上游充通大学 SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 28 Chapter 7 Entropy (Section 7.1) Spring,4/16/2019 福 Prof.,Dr.Yonghua HUANG 月是 http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日G
Engineering Thermodynamics I Lecture 28 Spring, 4/16/2019 Prof., Dr. Yonghua HUANG Chapter 7 Entropy (Section 7.1) http://cc.sjtu.edu.cn/G2S/site/thermo.html
Chapter objective Up to this point,2nd law concerning systems undergoing thermodynamic cycles 国 To introduce means for analyzing systems using 2nd law for processes 国 To introduce entropy 上游充通大学 April 16,2019 2 SHANGHAI JIAO TONG UNIVERSITY
April 16, 2019 2 Chapter objective To introduce means for analyzing systems using 2nd law for processes To introduce entropy Up to this point, 2nd law concerning systems undergoing thermodynamic cycles
Clausius inequality Reservoir at Tres To realize Heat transfer with No irreversibility Intermediary! Combined cycle Kelvin scale for the cycle: system boundary 60' Tres (1) System Combined system:Energy balance w.o.baacoobaace...a.a.ceobeacoooo System boundary dEc=δQ' δWc (2) EliminateδQ' ->6W+6W' System:receive 80 from 0 reservoir at Tres δ0 WC =Tres -dEc Integration along a single cycle Energy exchange Wc with single reservoir Kelvin-Plank statement 上海充通大学 Cons April 16,2019 3 SHANGHAI JIAO TONG UNIVERSITY
April 16, 2019 3 Clausius inequality System: receive Q from reservoir at Tres To realize Heat transfer with No irreversibility Kelvin scale for the cycle: Combined system: Energy balance Eliminate δQ’ δW+δW’ Integration along a single cycle Const. Energy exchange with single reservoir Kelvin-Plank statement (1) (2)
Clausius inequality boundary Reservoir at Tres 80 ≤ T Intermediary cycle_- Kelvin-Plank statement Combined system δW --A corollary of the 2nd law boundary Applicable to any cycle System δW "="no irreversibility within the system System boundary “<“:internal irreversibilities are present No irreversibility for irreversibility only the intermediary cycle within the system 上游充通大 April 16,2019 4 SHANGHAI JIAO TONG UNIVERSITY
April 16, 2019 4 Clausius inequality -- A corollary of the 2nd law Applicable to any cycle No irreversibility for the intermediary cycle “=”: no irreversibility within the system “<“: internal irreversibilities are present Kelvin-Plank statement irreversibility only within the system boundary
General form of Clausius inequality (9-园 "strength"or degree of the inequality Ocyele= 0 no irreversibilities present within the system Ceycle irreversibilities present within the system Ceycle <O impossible 上游充通大学 April 16,2019 5 SHANGHAI JLAO TONG UNIVERSITY
April 16, 2019 5 General form of Clausius inequality “strength” or degree of the inequality