Continue Exergy Analysis for Closed Systems 77? ?? Wuse.max =-(AUCM2 +AKECM2 +APECM2 +AU) The changes in internal energy of the system(CM2)and the environment can be calculated by: .Environment ToPo AUcM2=(U。-U)cM2 I CM2 Closed AU.Q。-W,=IAS.-P,AV System Constant for environment △KEe=0,△PEe=0 Substitution into the equation for useful work leads to: Wuse.masx =(U-U)CM2 +AKECM2+APECM2 -TASe+PoAVe 27 上游通大学 Monday,April 24,2017 6 SHANGHAI JIAO TONG UNIVERSITY
Monday, April 24, 2017 6 Continue Exergy Analysis for Closed Systems The changes in internal energy of the system (CM2) and the environment can be calculated by: Substitution into the equation for useful work leads to: CM2 o CM2 e e e o e o e U (U U) U Q W T S p V Constant for environment W (U U ) KE PE T S p V use,max o CM2 CM2 CM2 o e o e Closed System Environment @ To ,po Qi CM2 CM1 Wi Wuse W ( U KE PE U ) use,max CM2 CM2 CM2 e ?? ?? ?? ?? ΔKEe = 0, ΔPEe=0
Continue Exergy Analysis for Closed Systems Wuse.max =(U-U)CM2 +AKECM2 +APECM2 -TAS +PoAVe Note: ?? △V。=-AVcM2=-(V。-V)cM2=(V-V)cM2 and △SCMI=△ScM2+ASe →ASe=AScMI-AScM2=AScM1-(S。-S)CM2 =△SCM1+(S-S)cM2 Then,substituting△V。and△S.into the equation for useful work: Wuse.max=(U-U)CM2 +AKECM2+APECM2 Po(V-Vo)CM2-To(S-So)CM2 ToASCMI 上游充通大学 Monday,April 24,2017 7 SHANGHAI JLAO TONG UNIVERSITY
Monday, April 24, 2017 7 Continue Exergy Analysis for Closed Systems Note: ΔVe = – ΔVCM2 = – (Vo – V)CM2 = (V – Vo )CM2 and ΔSCM1 = ΔSCM2 + ΔSe ΔSe = ΔSCM1 – ΔSCM2 = ΔSCM1 – (So – S)CM2 = ΔSCM1 + (S – So )CM2 Then, substituting ΔVe and ΔSe into the equation for useful work: Wuse,max = (U – Uo )CM2 +ΔKECM2 +ΔPECM2 + po (V – Vo )CM2 – To (S – So )CM2 + To ΔSCM1 W (U U ) KE PE T S p V use,max o CM2 CM2 CM2 o e o e ?? ??
Continue Exergy Analysis for Closed Systems In order to maximize Wuse,we assume a reversible process for CM1 and thus,AScMI=0! In addition,we will drop the subscript CM2: →Wrev.use,max=U-U。+KE+PE+p(V-V,)-T(S-S,) Definition of exergy (availability)for closed system >①=Wrevuse.max is a property! >=0 Φ=U-U。+p(V-Vo)-T,(S-So)+KE+PE in specific terms = u*g-[u--片T6-】 Available Energy in Env. Min.work Min.heat transfer Total Energy on or by to or from Energy Environment Environment Can be Converted to work Unavailable energy,Anergy cannot be converted to work Note:available unavailable constant! 上游充通大粤 Monday,April 24,2017 8 SHANGHAI JIAO TONG UNIVERSITY
Monday, April 24, 2017 8 Continue Exergy Analysis for Closed Systems In order to maximize Wuse, we assume a reversible process for CM1 and thus, ΔSCM1 = 0! In addition, we will drop the subscript CM2: Wrev,use,max = U – Uo + KE+PE+po (V – Vo ) – To (S – So ) Definition of exergy (availability) for closed system : F = Wrev,use,max F = U – Uo +po (V – Vo ) – To (S – So ) + KE + PE is a property! >=0 2 o o o o o v u gz u p v v T s s 2 Note: available + unavailable = constant! Available Energy Min. work on or by Environment Min. heat transfer to or from Environment Total Energy = - Can be Converted to work Unavailable energy, Anergy cannot be converted to work in specific terms Energy in Env