Chapter6TheSecondLawofThermodynamics

6-1SpontaneousAccidents6-1-1DirectionofspontaneousAccidentHeattransferundertemperaturedifferenceProduceworkunderpressuredifferenceWorktoheatOrderlinesstoChaos6-1-2IrreversibilityofspontaneousAccidentIfreversed,tracewillbeleftonthesurroundings

6-1-3EquivalenceofspontaneousAccident

6-2-1Kelvin-PlanckStatement(1)ThermalenergyreservoirAbodywitharelativelargethermalenergycapacitythatcansupplyorabsorbfiniteamountsofheatwithoutundergoinganychangeintemperature(2)Heatengines6-2TheSecondLawofThermodynamics

High-temperatureSOURCELow-temperatureSINKEngineQinQoutThermalEnergyReservoirThermalEnergyReservoirWnet

CanweSaveQout?

(3)RefrigeratorandAirConditionerHigh-temperatureSOURCELow-temperatureSINKRefrigeratorWQLQH

(3)Kelvin-PlanckStatementIt’sImpossibleforanydevicethatoperatesonacycletoreceiveheatfromasinglereservoirandproduceanetamountofwork6-2-2ClausuisStatementItisimpossibletoconstructadevicethatoperatesinacycleandproducesnoeffectotherthanthetransferofheatfromalowertemperaturebodytoahighertemperature

6-2-3EquivalenceofthetwoStatementsIfdisobeyKelvin-Planckstatement:thenwecanproduceanenginewith100%efficiencyLowtemperaturereservoirHightemperaturereservoirengineQHW=QHRefrigeratorQH+QLQL=refrigeratorLowtemperaturereservoirhightemperaturereservoirQLQL

6-3TheCarnotCycle6-3-1CarnotCycle(1)ConstructionofCarnotcycle

(2)Efficiencyq1q2w

Since1-4、2-3areadiabaticprocess

6-3-2ThereversedCarnotCycle

6-3-3TheCarnotPrinciplesTheefficiencyofanirreversibleheatengineisalwayslessthanthatofareversibleoneoperatingbetweenthesametworeservoirsTheefficiencyofallreversibleheatenginesoperatingbetweenthesametworeservoirsarethesa