未来的热舒适性优越性和期望值毕业设计外文翻译.docx

未来的热舒适性优越性和期望值毕业设计外文翻译.docx

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未来的热舒适性优越性和期望值毕业设计外文翻译

Thermalcomfortinthefuture-Excellenceandexpectation

P.OleFangerandJørnToftum

InternationalCentreforIndoorEnvironmentandEnergy

TechnicalUniversityofDenmark

Abstract

Thispaperpredictssometrendsforeseeninthenewcenturyasregardstheindoorenvironmentandthermalcomfort.Onetrenddiscussedisthesearchforexcellence,upgradingpresentstandardsthataimmerelyatan“acceptable”conditionwithasubstantialnumberofdissatisfied.Animportantelementinthisconnectionisindividualthermalcontrol.Asecondtrendistoacknowledgethatelevatedairtemperatureandhumidityhaveastrongnegativeimpactonperceivedairqualityandventilationrequirements.FuturethermalcomfortandIAQstandardsshouldincludetheserelationshipsasabasisfordesign.ThePMVmodelhasbeenvalidatedinthefieldinbuildingswithHVACsystemsthatweresituatedincold,temperateandwarmclimatesandwerestudiedduringbothsummerandwinter.Innon-air-conditionedbuildingsinwarmclimatesoccupantsmaysensethewarmthasbeinglessseverethanthePMVpredicts,duetolowexpectations.AnextensionofthePMVmodelthatincludesanexpectancyfactorisproposedforuseinnon-air-conditionedbuildingsinwarmclimates.TheextendedPMVmodelagreeswellwithfieldstudiesinon-air-conditionedbuildingsofthreecontinents.

Keywords:

PMV,Thermalsensation,Individualcontrol,Airquality,Adaptation

ASearchforExcellence

Presentthermalcomfortstandards（CENISO7730,ASHRAE55）acknowledgethatthereareconsiderableindividualdifferencesbetweenpeople’sthermalsensationandtheirdiscomfortcausedbylocaleffects,i.e.byairmovement.Inacollectiveindoorclimate,thestandardsprescribeacompromisethatallowsforasignificantnumberofpeoplefeelingtoowarmortoocool.Theyalsoallowforairvelocitiesthatwillbefeltasadraughtbyasubstantialpercentageoftheoccupants.

Inthefuturethiswillinmanycasesbeconsideredasinsufficient.Therewillbeademandforsystemsthatallowallpersonsinaspacetofeelcomfortable.Theobviouswaytoachievethisistomovefromthecollectiveclimatetotheindividuallycontrolledlocalclimate.Inoffices,individualthermalcontrolofeachworkplacewillbecommon.Thesystemshouldallowforindividualcontrolofthegeneralthermalsensationwithoutcausinganydraughtorotherlocaldiscomfort.Weknowtherangeofoperativetemperaturesrequiredinaworkplacetosatisfynearlyeverybody（Wyon1996;Fanger1970）andweknowthesensitivitytodraughtfromawiderangeofstudies.Asearchforexcellenceinvolvesprovidingallpersonsinaspacewiththemeanstofeelthermallycomfortablewithoutcompromise.

ThermalComfortandIAQ

Presentstandardstreatthermalcomfortandindoorairqualityseparately,indicatingthattheyareindependentofeachother.Recentresearchdocumentsthatthisisnottrue（Fangetal.1999;Toftumetal.1998）.Theairtemperatureandhumiditycombinedintheenthalpyhaveastrongimpactonperceivedairquality,andperceivedairqualitydeterminestherequiredventilationinventilationstandards.Researchhasshownthatdryandcoolairisperceivedasbeingfreshandpleasantwhilethesamecompositionofairatanelevatedtemperatureandhumidityisperceivedasstaleandstuffy.Duringinhalationitistheconvectiveandevaporativecoolingofthemucousmembraneinthenosethatisessentialforthefreshandpleasantsensation.Warmandhumidairisperceivedasbeingstaleandstuffyduetothelackofnasalcooling.Thismaybeinterpretedasalocalwarmdiscomfortinthenasalcavity.ThePMVmodelisthebasisforexistingthermalcomfortstandards.Itisquiteflexibleandallowsforthedeterminationofawiderangeofairtemperaturesandhumiditiesthatresultinthermalneutralityforthebodyasawhole.Buttheinhaledairwouldbeperceivedasbeingverydifferentwithinthiswiderangeofairtemperaturesandhumidities.Anexample:

lightclothingandanelevatedairvelocityorcooledceiling,anairtemperatureof28ºCandarelativehumidityof60%maygivePMV=0,buttheairqualitywouldbeperceivedasstaleandstuffy.Asimultaneousrequestforhighperceivedairqualitywouldrequireanairtemperatureof20-22oCandamodestairhumidity.ModerateairtemperatureandhumiditydecreasealsoSBSsymptoms（Krogstadetal.1991,Anderssonetal.1975）andtheventilationrequirement,thussavingenergyduringtheheatingseason.Andevenwithair-conditioningitmaybebeneficialandsaveenergyduringthecoolingseason.

PMVmodelandtheadaptivemodel

ThePMVmodelisbasedonextensiveAmericanandEuropeanexperimentsinvolvingoverathousandsubjectsexposedtowell-controlledenvironments（Fanger1970）.Thestudiesshowedthatthethermalsensationiscloselyrelatedtothethermalloadontheeffectormechanismsofthehumanthermoregulatorysystem.ThePMVmodelpredictsthethermalsensationasafunctionofactivity,clothingandthefourclassicalthermalenvironmentalparameters.Theadvantageofthisisthatitisaflexibletoolthatincludesallthemajorvariablesinfluencingthermalsensation.ItquantifiestheabsoluteandrelativeimpactofthesesixfactorsandcanthereforebeusedinindoorenvironmentswithwidelydifferingHVACsystemsaswellasfordifferentactivitiesanddifferentclothinghabits.ThePMVmodelhasbeenvalidatedinclimatechamberstudiesinAsia（deDearetal.1991;Tanabeetal.1987）aswellasinthefield,mostrecentlyinASHRAE’sworldwideresearchinbuildingswithHVACsystemsthatweresituatedincold,temperateandwarmclimatesandwerestudiedduringbothsummerandwinter（Cenaetal.1998;Doninietal.1996;deDearetal.1993a;Schilleretal.1988）.ThePMVisdevelopedforsteady-stateconditionsbutithasbeenshowntoapplywithgoodapproximationattherelativelyslowfluctuationsoftheenvironmentalparameterstypicallyoccurringindoors.Immediatelyafteranupwardstep-wisechangeoftemperature,thePMVmodelpredictswellthethermalsensation,whileittakesaround20minattemperaturedown-steps（deDearetal.1993b）.

Fieldstudiesinwarmclimatesinbuildingswithoutair-conditioninghaveshown,however,thatthePMVmodelpredictsawarmerthermalsensationthantheoccupantsactuallyfeel（BrageranddeDear1998）.Forsuchnon-air-conditionedbuildingsanadaptivemodelhasbeenproposed（deDearandBrager1998）.Thismodelisaregressionequationthatrelatestheneutraltemperatureindoorstothemonthlyaveragetemperatureoutdoors.Theonlyvariableisthustheaverageoutdoortemperature,whichatitshighestmayhaveanindirectimpactonthehumanheatbalance.Anobviousweaknessoftheadaptivemodelisthatitdoesnotincludehumanclothingoractivityorthefourclassicalthermalparametersthathaveawell-knownimpactonthehumanheatbalanceandthereforeonthethermalsensation.Althoughtheadaptivemodelpredictsthethermalsensationquitewellfornon-air-conditionedbuildingsofthe1900’slocatedinwarmpartsoftheworld,thequestionremainsastohowwellitwouldsuitbuildingsofnewtypesinthefuturewheretheoccupantshaveadifferentclothingbehaviourandadifferentactivitypattern.

WhythendoesthePMVmodelseemtooverestimatethesensationofwarmthinnonair-conditionedbuildingsinwarmclimates?

Thereisgeneralagreementthatphysiologicalacclimatizationdoesnotplayarole.Onesuggestedexplanationisthatopenablewindowsinnaturallyventilatedbuildingsshouldprovideahigherlevelofpersonalcontrolthaninair-conditionedbuildings.Wedonotbelievethatthisistrueinwarmclimates.Althoughanopenablewindowsometimesmayprovidesomecontrolofairtemperatureandairmovement,thisappliesonlytothepersonswhoworkclosetoawindow.Whathappenstopersonsintheofficewhoworkfarawayfromthewindow?

Andinwarmclimates,thenormalstrategyinnaturallyventilatedbuildingsistocoolthebuildingduringthenightandthenclosethewindowssometimeduringthemorningwhentheoutdoortemperatureexceedstheindoortemperature.Anotherobstacleisofcoursetrafficnoise,whichmakesopenwindowsinmanyareasimpossible.Webelievethatinwarmclimatesair-conditioningwithproperthermostaticcontrolineachspaceprovidesabetterperceivedcontrolthanopenablewindows.

Anotherfactorsuggestedasanexplanationtothedifferenceistheexpectationsoftheoccupants.WethinkthisistherightfactortoexplainwhythePMVoverestimatesthethermalsensationofoccupantsinnon-air-conditionedbuildingsinwarmclimates.Theseoccupantsaretypicallypeoplewhohavebeenlivinginwarmenvironmentsindoorsandoutdoors,maybeeventhroughgenerations.Theymaybelievethatitistheir“destiny”toliveinenvironmentswheretheyfeelwarmerthanneutral.Ifgivenachancetheymaynotonaveragepreferanenvironmentthatisdifferentfromthatchosenbypeoplewhoareusedtoair-conditionedbuildings.Butitislikelythattheywouldjudgeagivenwarmenvironmentaslesssevereandlessunacceptablethanwouldpeoplewhoareusedtoair-conditioning.Thismaybeexpressedbyanexpectancyfactor,e,tobemultipliedwithPMVtoreachthemeanthermalsensationvoteoftheoccupantsoftheactualnon-air-conditionedbuildinginawarmclimate.Thefactoremayvarybetween1and0.5.Itis1forair-conditionedbuildings.Fornon-air-conditionedbuildings,theexpectancyfactorisassumedtodependonthedurationofthewarmweatherovertheyearandwhethersuchbuildingscanbecomparedwithmanyothersintheregionthatareair-conditioned.Iftheweatheriswarmallyearormostoftheyearandtherearenoorfewotherair-