上游充通大学 SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 35 Chapter 7 Entropy Section7.4,7.9,7.12) Spring,2017 Prof.,Dr.Yonghua HUANG 强 ALnn是。 http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日
Engineering Thermodynamics I Lecture 35 Spring, 2017 Prof., Dr. Yonghua HUANG Chapter 7 Entropy (Section 7.4, 7.9, 7.12) http://cc.sjtu.edu.cn/G2S/site/thermo.html
Isentropic process Isentropic constant entropy Fixed by 2 independent internal reversible,adiabatic properties T P P3 2 T T3 p1,T1)S1iS1=S2=S31 T,or p>other properties,like v,u,h,p,Tx 上游充通大 Tuesday,April 18,2017 2 SHANGHAI JLAO TONG UNIVERSITY
Tuesday, April 18, 2017 2 Isentropic process Isentropic = constant entropy = internal reversible, adiabatic Fixed by 2 independent properties (p1 ,T1 )s1 ; s1=s2=s3 + T, or p other properties, like v, u, h, p, T, x
Isentropic process for Ideal gas Ideal gas:reference state:s=0 at(T=OK and p=1 atm) s(T2.P2)-s(Ti;P) =(T)-s(T)-R1n2 P2 不 Isentropic:s(T2,P2)=s(T1,p) D 0=s(T2)-s(T)-RIn P2 P2 s(T2)=s(T)+R In Pi 「s(T2)-s(T1) R 上游通大学 Tuesday,April 18,2017 3 SHANGHAI JLAO TONG UNIVERSITY
Tuesday, April 18, 2017 3 Isentropic process for Ideal gas Ideal gas: reference state: s =0 at (T=0K and p=1 atm) Isentropic:
Isentropic process for Ideal gas -air For the special case of air: 「s(T2)-s(T) Only f(T),marked as p.(T) i Relative pressure P2 exp[s(T2)/R] iBut not truly a pressure exp[s(T)/R] PROPERTY TABLES AND CHARTS TABLE A-17 Ideal-gas properties of air T h 以 Pr2 K kJ/kg P kJ/kg V kJ/kg.K P2 (s $2,air only) 200 199.97 0.3363 142.56 1707.0 1.29559 210 209.97 0.3987 149.69 1512.0 1.34444 Pr 220 219.97 0.4690 156.82 1346.0 1.39105 230 230.02 0.5477 164.00 1205.0 1.43557 240 240.02 0.6355 171.13 1084.0 1.47824 250 250.05 0.7329 178.28 979.0 1.51917 where pr=p(T1)and pr2 p(T2) 260 260.09 0.8405 185.45 887.8 1.55848 270 270.11 0.9590 192.60 808.0 1.59634 280 280.13 1.0889 199.75 738.0 1.63279 285 285.14 1.1584 203.33 706.1 1.65055 llay,April 18,2017 4 SHANGHAI JIAO TONG UNIVERSITY
Tuesday, April 18, 2017 4 Isentropic process for Ideal gas -air Only f(T), marked as pr (T) For the special case of air: Relative pressure But not truly a pressure
Isentropic process for Ideal gas -air,cont. For the special case of air: -(）… P2 Pr (s=S2,air only Only f(T),marked as v(T) Pr Relative volume PROPERTY TABLES AND CHARTS But not truly a volume TABLE A-17 Ideal-gas properties of air U2 T t U2 K kJ/kg P kJ/kg V. kJ/kg.K (s=52,air only) 200199.97 0.3363 142.56 1707.0 1.29559 Url 210 209.97 0.3987 149.69 1512.0 1.34444 220 219.97 0.4690 156.82 1346.0 1.39105 230 230.02 0.5477 164.00 1205.0 1.43557 240 240.02 0.6355 171.13 1084.0 1.47824 250 250.05 0.7329 178.28 979.0 1.51917 260 260.09 0.8405 185.45 887.8 1.55848 where vri=v-(T1)and vr2 =v(T2) 270 270.11 0.9590 192.60 808.0 1.59634 280 280.13 1.0889 199.75 738.0 1,63279 285 285.14 11584 203.33 706.1 1.65055 上通大学 Tuesday,April 18,2017 5 SHANGHAI JIAO TONG UNIVERSITY
Tuesday, April 18, 2017 5 Isentropic process for Ideal gas –air, cont. For the special case of air: Only f(T), marked as vr (T) Relative volume But not truly a volume where vr1 =vr (T1 ) and vr2 =vr (T2 )