BI 1: THC HNH TRUYN NHIT NG XON

1.1.Mc ch Th Nghim: Kho st c tnh ng lc hc lu cht v kh nng hot ng ca thp m bng cch xc nh: - nh hng ca vn tc kh v lng ln gim p sut ca dng kh qua ct. - S bin i ca h s ma st fck trong ct theo chun s Reynolds ca dng kh v suy ra cc h thc thc nghim. - S bin i ca tha s lin h gia gim p ca dng kh khi ct kh v khi ct t vi vn tc dng lng. 1.2.C s l thuyt Cc qu trnh trao i nhit gia dng lu cht qua mt b mt ngn cch rt thng gp trong cc lnh vc cng nghip ha cht, thc phm, ha duTrong nhit lng do dng nng s ta ra s c dng lnh thu vo. Mc ch ca qu trnh nhm thc hin mt giai on no trong qui trnh cng ngh, c th l un nng, lm ngui, ngng t hay bc hi Ty thuc vo bn cht ca qu trnh m ta b tr s phn b cc dng sao cho gim tn tht, tng hiu sut ca qu trnh. Hiu sut ca qu trnh trao i nhit cao hay thp ty thuc vo cch b tr thit b, iu kin hot ng Trong chiu chuyn ng c ngha rt quan trng: Cn bng nhit lng kh 2 dng lng trao i nhit gin tip:

Nhit lng do dng nng ta ra. QN = GN.CN.TN Nhit lng do dng lnh thu vo QL = GL.CL.TL Nhit lng tn tht (phn nhit lng m dng nng ta ra nhng dng lnh khng thu vo c do trao i nhit vi mi trng xung quanh). Qf = QN - QL Cn bng nhit lng. QN = QL Qf Mt khc nhit lng trao i cn c th tnh theo cng thc: Q = K.F.tlog T cng thc (5) ta thy nhit lng trao i s ph thuc vo kch thc thit b F, cch b tr cc dng tlog. Do thit b l phn cng ta rt kh thay i nn c th xem nhit lng trao i trong trng hp ny ph thuc vo cch b tr dng chy. Tuy nhin trong thit b truyn nhit ng xon ny ta khng xt tt c cc trng hp b tr dng trn, chng ta ch xt trng hp dng xui chiu v ngc chiu. Chy xui chiu: lu th 1 v 2 chy song song, cng chiu vi nhau 1 2 Chy ngc chiu: lu th 1 v 2 chy song song nhng ngc chiu 1

2 Ty thuc vo cch b tr m ta c phng php xc nh hiu s nhit hu ch logarit tlog khc nhau Trng hp chy xui chiu Nhit lu th nng gim dn, lu th ngui tng dn. c trng thay i nhit khi xui chiu. tmax = t1 = T1 T2 tmin = t2 = T1c T2c Trng hp chy ngc chiu c trng thay i nhit khi ngc chiu Nu (t1 t2c) > (t1c t2) tmax = t1-t2c , tmin = t1c-t2 Nu (t1 t2c) < (t1c t2) tmax = t1c-t2 , tmin = t1-t2c Nu trong qu trnh bin i nhit m nhit ca lu th t bin i, tc t s th hiu s nhit trung bnh tlog c th c tnh gn ng theo

trong bnh s hc tlog = 0.5 ( tmax + tmin) 1.3.Bng s liu th Kho st qu trnh truyn nhit trn TB2 Trng hp xui chiu

Tin hnh th nghim trn thit b TB2 ch xui chiu vi cc gi tr lu lng ca cc dng theo bng 3. Bng 3: Bng b tr th nghim trn thit b TB2 khi xui chiu

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

VN

VL

T5 (0C) 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26

T6 (0C) 62 61 59 56 54 52 51 50 49 47 46 45 43 42 41 41 41 40 39 38

T7 (0C) 38 36 35 32 31 36 35 34 32 31 35 33 32 30 29 33 32 31 30 29

T8 (0C) 43 42 39 37 35 42 40 38 36 35 39 38 36 34 33 36 34 34 33 32

(lt/pht) (lt/pht) 4 7 4 10 13 16 4 7 7 10 13 16 4 7 10 10 13 16 4 7 13 10 13 16

21 22 23 24 25 16

4 7 10 13 16

26 26 26 26 26

38 38 38 37 37

32 31 30 29 28

35 34 33 32 32

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

GN kg/s

GL kg/s 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166

Dng nng Tv(0C) 62 61 59 56 54 52 51 50 49 47 46 45 43 42 41 41 41 40 39 38 38 38 38 Tr(0C) 43 42 39 37 35 42 40 38 36 35 39 38 36 34 33 36 34 34 33 32 35 34 33

Dng lnh Tv(0C) 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 Tr(0C) 38 36 35 32 31 36 35 34 32 31 35 33 32 30 29 33 32 31 30 29 32 31 30

0.066

0.115

0.165

0.215

0.265

24 25

0.216 0.266

37 37

32 32

26 26

29 28

Trng hp ngc chiu Tin hnh th nghim trn thit b TB2 ch ngc chiu vi cc gi tr lu lng ca cc dng theo bng 4. Bng 4: Bng b tr th nghim trn thit b TB2 khi ngc chiu TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 13 10 7 4 VN VL T5 (0C) 42 37 34 32 31 38 36 34 32 31 35 34 32 32 30 33 32 T6 (0C) 65 64 61 59 57 55 54 53 52 51 50 49 49 48 46 45 45 T7 (0C) 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 26 T8 (0C) 47 45 42 39 38 46 44 42 41 39 44 42 41 39 38 41 40

(lt/pht) (lt/pht) 4 7 10 13 16 4 7 10 13 16 4 7 10 13 16 4 7

18 19 20 21 22 23 24 25 16

10 13 16 4 7 10 13 16

31 30 29 32 31 30 29 29

44 43 42 42 42 42 41 40

26 26 26 26 26 26 26 26

39 37 36 39 38 37 36 =35

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

GN kg/s

GL kg/s 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266

0.066

0.115

0.165

0.215

dng nng Tv (0C) Tr(0C) 65 47 64 45 61 42 59 39 57 38 55 46 55 44 53 42 52 41 51 39 50 44 49 42 49 41 48 39 46 38 45 41 45 40 45 39 43 37 42 36

dng lnh Tv(0C) Tr(0C) 26 42 26 37 26 34 26 32 26 31 26 38 26 36 26 34 26 32 26 31 26 35 26 34 26 32 26 32 26 30 26 33 26 32 26 31 26 30 26 29

21 22 23 24 25

0.265

0.066 0.116 0.166 0.216 0.266

42 42 42 41 40

39 38 37 36 35

26 26 26 26 26

32 31 30 29 29

1.5. Kt qu tnh ton Trng hp xui chiu Hiu sut nhit TN (0C) 19 19 20 19 19 10 11 12 13 12 7 7 7 8 8 5 7 6 6 6 Tl (0C) 12 10 9 6 5 10 9 8 6 5 9 7 6 4 3 7 6 5 4 3 n ( C)0

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

l ( C)0

hi (0C) 43.06 41.43 43.94 41.67 42.86 38.46 40.00 41.67 41.30 40.48 40.00 36.84 38.24 37.50 36.67 40.00 43.33 39.29 38.46 37.50

52.78 54.29 60.61 63.33 67.86 38.46 44.00 50.00 56.52 57.14 35.00 36.84 41.18 50.00 53.33 33.33 46.67 42.86 46.15 50.00

33.33 28.57 27.27 20.00 17.86 38.46 36.00 33.33 26.09 23.81 45.00 36.84 35.29 25.00 20.00 46.67 40.00 35.71 30.77 25.00

21 22 23 24 25

3 4 5 5 5

6 5 4 3 2

25.00 33.33 41.67 45.45 45.45

50.00 41.67 33.33 27.27 18.18

37.50 37.50 37.50 36.36 31.82

Hiu sut truyn nhit GN kg/s GL kg/s 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 0.216 0.266 0.066 0.116 0.166 QN (W) 5238.28 5238.28 5513.98 5238.28 5238.28 4836.88 5320.57 5804.26 6287.95 5804.26 4846.02 4846.02 4846.02 5538.30 5538.30 4506.81 6309.53 5408.17 5408.17 5408.17 3330.50 4440.67 5550.84 QL (W) 3327.53 4854.14 6241.98 5412.09 5551.64 2773.79 4369.38 5549.25 5412.09 5551.64 2496.79 3399.41 4163.14 3609.07 3331.91 1942.52 2914.20 3469.78 3609.07 3331.91 1665.26 2428.84 2776.21 Qf (W) 1910.76 384.14 -728.00 -173.80 -313.36 2063.09 951.19 255.01 875.86 252.62 2349.22 1446.60 682.87 1929.23 2206.40 2564.29 3395.33 1938.39 1799.10 2076.26 1665.25 2011.83 2774.63 (%) 63.52 92.67 113.20 103.32 105.98 57.35 82.12 95.61 86.07 95.65 51.52 70.15 85.91 65.17 60.16 43.10 46.19 64.16 66.73 61.61 50.00 54.70 50.01

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

0.066

0.115

0.165

0.215

0.265

24 25

0.216 5550.84 2707.17 2843.67 0.266 5550.84 2221.57 3329.27

48.77 40.02

H s truyn nhitTN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 QN (W) 5238.28 5238.28 5513.98 5238.28 5238.28 4836.88 5320.57 5804.26 6287.95 5804.26 4846.02 4846.02 4846.02 5538.30 5538.30 4506.81 6309.53 5408.17 5408.17 5408.17 3330.50 4440.67 5550.84 5550.84 5550.84 tmax (0C) 36 35 33 30 28 26 25 24 23 21 20 19 17 16 15 15 15 14 13 12 12 12 12 11 11 tmin (0C) 5 6 4 5 4 6 5 4 4 4 4 5 4 4 4 3 2 3 3 3 3 3 3 3 4 tlog (0C) 15.704 16.444 13.743 13.953 12.334 13.639 12.427 11.162 10.862 10.252 9.941 10.487 8.985 8.656 8.322 7.456 6.452 7.141 6.820 6.492 6.492 6.492 6.492 6.157 6.920 KTN N L KLT 2 2 2 (W/m K) (W/m K) (W/m K) (W/m2K) 469.823 448.673 565.113 528.774 598.194 499.472 603.037 732.383 815.336 797.414 686.563 650.849 759.674 901.141 937.296 851.341 1377.367 1066.708 1116.930 1173.289 722.544 963.393 1204.241 1269.738 1129.826 7,386 7,350 7,253 7,160 7,085 11,243 11,146 11,058 10,969 10,879 14,598 14,513 14,351 14,231 20,611 17,613 17,506 17,458 17,356 17,255 20,559 20,494 20,434 20,313 20,316 232.20 277.44 309.65 332.39 352.76 223.90 267.73 299.34 323.67 342.75 217.67 259.42 287.99 310.79 329.95 210.64 252.83 281.85 304.40 322.67 205.56 246.72 276.93 298.69 319.14 216.76 255.63 282.59 301.24 317.72 211.57 250.23 277.58 298.32 314.38 206.87 244.20 269.29 289.07 307.62 200.98 239.02 264.78 284.56 300.43 196.66 234.00 261.00 280.22 298.14

Trng hp ngc chiu Hiu sut nhit TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Hiu sut truyn nhit TN (0C) 18 19 19 20 19 9 11 11 11 12 6 7 8 9 8 4 5 6 6 6 3 4 5 5 5 Tl (0C) 16 11 8 6 5 12 10 8 6 5 9 8 6 6 4 7 6 5 4 3 6 5 4 3 3 n ( C) 46.15 50.00 54.29 60.61 61.29 31.03 37.93 40.74 42.31 48.00 25.00 30.43 34.78 40.91 40.00 21.05 26.32 31.58 35.29 37.50 18.75 25.00 31.25 33.33 35.710

l ( C) 41.03 28.95 22.86 18.18 16.13 41.38 34.48 29.63 23.08 20.00 37.50 34.78 26.09 27.27 20.00 36.84 31.58 26.32 23.53 18.75 37.50 31.25 25.00 20.00 21.430

hi (0C) 43.59 39.47 38.57 39.39 38.71 36.21 36.21 35.19 32.69 34.00 31.25 32.61 30.43 34.09 30.00 28.95 28.95 28.95 29.41 28.13 28.13 28.13 28.13 26.67 28.57

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

GN kg/s

GL kg/s

QN (W)

QL (W)

Qf (W) 520.23

(%) 89.50

0.066 4954.08 4433.85 0.116 5229.31 5338.74 0.066 0.166 5229.31 5549.25 0.216 5504.54 5412.09 0.266 5229.31 5551.64 0.116 5312.20 4854.14 0.115 0.166 5312.20 5549.25 0.216 5312.20 5412.09 0.266 5795.13 5551.64 0.116 4836.88 3884.47 0.165 0.216 6218.85 5412.09

-109.43 102.09 -319.94 106.12 92.45 98.32 76.56 91.38 -322.33 106.16 458.06

0.066 4346.35 3327.53 1018.82

-237.05 104.46 -99.89 101.88 243.48 952.41 806.76 95.80 60.22 80.31 75.31 87.03 80.36 53.97 64.77 64.27 66.85 61.72 50.07 54.78 50.09 48.84 60.11

0.066 4145.90 2496.79 1649.11 0.166 5527.87 4163.14 1364.72 0.266 5527.87 4441.93 1085.93 0.066 3599.17 1942.52 1656.65 0.116 4498.96 2914.20 1584.76 0.215 0.166 5398.76 3469.78 1928.98 0.216 5398.76 3609.07 1789.69 0.266 5398.76 3331.91 2066.85 0.066 3325.60 1665.26 1660.34 0.116 4434.13 2428.84 2005.29 0.265 0.166 5542.66 2776.21 2766.45 0.216 5542.66 2707.17 2835.49 0.266 5542.66 3331.91 2210.76

H s truyn nhit

TN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

QN (W) 4954.08 5229.31 5229.31 5504.54 5229.31 4346.35 5312.20 5312.20 5312.20 5795.13 4145.90 4836.88 5527.87 6218.85 5527.87 3599.17 4498.96 5398.76 5398.76 5398.76 3325.60 4434.13 5542.66 5542.66 5542.66

tmax (0C) 23 27 27 27 26 17 19 19 20 20 15 15 17 16 16 12 13 14 13 13 10 11 12 12 11

tmin (0C)

tlog (0C)

KTN N L KLT 2 2 2 (W/m K) (W/m K) (W/m K) (W/m2K) 7513 7459 7345 7253 7199 11449 11382 11263 11206 11117 14954 14827 14791 14670 21193 18055 18002 17953 17751 17656 21030 20965 20906 20787 20670 235.79 280.28 310.85 335.57 356.37 227.24 272.27 302.89 327.67 348.78 221.68 264.97 296.83 322.24 340.34 215.68 258.88 290.59 312.68 332.08 211.56 253.92 285.01 308.10 327.68 219.992 258.172 283.722 304.017 320.878 214.616 254.319 280.757 301.882 319.641 210.555 249.198 277.163 299.142 316.770 205.617 244.508 272.595 291.889 308.703 202.189 240.535 268.247 288.577 305.663

21 21.985 317.3815 19 22.766 323.5155 16 21.023 350.3491 13 19.155 404.7482 12 18.107 406.7655 20 18.459 331.6261 18 18.495 404.5295 16 17.457 428.593 15 17.380 430.4859 13 16.249 502.3023 18 16.454 354.8765 16 15.495 439.6695 15 15.979 487.2431 13 14.448 606.2339 12 13.904 559.9536 15 13.444 377.0572 14 13.494 469.5903 13 13.494 563.5084 11 11.972 635.1299 10 11.434 664.9957 13 11.434 409.6328 12 11.493 543.4081 11 11.493 679.2601 10 10.970 711.6526 9 9.967 783.2745