Th nghim cc QT&TBGVHD: V Vn Sim

BI 1: TH NGHIM TRUYN NHIT NG KP

1.1 Mc ch th nghim:- Lm quen vi thit b truyn nhit ng lng ng, cc dng c o nhit v lu lng lu cht.- Xc nh h s truyn nhit trong qu trnh truyn nhit gia hai dng lnh v nng qua vch kim loi cc ch d chy khc nhau.- Thit lp cn bng nhit lng.1.2 C s l thuyt:1.2.1 Cc khi nim: Truyn nhitTruyn nhit l mt qu trnh phc tp xy ra ng thi 3 dng trao i nhit: trao i nhit bng dn nhit, trao i nhit bng i lu nhit v trao i nhit bng bc x nhit. Chiu qu trnh Trong t nhin qu trnh truyn nhit ch xy ra theo mt chiu t ni c nhit cao ti ni c nhit thp. Cht ti nhit Cht ti nhit l cht mang nhit t ni ny ti mi trng khc theo quy lut t nhin. Truyn nhit trc tipTruyn nhit trc tip l qu trnh truyn nhit m cht ti nhit tip xc trc tip vi vt liu. Truyn nhit gin tipTruyn nhit gin tip l qu trnh truyn nhit m cht ti nhit khng tip xc trc tip vi vt liu m thng qua vt ngn. Truyn nhit n nhTruyn nhit n nh l qu trnh truyn nhit m nhit ch thay i theo khng gian m khng thay i theo thi gian. Truyn nhit khng n nh Truyn nhit khng n nh l qu trnh truyn nhit m nhit thay i c theo khng gian v thi gian. Trng nhitTrng nhit c trng cho nng ca vt l nhit (toC, toK). Tp hp tt c nhng gi tr nhit ca vt hoc mi tng gi l trng nhit. Nhit trng n nhNhit trng n nh l nhit trng m nhit ch thay i theo khng gian m ch thay i theo thi gian.T = f(x,y,z) Nhit trng khng n nhNhit trng khng n nh l nhit trng m nhit thay i theo c khng gian v thi gian.T = f(x,y,z,t) Mt ng nhitMt ng nhit l tp hp cc im c nhit bng nhau. Qu trnh dn nhit khng xy ra trn mt mt ng nhit, m ch dn nhit t mt ng nhit ny n mt ng nhit kia.1.2.2 Cc qu trnh truyn nhit:Trong thc t qu trnh truyn nhit din ra theo 3 phng thc truyn nhit c bn sau. Dn nhitDn nhit l s truyn nhit nng t ni c nhit cao n ni c nhit thp. do s truyn ng nng hoc dao ng va chm vo nhau, nhng khng c s chuyn ri v tr gia cc phn t vt cht. dn nhit ch xy ra khi truyn nhit ca cc cht rn hoc truyn nhit ca cht lng, cht kh ng yn hay chuyn ng dng. nh lut FourienXt trn mt mt phng c din tch F c dng nhit dn qua theo phng vung gc vi mt phng, nh lut Fourien pht biu nh sau:Mt dng nhit truyn qua bng phng thc dn nhit theo phng quy nh t l thun vi din tch vung gc vi Phng truyn nhit v gradian nhit theo phng y.

(W)

(W/m2) Qx: dng nhit truyn qua din tch F (j/s) qx: mt dng nhit (W/m2) F: din tch b mt truyn nhit vung gc vi phng x (m2) : h s dn nhit W/m.Thc nghim chng t l mt thng s vt l biu din kh nng dn nhit ca vt liu. H s dn nhit ph thuc vo p sut, nhit , vt liu, cu trc vt liu. H s dn nhit ca cht kh trong khong 0,0060,6 (W/m.) H s dn nhit ca cht kh trong khong 0,0070,7 (W/m.) H s dn nhit ca cht rn ph thuc vo kt cu, xp v m ca vt liu.T nh lut Fourien c bn ngi ta a ra cc dng phng trnh truyn nhit cho cc trng hp c th. y ta ch nu trng hp dn nhit n nh qua ng Dn nhit n nh qua ngNghin cu qu trnh dn nhit qua vch tr (ng) nhit b mt vch trong t1, nhit vch ngoi t2 khng thay i. vt liu c h s dn nhit khng i.Ta c phng trnh dn nhit nh sau:

(W) L: chiu di ca ng (m) d1, d2: ng knh trong v ngoi ca ng (m)

Cn (m)V din tch b mt trung bnh:

(m2)T s d2/d12 th F tnh bng cng thc sau:

(m2) thun tin cho vic tnh ton ta tnh

(w/m)Nhiu lp Vi tng hnh ng nhiu lp vt liu khc nhau

n: s lp t1: nhit vch trong (oC) tn+1: nhit vch ngoi th n+1 (oC) i lu nhit Nhit i lu l s truyn nhit m cc phn t lng hoc kh nhn nhit ri i ch cho nhau; s i ch do chnh lch khi lng ring hay do cc tc ng c hc nh: bm, khuy.Qu trnh ta nhit i lu xy ra khi c s trao i nhit gia cht lng, cht kh v b mt rn. nh lut Newton tnh nhit i lu ngi ta dng cng thc NewtonQ=.F.(tr-tv) (w)Trong : : h s ta nhit (W/m.) ph thuc vo rt nhiu thng s =f(tv,tf,, , cp, , ,l) tf: nhit lu cht tv: nhit vch : tc truyn nhit ca cht lng l: kch thc b mt troa i nhit q=(tr-tv) (W/m2) tnh ton c phng trnh trn ta cn phi xc nh c 1.2.3 Cc chun s:V qu trnh ta nhit i lu ph thuc vo nhiu chun s do mun xc nh ta cn tnh cc chun s sau:

Chun s Nusselt: Chun s Prandtl:

Chun s Reynolds: Chun s Grashof: : vn tc chuyn ng ca lu cht (m/s) a: h s dn nhit (m2/s) cp: nhit dung ring ng p (j/kg.oC) g: gia tc trng trng (m/s2) l: kch thc hnh hc (c th l ng knh nu l ng) (m) t: k hiu nhit vch v nhit lu cht (oC) : h s gin n th tch (1/oK; 1/oC) vi cht kh =1/T1.2.4 Cc phng trnh thc nghim cho cc loi lu cht chuyn ng: tnh ngi ta dng chun s Nu v trong tng trng hp c th th Nu c biu thc ring Ngoi ra ngi ta tnh trc mt s trng hp c th, ta c th tra bng cho tng trng hp y1.2.5 Cc kiu truyn nhit trong thit b v ng: Kiu xui chiu: 2 dng lu cht lnh v nng chuyn ng cng chiu. Khi b tr kiu ny th hiu qu truyn nhit u vo l rt cao v u ra l thp. Kiu ngc chiu: 2 dng lu cht lnh v nng chuyn ng ngc chiu, kiu b tr ny thng c dng, s trao i nhit c phn b u trn khp chiu di ca thit b .1.2.6 T chc dng chy trong thit b v ng: T chc dng chy phi m bo iu kin: hiu qu qu trnh trao i nhit l cao nht. trong gm: dng nng v dng lnh. Dng nng v dng lnh c th b tr bn trong hay bn ngoi v ng dng lu cht cng chiu hay ngc chiu.1.2.7 Nhit ra ca cc dng chy:Trng hp xui chiu: 2 u thit b nhit nng ra ln hn lnh ra 1.3 Tnh ton th nghim:Phng trnh cn bng nhit lng cho 2 dng lu cht nng v lnh c dngQ= GN.CN(tNV-tNR)=GL.CL(tLR-tLV)Trong GN, GL: lu lng khi lng ca dng nng v dng lnh (kg/s) CN, CL: nhit dung ring ng p ca nc nng v nc lnh (J/kg.) tNV, tNR: nhit vo, ra ca dng nng (oC) tLV, tLR: nhit vo, ra ca dng lnh (oC)Qu trnh truyn nhit c biu din bng phng trnh sau:Q= KL.tlog.LTrong : Q: nhit lng trao i (W hoc j/s) KL: h s truyn nhit di (W/m.) t log: hiu nhit logarit c hai dng lu cht (oC) L: chiu di ng, bi th nghim ny ta ly L=1050mmHiu nhit ca 2 lu cht

H s truyn nhit di KL:

Trong : dtr, dng: ng knh trong v ng knh ngoi ca ng truyn nhit (m). inox: h s dn nhit ca kim loi ch to ng (w/m.) 1, 2: h s cp nhit ca dng nc nng, dng nc lnh (w/m2.) rb: h s nhit ca cn bn (m2./w) db: ng knh lp bn (m) KL: h s truyn nhit di (w/m.)H s cp nhit 1, 2 gia vch ngn v cc dng lu cht c tnh t chun s Nusselt (Nu)Phng trnh tng qut ca chun s Nusselt l:

Trong :Cc h s: A, n, m, L, P l cc h s thc nghim ph thuc cc yu t sau:Ch chy ca cc dng lu cht . S tng quan gia cc dng chy v b mt truyn nhit.c im ca b mt truyn nhit ( nhm, hnh dng ,)Ta c cc phng trnh Nusselt cho dng chy ngang ng nh sau:

Khi 5 Re 103 :

Khi 103 Re 2.105:

Khi 2.105 Re 2.106: Ta c phng trnh tnh Nusselt cho ch chy dc theo thn ng:Ch chy mng Re 2320

Ch chy chuyn tip 2320 Re 10000:

Ch chy ri Re 10000:

Trong gi tr C ph thuc Re theo bng sau:Re21002200230024002500

C1,92,23,33,84,4

Re3000400050006000800010000

C6,010,315,519,527,033,0

Gi tr L ph thuc vo t l L/d khi Re 10000L/d1,02,05,010,015,029,030,040,050,0

L1,91,71,441,281,181,131,051,021,00

Khi Re 10000 th h s P ph thuc vo Re v L/d nh sau:L/dRe10,020,030,040,050

1.1041,231,131,071,031,00

2.1041,181,101,051,021,00

5.1041,131,081,041,021,00

1.1051,101,061,031,021,00

1.1061,051,031,021,011,00

Chun s Grashof (Gr)Chun s Grashof c trng cho quan h gia lc ma st phn t v lc ko do t trng khc nhau, nhng im c nhit khng ging nhau trong cng mt dng lu cht (nc).

Trong Gr: chun s Grashof : nht ng hc ca lu cht (m2/s) dtd: ng knh tng ng ca tit din dng chy (m) : khi lng ring ca lu cht (nc), (kg/m3) : nht ng lc hc ca nc (N.S/m2). t: hiu nhit gia lu cht v thnh ng, trong bi th nghim ny ta ly t=6oC : h s gin n th tch (ph thuc vo nhit ), (1/oC)T(oC)020406080100120

(1/oC)-0,6.10-42,1.10-43,9.10-45,3.10-46,3.10-47,5.10-48,6.10-4

1.4. Thit b th nghim: H thng thit b th nghim c cc thit b thnh phn sau: Ni un nc nng c gia cng bng thp khng g c dng lng tr ng vi ng knh D=395mm, chiu cao ni l H=500mm Thnh ni c lp bo n dy 30mm, trong ni c hai in tr gia nhit un si nc. Mt bm nc nng c cng sut 0,5 HP dng bm nc nng t ni un h thng trao i nhit.Hp iu khin h thng thit b. ng kp chy ngang l loi ng lng ng m lu cht lnh chy ngang mt ngoi ca ng trong . ng kp chy dc l loi ng lng ng n gin, lu cht nng chy dc mt trong ca ng trong v lu cht lnh chy dc trong khong khng gian gia hai ng. Mt lu lng k dng phao dng o lu lng ca nc nng v nc lnh.Loi ng Kch thcng trong (mm)Kch thcng ngoi (mm)Chiu di (mm)

Chy dc18/2230/341050

Chy ngang18/2230/341050

1.5 S nguyn l thit b:

S NGUYN LA. in tr un nc a. Cng tc tngB.Ni un nc nng b. Cng tc bmC.Bm nc nng c. Cng tc in tr un nng.D. Lu lng k d. ng h hin th nhit .E. TBTN kiu chy ngang F. TBTN kiu chy dcV. Cc van

1.6 Kt qu th nghim:Bng s liu t phng th nghimLu lng dng nng G'N (L/P)Lu lng dng lnh G'L (L/P)Nhit dng nngNhit dng lnh

tNVtNRtLVtLR

3 L/PG'L1=375713039

G'L2=678723040

G'L3=980773041

6 L/PG'L1=378743039

G'L2=679763040

G'L3=982823041

9 L/PG'L1=379773039

G'L2=680783040

G'L3=983803041

Cc bng s liu tnh tonBng 1: Nhit lng ta ra ca dng nng QNGN(L/P)GN(kg/s)tNV(0C)tNR(0C)tNTB(0C)

(kg/m3)C1(J/kg.)QN(W)

30,0488757173975.854190817.888

0,0487787275974.7541901224.318

0,0486807778.5972.834190610.902

60,0974787476974.2041901632.424

0,0973797677.5973.3841901224.318

0,0970828282970.6041940.000

90,1460797778973.1041901223.480

0,1459807879972.5541901222.642

0,1451838081.5967.4542031829.566

QN = GN .CN (TNV TNR )

Bng 2: Nhit lng thu vo ca dng lnh QLGL(L/P)GL(kg/s)tLV(0C)tLR(0C)tLTB(0C)

(kg/m3)C2(J/kg.)QL(W)

30,04968303934.5993.654176.381867.343

0,04968304035993.504176.252074.761

0,04967304135.5993.354176.132281.712

60,09937303934.5993.654176.383735.062

0,09935304035993.504176.254149.104

0,09934304135.5993.354176.134563.424

90,14905303934.5993.654176.385602.405

0,14903304035993.504176.256223.865

0,14900304135.5993.354176.136844.677

Bng 3: Tnh Q, tlog, KL*

(W)

(W)

(W)

()

()

()

()

(m)

()

(W/m.)

817.8881867.3431049.455757130391.0538.1346.64

1224.3182074.761850.443787230401.0539.4650.08

610.9022281.7121670.81807730411.0542.6250.99

1632.4243735.0622102.638787430391.0541.1686.42

1224.3184149.1042924.786797630401.0542.1793.70

0.0004563.4244653.424828230411.0546.2893.91

1223.4805602.4054378.925797730391.0543.27123.31

1222.6426223.8655001.223807830401.0543.73135.55

1829.5666844.6775015.111838030411.0545.64142.83

Q =

(vi chiu di ng L= 1050 mm=1,05m)

Bng 4: Chun s Re ca dng nng ReN (Re1)

(L/P)FN(m2)dtN(m)

(m/s)tNV(oCtNR(oC)tNTB(oC)

(Kg/m3).10-3(N.s/m2)ReN

3

2.545.10-4

0.0180,1965757173975.850.39588720.52

787275974.750.38468964.35

807778.5972.830.36499429.71

60,3929787476974.200.379018178.73

797677.5973.380.370518580.13

828282970.600.349219657.15

90,5894797778973.100.367728076.73

807879972.550.362128494.83

838081.5967.450.351029241.80

Tnh din tch tit din dng nng FN

vi 3 Lt/pht = 3.10-3 m3 / p = = 0,1965 (m/s) = = 0,3929 (m/s) = = 0,5895 (m/s)

Bng 5: Chun s Re ca dng lnh ReL (Re2)

(L/P)FL(m2)dtN(m)

(m/s)tLV(oC)tLR(oC)tLTB(oC)

(Kg/m3).10-3(N.s/m2)ReL

3

3.266.10-4

0.0080,15303934.5993.650.752015856.12

304035993.500.743316039.28

304135.5993.350.734516229.00

60,31303934.5993.650.752032769.31

304035993.500.743333147.85

304135.5993.350.734533539.93

90,46303934.5993.650.752048625.43

304035993.500.743349187.14

304135.5993.350.734549768.93

Tc chy ca dng lnh 2 (m/s)

Vi mi gi tr {3, 6, 9} th tng ng cho cc gi tr LGL = 3 lt/pht = 3.10-3 (m3 / p) = = 0,15 (m/s) = = 0,31 (m/s) = = 0,46 (m/s)Tnh chun s Reynol ca dng lnh

Ch nu tnh dt cho mt ct t th dtdL = Dt dng tnh theo chu vi tdt = 4F/ U vi U = (Dt + dng ); F = trong : U l chu vi t; Dt l ng knh trong ca ng ngoi, dng l ng knh ngoi ca ng trong.Dt = 30 mm = 0,03 m; dng = 22 mm = 0,022 mdtdL = Dt dng = 0,03 0,022 = 0,008 (m)F = = = 3,266.10-4 (m2)U = (Dt + dng) = (0,03 + 0.022) = 0,163 (m)dt = 4F/ U = 4.3,266.10-4 / 0,163 = 0,008 (m)suy ra: dt = dtdL

Bng 6: Chun s Pranlt ca dng nng Pr1

tNV(oC)tNR(oC)tNTB(oC)C1(J/kg.).10-3(N.s/m2)

(w/m.)Pr1

75717341900.39580.666752.487

78727541900.38460.668252.011

807778.541900.36490.670882.279

78747641900.37900.669002.374

797677.541900.37050.670132.317

82828241940.34920.672802.177

79777841900.36770.670502.298

80787941900.36210.671252.260

838081.542030.35100.672602.193

Da vo bng tra thng s ha l ca lu cht, p dng cng thc ni suy tnh Tnh chun s Prank dng nng

Bng 7: Chun s Pranlt ca dng lnh Pr2tLV(oC)tLR(oC)tLTB(oC)C2(J/kg.).10-3(N.s/m2)

(w/m.)Pr2

303934.54176.380.75200.629634.988

3040354176.250.74330.630754.921

304135.54176.130.73450.631884.854

303934.54176.380.75200.629634.988

3040354176.250.74330.630754.921

304135.54176.130.73450.631884.854

303934.54176.380.75200.629634.988

3040354176.250.74330.630754.921

304135.54176.130.73450.631884.854

Da vo bng tra thng s ha l ca lu cht, p dng cng thc ni suy tnh Tnh chun s Prank dng lnh

Bng 8: H s cp nhit ca dng nng

Re1Pr1

Nu1dt1(m)

(w/m.)

(W/m2.)

8720.522.4870. 9881.3630.0180.666753013. 821

8964.352.0110. 9876.3050.0180.668252832. 823

9429.712.2790. 9882.4880.0180.670883074.419

18178.732.3740. 98124.2130.0180.669004616.583

18580.132.3171.00125.3260.0180.670134665.817

19657.152.1771.00126.6010.0180.672804732.064

28076.732.2981.0113.2670.0180.670503841.639

28494.832.2601.0113. 9100.0180.671254247.893

29241.802.1931.0115.0050.0180.672604297.353

Tnh h s cp nhit cho dng nng 1

p dng cng thc :

Bng 9: H s cp nhit ca dng lnh Re2Pr2

Nu2dt2(m)

(w/m.)

(W/m2.)

15856.124.9880. 99152.1170.0080.6296311972.178

16039.284.9210. 99152.3840.0080.6307512014.526

16229.004.8540. 99152.6660.0080.6318812058.324

32769.314.9880. 99170.3110.0080.6296313404.114

33147.854.9210. 99171.0250.0080.6307513484.252

33539.934.8540. 99171.7680.0080.6318813567.095

48625.434.9880. 99233.5390.0080.6296318380.395

49187.144.9210. 99234.5190.0080.6307518490.375

49768.934.8540. 99235.5380.0080.6318818603.968

Tnh h s cp nhit ca dng lnh 2

Bng 10: H s truyn nhit di l thuyt KL

(W/m2.)

(W/m2.)D1(m)D2(m)

(w/m.)

KL(w/m.)

3013. 82111972.1780,0180,02246,50128.817

2832. 82312014.5260,0180,02246,50122.947

3074.41912058.3240,0180,02246,50130.913

4616.58313404.1140,0180,02246,50178.675

4665.81713484.2520,0180,02246,50180.183

4732.06413567.0950,0180,02246,50182.139

3841.63918380.3950,0180,02246,50164.549

4247.89318490.3750,0180,02246,50177.548

4297.35318603.9680,0180,02246,50179.224

Bng 11: Quan h gia h s truyn nhit v ch chy ca dng nng

15856.1246.64128.817

16039.2850.08122.947

16229.0050.99130.913

32769.3186.42178.675

33147.8593.70180.183

33539.9393.91182.139

48625.43123.31164.549

49187.14135.55177.548

49768.93142.83179.224

th

KL: h s truyn nhit di thc tKLK*LKL

K*L: h s truyn nhit di l thuyt

Nhn xt: H s truyn nhit thc t v l thuyt ca ng chy ngang v chy dc u rt khc xa nhau. Trong bi th nghim ny sai s ln ti hang trm n v.Qu trnh tnh ton cng gp mt phn vo s sai s rt nhiu.Trong cng nghip th ngi ta thng p dng chy dc v h s dn nhit ca n cao hn, tit kim c din tch v chi ph hn so vi ng chy ngangCu hi chun b0. Mc ch bi th nghim?Tr li: Mc ch th nghim- Lm quen vi thit b truyn nhit ng lng ng, cc dng c o nhit v lu lng lu cht.- Xc nh h s truyn nhit trong qu trnh truyn nhit gia hai dng lnh v nng qua vch kim loi cc ch d chy khc nhau.- Thit lp cn bng nhit lng.0. Cc thng s cn o?Tr li: GL, GN: lu lng th tch ca dng lnh v dng nng (lt/pht) tNV, tNR: nhit vo, ra ca dng nng (oC) tLV, tLR: nhit vo, ra ca dng lnh (oC)0. Trnh t th nghim?Tr li: Chun b th nghim Kho st qu trnh truyn nhit trong ng chy vung gc Kho st qu trnh truyn nhit trong ng chy dc Ngng- tt my4.Thit b truyn nhit ng lng ng c phi l thit b truyn nhit kiu v ng khng?Tr li: Thit b truyn nhit ng lng ng l thit b truyn nhit kiu v ng.5.Ch r ng i ca dng nng trong h thng thit b th nghim. 6. Ch r ng i ca dng lnh trong h thng thit b th nghim. 1. u nhc im ca thit b truyn nhit ng lng ng?Tr li: u im: s trao i nhit c phn b u trn khp chiu di ca thit b Nhc im: Hiu sut truyn nhit thp. Din tch tip xc gia lu cht v ng nh1. Hy cho bit cc phng thc truyn nhit c bn? Trong bi th nghim ny c nhng phng thc truyn nhit no?Tr li: Cc phng thc truyn nhit c bn l: Truyn nhit trc tip Truyn nhit gin tip Truyn nhit n nh Truyn nhit khng n nh Trong bi th nghim ny co phng thc truyn nhit gin tip v n nh1. V v gii thch s c ch truyn nhit gia 2 lu cht qua vch ngn thit b truyn nhit ng lng ng.Tr li:

Dng nngDng lnhDng lnh

Nhit truyn t dng lu cht lnh qua vch bng dng bc x hoc i lu nhit trong vch ng v lm lnh dng nng bn trong.1. Vit phng trnh cn bng nhit lng. Gii thch cc thng s v cho bit n v o ca chng?Tr li: Phng trnh cn bng nhit lng cho 2 dng lu cht nng v lnh c dngQ= GN.CN(tNV-tNR)=GL.CL(tLR-tLV)Trong GN, GL: lu lng khi lng ca dng nng v dng lnh (kg/s) CN, CL: nhit dung ring ng p ca nc nng v nc lnh (J/kg.) tNV, tNR: nhit vo, ra ca dng nng (oC) tLV, tLR: nhit vo, ra ca dng lnh (oC)1. ngha vt l ca h s truyn nhit di KL? Cng thc tnh? Gii thch cc thng s v cho bit n v o ca chng?Tr li: ngha vt l ca h s truyn nhit di l: cho ta bit c kh nng truyn nhit ca lu cht.

H s truyn nhit di thc nghim: Trong : Q: nhit lng trao i (W hoc j/s) KL: h s truyn nhit di (W/m.) t log: hiu nhit logarit ca hai dng lu cht (oC) L: chiu di ngH s truyn nhit di KL:

Trong : dtr, dng: ng knh trong v ng knh ngoi ca ng truyn nhit (m). inox: h s dn nhit ca kim loi ch to ng (w/m.) 1, 2: h s cp nhit ca dng nc nng, dng nc lnh (w/m2.) rb: h s nhit ca cn bn (m2./w) db: ng knh lp bn (m) KL: h s truyn nhit di (w/m.)H s cp nhit 1, 2 gia vch ngn v cc dng lu cht c tnh t chun s Nusselt (Nu)1. Vit phng trnh truyn nhit? Gii thch cc thng s v cho bit n v o ca chng?Tr li: Phng trnh truyn nhit dQ=k(t1 t2)dF=ktdFk: h s truyn nhit (W/m2.oC)t1 t2: chnh nhit gia cht lng nng v lnh trn b mt phn b dF.

Q=

Vi =tTB=tlog1. nh hng ca ch chy n qu trnh truyn nhit? Gii thch.Tr li: Ch chy ri lm tng kh nng truyn nhit v ch chy ri xy ra khi vn tc chy ln lm tng kh nng va chm ca lu cht ln thnh ng nn kh nng truyn nhit ln.Ch chy mng tuy dng chy tc thp nhng cng c kh nng truyn nhit nhng dng nhit ny c cung cp u ln tng theo dng chy.Chy chuyn tip l ch chy giao toa gia hai ch chy trn v th kh nng truyn nhit cng nm trong khong gia ca hai ch 14. Phn bit qu trnh truyn nhit n nh v khng n nh.Tr li: Truyn nhit n nhTruyn nhit n nh l qu trnh truyn nhit m nhit ch thay i theo khng gian m khng thay i theo thi gian. Truyn nhit khng n nh Truyn nhit khng n nh l qu trnh truyn nhit m nhit thay i c theo khng gian v thi gian1. Nu cc yu t nh hng n h s cp nhit ?Tr li: Cc yu t nh hng n h s cp nhit l: Ch chy ca dng lu cht. Mi cht. Nhit vch. Vt liu lm ng. Kch thc ng. 16. So snh hiu qu qu trnh truyn nhit xui chiu v ngc chiu?Tr li: Qu trnh truyn nhit ngc chiu c hiu qu hn ti v s trao i nhit c phn b u trn khp chiu di ca thit b v lm cho sn phm c cht lng truyn nhit ng u. Cn truyn nhit xui chiu th nhit truyn u vo l rt cao cn u ra l rt thp nn hiu qu km hn.

BI 2: C C2.1 Mc tiu th nghim: Trnh by c cu to, nguyn l lm vic v u nhc im thit b c c gin on 1 ni, hot ng trong iu kin chn khng. Vn hnh c h thng c c. Tnh ton c cn bng vt cht, cn bng nng lng v cc i lng c trng cho qu trnh c c.2.2 C s l thuyt: 2.2.1 Cc khi nim trong c c: Khi nim c c C c l qu trnh lm tng nng ca dung dch bng cch tch mt phn dung mi nhit si, dung mi tch ra khi dung dch bay ln gi l hi th. Mc ch ca qu trnh c c Lm tng nng ca cht ha tan trong dung dch. Tch cht rn ha tan dng rn (kt tinh). Tch dung mi dng nguyn cht (ct nc)2.2.2 Cc phng php c c: C c p sut kh quyn: l phng php n gin nhng khng tinh t. C c p sut chn khng: dng cho cc dung dch c nhit si cao, d phn hy v nhit, C c p sut d: dng cho cc dung dch hng phn hy nhit cao, s dng hi th cho cc qu trnh khc.

2.2.3 Cn bng vt liu trong h thng c c 1 ni: Xt h thng mt niTrong : G - khi lng nguyn liu, [kg]; kg/s Gc - khi lng sn phm. [kg]; kg/s W - lng hi th, [kg]; m/s x - nng cht kh trong nguyn liu, [phn khi lng] xc - nng cht kh trong sn phm, [phn khi lng]Theo nh lut bo ton vt cht: Bo ton khi lng: G=Gc+W Bo ton cht kh: G.x=Gc.xcGii ra ta c:

Lng hi th:

Nng sn phm cui2.2.4 Cn bng nhit lng:K hiu: t: nhit nguyn liu. []. tc: nhit sn phm, []. tn: nhit nc ngng, []. c: nhit dung ring nguyn liu, [J/kg.]. cc: nhit dung ring sn phm, [J/kg.]. cn: nhit dung ring nc ngng, [J/kg.]. i: hm nhit trong hi t, [J/kg]. i: hm nhit trong hi th, [J/kg]. Qc: tn tht nhit c c, [J]; Qc=0,01.q.Gc. q: tn tht nhit c c ring, [L/kg]. Qmt: tn tht nhit ra mi trng, [J].Theo nh lut bo ton nhit:Qv=QrG.c.t+D.i=Gc.cc.tc+W.i+D.cn.tn+Qc+QmtRt ra:Lng hi t tiu tn:

Trong qu trnh tnh ton nhit c th xem cccTnh b mt truyn nhit: Q=K.F..thi=D.(i-cn.tn)Trong : Q: lng nhit truyn, [J]. K: h s truyn nhit, [W/m2.]. F: Din tch b mt truyn nhit : thi gian c c, [s].thi: hiu s nhit hu ch, [] Rt ra b mt truyn nhit

, [m].2.3 Thit b th nghim:Dung dch c c c theo tng m, nhp liu mt ln t thng cha dung dch u. dung dch si trong bung bc hi do nhit truyn t nc nng bn v ngoi. Hi th bc ln t dung dch si c dn qua thit b ngng t ng xon ngng t thu hi v nh lng. Mt bm chn khng loi vng nc c s dng to chn khng cho h thng.H thng c c gm cc thit b chnh sau: Ni c c 2 v cnh khuy. My khuy trn. Thit b ngng t ng xon. Bnh cha nc ngng. Bm chn khng loi vng nc. p k o chn khng. Nhit k in t. H thng in. X nha cha dung dch u.2.3.1 Ni c c 2 v:Ni cha dung dch ng c ng knh D=250mm, cao H=500mm, b dy = 5mm.Ni c ch to bng thp khng g AISI304.2.3.2 Thit b ngng t ng xon:ng xon c ng knh 16 c qun thnh cc vng xon c ng knh D= 150mm. ng xon cj gia cng bng thp khng g AISI304.2.3.3 Bm chn khng:H thng s dng bm chn khng loi vng nc 1HP.2.4 S thit b:

2.5 Tnh ton th nghim:Bng s liu t phng th nghim:TBxV(ml)

011650

1011490

2011.5520

3013490

4013.2450

5014410

6015.2350

7016270

8017330

9018330

10020335

11021330

12022260

Nng phn khi lng ca ng nhp liu: 11Bx vy x=0,11 (phn khi lng) tra bng S tay Cng Ngh Ha Cht tp 1: 11Bx l = 1044.13 (kg/m3) Tnh lng nc ngng thc t Vngng = 650+490+520+490+450+410+350+270+330+330+335+330+260= 5215 (ml) = 5.215 (lt)W*=Vngng.ngng = 5,215.10-3.995,68 = 5.192 (kg) Vngng: tng th tch nc ngng thu c trong qu trnh th nghim (lt) ngng: khi lng ring ca nc ngng (kg/m3) (ngng = 995,68(kg/m3) tra S tay Cng Ngh Ha Cht tp 1, nhit phng l 300C) Tnh khi lng dung dch ng nhp liuTa c: V= 5 (lt) =1044.13 (kg/m3) mng = 1 (kg)

M: G= mng + mnc mnc pha= G mng = 5.221 1 = 4.221 (kg)= mnc ngng + mnc cn li mnc cn li = mnc pha - mnc ngng = (vi mnc ngng = W* = 5.192 (kg)) Tnh Gc , xc v W:Ta c: Gc = mng + mnc cn li = 1 + 0,971 = 1,971 (kg)p dng nh lut bo ton vt cht:+ Bo ton khi lng: G = Gc + W+ Bo ton cht kh: G.x = Gc.xcNh :+ Nng sn phm cui:

+ Lng hi th:

Tnh phn trm sai s ca dung dch sau c c:Ta c:

%nh gi sai s: %SS = 62,199 % % 5%: Phn trm sai s ca dung dch sau c c l ng k.Trong : Gii thch kt qu: V thi gian c hn nn c c nc ng cha ti mc gii hn c. Trong qu trnh c c ly mu th Bx hi nhiu nn lm mt sn phm. Trong qu trnh rt ra ca cn nn b hao ht mt t. Tnh phn trm sai s ca lng nc ngng thu c trong qu trnh c c:Gi nh Gc= Gc* W W*Ta c:

59.901 %Trong : W: lng hi th (lng nc bc hi). W*: lng nc ngng thc tnh gi sai s: Ta c %SSW= 59.901 % > 10 % Phn trm sai s ca lng nc ngng thu c trong qu trnh c c l ng k.Gii thch kt quV thi gian c hn nn qu trnh c c cha hon chnh.Lng mu th ly ra lc u hi nhiu. th th biu din quan h gia ch s Bx v thi gian c c TBx

Nhn xt: th biu din Bx v thi gian sy ta thy nng Bx c xu hng tng theo thi gian. th biu din quan h gia khi lng nc ngng thu c v thi gian T

Ta c: W* = Vngng ngngWi = () ngngW: khi lng nc ngng (kg)

Nh ta thu c bng s liu sau:V (pht)W (kg)

0647.192

10487.883

20517.754

30487.883

40448.056

50408.229

60348.488

70268.834

80328.574

90328.574

100333.553

110328.574

120258.877

Nhn xt: Qu trnh lm th nghim cn c nhiu sai st, cha nm k cc thao tc thc hnh v dn n sai s cho qu trnh tnh ton. Cch khc phc: iu chnh pH , nhit sao cho ph hp Kim tra trang thit b trc khi thc hnh, nu c trc trc th tin hnh sa cha Phn cng tng ngi lm cng vic hp l o thi gian ly mu, ly nc ngng cn chnh xc Ch quan st Bx cho ng Cu hi chun b1. Mc ch ca qu trnh c c l g?Tr li: Lm tng nng ca cht ha tan trong dung dch. Tch cht rn ha tan dng rn (kt tinh). Tch dung mi dng nguyn cht (ct nc)1. Cc bc chun b tin hnh th nghim?Tr li: Tm hiu h thng thit b, cc van v tc dng ca n. Tm hiu thit b o nhit , cc v tr o v cch iu chnh cng tc o nhit . Tm hiu cc thit b o nng cht kh (Brix k). Xc nh cc i lng cn o. Chun b dung dch ng em i c c. Chun b bng s liu th nghim.1. Cc phng php o nng ca dung dch ng?Tr li: C 2 phng php: Phng php 1: s dng Brix k theo nguyn tc khc x quang hc (nng gc cng ln gc khc x cng ln).

Phng php 2: dng ph k (t trng k) theo nguyn tc nng cng cao th lc y cng mnh.1. M t cu to h thng thit b c c dng trong th nghim?Tr li:H thng c c gm cc thit b chnh sau: Ni c c 2 v cnh khuy. My khuy trn. Thit b ngng t ng xon. Bnh cha nc ngng. Bm chn khng loi vng nc. p k o chn khng. Nhit k in t. H thng in. X nha cha dung dch u.1. Nu cc dng thit b c c khc nhau?Tr li: Dng thit b c c mt ni Dng thit b c c nhiu ni Dng thit b c c lin tc Dng thit b c c gin on. Dng thit b c c p sut chn khng, p sut thng hay p sut khc.1. Cc thng s cn o trong bi?Tr li: Thi gian T Nng dung dch ng (Bx) Lng nc ngng thu c Vngng (ml)1. Vit cn bng nhit lng cho qu trnh c c?

Tr li: phng trnh cn bng nhit lng trong qu trnh c c: G.c.t + D.i = Gc.cc.tc + W.i + D.cn.tn + Qcd + QmtTrong t: nhit nguyn liu. []. tc: nhit sn phm, []. tn: nhit nc ngng, []. c: nhit dung ring nguyn liu, [J/kg.]. cc: nhit dung ring sn phm, [J/kg.]. cn: nhit dung ring nc ngng, [J/kg.]. i: hm nhit trong hi t, [J/kg]. i: hm nhit trong hi th, [J/kg]. Qc: tn tht nhit c c, [J]; Qc=0,01.q.Gc. Qmt: tn tht nhit ra mi trng, [J]. D: lng hi tiu tn

BI 3: MCH LU CHTI. C s l thuyt Tnh hc lu chtPhng trnh thy tnh: (phng trnh thy tnh i vi lu cht khng nn c)Khi khi lng ring thay i khng ng k ta xem = const, phng trnh thy tnh c dng:P+.g.z = constP: p sut ti im ang xtg: gia tc trng trngz: chiu cao ca im ang xt so vi gc ta ta chnpht biu: vi mt im bt k trong lng lu cht u tun theo phng trnhnu ta xt mt im B bt k trong lng lu cht th ti B p sut, khi lng ring quan h theo phng trnh:pB+ .g.zB = constV ti im A no th p sut, khi lng ring cng c phng trnhpA + .g.zA = constLc pB +.g.zB = pA + g.zApB pA = .g.(zA zB)pAB = p.g.hABpAB: l chnh p gia v tr A v B trong lng cht lngT biu thctrn ta thykhizA =zB (tc A v B cng nm trn mt mt phng ) th pAB = 0 hay pB = pAp sut thy tnh ti mt im trong lng cht lngpA po = .h (kg/m.s2 = N/m2)

trong : = p.g: trnglngring ca cht lng (kg/m2.s2) p: l khi lng ring ca cht lng (kg/m3) h: chiu cao t A n mt thong (m) po: psuttrn mt thongi t m cht lng (du, ru...) so vi mH2OPdu= . = .Pchtlng= . = . o p sut o p sut kh quynp sut kh quyn: p sut kh quyn tnh theo p sut tuyt iPkq = p.g.h (N/m2)Trong : p: l khi lng ring ca thy ngn( kg/m3) g:gia tc trng trng(m/s2) h: chiu cao ct thy ngn(m) o p sut cht khTrong bnh ang c p sut tuyt i l p, p sut d trong bnh so vi kh quyn l:pd = p po = p.g.hL (N/m2) p: khi lng ring ca cht lng vo manometer(kg/m3) hL: chiucaoct cht lng chnh trong manometer(m)o p sut chn khng cakhtrongbnh ta dngVacumeter o p sut chn khngTrong bnh ang c p sut tuyt i l p, p sut chn khng trong bnh lpck = po p = p.g.hL o p sut lu cht ang chuyn ngp k o chnhTrng hp 1h = h1 = (zA +) (zB+ ) (m)

Trng hp 2h = h1 . (m) h: l chnh p sut gia 2 im A, B Ch chy trong ngChun s Reynolds:Re = = d: ng knh trong ca ng, hoc ng knh tng ng ca knh.(m) vntcdngchy (m/s) : nht ng lc hc ca lu cht tra bng vi mt lu cht nht nh (N.s/m2;kg/m.s) : nht ng hc (m2/s)Chun s Reynolds c trng cho ch chy trong ng, trong knh ca lu cht.Nu Re 2300 th ch chy l chy tngNu Re> 2300 ch chy l chy ri Tr lc v ma stKhi chuyn ng trong ng lu cht tip xc vi ng ng dn s lm cn tr tc chy ca lu cht. Mt khc khi i qua nhng ch quanh co, khp ni ng, nhng ch thu hp, phnh to... cht lng b cn tr lm vn tc chy chm li v p sut cng gim.Cc k hiu: : H s tn tht dc ng hoc h s ma st : H s tn tht cc bTn tht dc ng c tnh theo cng thc Darcy:Tn tht dc ng gy ra bi chiu di ng nghL = . = (m cht lng)Trong : L: chiu di ng (m) V: vn tc lu cht trong ng (m/s) D: ng knh ng trn R: bn knh ng trn hoc bn knh thy lc Bn knh thy lc R = (m) S: tit din mt ct t (m2) : Chu vi t (l chu vi ca mt ct t tip xc vi thnh rn)Vi dng chy tng ReNu chy ri: Nu 3000 v thng c ly: 3. S thit b.

1. Ca kh vo5. Bung sy2.Qut ly tm6. Khy sy3.Caloriphe7. Ca ra kh thi4. Cn

4. S liu v x l s liu.BNG S LIU 50OC

SSTt (ph)G (g)Tk(0C)T(0C)

109153835.5

259005343.5

31089554.546

41588054.547.5

52086054.548.5

62585054.549.5

73085054.549.5

83584054.550.5

94083554.549.5

10458255550.5

115081554.549.5

125580554.549.5

136079554.549.5

14657805550

157077554.549

167577054.549

178076054.549

188575054.549

199074554.549

209573554.549

2110073054.549

221057255548.5

2311072056.550

241157205549

2512072054.549.5

261257205549.5

Tnh theo thc nghim: m vt liu Theo vt liu kh:

Da vo cng thc trn ta tnh c cc W nh bn di:

Tc sy:

S LIU SAU KHI X L 50OCSTTT (pht)Gi (g)Wi (%)N (%h)Tk tbT tbPb (mmHg)Ph (mmHg)

1091552.53835.54240

259005030.015343.56258

31089549.29.6054.5466866

41588046.6730.3754.547.57270

52086043.3340.0954.548.58284

62585041.6719.9254.549.59286

73085041.67054.549.59286

8358404020.0554.550.59899

94083539.29.6054.549.59286

104582537.520.415550.59899

115081535.8320.1254.549.59286

125580534.219.5754.549.59286

136079532.520.454.549.59286

14657803030.155509592

157077529.29.654.5498890

167577028.3310.4454.5498890

178076026.6719.954.5498890

18857502520.0454.5498890

199074524.29.654.5498890

209573522.520.454.5498890

2110073021.215.654.5498890

2210572520.834.445548.58282

23

110720209.9656.5509594

2411572020055498884

2512072020054.549.59286

261257202005549.59292

Gi tr trung bnh85.9284.3

Tnh theo l thuyt. Cng m.

: Cng m.B: p sut phng sy, B = 760 mmHg.am : H s trao i m tnh theo chnh lch p sut ( kg/m2.h.mmHg)am=0,0229+0,0174*Vk=0,0229+0,0174*1.6=0,051 (kg/m2.h.mmHg)Vk : Tc kh trong phng sy ( chn Vk = 1,6 m/s)Pb(TB) = 85.92 mmHgPh(TB) = 84.3 mmHg

Vy: Jm = 0,051*(85.92-84.3)*= 0.083 (kg/m2.h) Tc sy ng tc:Nt =100.Jm.F/G0 (%/h)Vi F: din tch b mt syGo=600gF = F1+F2=(676.10-4)+(780.10-4) =0,1456 (m2)

(%/h) m ti hn:

Wth= + WcW1 : m ban u trc khi sy (%)Wc: m cn bng =3%

Wth = +3=32.17 (%) Thi gian sy: Thi gian sy ng tc:

T1= (h) Thi gian sy gim tc:

Wcuoi: m cui ca qu trnh sy

T2 =Thi gian tng cng qu trnh sy gn ngVy: Tsy= T1 + T2= 10.09 + 7.82=17.91 (h)

5. V th.

Nhn xt: Bi sy cha c hon chnh v khng thi gian nn cha sy ti khi lng khng i sn phm vn cha kh hon ton v th lm sai s nh hng n kt qu tnh ton.Tr li cu hi chun b:1. nh ngha qu trnh sy i lu?Tr li: Qu trnh sy din ra rt phc tp, c trng cho tnh khng thun nghch v khng n nh. N din ra ng thi 4 qu trnh: truyn nhit cho vt liu, dn m trong lng vt liu, chuyn pha v tch m vo mi trng xung quanh.2. Th no l truyn nhit v truyn m bng phng php i lu?Tr li:3. Cc giai on sy?Tr li: gm c 3 giai on sy: Giai on un nng vt liu Giai on sy ng tc Giai on sy gim tc4. C my qu trnh sy?Tr li: Qu trnh sy c hi lu Qu trnh sy c t nng trung gian5. K tn mt vi loi thit b sy?Tr li: Thit b sy bng ti Thit b sy tng si Thit b sy kh ng (hay cn gi l thit b sy kh thi) Thit b sy phun loi thng Thit b sy bc x - i lu Thit b sy thng hoa Thit b sy in cao tn6. Cc thng s cn o trong qu trnh th nghim?Tr li:Khi lng, nhit bu kh, bu t v thi gian.7. Ni dung th nghim?Tr li:Tin hnh sy bnh trng 2 ch ca Caloriphe: 400C v 500C. t vt liu vo bung sy, ghi nhn khi lng vt liu sau khi lm m (G1). Sau c 3 pht ghi nhn gi tr cn v gi tr nhit bu kh, bu t. Tip tc n khi gi tr khi lng vt liu khng i trong vng 15 pht th dng ch th nghim ny v chuyn sang ch th nghim khc.8. Cch thc tin hnh th nghim?Tr li:Bc 1: Chun b th nghim: Xc nh khi lng vt liu kh ban u (G0) ca vt liu: M ca bung sy ra, t cn thn c gi tr cn (G0) Lm m vt liu: Sau khi cn xong, ly vt liu ra v nhng nh nhng (trnh rch vt liu) vo chu nc. Ch khong 30 giy cho nc thm u, ly vt liu ln v ro nc sau xp vo gi. Chun b ng h eo tay o thi gian. Kim tra h thng: Lp li ca bung sy. M ht cc van ca hai ca kh vo ra Chm y nc vo bu t (pha sau h thng)Bc 2:Khi ng h thng: Khi ng qut: bt cng tc ca qut ht dng tc nhn vo v thi qua caloriphe gia nhit dng tc nhn. Khi ng caloriphe, bt cng tc Caloriphe. Ci t nhit cho Caloriphe nhit th nghim.Bc 3: Tin hnh th nghim

Ch h thng hot ng n nh khi: nhit ca Caloriphe t gi tr mong mun (). Tin hnh sy vt liu nhit kho st. o s liu trong ch th nghim. Cc s liu cn o: Khi lng, nhit bu kh, bu t v thi gian. Cch c: Khi lng (gam) khi t gi vt liu sy, c s hin th trn cn. Nhit (0C) : Nhn nt tng ng cc v tr cn o v c s trn ng h hin s. Chuyn ch th nghim: M ca bung sy, ly vt liu ra lm m tip (lp li nh ban u). Ci nhit Caloriphe gi tr tip theo cho ch sy mi. Ch h thng hot ng n nh. Lp li trnh t nh ch u.Bc 4: Kt thc th nghim Tt cng tt ca in tr Caloriphe. Sau khi tt Caloriphe c 5 pht, tt qut cho Caloriphe ngui.9. Mc ch th nghim?Tr li: Vn hnh c h thng thit b sy. Tnh ton c cc thng s sy: tc sy ng tc, m ti hn, m cn bng, thi gian sy ng tc v gim tc. Xy dng ng cong sy v ng cong tc sy da trn s liu thc nghim.10. ng cong sy?Tr li: L ng cong biu din s thay i ca m vt liu (U) theo thi gian sy Ph thuc vo nhiu yu t nh lin kt gi m v vt liu, hnh dng kch thc; cu trc vt liu, phng php v ch sy. ng cong sy l hm ca qu trnh sy11. ng cong tc sy?Tr li: L ng cong biu din mi quan h gia tc sy v m ( hm m) ca vt liu sy ng cong tc sy l o hm ca ng cong sy.12. Phng trnh c bn ca ng hc qu trnh sy?Tr li:

13. Sy l g? S khc nhau gia sy v c c?Tr li: Sy i lu l qu trnh tch m ra khi vt liu bng cch cp nhit cho m bay hi. Trong , c hai qu trnh truyn nhit v truyn m u c thc hin bng phng php i lu. S khc nhau gia sy v c c: Sy l qu trnh bc hi nc lm cho vt liu kh i khng cn m trong C c cng l qu trnh lm bc hi nc nhng n lm giu cc cu t ha tan trong v lm cho vt liu c c li.14. Thi gian sy ca vt liu?Tr li: Ta phi ph thuc vo ch sy ca vt liu m ta mi bit c thi gian sy ca vt liu. V vy i vi mi vt liu c cc ch sy khc nhau th thi gian sy cng khc nhau.

BI 5: CT CHM

1. Mc ch th nghimKho st c tnh ng lc hc lu cht v kh nng hot ng ca ct chm bng cch xc nh:nh hng ca vn tc dng kh v lng ln tn tht p sut ( gim p) khi i qua ct.S bin i ca h s ma st ct kh fcktheo chun s Reynolds (Re) 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 qua ct kh v qua ct t theo vn tc dng lng.Gin gii hn kh nng hot ng ca ct (gin ngp lt v gia trng).2. C s l thuyt2.1 Khi nim qu trnh hp th (hp thu)Qu trnh hp thu l qu trnh cho mt hn hp kh tip xc vi dung mi lng nhm mc ch ha tan chn lc mt hay nhiu cu t ca hn hp kh to nn mt dung dch cc cu t trong cht lng, pha kh sau hp thu gi l kh sch, pha lng sau hp thu gi l dung dch sau hp thu.Vy qu trnh hp thu l qu trnh truyn vn cu t vt cht t pha kh vo pha lng. nu qu trnh xy ra theo chiu ngc li, ngha l truyn vn cu t t pha lng sang pha kh, ta c qu trnh nh hp thu.Mc ch ca qu trnh hp thu l ha tan chn lc mt s cu t.2.2 ng dng ca qu trnh hp thu Cng ngh thc phm Cng ngh ha hc Cng ngh sinh hoc K thut mi trng Ngnh cng nghip du kh2.3 Phng php la chn dung mi hp thuKhi la chn dung mi cho qu trnh hp thu ngi ta da vo cc tnh cht sau: ha tan chn lcy l nhng tnh cht ch yu ca dung mi, l tnh cht ch ha tan tt cu t cn tch ra khi hn hp m khng ha tan cc cu t cn li hoc ha tan khng ng k. Tng qut, dung mi v dung cht c bn cht tng t nhau th cho ha tan tt. Dung mi v dung cht to nn phn ng ha hc th lm tng bn ha tan ln rt nhiu, nhng nu dung mi c thu hi dng li th phn ng phi c tnh hon nguyn. bay hi tng iDung mi nn c p sut hi thp v pha kh sau qu trnh hp thu s bo ha hi dung mi do dung mi b mt. Tnh n mn ca dung miDung mi nn c tnh n mn thp vt liu ch to thit b d tm v r tin. Chi phDung mi d tm v r tin s tht thot khng tn km nhiu. nhtDung mi c nht thp s tng tc hp thu, ci thin iu kin ngp lt trong thp hp thu, gim p thp v truyn nhit tt. Cc tnh cht khcDung mi nn c nhit dung ring thp t tn nhit khi hon nguyn dung mi, nhit ng rn thp trnh hin tng ng rn lm tc thit b, khng to kt ta, khng c.Trong thc t, khng mt dung mi no trong mt lc p ng c tt c cc tnh cht trn, do khi chn phi da vo nhng iu kin c th khi thc hin qu trnh hp thu. D sao tnh cht th nht cng khng th thiu c trong bt c trng hp no.2.4 Phng php hp thu: C 2 phng php hp thu nghch dng v hp thu xui dng y ta ch xt hp thu nghch dng. Hp thu nghch dngPha kh l hn hp kh G vo cha nhiu cht: Trong Cc cht tr Gtr (khng hp thu vo lng) Cht hp thu vo lng gi l cu t APha lng: Lng dung mi gi l L Cu t A c sn trong pha lng L Lng dung mi tr l Ltr l lng dung mi tng cng L tr i cu t A.2.5 Mt s nh nghaPhn mol ca cu t i l s mol (sut lng mol) ca cu t i chia cho tng s mol hn hp (sut lng mol hn hp).Phn khi lng ca cu t i l khi lng (sut lng khi lng) ca cu t i chia cho tng khi lng hn hp (sut lng khi lng hn hp)T s mol ca cu t i l s mol (sut lng mol) ca cu t i chia cho tng s mol (sut lng mol) tr i s mol (sut lng mol) ca i.Cc n v: Sut lng mol: mol/h; (kmol/h.m2); (mol/h.m2). Sut lng khi lng: kg/h; (kg/h.m2); (g/h.m2). Phn mol v t s mol khng c n v.2.6 nh hng ca nhit v p sut ln qu trnh hp thuNhit v p sut l nhng yu t c nh hng quan trng ln qu trnh hp thu. Chng nh hng ln trng thi cn bng v ng lc ca qu trnh.Nu nhit tng th gi tr h s ca nh lut Henry tng, ng cn bng s chuyn dch v trc tung, ng lc truyn khi s gim. Nu tng nhit ln mt gii hn no th khng nhng ng lc truyn kh gim m ngay c qu trnh cng khng thc hin c. Mt khc khi nhit tng cao cng nh hng tt v nht ca dung mi gim (c li i vi trng hp tr lc khch tn ch yu nm trong pha lng).Thit b hp thuTrong cng nghip, thc t sn xut ngi ta c th dng nhiu loi thit b khc nhau thc hin qu trnh hp thu. Tuy nhin, yu cu c bn ca thit b vn l din tch b mt tip xc pha phi ln tng hiu sut ca qu trnh hp thu. Bi th nghim ny ta xt loi thp hp thu l thp m (ct chim).3. S thit bI-My thi kh1,2-Van iu chnh lu lng dng khII-Lu lng k dng kh3-Van x nc ng trong ng khIII-Ct chm 4,6-Van iu chnh lu lng dng lngIV-Bn cha 5-Van to ct lng ngn khV-Bm7-Van iu chnh mc nc trong ct chmVI- Lu lng k dng lng8-Van x nhanh khi lt ct chmD-lp m vng s Raschig 9-Van x y bn cha

4. Kt qu th nghim Ta i V(fit3/pht)

1fit3/pht=2,83.m3/pht=(m3/s)

Tng t:2fit3/pht =(m3/s)9,43. Tnh GCt kh ang vn hnh nhit 50oC kk=1,1(kg/m3), =1,96.10-5(kg/m.s)

Trong : S=.d2./4= .0,12.0,585/4=0,00459225 Tnh PCK: PCK=(39,3 - 38,8).102.10 = 400 (N/m2)

Tnh Re:

Tnh fCK

fCKLm tng t ta c bng x l s liu ct kh: Ct kh

iV(m3/s)GPCK (N/m2)PCK/ZLog (PCK/Z)log GRefCKlogfCKlogRe

10,0009430,226400555,62,7-0,6461870,60,842-0,0753,272

20,0018870,45290012503,1-0,3453741,3 0,733-0,1353,573

30,002830,67814001944,43,3-0,1695611,90,676-0,173,749

40,0037730,90412001666,73,2-0,0447482,60,638-0,1953,874

50,0047171,13011001257,83,10,0539353,20,610-0,2153,971

60,005661,35620002777,83,40,13211223,80,589-0,2304,05

Tnh ton cho bng ct tT bng s liu ca ct t ta tnh cho hng u tin trong bng Tnh GCt t ang vn hnh nhit 30oC C =1,177(kg/m3); =1,86.10-5 (kg/m.s)

(kg/m2.s)PC =(20 - 38).10 = 2 (cmH2O) = 2000 N/m2PC/Z= = 2777,8 (N/m2.m) Tnh :Tnh fC= .fCK = 5.0,842 = 4,21Lm tng t ta c bng x l s liu ca cc ct t nh sau:

L=4

iV(m3/s)GPC (N/m2)PC/ZLog(Pc/Z)log GRefClogfClogRe

10,0009430,24220002777,83,444-0,6462110,84,210,6243,272

20,0018870,48424003333,33,53-0,3454221,52,060,3143,573

30,002830,72530004166,73,620-0,1696323,61,450,1613,749

40,0037730,96740005555,63,745-0,0448434,32,120,3263,874

50,0047171,20953007361,13,8830,05310545,12,940,4683,971

60,005661,45170009722,23,9880,13212655,92,060,3144,05

L=5

iV(m3/s)GPC(N/m2)PC/ZLog(Pc/Z)log GRefClogfClogRe

10,0009430,24220002777,83,444-0,6462110,83,3680,5273,272

20,0018870,48424003333,33,53-0,3454221,51,960,2923,573

30,002830,72530004166,73,620-0,1696323,61,450,1613,749

40,0037730,96750006944,43,842-0,0448434,32,660,4253,874

50,0047171,20962008611,13,9350,05310545,13,440,5373,971

60,005661,451800011111,14,0460,13212655,92,360,3724,05

L=6

iV(m3/s)GPC (N/m2)PC/ZLog (Pc/Z)log GRefClogfClogRe

10,0009430,242270037503,574-0,6462110,85,6840,7553,272

20,0018870,48433004583,33,661-0,3454221,52,6900,4303,573

30,002830,72550006944,43,842-0,1696323,62,4130,3833,749

40,0037730,96760008333,33,921-0,0448434,32,2780,3583,874

50,0047171,209820011388,94,0560,05310545,14,54506583,971

0,005661,4511000013888,94,1430,13212655,92,9450,4694,05

L=7

iV(m3/s)GPC(N/m2)PC/ZLog (Pc/Z)log GRefClogfClogRe

10,0009430,24247006527,83,815-0,6462110,85,6840,7553,272

20,0018870,48460008333,33,921-0,3454221,52,6900,4303,573

30,002830,725800011111,14,046-0,1696323,62,4130,3833,749

40,0037730,9671000013888,94,143-0,0448434,32,8780,3583,874

50,0047171,2091400019444,44,2890,05310545,14,5450,6583,971

60,005661,4511700023611,14,3730,13212655,92,9450,4694,05

L=8

iV(m3/s)GPC(N/m2)PC/ZLog (Pc/Z)log GRefClogfClogRe

10,0009430,24247006527,83,815-0,6461870,69,8940,9953,272

20,0018870,48460008333,33,921-0,3453741,3 4,8890,6893,573

30,002830,725800011111,14,046-0,1695611,93,860,5873,749

40,0037730,9671000013888,94,143-0,0447482,65,3150,7263,874

50,0047171,2091400019444,44,2890,0539353,27,7590,893,971

60,005661,4511700023611,14,3730,13211223,85,0070,74,05

L=9

iV(m3/s)GPC(N/m2)PC/ZLog (Pc/Z)log GRefClogfClogRe

10,0009430,242800011111,14,046-0,6461870,616,841,233,272

20,0018870,4841000013888,94,143-0,3453741,3 8,1360,913,573

30,002830,7251600022222,23,347-0,1695611,97,7270,893,749

40,0037730,9672000027777,84,444-0,0447482,610,6351,033,874

50,0047171,2091600022222,23,3470,0539353,28,8760,953,971

60,005661,4512100029166,674,4650,13211223,86,1850,794,05

Tnh ton cho bng ct ngp ltTa tnh cho dng u tin ca ct ngp lt Tnh chun s th nht 11=[(fCK.a.V12.KK)/(3.2g.L)].td0,2Ta c: KK=1,1 (kg/m3)=0,585g= 9,81 (m/s2)lng=995,7(kg/m3)fCK= 0,842a=24,656 (m2/m3)

(m/s) (vn tc dng kh qua ct) (m2)

Vy Log1= -4,23 Tnh chun s th 2 2

L=9 (lt/pht) = 9.10-3/60=0,00015 (m3/s)V= 0,000943 (m3/s)K =1,177 (kg/m3)lng= 995,7 (kg/m3)

Log 2= -2,26Lm tng t cho cc dng tip theo ta c bng x l s liu ca ct ngp lt nh sau:V(m3/s)12log1log2

0,0009430,00005890,00547-4,23-2,26

0,0018870,00003040,00273-4,12-2,56

0,002830,00006420,00182-4,19-2,74

0,0037730,0001080,00137-3,97-2,86

0,0047170,0001610,00109-3,79-2,96

0,005660,0002240,00091-3,65-3,04

4.3 V biu Ct kh th Log (PCK/Z) log G

Ct t th Log (PCK/Z) logG

Ct ngp lt th Log1- log2

Nhn xt: qu trnh th nghim gip sinh vin bit cch vn hnh my, thng qua x l s liu s gip sinh vin nhn bit c sai s l thuyt v thc t.

CU HI CHUN B1.Cc yu t nh hng n gim p ca ct kh?Tr li:- Chiu cao phn cha vt chm.- ng knh tng ng ca vt chm.- Th tch t do ca vt chm.- Din tch b mt ring ca vt chm.- Khi lng ring ca pha kh.- Sut lng biu kin ca pha kh qua mt n v tit din thp.2. Thp chm c ng dng trong lnh vc no?Tr li:Thp chm c ng dng nhiu trong ngnh cng nghip thc phm.3. C my loi vt chm? Chng c ch to t vt liu g?Tr li:Vt chm s dng gm c nhiu loi khc nhau, ph bin nht l mt s loi vt chm sau: Vng Raschig: hnh tr rng bng s hoc kim loi, nha, c ng knh bng chiu cao(kch thc t 10- 100mm). Vt chm hnh yn nga: c kch thc t 10- 75mm. Vt chm vng xon: ng knh dy t 0,3- 1mm, ng knh vng xon t 3- 8mm v chiu di nh hn 25mm.4. Kch thc vt chm cn phi tha mn iu kin g?Tr li:Vt chm phi c din tch b mt ring ln,ngoi ra rng cng phi ln.5. La chn vt chm cn phi tha mn nhng iu kin g? Tr li:Phi c din tch b mt ring ln,c rng ln gim tr lc chop pha kh v phi bn.6. u v nhc im ca vt chm bng s?Tr li: - u im:gi thnh r,khng b oxy ha,khng b n mn.-Nhc im:d v.7. Trong th nghim cc s liu o c cng nh lu lng ca cc dng c n nh khng? Ti sao?Tr li:Trong th nghim cc s liu o c cng nh lu lng ca cc dng khng n nh.Ti v8. Trong th nghim c my im cn lu ? im no quan trng nht?Tr li:Trong th nghim c 2 im cn lu .im quan trng nht l: Trong qu trnh o gim p ca ct t,cn canh gi mc lng y ct lun n nh chiu cao y bng cch chnh van7. Nu cn, tng cng van 8 nc trong ct thot v bnh cha.9. Ti sao phi duy tr mc lng y ct?Tr li: V nu ta cho y th kh khng tip xc c vi nc(khng i vo ct hp thu). Nu cho t nc th kh t tip xc vi dung mi,v c nhiu bt kh th s liu o dc s b sai.10. C my loi qut?k tn?qut trong bi ny l loi g? Cao p hay thng?Tr li: c 2 loi qut l qut cao p v qut thngQut trong bi ny l qut cao p11. Ti sao phi nghin cu th ca thp chm t im gia trng n im lt?Tr li: V xc nh gii hn kh nng hot ng ca ct l t im gia trong n im ngp lt12. Cng thc tnh vn tc lm vic ti u trong thp chm?13. Cng thc tnh h s tr lc do ma st trong thp chm cc ch chy (Re) khc nhau?Tr li:

Ct kh:vin = 1,8 2,0Ct t:Pc = Pckvi: = 10Lhaylog = LGi tr ty thuc vo loi, kch thc, cch thc sp xp vt chm (xp ngu nhin hay theo th t) v ln ca lu lng lng L. Th d vi vt chm l vng s Raschig 12,7 mm, chm ngu nhin, xp = 0,586; gi tr ca L t 0,39 n 11,7 kg/m2s v ct hot ng trong vng di im gia trng. = 0,08414. Cng thc tng qut tnh tn tht p sut trong thp chm? Gii thch cc tha s trong cng thc v mc nh hng ca chng n gim p.Tr li:Tn tht Tr lc thp kh:

Trong : h - chiu cao lp m, mwo- vn tc pha kha - b mt ring, m2/m3 - xp, m3/m3k khi lng ring ca khng kh, kg/m3fck - h s ma sat ca dng chy qua lp ht, ph thuc vo Rek

Khi Rek40: 15. Thp chm lm vic ch no l tt nht? Thc t c th vn hnh ch ny hay khng? Ti sao?Tr li: Thp chm lm vic ch chn khng l tt nht.nhng khng th vn hnh cho thc t.V thc t s mau lm dng lng t n im lt.16. Th no l im gi trng? Chopha kh tip xc pha lng phi qua vt liu im tng tip xc. Khi vn tc kh lng s phn tn trong kh, tng tc kh lng b t li, im gia trng : im p sut pha kh ln xuyn qua pha lng lin tc. u im: t tn dung mi.

Bi 6: Th nghim lc khung bn

1. C s l thuyt Lc cht lng

L qu trnh c thc hin phn ring cc hn hp nh 1 vt ngn xp, vt xp c kh nng cho mt pha i qua cn gi pha kia li nn cn gi l vch ngn lc. Nguyn tc lcTo ra trn b mt huyn ph mt p sut P1 di P1 pha lng xuyn qua cc l mao dn, pha rn b gi li, chnh lch p sut 2 bn vch ngn lc gi l ng lc ca qu trnh lc. P= P1- P2 (p sut to ra bng my bm, my nn, ct nc,Lng li lc thu c: W= (m/s) {tc lc} V: th tch nc lc thu c S: din tch b mt lc : thi gian ly mu (k t lc bt u chy)Tnh lng nc lc, lng b m lng pha rn, lng pha lng. + G : khi lng v th tch hn hp huyn ph em i lc : th tch v khi lng cht rn kh : th tch v khi lng nc lc nguyn cht V,G: th tch v khi lng nc lc cha nguyn cht m ca b: Wa= (%kg m/kg vt liu t)p sut lcKhi lc vi p sut khng i

Trong : : nht( kg/m.s) V: th tch nc lc( m3) S: din tch b mt lc( m2) : thi gian lc c n nh trc r0: tr lc ring( 1/m2) tr lc lp b to thnh( 1 kg b kh/1 m2 b mt) X0= Va/V0: t s gia lng b m( m3/lng n lc( m3) Rv: tr lc vch ngn( 1/m)Lc vi tc khng i: W=const( km hiu qu) (N/m2) Vt ngn lcPhi c tnh cht ph hp vi huyn ph, gm cc loi vi c an bng cc loi sau: si bng len polypropylene, clorinaxeton, pvc, si thy tinhchu axit Cht tr lcDiatomit trng to t 94% SiO2, b mt ring 20m2/g, bn axit, c x dng rng ri, to xp 93%, perolit: to t cc sn phm ni la cc cht tr lc khng c tan trong dung dch lc. My lc khung bn Cu toMy lc khung bn gm c 1 dy cc khung v bn cng kch thc xp lin nhau, gia khung v bn c vi lc. Huyn ph c a vo rnh di tc dng ca p sut ri vo khong trng ca khung. Cht lng qua vi lc sang cc rnh ca bn ri theo van ra ngoi. Cc ht rn c gi li to thnh b cha trong khung. Qu trnh lc- tr lc ca vi lc v b lcLc p a ti kt qu l mt lp ht rn to thnh trn vi lc gm cc mao qun ca b lc v vt ngn l chuyn ng dng cn phi c p sut khc phc tr lc ca vt ngn v tr lc ca b lc. Tr lc ca ng dn khng ng k. Tr lc ca b lcPhng trnh kozeny- carman o hiu p sut qua tng ht rn c dng chy dng tnh hiu p sut qua lc: (1)Trong : : nht ca nc lc X0= ; : th tch b lc; V: th tch nc lc S: din tch b mt lc : thi gian lc r0: tr lc ca b lc Tr lc ca b lc thay i ty theo tnh cht ca b lc r0= r0.Ps (2) r0: hng s s: ch s chu nn, s=0 cho b lc khng nn c, thng thng s c gi tr t 0,1-1,0 tr lc ca vi lc (3) : tr lc ca vt ngn lcPhng trnh lc tng qutPhng trnh (1) v (3) a v phng trnh vi phn ca qu trnh lc (4)Tch phn vi =const, thu c: . (5)t q= : lng nc lc ring (m3/m2)Phng trnh (5) c vit gn li nh sau: q2 + 2.C.q= K.Trong : C=1. Tnh ton: Bng s liu lc cp 1:1= 0,1

(s)510152025

V(lit)1,32,63,95,26,6

2= 0,2

(s)510152025

V(lit)1,63,24,96,58,1

3= 0,3

(s)510152025

V(lit)1,73,65,57,49,3

Bng x l s liu:1= 0,1

V1,3.10-32,6.10-33,9.10-35,2. 10-36,6. 10-3

Q2,69. 10-35,37. 10-38,06. 10-310,74. 10-313,64. 10-3

55555

2,68. 10-32,69. 10-32,69. 10-32,89. 10-3

18587185871858717301

2= 0,2

V1,6. 10-33,2. 10-34,9. 10-36,5. 10-38,1. 10-3

Q3,31. 10-36,61. 10-310,12. 10-313,43. 10-316,74. 10-3

5555

3,31. 10-33,51. 10-33,31. 10-33,31. 10-3

15105142451510515105

3= 0,3

V1,7. 10-33,6. 10-35,5. 10-37,4. 10-39,3. 10-3

Q3,51. 10-37,44. 10-311,36.10-315,29. 10-319,21. 10-3

55555

3,93. 10-33,93. 10-33,93. 10-33,93. 10-3

12722127221272212722

CK

0,11,34.10-32,88.10-6

0,2

0,3

1. th 1= 0,1

2= 0,2

3= 0,3

SVTH: Phm Huyn Trn Page 60