use.i.man.o.th.sam.appIications.an.i.stiI.th.refrigera

n.o.choic.i.man.reciprocatin.an.sere,chiller.a.weI.a.smaI.commercia.an.residentia.

package,equipment.I.operate,a..muc.highe.pressur.tha.eithe.R—1.o.R—

12.Restriction.o.th.productio.o.HCFC.wiI.star,i.2004.I.2010.R—

2.canno.b.use.i.ne.ai.conditionin.equipment.R-2.canno.b.produce.afte.202.

(EPA.1993b).

R—407.an.R-410.ar.bot.mixture.o.HFCs.Bot.ar.considere.replacement,fo.R-22.R

—407.i.expecte.t.b..drop一

i.repIacemen.refrigeran.fo.R-22.11.evaporatin.an.condensin.pressure.fo.ai.conditio

nin.appIication.ar.cIos.t.thos.o.R-2.(Tab1.4.2o3).However,replacemen.o.R-

2.wit.R-407.shouI.b.don.onI.afte.consuItin.wit.th.equipmen.manufacturer.A..minimum

.th.Iubrican.an.expansio.devic.wiI.nee.t.b.repIaced.Th.firs.residential——

size,ai.conditionin.equipmen.usin.R-410.wa.introduce.i.th.U。

S.i.1998.System.usin.R-410.operat.a.approximate1.50.highe.pressur.tha.R-2.(Tab1.4.

2.3).thus.R-410.canno.b.use.a..drop-i.refrigeran.fo.R-22.R-

410.system,utiIiz.compressors,expansio.vaIves.an.hea.exchanger,designe.specificaII

.fo.us.wit.tha.refrigerant.

Ammoni.i.wideI.use.i.industria.refrigeratio.appIication.an.i.ammoni.wate.absor

ptio.chiIIers.I.i.moderateI.fIammabI.an.ha..cIas..toxicit.ratin.bu.ha.ha.Iimite.ap

pIication,i.commercia.buiIding,unIes.th.chiIIe.plan.ca.b.isoIate.fro.th.buiIdin.be

in.coole.

(Toth.1994.Stoecker.1994).A..refrigerant.ammoni.ha.man.desirabI.quaIities.I.ha..

hig.specifi.hea.an.hig.therma.conductivity.It.enthaIp.o.vaporizatio.i.typicaII..t.

.time.highe.tha.tha.o.th.conmonI.use.haIocarbons.an.i.provide.highe.hea.transfe.co

mpare.t.haIocarbons.I.ca.b.use.i.bot.reciprocatin.an.centrifuga.compressors.

Researc.i.underwa.t.investigat.th.us.o.natura.refrigerants.sue.a.carbo,dioxid.

(R-744.an.hydrocarbon,i.ai.conditionin.an.refrigeratio.system.

(Builock.1997.an.Kramer.1991).Carbo,dioxid.operate,a.muc.highe.pressure,tha.conve

ntiona.HCFC.o.HFC.an.require.operatio.abov.th.critica.poin.i.typica.ai.conditionin

・appIications.Hydrocarbo,refrigerants.ofte.though,o.a.to.hazardou.becaus.o.fIammab

iIity.ca.b.use.i.conventiona.compressor,an.hav.bee.use.i.industria.appIications.R

290.propane,ha.operatin.pressure,clos.t.R-2.an.ha.bee.propose,a..replacemen.fo.R-2.

(Kramer.1991).Currently,ther.ar.n.commercia.system,sol.i.th.U.S.fo.buiIdin,operat

ion.tha.us.eithe.carbo,dioxid.o.fIammabI.refrigerants.

3o1ChilledWaterSystems

ChiIIe.wate.system.wer.use.i.les.tha.4.o.commercia.building.i.th.U.S.i.1995.Howeve

r.becaus.chiller.ar.usuaII.instalie.i.Iarge.buiIdings.chiller.coole.ove.28.o.th.U。

S.commercia.buiIdin,fIoo.spac.tha.sam.yea.(DOE.1998).Fiv.type.o.chi11er.ar.common

I.appIie.t.commercia.buiIdings.reciprocating.screw,scroII.centrifugaI.an.absorptio

n.Th.firs.fou.utiIiz.th.vapo.compressio.eyeI.t.produc.chiIIe.water.The.diffe.prima

riI.i.th.typ.o.compresso.used.Absorptio.chiIIer.utiIiz.therma.energ.

(typicaII.stea.o.combustio.source.i.a.absorptio.eyeI.wit.eithe.a.ammonia-

wate.o.water-1ithiu.bromid.solutio.t.produc.chiIIe.water.

3.2OveralISystem

A.estimate.86.o.chiIIer.ar.appIie.i.mu11ipI.chiIIe.arrangement.Iik.tha.show,i.

th.figur.(Bitond.an.Tozzi.1999).I.chiIIe.wate.systems,retur.wate.fro.th.buiIdin,i

.circulate.throug.eac.chiIIe.evaporato.wher.i.i.cooIe.t.a.acceptabI.temperatur.(ty

picalI..t.7C.(3.t.45F).Th.chiIIe.wate.i.the.distribute.t.water-to—

ai.hea.exchanger,sprea.throughou.th.faciIity.I.thes.hea.exchangers,ai.i.cooIe.an.d

ehumidifie.b.th.col.water.Durin.th.process,th.chiIIe.wate.increase.i.temperatur.an

.mus.b.returne.t.th.chiIler(s).

Th.chiIler.ar.water—

cooIe.chiIIers.Wate.i.circuate.throug.th.condense,o.eac.chiIIe.wher.i.absorb,hea.

energ.rejecte.fro.th.hig.pressur.refrigerant.Th.wate.i.the.pumpe.t..cooIin.towe.wh

er.th.wate.i.cooIe.throug.a.evaporatio.process.CooIin.tower,ar.describe.i..Iate.se

ction.Chiller.ca.aIs.b.ai.cooIed.I.thi.configuration.th.condenserwouI.b..refrigera

nt-to-ai.hea.exchange,wit.ai.absorbin.th.hea.energ.rejecte.b.th.hig.pressur.refrig

erant.

ChiIIer.nominaII.rang.i.capacitie.fro.3.t.18,00.k.(.t.510.ton).Mos.chiller.so

I.i.th.U.S.ar.eIectri.an.utiIiz.vapo.compressio.refrigeratio.t.produc.chiIIe.water

.Compressor,fo.thes.system.ar.eithe.reciprocating.screw,scroII.o.centrifuga.i.desi

gn..smaI.numbe.o.centrifuga.chiIler.ar.sol.tha.us.eithe.a.interna.combustio.engin.

o.stea.driv.instea.o.a.eIectri.moto.t.driv.th.compressoro

Th.typ.o.chiIIe.use.i..buiIdin.depend,o.th.appIication.Fo.Iarg.offic.buiIding.o.i.

chiIIe.plant.servin.mu11ipI.buiIdings.centripressor,ar.ofte.used.I.appIica

tion.unde.100.k.(28.tons,cooIin.capacities.reciprocatin.o.sere,chiller.ma.b.mor.ap

propriate.I.smaIIe.appIications.beIo.10.k.(3.tons).reciprocatin.o.scroI.chiIIer.a

r.typicaII.used.

3o3VaporCompressionChiIlers

Th.nomina.capacit.range,fo.th.fou.type.o.eIectricaII.drive.vapo.compressio.chi

IIers.Eac.chiIIe.derive.it.nam.fro.th.typ.o.compresso.use.i.th.chiIIer.Th.system,r

ang.i.capacitie.fro.th.smaIles.scroI.(3.kW..tons.t.th.larges.centrifuga.(18,

00.kW.500.tons).ChiIler.ca.utiIiz.eithe.a.HCF.(R-2.an.R-123.o.HF.

(R-134a.refrigerant.Th.stead,stat,efficienc.o.chiIIer.i.ofte.state.a..rati.o.th.p

owe.inpu.(i.kW.t.th.chiIIin.capacit.(i.tons)..capacit.ratin.o.on.to.i.equa.t.3。

5.k.o.12,00.btu/h.Wit.thi.measur.o.efficiency.th.smaIIe.numbe.i.better,centrifuga.

chiller.ar.th.mos.efficient.whereas.reciprocatin.chiIIer.hav.th.wors.efficienc.o.t

h.fou.types.Th.efficienc.number,provide.i.th.tabi.ar.th.stead,stat.fuIHIoa.effici

enc.determine.i.accordanc.t.ASHRA.Standar.3.

(ASHRAE.1995).Thes.efficienc.number,d.no.incIud.th.auxiIiar.equipment.sue.a.pump,

an.coolin.towe.fan.tha.ca.ad.fro.0。0.t.0.3.kW/to.t.th.number,show.

ChiIIer.ru.a.par.Ioa.capacit.mos.o.th.time.OnI.durin.th.highes.therma.load,i.t

h.buiIdin.wiI..chiIIe.operat.nea.it.rate,capacity.A..consequence,i.i.importan.t.kn

o.ho.th.efficienc.o.th.chiIIe.varie.wit.par.Ioa.capacity..representativ.dat.fo.th.

efficienc.

(i.kW/ton.a..functio.o.percentag.ful.Ioa.capacit.fo..reciprocating.screw,an.scroI

.chiIIe.pIu..centrifuga.chiIIe.wit.inIe.van.contro.an.on.wit.variabI.frequenc.driv

.(VFD.fo.th.compressor.Th.reciprocatin.chiIIe.increase.i.efficienc.a.i.operate,a..

smaIIe.percentag.o.fuI.load.I.contrast,th.efficienc.o..centrifuga.wit.inle.van.con

tro.i.relative!,constan.unti.theIoa.faII.t.abou.60.o.it.rate.capacit.an.it.kW/to.i

ncrease.t.aImos.twic.it.full,loade.value.

1.1998.th.Ai.Conditionin.an.Refrigeratio.Institut.(ARI.deveIope..ne.standar.th

a.incorporate.int.thei.rating.par.Ioa.performanc.o.chiIIer.

(AR.1998c).Par.Ioa.efficienc.i.expresse.b..singl.numbe.calIe.th.integrate.par.Ioa

.vaIu.(IPLV).Th.IPL.take.dat.simiIa.t.tha.i.Figur.40

2..an.weight.i.a.th.25%.50%.75%,an.100.load.t.produc..singI.integrate.efficienc.n

umber.Th.weightin.factor,a.thes.load.ar.0。12.0.，5.0。42.an.0。

01.respectiveIy.Th.equatio.t.determin.IPL.is:

IPLV=----------------i----------------

0.01^0.42^0.45^0.12

ABCD

where,

A=efficiencyat100%load

B=efficiencyat75%load

C=efficiencyat50%load

D=efficiencyat25%load

MostoftheIPLVisdeterminedbytheefficiencyatthe50%and75%partIoadvaIueso

ManufacturerswiIIprovide,onrequest,IPLVsasweIIaspartIoadefficiencieso

Th.fou.compressor,use.i.vapo.compressio.chiIIer.ar.eac.briefl.describe.beIow.WhiI.

centrifuga.an.sere.compressor,ar.primariI.use.i.chiIIe.appIications,reciprocatin.a

n.scrol.compressor,ar.aIs.use.i.smaIIe.unitar.package,ai.conditioner,an.hea.pumps.

3.4ReciprocatingCompressors

Th.reciprocalin.compresso.i..positiv.dispIacemen.compressor.0.th.intak.strok.o

.th.piston..fixe,amoun.o.ga.i.puIIe.int.th.cyIinder.0.th.compressio.stroke,th.ga.i

.compresse.unti.th.discharg.vaIv.opens.Th.quantit.o.ga.compresse.o.eac.strok.i.equ

a.t.th.dispIacemen.o.th.cyIinder.Compressor,use.i.chiller.hav.multipl.cylinders.de

pendin.o.th.capacit.o.th.compressor.Reciprocatin.compressor,us.refrigerant.wit.Io.

specifi.voIume.an.reIativeI.hig.pressures.Mos.reciprocatin.chiIIer.use.i.buiIdin.a

ppIication.currentI.empIo.R-22.

Moder,high-spee.reciprocatin.compressor,ar.generaII.Iimite.t..pressur.rati.o.a

pproximateI.nine.Th.reciprocatin.compresso.i.basicaII..constant-voIum.variabIe-

hea.machine.I.handIe.various

discharg.pressure,wit.relative!,smaI.change,i.inIet-voIum.fIo.rat.a.show.b.th.

heav.Iin.

(Iabele.1.cyIinders).Condense,operatic,i.man.chiller.i.reIate.t.ambien.condition

s.fo.exampIe.throug.cooIin.towers,s.tha.o.cooIe.day.th.condense,pressur.ca.b.reduc

ed.Whe.th.ai.conditionin.Ioa.i.Iowered.Ies.refrigeran.circuIatio.i.required.Th.res

ultin.loa.characteristi.i.represente.b.th.soli.Iin.tha.run.fro.th.uppe.righ.t.Iowe

.lefto

ThecompressormustbecapabIeofmatchingthepressureandfIowrequirements

imposedbythesystemoThereciprocatingcompressormatchestheimposeddischarge

pressureatanyIeveIuptoitsIimitingpressureratiooVaryingcapacityrequirements

canbemetbyprovidingdevicesthatunIoad

individua.o.mu11ipI.cyIinders.Thi.unIoadin.i.accompIishe.b.bIockin.th.suetio.o

.discharg.vaIve.tha.ope.eithe.manuaII.o.automaticaIIy.Capacit.ca.aIs.b.controIIe.t

hroug.th.us.o.variabI.spee.o.mu11i-spee.motors.

Whe.capacit.contro.i.implemente.o..compressor,othe.factor,a.part一

Ioa.condition.nee.t.considered.sue.a.(a.effec.o.compresso.vibratio.an.soun.whe.unI

oader.ar.used.

(b.th.nee.fo.goo.oi.retur.becaus.o.Iowe.refrigeran.veIocities.an.(c.prope.functio

nin.o.expansio.device.a.th.owe.capacities.

Wit.mos.reciprocatin.compressors,oi.i.pumpe.int.th.refrigeratio,syste.fro.th.c

ompresso.durin.norma,operation.System,mus.b.designe.carefuII.t.retur.oi.t.th.compr

esso.crankcas.t.provid.fo.continuou.Iubricatio.an.aIs.t.avoi.contaminatin.heat一

exchange,surfaces.

Reciprocatin.compressor,usuaII.ar.arrange.t.star,unIoade.s.tha.norma,torqu.motor,a

r.adequat.fo.starting.Whe.ga.engine.ar.use.fo.reciprocatin.compresso.drives.carefu

.matchin.o.th.torqu.requirement.o.th.compresso.an.engin.mus.b.considered.

3.5ScrewCompressors

Sere,compressors,firs.introduce.i.195.

(Thevenot.1979).ar.positiv.dispIacemen.compressors.The.ar.avaiIabI.i.th.capacit.r

ange.tha.overla.wit.reciprocatin.

compressor,an.smaI.centrifuga.compressors.Bot.twin-sere.an.singIe-

sere,compressor,ar.use.i.chiIlers.Th.twin一

sere,compresso.i.aIs.caIIe.th.heIica.rotar.compressor..cutawa.o..twin一

sere.compresso.design.Ther.ar.tw.mai.rotor,(screws).On.i.designate.maI.an.th.othe.

femaI.0

Th.compressio.proces.i.accompIishe.b.reducin.th.voIum.o.th.refrigeran.wit.th.r

otar.motio.o.screws.A.th.Io.pressur.sid.o.th.compressor..voi.i.create.whe.th.rotor

,begi.t.unmesh.Lo.pressur.ga.i.draw.int.th.voi.betwee.th.rotors.A.th.rotor,continu

.t.turn.th.ga.i.progressivel.compresse.a.i.move.towar.th.discharg.port.One.reachin

..predetermine,voIum.ratio.th.discharg.por.i.uncovere.an.th.ga.i.discharge.int.th.

hig.pressur.sid.o.th.system.A..rotatio.spee.o.360.rpm..sere,compresso.ha.ove.14,00

.discharge.pe.minut.(ASHRAE.1996).

Fixe,suetio.an.discharg.port.ar.use.wit.sere.compressor,instea.o.vaIves.a.use.

i.reciprocatin.compressors.Thes.se.th.built—

i.voIum.rati..th.rati.o.th.voIum.o.fIui.spac.i.th.meshin.rotor,a.th.beginnin.o.th.

compressio.proces.t.th.voIum.i.th.rotor,a.th.discharg.por.i.firs.exposed.Associate

.wit.th.buiIt-

i.voIum.rati.i..pressur.rati.tha.depend,o.th.propertie.o.th.refrigeran.bein.compre

ssed.Sere,compressor.hav.th.capabiIit.t.operat.a.pressur.ratio,o.abov.20:.(ASHRAE

.1996).Pea.efficienc.i.obtaine.i.th.discharg.pressur.impose,b.th.syste.matche.th.

pressur.deveIope.b.th.rotor,whe.th.discharg.por.i.exposed.I.th.interIob.pressur.i.

th.screw,i.greate.o.Ies.tha.discharg.pressure,energ.Iosse.occu.bu.n.har.i.don.t.th

,compressoro

Capacit.moduIatio.i.accompIishe.b.sIid.vaIve.tha.provid..variabI.suetio.bypas.

o.deIaye.suetio.por.cIosing.reducin.th.voIum.o.refrigeran.compressed.ContinuousI.v

ariabI.capacit.contro.i.mon,bu.steppe,capacit.contro.i.offere.i.som.manufac

turers.machines.VariabI.discharg.portin.i.avaiIabI.o.som.machine.t.aIlo.contro.o.t

h.built-i.volum.rati.durin.operationo

Oi.i.use.i.sere,compressor,t.sea.th.extensiv.cIearanc.space,betwee.th.rotors.t.coo

.th.machines.t.provid.lubrication.an.t.serv.a.hydrauIi.fIui.fo.th.capacit.controls

.A.oi.separate,i.require.fo.th.compresso.discharg.fIo.t.remov.th.oi.fro.th.high一

pressur.refrigeran.s.tha.performanc.o.syste.hea.exchanger.wiI.no.b.penaIize.an.th.

oi.ca.b.returne.fo.reinjectio.i.th.compressor.

Sere,compressor,ca.b.direc.drive.a.two-poI.moto.speed.

(5.o.6.Hz).Thei.rotar.motio.make.thes.machine.smoot.runnin.an.quiet.ReiiabiIit.i

.hig.wh