暖通毕业设计外文翻译.doc
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暖通毕业设计外文翻译.doc
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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).Thestudiesshowedthatthethermalsensationiscloselyrelatedtothethermalloadontheeffectormechanismsoftheh
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