上游充通大学 SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 31 Chapter 7 Entropy (Section 7.3) Spring,4/18/2019 强 Prof.,Dr.Yonghua HUANG MMMAMA http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日G
Engineering Thermodynamics I Lecture 31 Spring, 4/18/2019 Prof., Dr. Yonghua HUANG Chapter 7 Entropy (Section 7.3) http://cc.sjtu.edu.cn/G2S/site/thermo.html
Retrieve property data Tables,graphs,equations,software TABLE A-17 Ideal-gas properties of air h U K kJ/kg P kJ/kg V. :kJ/ke.K 200199.97 0.3363 142.56 1707.01.29559 p,v,T 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 1205.01.43557 240 240.02 0.6355 171.13 1084.0:1.47824 u and h 250 250.05 0.7329 178.28 979.0:1.51917 Reference value 260 260.09 0.8405 185.45 887.81.55848 270 270.11 0.9590 192.60 808.01.59634 280 280.13 1.0889 199.75 738.01.63279 Entropy s 285 285.14 1.1584 203.33 706.1:1.65055 290 290.16 1.2311 206.91 676.1:1.66802 295 295.17 1.3068 210.49 647.9:1.68515 : 298 298.18 1,3543 212.64 631.91.69528 TABLE A-4 300 300.19 1.3860 214.07 621.2:1.70203 Saturated water-Temperature table ……305.305.22 1.4686 217.67 596.0 1.71865 Specific volume Internal energy Enthaipy. Entropy. 而En■ggg m-/kg kJ/kg kJ/kg kJ/kg-K Sat. Sat. Sat. Sat. Sat. Sat. Sat. : Sat. Sat. Temp. press. liquid, vapor, liquid, Evap.. vapor, liquid. Evap. vapor. liquid. Evap.. vapor TC Pat kPa U h hi 0.01 0.6117 0.001000 206.00 0.000 2374.9 2374.9 0.001 2500.9 2500.9 0.0000 9.15569.1556 0.8725 0.001000 147.03 21.019 2360.8 229R 21.020 2489.1 2510.1 0.0763 8.94879.0249 1.2281 0.001000 106.32 42.020 2346.6 2388.7 42.022 2477.2 259.2 0.1511 8.74888.8999 5 1.7057 0.001001 77.885 62.980 2332.5 2395.5 62.982 2465.4 2528.3 0.2245 8.55598.7803 20 2.3392 0.001002 57.762 83913 2318.4 2402.3 83.915 2453.5 2537,4 0.2965 8.36968.6661 25 3.1698 0.001003 43.340 104.83 2304.3 2409.1 104.83 2441.7 2546.5 0.3672 8.18958.5567 30 4.2469 0.001004 32.879 125.73 2290.2 2415.9 125.74 2429.8 2555.6 0.4368 8.01528.4520 5.6291 0.001006 25.205 146.63 2276.0 2422.7 146.64 2417.9 2564.6 0.5051 7.84668.3517 0 7.3851 0.001008 19.515 167.53 2261.9 2429.4 167.53 2406.0 2573.5 0.5724 7.68328.2556 9.5953 0.001010 15.251 188.43 2247.7 2435.1 188.44 2394.0 2582.4 0.6386 7.52478.1633 0 12.352 0.001012 12.026 209.33 2233.4 2442.7 209.34 2382.0 2591 0.7038 7.37108.0748 15.763 0.001015 9.5639 230,24 2219.1 2449.3 230.26 2369.8 2600.1: 0.7680 7.22187.9898 19.947 0.001017 7.6670 251.16 2204.7 2455.9 251.18 2357.7 26088 0.8313 7.07697.9082 的 25.043 0.001020 6,1935 272.09 2190.3 2462.4 272.12 2345.4 2617.5 0.8937 6.93607.8296 1.202 0.001023 5.0396 293.04 2175.8 2468.9 293.07 2333.0 2626.1 0.9551 6.79897.7540 上游究通大学 April 18,2019 2 SHANGHAI JIAO TONG UNIVERSITY
April 18, 2019 2 Retrieve property data p, v, T u and h Entropy s Tables, graphs, equations, software Reference value
Reference state for entropy definition of entropy change 4s=5-s-(川) int Arbitrarily choosing reference state x,then at any state y, replace state 1 replace state 2 Because of cancel" s=s+(9 int rev ____Only for constant composition applications, for chemical reactions,use absolute values (3rd law) (Chap.15) 上游气通大粤 April 18,2019 3 SHANGHAI JIAO TONG UNIVERSITY
April 18, 2019 3 Reference state for entropy definition of entropy change Arbitrarily choosing reference state x, then at any state y, replace state 1 replace state 2 Only for constant composition applications, for chemical reactions, use absolute values (3rd law) (Chap. 15) Because of “cancel
Retrieve from table Tables C_A-6,C_A7 for water and C_A-13,C_A14 for refrigerant R134a 个 S0.01℃，sat liq.=0 S.40r，℃sat li.=0 (superheated)Vapor data:s~f(T,p) ·Example:water,state1(3MPa,500°C)→state2(0.3MPa,T2), S2=S1.T2=? IC_Tab.A-6 C_Tab.A-6 S1=7.2338k/kgK=S2 interpolating T2=183℃ (sub-cooled)Liquid data:s~fT,p) s(T,p)~s(T) ·Example:water,state1(25bar,200°C C Tab.A-4 C Tab.A-7 SE200c=2.3309k/kgK S1=2.3294k/kgK 上游气通大粤 April 18,2019 4 SHANGHAI JLAO TONG UNIVERSITY
April 18, 2019 4 Retrieve from table Tables C_A-6,C_A7 for water and C_A-13,C_A14 for refrigerant R134a (superheated) Vapor data: s~f(T, p) • Example: water, state 1 (3MPa, 500˚C) state 2 (0.3MPa, T2 ), s2=s1 . T2=? (sub-cooled) Liquid data: s~f(T, p) s(T,p)~sf (T) • Example: water, state 1 (25bar, 200˚C) C_Tab.A-6 s1=7.2338 kJ/kg·K=s2 C_Tab.A-6 interpolating T2= 183 ˚C C_Tab.A-7 s1=2.3294 kJ/kg·K C_Tab.A-4 sf, 200˚C=2.3309 kJ/kg·K s0.01 ˚C, sat. liq.=0 s-40˚C, sat. liq.=0
Retrieve from table-cont. Saturation data:Sp Sg Two-phase data: s=(1-x)st+xsg=st+x(sg-St) Example:R134a,state 1 (0C,u1=138.43kJ/kg) C_Tab.A-11 u=49.79,ug=227.06---two-phase C_Tab.A-11 s-(1-x)st xsg W一Uf =0.5 ug -uf =0.5580kJ/kg·K 上游充通大学 April 18,2019 5 SHANGHAI JIAO TONG UNIVERSIT
April 18, 2019 5 Retrieve from table - cont. Saturation data: sf , sg Two-phase data: • Example: R134a, state 1 (0˚C, u1=138.43kJ/kg) uf=49.79, ug=227.06 C_Tab.A-11 two-phase =0.5 C_Tab.A-11