工程热力学高教第三版习题答案第5章

1、(ED-520#2.5x10995%kWli7； = (20 + 273)K = 293K7； = (-5 + 273)K = 268K g© =2.5 xl04kJ/li二鬻|x2.5 曲 kJ/hf。叭293K#q, = q© = (2.5 - 2.287) xlO°kJ/h = 0.213xlO°kJ/h95%= 0.213 xlO：kJ/h=()623kw 3600s/hx0952.5xl04kJ/hPF皿kJ"计kJX6.94kW7； = 300K 必=0.1MPa7； =1000K400kJ/ kgcz, =1.004 kJ/(kg

2、 K)5-34厲=912 +的3 = 5，(5-7；)+的3=1.004kJ/(kg K)(1000 - 300)K + 400kJ/kg = 1102.8 kJ/kgT3 = T2 = 1000K T4 = Ty= 300K4-1 = y-2-3 =x 400kJ/kg = 120 kJ/kg<72 = 73-4 + 如-1 二 J d 7；) + 4-1= 1.004kJ/(kg K)(1000 一 300)K +120kJ/kg = 822.8kJ/kg坐“一竺世坐= 0254qx 1102.8kJ/kg1-23-4=%-3 = 400kJ/kg q2 = q- = -q2_3 =

3、x 400kJ/kg = 120 kJ/kg/->1.UUUKAB的 _1 120kJ/kg_ _ - 400kJ/kgCD1-2 2-33-10.70541-2-3-1lkinol7；=1500K T2 = 300KPiK = l4T-sn1-2Pi =P2 =1.41500K)E300K 丿1-2-3-1 卩$a =臥15-35= 0.1MPaP2x0.1MPa = 27.951MPa7 = 7；= 300K P3 = /?! = 27.951MPa CpmK-l£1PiRT3 In01 1Q %-右)2=1旦“a” i 27.95IMPa300Kxlii1- OlWa =

4、0.598x(1500K-300K) 0.4Ti=1500K72=3 OOK80%丄亠進=0.8Tx 1500KQn = n = -=丁 Cptnn陰”一可C In互PM T1500K-300K = 745>6Kt 1500Kui300K5-36Th To0H7； =1000KTh = 360K7o=29OK fl = lOOkJ% = 40%ChQhQh>QiW切=q上 a = 0.4xl00kJ = 40kJThQ = £ = 3.5 x 40kJ = 140kJ= 1_Zo=1_ = o,717；1000KToTh%v = 071xl00kJ=71kJ360K= =

5、 5.14"" ThTo 360K - 290KOh“ = £爲 = 5.14x71kJ = 364.94kJ6hTh Tq55Q2=Qr- Wnet = lOOkJ- 4OkJ = 60kJ Q = © - W = 140kJ - 40kJ = lOOkJ%60kJlOOkJlOOkJ7TfllOOkJ5-67； = 2000KT2 = 300K40kJ Th40kJQ、= lkJ Wnct = 0.9kJ© = 2 kJQx = O.5kJ Wnel =1.5kJQ = 0.3kJT TiHe300K2000K= 0.8557#Q = 0i

6、 _ Wne,=山-0.9kJ = O.lkJ=1_a=1_oai2i lkJ=0.9 > r)c#Q 0.3kJ 0 2kJ05kJ20kJ=0.75 < rjc心-計1-ft = e2 + VVr/ = 0.5kJ + 1.5kJ = 2.0kJlkJ + 0，lkJ = +0.000167kJ/K > 02000K300K* T 7； T2 2000K300K翌但+鱼=王+沁.00067RJ/K < 0 亠 T 7； T2 2000K300K7； = 800K T2 = 500KQzQ= 15 00k J Q2 = 500kJ% = 300KIV , =1000k

7、Jnet1Qi = 1500RJ Q2 = 500kJ Wnel = 1000RJ03 = _ + Q) -阵J = - Q500 + 500)kJ-1000kJ = -lOOOkJ4.80ft Q.031500kJ500kJlOOOkJ°cL = + + =F= 0.4583kJ/K v 0丄 7；T2T3800K500K300K« Ff+t=°=-300K'1500kJ,300K500kJ、500K,= 8625kJ#比“gx = Q + Q+03 = 1500kJ + 500kJ-8625kJ = 11375kJ(c)20kJ 20kJ20kJ -2

8、0kJ,20kJ -5kJlOkJU = Q-W = 20kJ-20kJ=0A« = /(DAT = 0#J LAS >00 8MPa 4200 1 MPa 130cp = 1.01kJ(kg K) cv = 0.732kJ(kg K)1kgR=c -c =1.01kJ(kg K)-0.732kJ(kg K) = 0.278kJ(kg K) o P= cp 1117?g hl P=1.01kJ/(kg K)ln(130+273)K(420+273)K0.278kJ/(kgK)ln0. IMPa0.8MPa59#= 0.03057kJ/(kgK)A5 >0<7 = 0

9、叫= w, = A_ = Cp(7；_ 巧)=1.01kJ/(kg K) x (693 - 403)K = 292.9kJ/kg$10 0 25kg COPj = 0.25MPa= 120°C p2 = 0.125 MPa匚=25 °C48 0kJtQ = 25°C CO« = 0.297kJ/(kg K) cv = 0.747kJ/(kg-K)7； = (120 + 273)K = 393K7； = (25 + 273)K = 298Kg = A(/ + W = /ncv(7；-7；)+WQ = 0.25kg x 0.747kJ/(kg K) x (2

10、98 - 393)K + 8kJ=-17.74RJ + &0kJ = -9.74kJTAS = m(cp In 丄ARn P?)Pi=0.25kg x0.747kJ/(kg K)ln 298K 0.297kJ/(kg K)In 0125MPa393K025MPa-0.0002 lkJ/(kg K)0= -0 = 9.74kJ ASJ( ” =- = 9 74kJ = 0.03268kJ/K呦Tq 298KS' MS + A5_=-000021kJ/K + 0.03268kJ/K = 0.03247kJ/K > 0#crw=0.42kJ/(kg-K)Tw = 295Kc;.

11、 = 4.187kJ/(kgK)&=9kgT“ = 1060K#Tf= Q-WQ=Q W=O = 0 =0Kfft#Hg (Tf - TJ + WTf -= 0叫讥+ my厲叫 J + rnmcm9kgx4.187kJ/(kg K)x295K+0.36kgx0.42kJ/(kg K) X1060K “c=298.IK9kg x 4.187kJ/(kg K)+0.36kg x 0.42kJ/(kg K)= A5m + A5h.T298 1K5 =亍 0.36® 0.42kJ/阳K)g歸叩kJ/Kg = -.Ain 土 = 9.0kg x 4.187kJ/(kg. K) In 器

12、=03939kJ/KASq =-01918kJ/K+03939kJ/K= 02021kJ/K1kgPi = 0.1013MPaTr = 283°CZ2=317°C5-377； = (7 + 273)K = 280KTz = (317 + 273)K = 590K Tr = (283+273)K = 556K邑厶込2.107Pi 7；280K= 282.22kJ/kg f = 6.6380kJ/(kgK)Ik = 598.52kJ/kg5? = 7.3964kJ/(kg K)A/ = A/i- A(pv) = A/ - /?6AT=598.52kJ/kg 一 282.22kJ

13、/kg 一 0.287kJ/(kg K)x (590一 280)K = 227.33kJ/kg阿呱=227.33 + 0呱S2Sl = S2-SfRz61=7.3964kJ/(kg K)一 6.6380kJ/(kg K)- 0.287kJ/(kg K)hi 2.107 =0.5445k J/(kg K)#7； = 590K 7；=556K T2 >TrTa = Tr = 556Kha = 563.0kJ/kg£ = 73343kJ/(kg K)忙“ =ha 一 lh = 563.0kJ/kg - 282.22kJ/kg = 280.78kJ/kg叽=必“ - R理=280.78

14、kJ/kg - 0.287kJ/(kg K) x (556 - 280)K = 201.57kJ/kg q = A" = 201.57kJ/kg山爲=_4化2 = _(4”12_4"】“)(227.33-201.57)kJ/kg=-25.76kJ/kg556K= 0.18196kJ/(kgK)#(3)二屯_» = 0.5445kJ/(kg K)EWr2 = 57°c叫瘁=一側2 = - 227.33kJ/kg 人=17七Ip = 0.1MPa1kgP? = Pi= O.IMPa5-40#1怙和水戴代Pj-OJ MPa空代Pj-O.l MPaq“/:=57

15、T p2=0.l MPa g-itt n二r=2如,p.-O I MPa'饱和水 p"l MPa/?3 = 2675.14k J/k /4 = 417.52kJ/kg53 = 7.3589kJ/(kg K)54 = 1.3028kJ/(kgK)7； = (17 + 273)K = 290K7；= 57 + 273 K = 330K小一® = $f+%* = $2 S = £ f 一 111= £ _ 5° PlT25° = 6.6732kJ/(kg K) 5? = 6.8029kJ/(kg K)56 = 52-51 = 5&#

16、176;-5°=6.8029kJ/(kg K) - 6.6732kJ/(kg K) = 0.1297kJ/(kg K)q 沁(t - $)+得(t - 昌)= 5f + se#sSg = -= ($2 -&) +如(为_$3)a力q”“q,”3居一人Gnl人一人T1 T2 ! = 292.25kJ/kg A2 = 332.42kJ/kgq”3 = 332.42kJ/kg-292.25kJ/kg =Q0178q 2675.14kJ/kg-417.52kJ/kg aS s =亠=6.8029kJ/(kg K) 一 6.6732kJ/(kg K)+ 0.0178 x1.3028kJ

17、/(kg K)-7.3589kJ/(kg K) = 0.022kJ/(kg K)2 1J-14 /n = 106kg r = 45°Ccw, =4.187kJ/(kg K)/0=10°C7； = / + 273 二(45 + 273)K = 318K7 = (10 + 273)K = 283K318K283K_ o /(To)(318 - 283)Kt 318KIn283K= 300.16K= 106kgx4.187kJ/(kg K) x (318 - 283)K 1-283K、300.16K 丿= 8.38xl06kJ283K300.16Kx4.187kJ/(kg-K)x

18、l06kgx(318-283)K = 13 8.16xl06kJ=mT0s = mTQcwn= 106kgx283Kx34.187kJ/(kgK)ln283K=138.17 xl06kJ63Eg = Q-4,2 =叫(7； - 耳)-心= 106kgx4.187kJ/(kg K)x(318-283)K-138.17kJ/kgxl06kg= 8.38xl06kJ,15)Ci3-21-3Q> A2-4 > Al-4lOOOK300K50KCia-b-c-d-a% = 300K1000kJ(1) abcda300 + 50 K(1000-50)K=0.6322 Q =1000kJ350K

19、2 = O = -一xlOOOkJ = 368kJ T 1950K7h = 1000KlOOOkJ65#*“"一 0i 0i TOOOkJs 氓=ASh + A5“ =+ = 5 = 300Kx0.0526kJ/(kg-K) = 15.78kJ#350K368KJ300K#4=亿+絶诗+鬢離+離=0 1752kJ/K厶=TqAS2 = 30 OK x 0.1752kJ/(kg - K) = 5 2.5 6k J/ = /+/?= 15.78k J + 52.56kJ = 68.34kJ017100kg20200kg80cH. = 4.187kJ/(kgK)r0 = 20°c

20、#f _ 加山 + "Vl -100kg200 C+200kg80 °C "。小=60 C叫 + 叫100kg + 200kg7； = (20 + 273)K = 293K7； = (80 + 273)K = 353K T = (60 + 273)K = 333KSy = AS】+ AS2 =加q In + m2cw In 7ih333K333K= 100kgx4.187 kJ/(kg K) In+ 200K x4.187 kJ/(kg K) In293K353KSf = 0=47392kJ/KA% = %I = 7oSg = (20 + 273)K X43792

21、kj/K = 1388.6kJAS = 0.8239kJ/K70 = 298K#335kJ/kgI = T0Sz= 298Kx0.8239kJ/K = 245.5kJSI9 100kg0100kgQ = 100kg x 335 kJ/kg = 3.35 xl04kJT = Tice = 273KAS1,= g = -g=335xl°4kJ/k122.71kJ/KT Tlce273KAS = Sf + Sg5e = A5-Sf = 122.71kJ/K -11433kJ/K = & 38kJ/kI = TQSt= 293Kx938kJ/K = 2455 34kJ205-20 1

22、00kg020335kJ/kgc“ = 4.187kJ/(kgK)20T-s1OOkgOQi = 100kg x 335kJ/kg = 3.35 xl04kJ1OOkgO20Q2 = 100kg x 4.187kJ/(kg K) x (20-0)°C= 8374 xlO3kJQ = Qi+ Q2= 3.35 xl04kJ+&374 xl03kJ=41874 xlO“kJ+ In3.35xl04kJ273K+ 100kgx4.187kJ/(kg K)ln293K273K= 152.313kJ/K67#-4.1874 xlO4kJ293K=-142.915RJ/K= AS. 2

23、+ AS>4 = 152.313kJ/K 142.915kJ/K = 9.398kJ/K#T2I = T。 = 293x9 398 = 2753 7UJ I T-s23mn2A#L9Cic 一+力勺山= Ci-<z)"刃"-Ci-li)djiii =IT FpS 冃 Pg I -1 n3? 1=叫 yd'丄zi !zT=7T °書列。寸JIU -U JUlo = Tv + svJ +TvaO口0= SV«lJUI t I = SV(17P 7彳叫 djlu=djut=Z1(乙)Ciz-Zi + Xi)d =Izpb"Xm它丄

24、卜=fl (l)fl-S-G 讥一。-,ncPAT,x = mCl>dTi,x -叫：d7i,x =叫J： d©人层+ Q5弍叫警w峠W叫令"峠T2和AS = AS4 + g = mcp 111 仏 + me卩 In 如二T T27込=7/ ASbo = 2mcp hi心7?, = 2叫兀In*Qa = cp(T1-TJA”,04 =石=omcp h】y-血 0* = 0 一mcpTc In # = me0厂怜（几一丁2）Eg =Qb ,Qb =叫(Tnt-T2)- mcrT0 In * =/ = Eg- Eg = 4仞- A”. = 2TQmcp0畤m )(号忌咱T

25、,n#300kW#292kWqQ = -hA(Th-T0)#/z = 0.17kW/(nr-K)A = 1.2m2 Th69#To = 293KkW/K(kW)TqdU = dQ-dW#P = 292kW 一 300kW = 一 8kWqQ = -liA(Th-TQ)Tb#-(-8kW)523V = 0 lw3几巾,7； = 303K7； = + 7； =J一1 +293K = 3322KhA0.17kW/(m -K)xl.2nrT0S = 293K x 0.024kW/K = 7056kWd5 A . =Sf + 5g = 0S =-Sf = -= (8kW) = 0.0273RW/K6 f

26、 To 293KI = TqS = 293Kx0.0273kW/K = 8kWS , = S -Srl= 00273kW/K-0.0241RW/K = 0.0032kW/K厶=/ _ 厶=8kW - 7.056kW = 0.944kW#t2#dQ = dUc + heAne 一 儿 5心 +3ine = 0SQ = dUn, - ltodm凸=0u2m2 一 uxmx - ho（m2 -） = 0ni =hi = ho = CpTodS“TrdScv = sodm + 6S £S?-Si = j0 （m2 -） + Sg们4 J=0 8214x1 004ln =303/ = ToSg

27、 = 303 x 0.2775 = 84.087=0.2775 骸T2=TQ= 303/CpV 105 xO 1fU = 0» m2 = /?,"2 = h。cvT2 = cpT。, T2 = kTo = 1 4x303 = 424 2K"Vm； = nij =RkT2105x0 1=:=0 8?14kg0 287x103 x424.2dUcv 一 hodm = 0#Tr+ sodm + 瓦S? - S严孕+$。（加2 -"） + Sg nS2 =叫 $2 = m2So = 0冲1 = o翅=de - hodm0 = 5-5-九（性-叫）Q =加2% -

28、叫九=（u0 -九）匕=-PN叫=-py= 303x0 0330=10UraVp tqPoQu = P(y y-+ lit I Po Po Po)E、u = lkWh Po = lbai*V (m3) PoE,u =U-UQ-TQ(S-SQ)+pQ(V - %)1/_班=叫(丁_%) T = Tq,u-u° = oS- SQ = H lRWPPo=-mR In PoE.y,u = m花 hi 4- pQV- pQVQ = pV hi + pQV - pQVQ = p0V PoPo+厶上< V Po Po)6/ nV=p0 V (1 - + 1 n ) Pq Po PqlkWli

29、 = 3600kJ po = lbar = 1 OOkPa36_JL+JLnJL< Pq Pq Pq)P / Pov(m3)P/Pov(m3)100112.198o93 193121.9133273781131 687414 144141.50358.890151.35266 260200.88074723250 63883 736300 49393 0571000.0996102.56771V = 2.45xlO'3m3=0.7MPa 人= 867°Cr0 = 27°C p0 = 0.1013MPaR“ =0.296kJ/(kg K)ftcp=1.04kJ/

30、(kg K)#p2 = 0.3MPa r2 = 637°C#cv =cp-Rg=1.04kJ/(kg K)-0.296kJ/(kg K)=0.744kJ/(kg K)=0.00508kgpyx 0.7 xlO6Pax2.45 X10"3ill3 RJ 296J/(kg - K) x (867 + 273)K处还=丛 0.7MPax300K x2 45xl0-3m3 = 4 455小加 pQ PoA 0.1013MPaxll40K叫峙计鈔响“=0.00508kg0.744kJ/(kg K)(1140 - 300)K - 300K1.04kJ/(kg K) In 114

31、6;K300K-0.296kJ/(kgK)hi + 101.3kPa(2.45-4.455)xl0_3m30.1013MPa=1.93085kJ - 0.2031 lkJ = 1.7277kJJ = S - j =Ui-U2-T0(Sl-S2)+p0(% -岭)匕=巫 y 0.7MPax(637 + 273)Kx45xl0,3m3 = 4.5633xloF 0.3MPaxll40K弘？ = mcv (7； -巧)一加 © In £ - & In 旦)+ 戸(V； - 岭)T2 P2=0.00508kg0.774kJ/(kg K)(l 140 -910)K- 300K

32、(1.04kJ/(kg K) lii H4°K910K-0.296kJ/(kgK)lii + 101.3kPa(2.45-4.5633)xl0_3iii30.3MPa=0.89436kJ-0.21408kJ=0.6803kJ56JC-l /、Pop Kf T f , pi = Cpd)$一比二汕齐-&ln 7oPqK-lR =c.c产JrK-l“(T)一亦岭一孚讣土TTllii + hi ToToxr-1P *J?0>"1=0 1 MPalkg- = -l-hi + lii Cp%T2 = 33OK c2 = 30m/s/?6 =0.287kJ/(kg K)j

33、t-i必丿! - 0.4MPa 7J = 450K cfl = 130m/spQ = 0. IMPa To = 293Kcp=1.004kJ/(kgK)1-2,max'.t.Hi =片 _ 几 _ 珀($1 _50)= cp(T _ %)_ % Cp h】¥_111 I JQPqJ=1.004kJ/(kg K)(450 一 293)K-293K 1.004kJ/(kg K) ln-0.287kJ/(kg K)In ° 4MPa 290KO.IMPa=15 7.63kJ/kg -12.6745 kJ/kg = 144.96kJ/kgex,H2 = Cp(T2-70)_

34、70 Cp 11】子- n 70Pq)=1.004kJ/(kgK)(330-293)K-293K 1.004kJ/(kg K)In- 0.287kJ/(k« K)ln ° ni?a _293K0. IMPa=37.148kJ/kg-34.844kJ/kg= 2.31kJ/kg1 2S =匕时+亍Cfi=144.96kJ/kg + y(130m/s)2 xlO-3 = 144.96kJ/kg +8.45kJ/kg = 153.41kJ/kg=2.31kJ/kg+y(3Om/s)2 xlO-3=2.31kJ/kg + 0.45kJ/kg = 2.76kJ/kg73#lvi-2,

35、max = 一 & = Si % = 153.4 lk J/kg- 2.76k J/kg = 15O.55kJ/kgq = bh + yACf + h;vv =-+-(6-4)= cp(7；-7；) + -(-4)=1.004kJ/(kg -K)(330-450)K + -(30m/s)2 -(130m/s)2 xlO-3 2= 128.48kJ/kgu; = vv. =128.48kJ/kgifidO5kg/i = 20°C px = 200kPap2 = 220kPacv = 0.717kJ/(kg K)p0 = 98kPa /0 = 20°CVW = Ul-U

36、2 = mcv(T1-T2)<220kPa>j200kPa 丿x293K = 322.3KW = O.5kg xO.717kJ/(kg K)(293 - 3223)K = -10.504RJ咕VWt = w = 一 10504kJ#-2 max = E“-=UX-U2-T.s-SJ + 必( -岭)叱唤=4一4 一 逐 Gin#2?93K-10.504kJ-0.5kgx0.717WgK)x293Kb=-10.504kJ +10.01 lkJ = -0.493kJ心恥Sr/TA+AS。)A5° = 0 hS秤沁 SgI =秘S"。= TQmcv In 苹322 3

37、K=293Kx0.5kgx0.717kJ/(kg K)xln= lO.OllkJw2 -WH= -0.493kJ -(-10.504kJ) = 10.01 lkJp2=0.12MPa t2 = 60°C弘=lkg/sq朴=08kg/s5-39ro=io°cpQ = O.IMPaPi =0.13MPa t = 20°C& = O.287kJ/(kgK)cp = 1.004kJ/(kg K) q = 4.187kJ/(kgK)%也一。=%£（5-心）心老Eg盟牆爲心“= 68.01°C«68°C7； = (20 + 27

38、3)K = 293K7； = (60+ 273)K = 333K Twl = (80 + 273)K = 353K75#Tw2 = (68 + 273)K = 34IK 7 = (10 + 273)K = 283KEg = K - 瓜 (S - So) = cp(Tl-T0)-T0 cp in -人 In 70 /70 丿=1.004kJ/(kg K)(293 - 283)Kr . , 一 293K. “ 一 0.13MPa-283K 1.004kJ/(ke K) 1110.287kJ/(kg K) In283KO.IMPa= 21.48kJ/kg% -血一人（归-5）= Cp-%）- 7；（

39、勺 1"¥一= 1.004kJ/(kg K)(333 - 283)K皿K卜丽gK)h隸皿71dgK)S 牆= 18.78kJ/kgi,眄=九 1 -(几i -50) = cw(Twl-Tq)-TocwIn半= 4.187kJ/(kg - K)(353- 283)K - 283K x 4.187kJ/(kg K)ln 兰=283K= 31.20kJ/kgT g =咕-叽-耳(sw2 - 50) = cw(Tw2-Tq) Tocwn活70=4.187kJ/(kg K)(341- 283)K - 283K x 4.187kJ/(kg K) In 里淫283K=21.93kJ/kg

40、1 = % Ch 一 冬H J + %“，(S,H" 一 ex.EH,)=lkg/s(21.48-18.78)kJ/kg + 0.8kg/s(31.20-21.93)kJ/kg= 10.12kW/?6 = 0.287kJ/(kg K)=0.75MPa人=750 Cp2=0.1MPa/2 = 320°CG = l004kJ/(kgK)lkg=0.1MPap0=0.1MPa To = 298Kt -h2 = J(71 -耳)=1 004(750-320) = 431 72>0AS =c lnZl-/? lnl=l 004In 320+273-0.287lii =0 031u p 7； k pi750 + 2730.75AS >0：ex Hl evHj =人一甩 一 （勺 一T21.004kJ/(kg K)(l 023 - 593)K 一298K 1.004kJ/(kgK)ln1023K”、，0.75MPa0.287kJ/(kg K) In593KO.IMPa= 431.72kJ/kg + 9.177kJ/kg = 440.897kJ/kgwu = wi = 431.72kJ