VAAL UNIVERSITY OF TECHNOLOGY

FACULTY OF ENGINEERING AND TECHNOLOGY

DEPARTMENT: CHEMICAL ENGINEERING

BACCALAUREUS TECHNOLOGIAE:ENGINEERING: CHEMICAL

SUBJECT

SUBJECT CODE

DATE

DURATION

EXAMINER

MODERATOR

MARKS

REQUIREMENTS:

FLUID FLOW IV (EHCIX4A)

808509006

JUNE. 2007

3 HOURS

Dr PO OSIFO

Mr WA du Plessis

TOTAL: 131

FULL: 125

CalculatorsGraph paper must be provided

INSTRUCTIONS:

Answer all questions

Number clearly and correctlyENGLISH QUESTION PAPER CONSISTS OF: 4 TYPED PAGES PLUS ANNEXURE1, 2, 3, 4, 5, 6, 7, & 8

DO NOT TURN THE PAGE BEFORE PERMISSION IS GRANTED.

Question 1 [32]

(a) State whether the behavior between shear stress and shear rate is time independentfor the following fluids. Explain briefly the effect of increasing shear rate on theirapparent viscosity.

i) thioxotropicii) rheopecticiii) shear thinningiv) shear thickening

[8](b) Show that the pressure drop through a centre line for non-Newtonian fluid

obeying Power Law flowing through a pipe is:

Where n is the power law index

k is the consistence factor

L is the pipe length

[12](c) A Newtonian liquid of viscosity 0.1 N-s/m2 is flowing through a pipe of 25 mm

diameter and 20 m in length, and the pressure drop is 10s N/m2. As a result of aprocess change a small quantity of polymer is added to the liquid and this causesthe liquid to exhibit non-Newtonian characteristics; its rheology is describedadequately by Power Law model and the flow index is 0.33. The apparentviscosity of the modified fluid is equal to the viscosity of the original liquid atshear rate of 1000 s"1. Determine the liquid maximum velocity in the pipe andalso the velocity if the liquid is a Newtonian liquid.

[12]

Question 2 [32]

(a) Show that the frictional pressure drop for fluid of density p flowing through astraight pipe of diameter D and length L is:

APS 2fpV2L D

/ i s the fanning friction factor [8]

(b) Benzene is flowing steadily through a 150 m long horizontal pipe of 55 mm insidediameter. If the flow rate is 0.015 m/min, calculated the pressure drop in pipe.Compare the pressure drop of the benzene flow with that of kerosene flow, if thesame amount of kerosene is flowing through the pipe. Take the density ofkerosene to be PK = 820 kg/m3 and viscosity to be JJ.K = 0.0025 N.s/m2, and alsotake the density of benzene to be PB = 899 kg/m3 and viscosity to be \XB ~ 0.0008N.s/m2. The equivalent roughness for the pipe is e = 0.00026 m.

[12]

(c) Water (p = 988 kg/m and JJ, = 1 cP) is steadily pumped between two reservoirs.The difference in elevation of the two reservoir surfaces is 30 m. All the piping is51 mm diameter steel and its length is 122 m. if the volume flowrate is 0.006m3/s. Find the power required to run the pump. The steel pipe roughness is e =0.000051 m.

2

Open globevalve

30 m

entrancep

Fully open V / Kgate valve = 0.16gate valve Kstde,bow = 0.95

Kglobe = 6.90Kexit = 1.0

[12]

Question 3 [20]

(a) Differentiate between the type of velocity measurements that is obtained from aventure and pitot tube meters [4]

(c) A crude oil with a viscosity of 0.5 cP and specific gravity of 0.895 is flowingthrough a 0.1 m inside diameter horizontal pipe. An orifice meter consisting of anorifice plate and a differential mercury-glycol manometer (mercury is themanometric liquid (specific gravity 13.6) and glycol (specific gravity 1.15) is thesealing liquid) is used to measure the volumetric flowrate of crude oil. If themanometer reading is 0.6m, corresponding to a volumetric flow rate of 1.3 x 10"3

m3/s, estimated the diameter of the orifice and also the power lost due to thepressure drop by the orifice plate. Assume Co = 0.61.

[16]

Question 4 [22]

(a) A spray dryer containing a hot air (80 C, viscosity = 0.018 cP) is used to dry amolten detergent sprayed from the top of the dryer. The molten detergent formedinto a small size particle before it gets to the bottom of the dryer which is 30 mhigh. If the particle diameter is 1 mm and a density of 1200 kg/m3, what wouldbe the terminal velocity of the particles assuming free settling? Mw of air is 29kg/kmol

[12](b) A bed has a height of 5.0 m and a void fraction of 0.33. A gas with a density of

1.25 kg/m3 and dynamic viscosity of 1.5 x 10"5 N s/m2 flows steadily through it.The size of particles in the bed is 0.005 m diameter and the sphericity Os is 1.The pressure drop is 150 N/m2. Calculate the superficial velocity.

[10]

Question 5 [25]

(a) Suggest two methods to prevent swirling in a mixing tank. [5]

(b) A curve-blade turbine with six blades is installed centrally in a vertical tank. Thetank is 2 m in diameter; the turbine is 0.66 m in diameter and is positioned 0.66 mfrom the bottom of the tank. The turbine blades are 82.5 mm wide. The tank isfilled to the depth of 1.83 m with a base solution at 65.5 C which has a viscosityof 15 cP and density of 1200 kg/m3. The turbine is operated at 150 r/min. Thewidth baffled rod is 198 mm.

(a) What power will be required to operate the mixer?(10)

(b) What would be the power requirement be in the vessel if the tank is unbaffled?[10]

Annexure 11. Momentum correction factor

(3=! Ju2dSSV2 s

2. Kinetic correction factor

a =SV

J2 s3. Flow measurementFor an incompressible flow in a horizontal meter

V 1 ^4. Flow past immersed body

-=jx'pD'' K=D\gp(pyp)

For Re < 1

CD = 24/Re, u t = gDp(Pp ~P\ FD = 3 w D

For 1000200,000

C D = 0.44, F D =0.055:ru tDjip u t= 1^

5. Ergun equation for fluid flowing through a packed bed

2 1

gDp(P p - p )

Ap 150Vou(l-ey 1.75pV+ - --

L O2SD;V OsDp

6. Minimum fluidization

\.75pV2OM

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i CJ q C> oi o o' o o"

4ii

ico

10

l.o

0,!

s

Tm.. 1 ill,.

%

mm-.

':f| T M "

rJ IILI ' HI

_ i-

mP1,1,11

**"C ih _

V*

nirnfirJl;III 1 1 III

k *

III 1

' in* SphorDUkj

i ,_ Cvllnc

1 U

i MM :

n.

=

H

on :

s S

Raynolda numbor, Rap "**^ jT

Drag coefficients for sphorcs, disks, and cylinders. [By permission from J. H. Perry andD, W. Green (eds.), Chemical Engineers'Handbook, 7th ed.. p. 6-51. Copyright, 1997,McGraw-Hill Book Company,]

m

!9-JUL-2004_22:,18 From:URAL UNIUERSITY EXAM 01695fcm

~' 0169509773I o

Aimcxure3

0.33 d.33 0.25 0,20.33 0.33 0.29 0.12S

FIGURE 9.12Power number N, versm A/,, for nU-bltida turbine*. {After Chudaetk1 *; O / . f o W M Wiihportion of eurvo D, (he vuliie of N, reud from tho fifluro must be multiplied by /V-.

AOITATTON A,VD kfrXINO OP LIQUIDS

Ihe dinhd

Curva Pitch S, S, S,A T,S:1 O.30 0.SO 1.0B 1.SH 0.30 0.30 1.0

I !

10*N^ m O'.nola J

TCURE 9.13

P t U I D MBCHANtCS

i| TABLE 9JValues of constants Kc and ATr -

for baffled tanks having four baffles at tankwall, with width equal to 10 percent of the tankdiameter

rj three blAdeaPitch ].0*Pitch | . 5 "

TurbineSix-btade dlik" (S, - 0 . 2 5 , ^ - 0 2 )

c U , h d M ( f f 4 W jSix pitched blades" (45* SA ~ o >)Four pitched blade." (45*. St ."on

laLpaddlertworlJiaa*'"^

4155

6S70

0,320,87

5.7J4.B01.63T 2 7 "1.700.35

Fiflure i.

9.12

9.13

Lines

D

B

a

LO

VI

b

40.0

18.0

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\

111W

10'"

10*

. 10*

^ ' ' ' '"'I ' "I '

o - Absolute roughneea, mL. di-lnBldaplpodtamotor.m

10*

Figure 2.2Plot of-^fRe" against Reynolds numbor

FIGURE 7.7Plot of exponent/i versus Re,, for Eq. (7,46).

1.0

o.s

0,6

0.2

'i

" - ^

j

> S

MCM- 0,5 0.6 0-7 0-8 0.9 1.0P

FIGURE 8.19Ovorull pressure loss in orifice mcicra. (After American Society of

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Viscosities of Liquids'

No, Liquid

1 Acetaldehyda2 Acetic ucid, J00%3 Acetic nnhyclride4 Acetone, 100%5 Ammonin, 100%6 Ammonia, 26%7 Amyl acctolo8 Amyl alcohol9 Aniline

10 Aniaole ..-. .11 Benzene ,12 Blphenyl13 Brine, CaCJj, 25%14 Brino, NuCl, 25%15 Bromlna16 Butyl acetate17 Butyl alcohol ~18 Cnrbon dioxides19 Carbon disulflda20 Cnrbon tetrachlorlda21 Chlnrobenzuno22 Chloroform23 m-Crcsol24 Cyclohcxnnol25 Dicbloroeihune26 Dichloromethane27 Ethyl ucetale2a Bthyl nlcohol.l00%29 Bthyl alcohol, 95%30 Bthyl alcohol. 40%31 Ethyl benzeno

15.212.112-714.512.610.1II, 87.58.1

12.3- 1 2 . 5

12,06.6

10,214.212.38,6

ll.fi16.112.712,3J4.42.52.9

13.2J4.fi13.710.59,86.5

13.2

4.814.212.87,22.0

.13.912.518.41B.713.510.918.315.916.613.211.017.20.37.5

13.112.410.220,824.312.28.99.1

13,814.316.611.5

No. Liquid

32 Ethyl chloride33 Bthyl ether34 Ethyl formate35 Ethyl iodide36 Bthylone glycol37 . Formic acid38 Proon-1239 Olyccrol, 100%40 Olycerol. 50%41 ' Hepiano42 Hcxana43 Hydrochloric ncid, 31,5%44 I u o b u t y l A l c o h o l"45 l s o p r o p y l a l coho l46 Kerosene47 Linseed oil, raw48 Mercury49 Mothnnol, 100%50 Methyl ncotnio5J Methyl chloride52 Mothyl othyl koiono53 Nupthalenc54 Nitrfeacid, 95%55 Nitric;, add. 60%56 Nitrobenzene57 Nitnotolucnc58 Octane59 Octyl alcohol60 Psnwne61 Phenol 62 Sodium 16.4 .13.9

No.63646566676869

Liquid

Sodium hydroxide, 50%Sulfur dioxideSuiruricucld.98%Sulfuric odd, 60%TotruchloroaihnnoTetrachloroethyleneTitunlum letrnchlorido

X3.2*

15.27.0

10.211.914,214.4

y25,87.1

24,821.313,712.712.3

No.70717273747576

Liquid

TolueneTrichlorocthylena 'Vinyl ttcemtoWnteroXylcnom-Xylcno/-Xylono

A'13,714,814,010,213.513,913,9

y10.410,58.8

13.011110,610-9

Coordinates for use with figure on next pun.o.'By permluolOn, from J. H. Pnrry (odj, Chtmleat Engineers'HunAbvuk, Slhod., pp. 3-212 and 3-213- Copyrluhl 1973. McGraw-Hill Book Company, Now York.

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T:!JW ^.'l ?': :

t

u

Tomporatura

Dag. C200 -190-180 -170 -160 -150 -

140 -130 -

1 2 0 -

110 -

100 -

90 - i

00 -

7 0 -

60 -

50 -

40 r

30 -

20 . -

1 0 ->

Dog.F

- 380- 360

- 340

- 320

- 300

-2H0

- 260-

- 240

- 2 2 0

- 200

- 1B0

- 160

- UO

- 120

- 100

- 00

- 6 0

-40

- 1 0 -

-30 - f

- 2 0

- 0

.

p !$; y '

VlscotilyCnntlpoliaj

r- 100r 80

> 40

30

28

26

24

22

20

ia

16

U

12.

10'

S

6

4

2

>(

2 4 6-20

r 10

- 4

- 2

r o.B

0.2

Viscosities of liquids at I atm, For coordinates, see tablo on previous pager

M

09-JUL-2004 22:19 From:UAAL UNIUERSITY EXAM 0169509773

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APPENDIX W

' Viscosities of Gases1" -"A

No.123456789

1011.1213141516171819202122232425262728

GasAcetic addAcoionoAcetyleneAirAmmoninArgonBenzene ~DromlneButaneButyleneCarbon dioxideCarbon disulfiiloCarbon monoxideChlorineChloroformCyanogenCyclohcxnnoEthaneBthyl acetateEthyl alcoholEthyl chlorideBthyl etherEihylcncFluorineFroon*11Preonl2Prcon-21Preon-22

X

7.78.99,8

11.08.4

10.58.5 8.99.28.99.58,0

n.o9.08.99.29.29.18.59.28.58.99.57.3

IQ.611.110.H10.1

Y 'i14,313.014.920.016.022,413.2 .19.213.7.13-016.716,020.018.415,715.212.014.513.214.215.61.3.015.123.815.116.615.317.0

/ No.

293031

.' 32333435363738394041424344454647484950515253545556

GunFreon-113HeliumHcxaneHydrogen3Hj H- NjHydrogen bromideHydrogen chlorideHydrogen cyanidoHydiogen iodideHydrogen BulfideIodineMercuryMethaneMethyl ulcoholNitric oxidaNitrogen Nitrosyl chlorideNitrous oxideOxygenPenninePropanePropyl alcoholPropyleneSulfur dioxidoTbluene2,3,3-TrimelhylbuuineWaterXenon

X

11,310.9&.6

11.211.28iS8.B9.89.08.69.05.39.98.5

10.910,68,08.8

n.o7.09.78,49.09.68.69.58.09.3

y

14.0 .20.511.8 *12.417.-2 '2bl9'I8."714.921.318.0-18,422.915.515.620.520.017.619.021.3L2.812.9L3.413.81.7-012.410.516.023.0

Coordinates Tor use with figure on next page.'By permission, Irani J. H. Pony (od.). ChemicalEnEbwan'Handbook, 5lh d., pp.3-210 ond 3-21!. Copyriuhl 1B73, Moaraw-Hlll Rook Company, Now York. ,

1074

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: ~ " 0169509773

I o : *b3CO&iOOi3t)i iDJicoco

TamparaluroDag, C, Dag. F.-100 -

8: Viscosities of Gnaoa 1075

- L1

Vlscoilty'ContipoUosp 0.1- 0.09- 0,0Q

- 0.07

r 0.06

\- 0,05

-

_

*

-

-

-

0 10 12X

14 16 IB

- 0,03

- 0.02

-001- 0.009

- 0.008

- 0.007

r-O.006

'- 0.005

ViscoBities of gases nnd vnpors nt 1 fltmj for coordinates, sec tnble on previous page.

C

T l