外文翻译--标准62.1-2004：系统设置：动态重置操作.doc

9翻译Standard62.1-2004:SystemOperation:DynamicResetOptionSeventeenyearsago,theventilationratesestablishedbyANSI/ASHRAEStandard62-1989,ventilationforAcceptableindoorairquality,increasedsubstantiallyoverthosepreviouslyrequiredbythe1981versionofthestandard.Fifteenyearslater,standard62-2004prescribednewminimumbreathingzoneventilationrateandanewcalculationproceduretofindtheminimumintakeairflowneededfordifferentventilationsystems.Describedinpreviousarticles,thesenewratesandproceduresmustbeusedtofindthedesignor“worst-case”outdoorairintakeflow,whichestablishestherequiredcapacityofmechanicalsystemequipment.Inthisarticle,weturnfromventilationsystemdesigntooperation.VariationinoccupancyorventilationairflowThenumberofoccupantsinmanyventilationzoneschangesduringnormal.Actualzonepopulationoftenfallsshortofparkdesignpopulationusedtoestablishthehighestzoneoutdoorairflowandoutdoorairintakeflowneeded.Consequently,standard62.1allowsbreathingzoneand/orintakeairflowtoberesetinresponsetochangesinzonepopulationortheresultingchangesinthezoneventilationairflowperperson.Toresetventilationbasedonthecurrentpopulationwithinazonerequiresareasonablyaccurateestimateofpopulationorbreathingzoneoutdoorairrate.Standard62.1listsfourexamplemeasuresusedtoestimatevariationsinoccupancyandonemeasuretoestimatevariationinventilationairflow.DirectCountofPeople.Insomezones,occupantentryandexitmaybeorderly.Usingappropriatesensorsandcountingcontrols,thedifferencebetweenentryandexiteventscanbeusedtoestimatepopulationbasedonadirect“count”.Ticketsalesmightalsobeusedasanestimateofpopulation.Someretailstoresorauditoriumsmaybeconfiguredtousetheseapproaches.Sensorsthatactuallysenseindividualoccupantsalsomightbeused,althoughsucharenotcommon.PresenceofPeople.Avariationtocountingoccupantsdirectlyinvolvessimplysensingthepresenceofoccupants.Motiondetectorscansensehumanactivityinoffices,conferenceroomsandsoon.Upondetectingmotion,thecontrolsystemassumesthatthezoneisoccupiedatparkpopulationandcallsforventilationaccordingly.Time-of-dayschedule.Insomezones,populationcanbepredictedbasedontime-of-day.Forinstance,thepopulationinagivenclassroominanelementaryschoolmaybeestimatedquiteaccuratelyduringanyhouroftheday.ThedailyscheduleforMr.BrownsfifthgradersplacestheminMr.Brownsclassroomfrom8a.m.until10a.m.,intheartroomfrom10a.m.until11a.m.,thenbackintheclassroomfrom11a.m.untilnoon,andsoon.Ifthebuildingcontrolsystemincludesanoccupancyschedulefortheclassroom,currentpopulationcanbeestimateandoutdoorairflowcanberesettomatchprescribedventilationairflowtocurrentpopulation.EstimateofOccupancyBasedonCO2andAirflow.AsMummahasshown,inasingle-zonesystem,zoneandoutdoorCO2levelalongwithintakeairflowcouldbesensedandassuminganoccupantactivitylevel,usedtoestimatecurrentpopulation.Atsteady-stateCO2concentrationzonepopulationcouldbefound,butinpractice,zonesseldomreachsteady-statecondition.So,inadditiontoaccurateCO2andairflowsensors,thisapproachrequiresacontrollercapableofsolvinganon-steadystateequation.And,sinceoccupantactivitylevelandCO2generationratecanvarywidely,calculatedpopulationmaynotbeaccurate.Duetoitscost,itscomplexityanditspotentialforpooraccuracy,notmanydesignersusethisapproach.However,donotconfusethisCO2-based“peoplecounting”measurewithournexttopic:traditionCO2based“demand-controlledventilation.”CO2BasedEstimateofCurrentOutdoorAirflowperPerson.Sincechangesinpopulationchangeventilation“demand”,anydynamicresetapproachthatrespondstozonepopulationcouldbereferredtoasdemand-controlledventilation(DCV).However,thisacronymhasbeenusedforyearstoreferspecificallytocontrolmeasuresthatsenseCO2concentrationasasurrogatefortheconcentrationofhumanbioeffluents.Themostpopulardynamic-resetapproachtopart-loadventilation,DCVcontrolsadjustoutdoorairflowratetomaintainzoneCO2andtherebybioeffluents-atlevelsthatwouldresultfromventilatingat,orabove,prescribedminimumoutdoorairflowrates.AsexplainedbyTaylor,CO2basedCO2DVCassumesthatpeopleproducebothodorsandCO2inproportiontotheiractivitylevel,thatoccupantactivitylevelinazonecanbeestimatedwithreasonableaccuracy.Andthatsteady-stateequationscanbeusedtoestimateventilationload.Muchthesameassteady-stateequationscanbeusedtoestimateheating/coolingload.Forsingle-zonesystems.TheminimumrequiredoutdoorairintakeflowcanberelatedtothedifferencebetweenindoorandoutdoorCO2level.TaylorgoesotoexplainhowdifferentialCO2levelcanbeincorporatedinonepossibleDVCapproachalsodiscussedinthe62.1Usersmanualanddetailedbelowasoneofseveralapproachestocontrolintakeairflowtoequalorexceedtheminimumrequiredventilationrate.ThepopulationestimateresultingfromanyofthefirstfourmeasurescanbeusedtorecalculatetheminimumbreathingzoneoutdoorairflowrequiredbyStandard62.1forthecurrentpopulation.Thisnewoutdoorairflowvaluethencanbeusedtofindcurrentminimumzoneoutdoorairflowneeded.Forsingle-zonesystems,thezoneoutdoorairflowrequirementequalstheintakeairflow.Anycontrollerusedtoimplementthesefourresetapproachesmustbecapableofdoingsomesimplecalculation,sincethepopulationestimatemustbetranslatedtoacurrentoutdoorairflowsetpoint,andmustincludemeanstoadjustoutdoorairflowtomaintainthecurrentsetpoint.Thefifthmeasuredescribedearliercanbeusedtocontrolintakeairflowdirectly,withoutactuallycalculatingeithercurrentpopulationortheminimumoutdoorairintakeflowcurrentrequiredbyStandard62.1.inasense,anyDCVapproachthatmaintainscontrolsbioeffluentsdirectlyinresponsetobothcurrentpopulationandcurrentintakeairflow.DVCapproachesneedcontrolsthatsensedifferentialCO2andmaintainitbyadjustingoutdoorairflowincrementallywithoutsensingit.WediscussseveralpossibleDVCimplementationbelow.VariationinefficiencyThesecondoperatingconditionlistedinSection6.2.7relatestoventilationefficiency.Standard62.1requiresaccountingforbothzoneair-distributioneffectivenessandsystemventilationefficiency.Zoneair-distributioneffectivenessappliestoallventilationzonesinanysystemandindicatesthefractionofoutdoorairdeliveredtoazonethatactuallyentersthebreathingzone.Systemventilationefficiency,ontheotherhand,onlyappliestomultiple-zonerecirculationsystemsandindicatesthefractionofoutdoorairenteringthesystemthatactuallydilutescontaminantsinthebreathingzone.Changesintheseefficiencyvaluesduringoperationeffectivelychangeventilation“demand”notasaresultofvaryingpopulationbutasaresultofvaryingzoneandsystemairflowatdifferentloadconditions.Thedefaultvalueforzoneair-distributioneffectivenesscanchangeduringnormaloperation.Forinstance,ifthesameoverheaddiffusersdeliverwarmairduringheatingmodeandcoolairduringcoolingmode.Thelikelihoodofairbypassingthebreathingzonechanges.Whenheating,warmdischargeairtendstofloatabovecoolerzoneair.Ifitstoowarm,aportionofitbypassesthebreathingzone,inwhichcaseE=0.8,accordingtoStandard62.1.whencooling,however,allofthedischargeairdropsintothebreathingzone,soE=1.0.Fordesignpurposes,zoneoutdoorairflowmayneedtoexceedthebreathingzoneoutdoorairflowbyafactorof1.25intheheatingmode.However,duringnormaloperation,zoneair-distributioneffectivenessmayincreasefrom0.8whenheatingto1.0whencooling,sozoneoutdoorairflowcouldberesetdownwardtoequaltherequiredbreathingzoneoutdoorairflow.Variationsinzoneair-distributioneffectivenesscanbeusedtorecalculateanddynamicallyresetzoneoutdoorairflowinanyventilationsystem,butsingle-zoneheatingcoolingsystemsarelikelytobenefitmostfromthisresetapproach.Single-zonesystemswithincreasedE=needlesszoneoutdoorairflowandlessoutdoorairintakeflowduringcoolingoperationthanduringheating,whichreducescoolingenergy.Dedicatedoutdoorairsystemssupplying100%outdoorair,ontheotherhand,usuallydeliverventilationairatorbelowzonetemperature,soE=doesntvarywithloadandintakeairflowisusuallyconstant-nodynamicresetopportunities.And,formultiple-zonerecirculatingsystems,increasedE=inthe“critical=one”duringcanmeanlessintakeairflow.Systemventilationefficiency(E)-T=theratioofoutdoorairusedinallbreathingzonestooutdoorairintakeforthesystem(Ev=Vou/Vot)-varieswidelyinVAVmultiplyzonesystems,sincebothzoneandsystemairflowchangeinresponsetoload.Fordesignpurposes,minimumoutdoorairintakeflowforthesesystemsmustdeterminedusingthelowestefficiencyandthehighestoutdoorairintakeflow.Forproperoperation,however,minimumintakeairflowmaybedeterminedusingthesystemventilationefficiencyatcurrentoperatingconditions.ThisarticlefocusesonDCVforsingle-zonesystems.Adetaileddiscussionofdynamicresetapproachesinmultiple-zonesystemsisleftforafuturearticle.VariationsinIntakeAirflowStandard62.1citesathirdconditionthatmaybeusedasthebasisfordynamicresetcontrol.Itrelatestovariationsinthefractionofoutdoorairintheprimaryairstreamduetotheintroductionofexcessventilationairintheprocessofprovidingfree-coolingwithoutdoorairorprovidingintaketoVAVmultiple-zonesystemssinceitallowsresettingzoneminimumprimaryairflowsettingscansavelocalreheatenergyinsomesystemsatsomeloadconditions.Sincethisapproachworldcommonlybecombinedwith“variationsinefficiency”formultiple-zonesystems,amoredetaileddiscussionremainsforafuturearticle.WhatChanged?Thisarticlefocusesondynamicresetofoutdoorairintakeflowinresponsetovariationsinpopulationinsingle-zonesystems.Since1989,standard62hasspecifiedminimumventilationratesintermsofoutdoorairflowperpersonformostoccupancycategories.ThiswashandyforCO2-basedDCVbecauseitallowedtheventilationrateperpersontobeheldconstantbysimplyadjustingzoneoutdoorairflowasnecessarytomaintainthesensedzoneCO2levelconstant.AlthoughnotexplicitlyallowedbyearlierversionsofStandard62.1,DCVhasbeenusedeffectivelybymanysystemmanufacturersanddesigners,anditwassupportedbyseveralofficialinterpretationsofthestandard.Howdiditwork?Forexample,assumethatasingle-zone,constant-volumerooftopunitservesa1.000ft2lectureclassroomdesignedfor65people.Standard62-2001requiredaminimumbreathingzoneoutdoorairflowof970cfmatdesign.Withzoneair-distributioneffectivenessof1.0,zoneoutdoorairflowatdesignequaledbreathingzoneoutdoorairflow.Assumingaverageoccupantactivitylevelof1.25metandatypicalCO2generationrate,therequiredrateof15cfm/personresultedinadifferentialCO2levelof0.000700.withoutDCV,intakeairflowwouldbemaintainedat970cfmregardlessofchangesinpopulation.Ifpopulationdroppedto50people,diffe