深綠生態(tài)模擬分析綠色建筑設計咨詢人國外ecotect教程2 energy

Energy

Heat

HeatflowthroughmaterialsHeatflowinbuildingsModellingwithzonesThermalanalysis

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Energy

Heat

HeatflowthroughmaterialsHeatflowinbuildingsModellingwithzonesThermalanalysis

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Heatflow

Heatisenergy:

–

measuredinWatts(=J/s)

Temperatureistheamountofheatinamaterial.

–

MeasuredindegreesCelsius(Co)

–

MeasuredinKelvin(K)

–

0K(-273Co)=materialwithnoheat

Heatflow

Heatwillflowfromahotsubstancetoacoldsubstance.

Heatcanflowinthreeways:

–

Conduction

Vibrationofmoleculesinasubstance

–

Convection

–

Electromagneticradiation

Radiation

Heatflow

Vibrationofmolecules:

–

conduction

–

convection

Heatflow

Electromagneticradiation:

Heatflow

Conduction

Conductionoccursthroughthetransferofvibrationalenergyfromonemoleculetothenext.

Dependson:

–

Thecrosssectionalarea

–

Theconductivityofthematerial

–

Thetemperaturedifference

Heatflow

Conduction

Heatflow

Convection

Convectionoccursfromasolidtoafluidorgas

–

Astemperatureincreases,densityinthefluiddecreases

–

Thelowerdensityfluidrises

–

Thisresultsinconvectioncurrents

Heatflow

Convection

Heatflow

Radiation

Allobjectemitsomeelectromagneticradiation.

–

Thehottertheobject,theshorterthewavelength

–

Ahotfirewillemitinfraredradiation

–

Thesun(muchhotter)alsoemitsshortwaveradiation

Heatflow

Radiation

Energy

Heat

HeatflowthroughmaterialsHeatflowinbuildingsModellingwithzonesThermalanalysis

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Heatflowthroughmaterials

Heatflowthroughmaterialsoccursmainlybyconduction.Theabilityofamaterialtoconductheatvaries:

–

Metalsaregoodconductors

–

Gasesarepoorconductors

Heatflowthroughmaterials

Heatflowthroughmaterialsdependson:

–

Cross-sectionalarea

–

Temperaturedifference

–

Resistivityorconductivityofthematerial

Heatflowthroughmaterials

Resistivityofamaterial:

–

Abilitytoresistheatflow

Conductivityofamaterial

–

Abilitytoallowheatflow

Resistivityistheopposite(inverse)ofconductivity.Ifresistivityislow,conductivityishigh.

Heatflowthroughmaterials

Measuringresistivityandconductivity:

–

–

ResistanceismeasuresasaR-Value

m2K/W

–

–

ConductanceismeasuredasaU-Value

W/m2K

–

–

R=1/UandU=1/R

IfR=2,thenU=0.5

Heatflowthroughmaterials

Conductance:Howmuchenergy(inwatts)passesthroughthematerial?

–

–

1m2ofamaterial

subjectedto1oCoftemperaturedifference

1m2

20

oC

21

oC

Heatflowthroughmaterials

Abuildingstructureusuallyconsistsofdifferentmaterials.TheoverallR-ValueorU-Valuecanbecalculated:

Twopossibilities:

–

Materialsinseries

–

Materialsinparallel

Heatflowthroughmaterials

Inseries:

–

Resistancesareadded

–

R=R1+R2+R3…

Inparallel:

–

Conductancesareadded

–

U=U1+U2+U3…

Heatflowthroughmaterials

Cavities:

–

Cavitiesincreaseresistance

Heatflowthroughthecavity

–

Conduction:dependsondepth

–

Convection:dependsondepthandheight

–

Radiation:dependsonreflectivityofinternal

surface

Heatflowthroughmaterials

Insulation:

–

Anymaterialwithlowoverallconductance

Waystoreduceoverallconductance

–

Materialswithairbubbles.E.g.glassfibre,mineralwool,polystyrene

–

Reflectivematerialsthatreducetheabsorptionofinfraredradiation

Energy

Heat

HeatflowthroughmaterialsHeatflowinbuildingsModellingwithzonesThermalanalysis

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Heatflowinbuildings

Atypicalbuildingstructure

–

–

–

–

Manycomponents

Manybuildingsystems(e.g.walls,roofs)Manydifferentthermalconductances

Inseriesandinparallel

Heatflowinbuildings

Atypicalbuildingstructure

–

–

–

–

Manycomponents

Manybuildingsystems(e.g.walls,roofs)Manydifferentthermalconductances

Inseriesandinparallel

Whatistheoverallresult?

–

–

Whatistheoverallheatlossforabuilding

Whatistheoverallheatgainforabuilding?

Heatflowinbuildings

Coldclimate

Heatflowinbuildings

Hotclimate

Heatflowinbuildings

Heatloss=heatout:

–

–

–

ThroughthebuildingfabricWalls,floor,roof,etc

Ventilationthroughwindowsanddoors

Heatgain=heatin:

–

–

fromoutsidesources(e.g.sunlight)

frominternalsources(e.g.people,lighting,equipment)

Heatflowinbuildings

Ifheatlossislessthanheatgain

–

–

Buildingheatsup

ACisrequired

Ifheatlossisgreaterthanheatgain

–

–

Buildingcoolsdown

Heatingisrequired

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

1.

2.

3.

4.

5.

6.

FabricgainsIndirectsolargainsDirectsolargainsVentilationGainsInternalGains

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

Fabricgains:duetodifferentialsinairtemperaturebetweeninsideandoutsidethespace

–

–

–

–

–

IndirectsolargainsDirectsolargainsVentilationGainsInternalGains

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

Fabricgains

–

Indirectsolargains:duetotheeffectsofsolarradiationonexternalopaquesurfaces

–

–

–

–

DirectsolargainsVentilationGainsInternalGains

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

–

Fabricgains

Indirectsolargains

–

Directsolargains:duetosolarradiationenteringthespacethroughawindoworvoid

–

–

–

VentilationGainsInternalGains

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

–

–

FabricgainsIndirectsolargains

Directsolargains

–

VentilationGains:duetothemovementofairthroughthroughcracksandopeningsinthebuilding

–

–

InternalGains

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

–

–

–

FabricgainsIndirectsolargainsDirectsolargains

VentilationGains

–

InternalGains:duetopeople,equipment(suchascomputers)andlighting

–

Inter-zonalgains

Heatflowinbuildings

Therearesixmaintypesofheatloss/gain:

–

–

–

–

–

FabricgainsIndirectsolargainsDirectsolargainsVentilationGains

InternalGains

–

Inter-zonalgains:duetodifferentialsinairtemperaturebetweenzones

Heatflowinbuildings

Designersjob:

–

Reduceasmuchaspossiblethedifferencebetween

–

heatlossand

–

heatgain

Heatflowinbuildings

WhatisHVAC?

–

Heating,VentilationandAirconditioning

Itisexpensive!

Itusesalotofenergy

–

–

WhatisHVACfor?

–

–

Toaddorremoveheat

Tomakeupforthedifferencebetweenheatlossandheatgain

Energy

Heat

HeatflowthroughmaterialsHeatflowinbuildingsModellingwithzonesThermalanalysis

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Modellingwithzones

Withlighting,itwaspossibletosimulatejustoneroom.Thisisnotthecasewiththermalsimulations.

–

Spacesinthebuildinginteractwitheachother

–

Mustmodelallspacesinthebuilding

Therefore,thermalmodelsmustbehighlysimplified

Modellingwithzones

Thebasicunitofathermalsimulationisthezone:

–

Azoneisavolumeofairthatisrelativelyhomogeneous

–

Usuallyaroom

–

Noholesorgaps(windowsareOK)

Zone1

Zone2

Modellingwithzones

Thesimulationsoftwaremustcalculate

heatflowbetweenzones:

–

Adjacencyisimportant

–

Theconstructionmaybedifferent

adjacency

Modellingwithzones

Theenclosingsurfacesmusthavethermalproperties.

ForEcotecttheseare:

–

U-values(U:W/m2K)

Specificadmittance(Y:W/m2K)

Solarabsorption(Abs:0-1)

–

–

–

Thermaldecrement(Decr:0-1)

Thermallag(Lag:hrs)

–

Modellingwithzones

U-values(U:W/m2K)

–

thermalconductanceofmaterialsandtheconvectiveandradiativeeffectsofsurfacesandcavities

Specificadmittance(Y:W/m2K)

–

abilitytoabsorbandreleaseheatenergy

Solarabsorption(Abs:0-1)

–

portionofsolarradiationthatisabsorbed

Thermaldecrement(Decr:0-1)andlag(Lag:hrs)

–

dynamicthermalbehaviour

Modellingwithzones

Azonemaycontainpartitions

–

Partitionsmustbeinternal

–

Theaironbothsidemustbesimilar

–

Furniturecanalsobedefinedasapartition

partition

Modellingwithzones

Anumberofpropertiescanbesetforeachzone:

Modellingwithzones

Anumberofpropertiescanbesetforeachzone:

–

–

–

–

–

–

Operation:ACOn/offtimes

ComfortBand:MaxandmintemperaturesOccupancy:Numberofpeopleandactivity

AirChangeRates:Airinfiltration,windsensitivityHVACsystem:TypeofHVACsystem

HeatGains:people,lighting,equipment

–

Schedules:dailyandyearlybehaviour

Modellingwithzones

HVACsystem

None:

–

Allthewindowsaredoorsremainshut

NaturalVentilation:

–

Occupantsmayopenthewindows

Mixed-ModeSystem:

–

Acombinationofheating,ACandnaturalventilation

FullAirConditioning,HeatingOnlyorCoolingOnly:

–

Heatingand/orAC.Windowsareneveropened.

Modellingwithzones

Heatgains

Therearetwotypesofheatgains:

Sensibleheatgains:

–

–

lighting,computers,etc

valuegivenpersquaremetreoffloorarea

–

–

Typicalofficelighting:20W/m2Typicalofficeequipment:40W/m2

Latentheatgains:

–

ThisvalueisnotusedinEcotect,soignoreit

Modellingwithzones

Schedules:

–

–

operationalschedules

occupancyschedules

Schedulesallowyoutoassigndifferentprofilestoweekdays,holidays,weekends,etc:

–

–

–

aprofileconsistsofapercentageforeachhourinthedayp