热工基础练习题.pdf

180 1. 2. 3. 4. 5. p-v 6. 7. 8. 9. w =uwt =h 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. n 23. 24. 练习题 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. h = cpT 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 0 K 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. h 78. 79. 80. k 280 D AB CD 2C AB CD 3D AB CD 4A AB CD 5D Apg Bpb Cpv Dpb + pgpbpv 6pvB ABCD 7q = cVT + wC AB CD 8D ABCD 9B ABCD 10A AQ BQW CWQ=0DQW=0 11B AW0 BW=0 CW0 D 12 A AW0 BW=0 CW0 D 13C ABCD 14abcbA A cbabcbab SSUU B cbabcbab SSUU C cbabcbab SSUU D cbabcbab SSUU 15C ABCD 16 D AB CD 17100 kJ100 kJB AB CDAB 18C AB C D 19dS f =TC AB CD 20D ABCD 21A ABCD 22A AB CD 23C ttwtD AttwtD BttDtw Ct= tD = tw Dtw = tDt 24p2 = pb C AB CD 25C AB CD 26, C ABCD 27C A B C D 28 V D AB CD 29B AB CD 30B AB CD 31 B AB CD 32D AB CD 33Bi 0.1BiV 0.1MC AB C D 34D A B C D 35C ABCD 36X1,2B A1 B1/2 C1/3 D/2 37 B ABCD 38 T1T2 D AT1=T2BT1 = T2 CT1T2DT2T1 39D AB CD 40C AB C D 550 1 Q/kJ W/kJ U/kJ 1-2 1390 0 1390 2-30 395 -395 3-4-10000 -1000 4-10 -55 2bcuabuacsabsac uab= uacsabsac T1=1000KT2=400K1360 kJ833 kJ %60 1000 400 11 %25.61 1360 833 1 2 1 0 T T q w tc t ttc 4p1=0.3MPat1=240.1 MPa 4 . 1 =0.528 cf1 MPa3 . 0 01 pp MPa1 . 0 b p 528 . 0 3 . 0 1 . 0 / 1 ppb 5lg ph q2w0 6 BHd1d2 de=4A/U = 4BH/2H+B 12 12 2 1 2 2 4 1 4/4dd dd dd UAde 7800K400K 4 TEb 4 TE 4 2 4 1 TT 0625 . 0 5 . 0 800 400 4 4 4 2 4 1 T T 8123F 1 = 2 m2F 2 = 4 m2 F 3 = 6 m2, X3,2 = 0.16X3 1+2 = 0.18X1 3 X3 1+2 = X3 1 + X3,2 X3,1= X3 1+X3,2=0.1 F 1 X1 3=F 3 X3,1 X1 3=F 3 X3,1/F 1=60.02/2=0.06 9q 10 f1f 2f1f 2 f1f 2 k 12 ()() () 11 tttt qk tt r hh 10.4 m150 kPa 0.45 mW10 D1 = 0.4 mp1 =150 kPap = kD k =375 kPa/m kJ27. 2 )( 82 2 ) 6 ( 4 1 4 2 3 33 2 1 DDkdDkDW dDkDDdkDpdVdW D D 2.27 kJ A100cm2H10 cm m1195 kgpb102 kPat027 C 100 kg Qg9.8 m/s215 1 K300)27273( m10101010100 kPa1 .293 10100 108 . 9195 102 1 3324 1 4 3 1 b1gb1 T AHV A gm pppp 2 33-3 2 1 12 12 4 3 2 bg2b2 m101.5023 1 .195 1 .293 10 K300 kPa1 .195 10100 108 . 9)100195( 102 p p VV TT A gm pppp cm023. 5m05023 . 0 10100 10) 15023. 1 ()( 4 3 12 A VV H Q=U+WT2 = T1U = 0 Q =W=97.999 J 1pdVW 2 1 297.999 JVpg2Vpb 200 kPa20 84 kJ/kg100 kg/min200 kPa3003072 kJ/kg200 kPa100419 kJ/kg 10 k g/ m i n63.12 )( 0)()( 0 0, 0, 0 2 1 , 0 2 1 2 11 2 221121 2 2 hh hhm m hmhmhmm H WzmgcQ WzmgcHQ s s 12.63 kg 5gp1=6.0105 PaT1=600K V2=3V1Rg=0.208 kJ/(kgK)cp=0.523 kJ/(kgK)1T2p22 10 U = 0 T2 = T1 = 600 K Papp T Vp T Vp T Vp 5 12 1 12 2 22 1 11 100 . 2 3 13 U =H = 0 J/K)(1426. 1/101426 . 1 3ln208. 0005 . 0 lnln 3 1 2 1 2 KkJ p p mR V V mRsmS gg 5 (10) q =cpT u= cVT cp = cV+Rg w =RgT 6 2kg n=1.23300 60418.68 kJ83.736 kJcpcV (10) (15) K)kJ/(kg6978. 0 )573333(2 96.334 )( )( 12 12 TTm U c TTmcU V V kJ68.41868.4182 . 1736.83 t WQH K)kJ/(kg8723 . 0 )573333(2 68.418 )( )( 12 12 TTm H c TTmcH p p 7 3 kg805 kg204.187 kJ/(kg K) 15 HC cp = cV = c K5 .315 53 29353533 00 0 0, 0 11 2 1212 CH CCHH CVCHVHCH mm TmTm T TTcmTTcmUU U WQ WUQ cp = cV = c 1 2 2 1 ln T T cm T mcdT S T mcdT dS 1 2 1 2 lnln C C H HCHiso T T mc T T mcSSS KkJ/1249. 0 293 3 .315 ln5 353 5 .315 ln3187. 4 0 iso S 8t1 =27p1 =1.5 barpb= 1barcp=1.004 kJ/ kg K RgkJ/kg K12 3A2 = 0.02 m215 1c1 0.528667. 0 5 . 1 1 1 b p p 21c 2ccr m/s67.256)2 .267300(10004. 12)(2 K2 .267 5 . 1 1 300 3 212 4 . 1 14 . 1 1 1 2 12 hhc p p TT 3) /kgm7669. 0 10 2 . 267287 3 5 2 2 2 2 b gg p TR p TR v )kg/min(622.401)kg/s(6937. 6 7669. 0 67.25602. 0 2 22 v cA qm 9p1 =0.85 bart1 = 40=15 t4=2000p4 =75bart5=760 K1p-vT-s 21kg15 (1)p-vT-s 2 T1 T4T5T2T3 1p1 =0.85 barT1 =273+40=313 K 2 bar6658.371585. 0 4 . 1 1 2 1 12 k k p V V pp K253.88615300 14 . 11 1 1 2 1 12 k k T V V TT 3bar75 43 pp K8797.1724 6658.37 75 253.866 2 3 23 p p TT T4=2000+273=2273 KT5=760 K 1kg k J / k g446.1152312.550134.602 )880.17242273(004. 1)253.886880.1724(718. 0 )()( 3423111 TTcTTcqqq pV k J / k g5 .831946.320446.1152 210 qqw %15.727215. 01 1 2 1 0 q q q w t 10=14 1000 kJ/kg 100 kPa271215 kPa100 1 pK30027273 1 T14 k J / k g1000 43321 qqq 4 . 1 12. K1 .86214300 4 . 0 1 2 1 12 V V TT VV2VV14 1 234. K5 .15581 .862 718. 0 500 /500 23 TcT v K0 .20565 .1558 005. 1 500 /500 34 TcT p VVV 23 VV T T V319 . 1 3 3 4 4 45. 1 5 4 45 V V TTVVV14 15 K2 .799 14 319. 1 0 .2056 4 . 0 5 T %16.641 1 2 q q t 1120 C30 C 3.5 kW 13.86 k W K30327330 4 TK25327320 1 T kW5 . 3 12 HHP k J / k g450 54 hhM P a1 . 1 2 pk J / k g1825 2 h M P a17. 0 1 pk J / k g1570 1 h 47. 6 1 2 p p 39. 4 15701825 4501570 12 41 hh hh 98. 386. 3/ )4501570(0137. 0)( 412 hhmQ kg/s0137 . 0 15701825 5 . 3 12 hh P qm 123mm1 W/mK) 104 W m2110 t1t2 / 21 tt r t q 2 .127 1 003. 0 1024. 4 4 21 tqt 1320 mm 1 300 C30 C 2 2 1 1 t q m q t 2375 . 0 35 . 0 3 . 1 02 . 0 1830 301300 2 1 1 2 237.5 mm 1450mm450 h =24W/ m2 K = 3721 kJ/m3K=35W/mK10 min15 1 . 0017. 0 35 10 2 50 24 3 hR Bi 6285. 0 6010 1050103721 6246 0 33 eee cd h cV hA 6285 . 0 00f f tt tt 15 mm=85W/ (m)a=2.9510-5m2/s, 3003630 W/(m2) 9015 mm50d300 0 t 90 0088. 0 85 025. 030hR Bi )exp( 0 cV hA tt tt f f m i n17.211270 36300 3690 ln 4301095. 2 3 4 85 lnln 25 3 00 s R R tt tt ahA V tt tt hA cV f f f f 16800.08 m0.2m205 348954 kg/m3383.1 J/(kg) =386W/ (m)15 80 0 t20 f t34t 3 k g/ m8954 h f0 f ln tt tt A cV h m W/(m3355.277 2080 2034 ln 605 60 1 1 .3838954 2 h Bi 1 . 00287. 0 386 04. 03355.277hR Bi 1711200 K3600 K 1 =0.2 2=0.53 =0.8 2 2 15 A1A2AX1 2=X2 1 1 1111 111 22111 1 21 22 2 21111 1 21 21 AAA EE AXAA EE bbbb 1 2 3 1 11 100100 67