能源的应用范例.ppt

第三能源的應用範例ExamplesofEnergyApplication,3-1HomeEnergyConservationandHeat-TransferControl3-2AirConditioningandHeatPumps3-3HeatEngines,3-1HomeEnergyConservationandHeat-TransferControl,BuildingMaterials1,Materialthatisagoodconductorofelectricity,suchasametal,isusuallyagoodconductorofheat.Aninsulator,suchasfiberglassorStyrofoam,willretardtheflowofheatfromoneobjecttoanother.Wesaythatitprovidesahigh“resistance”toheattransfer.Aircanbeagoodinsulator,especiallyifitismotionless,andsoporousmaterialssuchasfiberglasshaveanexcellentresistancetoheatflowthankstotheairtrappedinside.,BuildingMaterials2,Thecolorofamaterialalsoinfluencesheattransferwhenradiationisconcerned.Ablackobjectisbothabetteremitterandabetterabsorberofradiantenergythanawhiteorshiny-surfacedobject.Tobeinthermalequilibriumwithitssurroundings,anobjectthatisagoodemittermustalsobeagoodabsorber.Conversely,apooremitterwillbeabadabsorber.,BuildingMaterials3,Startingfromthesametemperature,ahotblackobjectwillradiantenergyfasterthanasimilarhotlight-coloredobject.Icewaterwillremaincoldlongerifitisplacedinasilver-coloreddishratheracharcoal-coloredone.Lightcoloredclothesarepreferableonhot,sunnydays,astheyarepoorabsorbersofradiantenergy.Theabsorberplatesonsolarcollectorsarepaintedflatblacktobetterabsorbthesun’senergy.,,BuildingMaterials4,Addcreamimmediatelyorlater,BuildingMaterials5,Theansweristhatyoushouldaddcreamassoonaspossible.Thecreammakestheblackcoffeelighterincolor,whichmakesitapoorerradiator.Alsothetemperaturewilldropwhenthecreamisadded,sotherateofheattransferbyradiationandconductionwilldecreaseasaresultofthesmallerT.,,BuildingMaterials6,Thermosbottle,,HouseInsulationandHeatingCalculations1,R/k,,HouseInsulationandHeatingCalculations2,,HouseInsulationandHeatingCalculations3,,HouseInsulationandHeatingCalculations4,ToobtainanR-valueof22ft2-h-oF/Btu,youwouldhavetousetheindicatedthicknessofvariousmaterials,,HouseInsulationandHeatingCalculations5,SuperinsulatedofficebuildinginToronto,Canada,,HouseInsulationandHeatingCalculations6,,HouseInsulationandHeatingCalculations7,Thermaldrapesmountedinthisarrangementwillcontributetoheatlossratherthanstopthem.,,HouseInsulationandHeatingCalculations8,Thisarrangementisbetterforreducingconvectivelosses.,,HouseInsulationandHeatingCalculations9,Coldairinfiltrationcanaccountfor50oftheenergyneedsofahouse.,,HouseInsulationandHeatingCalculations10,Caulkingaroundthefoundationofahomereducesairinfiltration.,,HouseInsulationandHeatingCalculations11,,HouseInsulationandHeatingCalculations12,,HouseInsulationandHeatingCalculations13,,HouseInsulationandHeatingCalculations14,Averyimportantfactorinconvectiveheatlossisthewind.Heatlossthroughwallsandroofsaswellasthroughwindow,door,andfoundationcracksdirectlydependonthewindvelocity.Heatloadcalculationsindicatethatanincreaseinwindvelocityfrom10to15to20mphwillincreasethebuildinginfiltrationby100and200.,SiteSelection1,,SiteSelection2,Plantingtreesontheleewardsideofahillcansubstantiallyreducethewindvelocityoverthesite.Vegetationorwallscanblockordeflectnaturalairflowpatternsandsoreduceconvectiveheatloss.,Cooling1,Lessexpensivesolutionstosummercoolingloadscanbeachievedthroughmanytypesofpassivecoolingtechniques.Themainobjectivehereistocontroltheheatabuildinggainsfromitsenvironments.Theseprinciplesinvolve*Siteselection---location,orientation,vegetation*Architecturalfeatures---surface-to-volumeratio,overhangs,windowsizing,shades*Buildingskinfeatures---insulation,thermalmass,glazing,,Cooling2,,Cooling3,,Cooling4,,Cooling5,,Cooling6,Radiantbarrierscanreduceheatgainintheatticofahouse.,3-2AirConditioningandHeatPumps,,AirConditioningandHeatPumps1,AirConditioningandHeatPumps2,,AirConditioningandHeatPumps3,,AirConditioningandHeatPumps4,,AirConditioningandHeatPumps5,C.O.P.CoefficientofPeranceheattransferred/electricity,Becauseaheatpump’sperancevarieswiththelocalclimate,itisbettertospeakofaseasonallyaveragedC.O.P.TheseasonalperancefactorSPFisdefinedasSPFtotaloutput/totalenergyconsumed,AirConditioningandHeatPumps6,AirConditioningandHeatPumps7,AnelectricallydrivenheatpumpusingFreonasaworkingfluid.Inprinciple,thesystembecomesanairconditionerifthefluidflowdirectionisreversed.,,AirConditioningandHeatPumps8,Relativecostsofdifferenttypesofheatingfuels.,,3-3HeatEngines,TheEnergyContentofFuels1,Theburningofhydrocarbonfuelsismerelythecombiningofthecarbonandthehydrocarbonfromthefuelwithoxygenfromtheair.CO2-CO2heatenergyH2O2-H2OheatenergyThesetwosimplereactionsarebothincludedintheoverallreactionulaforanactualfuel.Forexample,C7H1611O2-7CO28H2O1.15x106caloriesper100gC7H16,TheEnergyContentofFuels2,Thegeneralpathwaysbywhichweutilizeenergyfromfossilfuels,TheThermodynamicsofHeatEngines1,1-Qcold/Qhotx100,Efficiencyworkdone/energyputintothesystemQhot-Qcold/Qhot,CarnotCycleQcold/QhotTcold/Thot1-Tcold/Thotx100,TheThermodynamicsofHeatEngines2,GenerationofElectricity1,Adiagramofafuel-burningelectricpowerplant.,Hereariverprovidescoolingwatertothecondenser.,GenerationofElectricity2,Anelementaryalternatingcurrentgenerator.,Aloopofwireisforcedtorotateinamagneticfield.,GenerationofElectricity3,Typicalefficiencyofanelectricpowerplantforconvertingchemicalenergyinthefuelintoelectricenergy.Thebestnewplantsnowachievenearly40.,GasolineEngines,Thefourstrokesofafour-cyclespark-ignitedinternalcombustionengine.acompression,bcombustion,cexhaust,anddfuel-airintake.,DieselEngines,Ignitionisaccomplishedbythehightemperatureproducedbythecompressionofair.,Cogeneration,Asmallcogenerationplantthatusesthecombustionofnaturalgastodriveagasturbinecoupledtoanelectricgenerator.Thehotexhaustgasesboilwatertosteamforuseinspaceheatingandcooling.,MultipleChoiceQuestions,The“R-value”ofmaterialisnotrelatedtoits________positionb.areac.thicknessd.resistancetoheatflow,MultipleChoiceQuestions,2.Infiltrationinahousewill________.a.increaseonwindydaysb.raisetheheatingloadbyabout10c.reducethenumberofairchangesd.beincreasedbycaulkingaroundwindows,MultipleChoiceQuestions,3.Hotwaterina_______canwillcoolofffasterthanhotwaterinanyothercolorcan.a.whiteb.redc.blackd.silver,MultipleChoiceQuestions,4.Aheatpumpwillhaveanefficiencyheatouttoelectricalinofabout________.a.35b.50c.75d.100e.200,MultipleChoiceQuestions,5.Atarestaurantyouareservedcoffeebeforeyouarereadytodrinkit.Inorderthatthecoffeebethehottestwhenyouarereadyforit,whenwoulditbebesttoaddcreamatroomtemperaturetoita.whenyouarereadytodrinkitb.rightwhenyouareservedthecoffeec.itdoesn’tmatter,asthefinaltemperaturewillbethesame,