Comparison Between Heat and WorkHeat and work are energy transfer mechanismsbetween a system and its surroundingsSimilarities: Both are recognized at boundaries of a systemas they cross the boundaries. That is ,both areboundary phenomenon.System processed energy, but not heat and work Both are associated with a process, not a stateHeat and work have no meaning at a stateBoth are path functionsDifference:
Comparison Between Heat and Work Similarities: • Both are recognized at boundaries of a system as they cross the boundaries. That is ,both are boundary phenomenon. • System processed energy, but not heat and work. • Both are associated with a process, not a state. Heat and work have no meaning at a state. • Both are path functions. Heat and work are energy transfer mechanisms between a system and its surroundings. Difference:
Forms of EnergyAlthough energy can take a large number of forms, we canconsider only:Externaland Internal.1-KineticEk-my22ExternalTotal EnergyPotential E,=mgz,e, = gz=Interna/+ExternalPhysicalInternal (U)=U+Ek+EpChemicalU= f(v,T)-State PropertyNuclearNote: U is state propertyΦdU =0dU=U,-UAU =
Forms of Energy Although energy can take a large number of forms, we can consider only: External and Internal. External Kinetic Potential Internal (U) State Property Physical Chemical Nuclear 1 1 2 2 ; 2 2 ; k k p p E mv e v E mgz e gz = = = = Total Energy =Internal+External U f v T = ( , ) =U+Ek+Ep Note: U is state property 2 2 1 1 d 0 d U U U U U = = = −
Energy Balance for Closed SystemEnergyEnteringCV}-{EnergyLeavingCV)=(EnergyAccumulatinginCV)ForClosed Systemm(c)CEin -Eou =Q-W =△U++ msAzou2Q=△U+WQ= dU + pdVSQ=dU+$Wq = △u+ pdydifferenceq= △u+w注意过程量和状态量数学表达的区别！
Energy Balance for Closed System For Closed System 2 2 1 2 ( ) 2 in out m c c E E Q W U mg z − − = − = + + δ d δ Q U W Q U W q u w = + = + = + {Energy Entering CV } － {Energy Leaving CV} ={Energy Accumulating in CV} δ d d d Q U p V q u p v = + = + difference 注意过程量和状态量数学表达的区别！
Energy Balance for Open SystemForOpen SystemDifferencewithclosedsystem·Energy in mass to and fromsystem·Massequilibriumlncluding volumetric work and flow work with surrounding推动质量进出系统的推动功，即保证质量流动耗费的功
Energy Balance for Open System For Open System Difference with closed system: •Energy in mass to and from system •Mass equilibrium •Including volumetric work and flow work with surrounding 推动质量进出系统 的推动功，即保证 质量流动耗费的功
Flow WorksWSW= PrAdx =pdV =Piydm1kg: Wfi = piVidx12Wf2 = P2V2Pr,Vr,AW = P2V2 -PiVi8QP2, V2,AO= pv+u+er +e,Total Energy ofFlowing Fluid0= pv+u++gz2烩一工质流动时具有的CEnthaply 焰与其热力状态有关的总O=h+gz2能量
Flow Work 1 2 1 1 A1 p ,v , 2 2 A2 p ,v , dx1 1 1 1 1 1 1 1 1 1 δ d d d W p A x p V p v m f = = = Total Energy of Flowing Fluid 2 2 k p pv u e e c pv u gz = + + + = + + + Enthaply 焓 2 2 c = + + h gz １kg : w p v f 1 1 1 = w p v p v f = − 2 2 1 1 δQ δWs 焓－工质流动时具有的 与其热力状态有关的总 能量。 w p v f 2 2 2 =