tEK 103/3 - UNIT OPERATIONS I

Academic Session 2003 /2004 February/March2004

tEK 103/3 - UNIT OPERATIONS I

Duration : 3

hours

Please check that the.examination paper consists of

EIGHT

(8) printed pages before you commence this examination.

Answer

FIVE

questions

only.

Students are allowed

to

answer

all

questions

in

English OR Bahasa Malaysia OR combinations of both.

1/

rEK

103/3

-z-

1.

^{(a) Water}

flows

^through

a pipe of

^0.15

m

^diameter

fitted with

^an

orifice

^meter

of

0.10 m diameter. A vertical manometer is fitted

^across

the orifice meter.

The manometer

fluid is mercury of specific gavity

13.6.

Water fills the arms of

the

manometer. The

reading

of the

manometer

is

0.254 cm.

If the coefficient of

the orifi.ce can be taken as 0.60, what is the voluuretric

flow

rate

of

water

at

15.56 oC

?

The density of water at 15.56 "C is 999.0

kd.'.

(70 marks)

(b) A

manometer

is fitted

on

to

a pipeline as shown

below. An oil of

specific gtavity 0.9

flows in

the pipe. The manometer

fluid is

mercury (S.G.

:

13.6), and the manometer reading is 4.0

in.

What is the value of pr

-

^{pz ?}

(30 marks)

A

horizontal steel pipe has a diameter

of

0.0526 m and a length of 30.48 m. The pipe roughness

is k :

_0.000045

m. A fluid of density

1200

kg/m'

and

viscosity

^0.01

N.s/m' flows

in the pipe at a late

of

9.085 m'Ar. Calculate

(D

pressure drop,

inN/m';

(ii)

power required for the

flow.

(a) A

tank

is filled with

a

fluid of

viscosity 0.08 N.s/m2 and

densi"$l ffi) ,r"

ank

is

without

baffle.

A 6

flat-blade turbine

of

diameter 0.15 m rotating

at

18 rps is

fitted

in the tank 0.15 m from the

bottom.

What power is required for the operation ^?

(50 marks)

O) Two

open water reservoirs as shown are connected through a smooth pipe

of

10 in diameter and 4000

ft long.

The water level in the upper tank

is nA

ftabove that of the

lowertank.

^The volumetric

flow

rate is 4.5

ft'ls

at 70

T.

Calculate

(i)

the

friction

loss for the system,

(iD

^What is the value of the pressure ^{p3 ?}

(50 _marks)

2.

3.

34

...3/-

-3-

(100 narks)

4' A liquid of

density 63-5 lb/ft3 _and

viscosity

1.35

cp

is pumped through _{a steel} pipe of 2

in

diameter to the top of a storage tank open to the atrrosphere. _The volumetric

flow

rate

of

the tigui-a

is

120

gy-in.

The idscharge of the prpe

is

60

ft

above the pump and the equivalent length of the steel pipe Aom tfre

pumpto

_{the tank}

is

175 ft.

If the

pressure at the suction

of

the pump

is)o turlini,

andthe pump

efficiency

_is

650/o, calculate

(i)

the brake horsepower of the

punp;

(iil

^pressure at the discharge of tire purnp;

(iii) If

the electrical energycost is

zceni io,

"rr"ry kWh (kilowatt-hour),

_{what is} the enerry cost

for

pumping _the

liquid

_{per aay}

t

5' consider the

heat-transfer

by

natural convection between

a hot f!103"ffPnr"4

nt^ajg wtth a height of.I, at uniform temperature

T-

and a surroundiog

firiatnafis

_cooler

of (hotter) with

a

uniform temperaturi T".

The

local

heat transfer

coefficient

h*

at

a

!"t$t x is

proportional

to the local

temperature difference _between the plate and the

fluid: !* : (dq/dA)i(T* - Tu) it is

founa that the

following

physicat _factors are involved in the process:

(h*,

_{x, k, Cp, p,}

p,

_B,

AT,g) :

₀

with the

use

of

Buckingham Theorem, obtain _the

relation

among the above variables.

The dimensional

matrix

is as follows.

000 00i -it0 00-2 01

1a

L-J

-20 -l

0

Ml0 L01

T-30 T-1

o

I

1

.Ja -1

1

-1

-i

0

I

120 ft

.. .4/-

rEK 103/3

-4-

6.

^(a)

A

horizontal

venturi

meter

of

throat diameter 2.50 cm

is fitted to

a pipeline

of

diameter

7.82 cm.

^Water

at

26.67 ^oC

flows

through the

pipeline.

Mercury (S.G.

:

13.6) manometer

is used. If

^the manometer reading

is

39.0 cm, what is the ^mass

flow

rate,

in kg/s

?

If

^10%

of the differential

^pressure

is lost, what is the

^power

consumption of the meter ?

(60 marks)

(b) Oil (p:900 kd-'and v:2 x

^{10a m2ls;}

flows

ⁱⁿ a smooth 5

x

5 cm square duct at an average

velocity

of 4.0 m/s. What is the pressure drop in 25 m long of the duct

?

(40 marks)

36

. .

.5./-

.fg+uf$T$S 3FNtr.Ytr

Mulriptl b/f To conrcrt lronr

IO

A\ otac.o Iumbcr ba.rcl (ixrroicu0)

b3:

BcrEnrnilx gonslaD!

Biu

Brrrb Brui4b-.;:

Bru/Il:.h Bru (r r_h-.F Bru.fr;,frr-hJF ca:r

m

cmJ cP (ccnri;:oisc)

cSr (dcIririokc) faracay It.

fr-lb/

f!.lb/is tr'ln ll, ftr-!tir

fr)7s 8al (u.s.) gravitltionrl _constant gravttl, rccclct:rt jon, standard h

hp hp/1000 gat in.

ln.'

J

kg kwh L Ib lb/f!r lb/lin..

lb mol/rit-h Iight, sFcc,J r,f

+t N n-/q:

Planck;o:rstrrr proof _{(L.S )} totr (long)

m:

N/m' tbr/in.1 paniclB/g mol ft) gal (U.S) mJ N/m' tb1/in.z

t/K

€lr

fr.tb/

r

KVr'h

qln/8 qltr/grc {mL'gVmt

kcafm:-b-K w-m/mr_.C ket/m-h-K Btu frJb/

J J in.

fl ftr gal (U.S) kg/m-s Ib/r-tr lb/fGs m2/s C/g mol m Btu

aln

J BtuA hp

mls m:/s fi!

gal (U.S.) L Bru

€ln

J gal (U.S)/min fr!

ln.' N-m,/kgr m/s:

min s

Btu^

kw kW/mr cm!

ftJb/

tb Btu m!

kg kg/m' 8/cmr N/m:

kg mol/nr-s g nol/cor-s m/s fr in.

fr!

gal (U.s) dyn lbr lb/lo.:

J-s

pcrccnr al@hol by volumc kg

lb

43J6d' ,t046.85 l.0l32Jr I 19:

t4.696 6.02169 x l0:r

5.6146

0.15899

lr I 1gr t4.504 1.380622 x t0-rl

25t.996

n8.n

1055.06 29307 x l0-.

0.55556

t'

3.1546 5.67E3 4.E82 t.73073 1.4E8

f.C6St x tO-,

3.0871 4.lE68r 4.t84.

. 0.393?0 0.0328084 3.531462 x t0-J

2-64172 x l0-.

I. x l0-r z4t9l

6.7197 x l0-.

l' x 10-6 9.648670 x r0.

0.3048, 1.2851 x l0-!

0.32383 tJ5582 4.6262 t.8tgtg x t0-l

2581 x t0-5

0.25E1 28316839 x 10.

7.48052 28.31684 2.7 t948 685.29 2.E692 x l0r 448.83 0.1 3368 6.573 x l0-'r

9.80665r 60r 3600.

2544.43 0.74624 0.t97 2.54.

ro.Jd / I lr x lOt 0.73756 2.20462 3412_l

lr x l0-!

0.45359237:

16.018 0.0160t8 6.894?3 x l0!

1.3562 x l0-r

1.3552 x l0-.

L997925 x l0r

3.280840 39.370t 35.3147 764.t't

l. x lOt 0.2248t 1.4498 x lO-.

5.626196 x l0-ra n<

10t6.

Fssss

ris si

*lN i \ s e

-ls

$s is

tt-S 8-

s-

rEK 103/3

-6-

Lr

.-r dI t*C

\J ,=

Jc)

IN

-i

.

..7 /-

oF LTQUTD

WATER

Temperature T,

"F

Viscosityf

y',

cP

Thermal

conductivityg &,

Btu/ft-h-"F

Densityg p,

lb/ft3

,1,=(y&)"'

32 40 50 60 70 80 90 100

t20

140 r60 r80 200 220 240 260 280 300

t.794 r.546

1.310 1.129 0.982 0.862 0.764 0.682 0.559 0.470 0.401 0.347 0.305 0.270 0.242 0.218 0.199 0.18s

0.320 0.326 0.333 0.340 0.346 0.352 0.358 0.36:2 0.371 0.378 0.384 0.388 0.392 0.394 0.396 0.396 0.396 0.396

62.42 62.43 62.42 62.37 62.30 62.22 62.11 62.00 6r.71 61.38 61.00 60.58 60.13 s9.63 59.10 58.53 57.94 57.31

1,410 1,590 1,810 2,050 2,290

\s30

2,780 3,020 3,530 4,030 4,530 5,020 5,500 5,960 6,420 6,830 7,210 7,510

f

From International critical Tables, vol. 5, McGraw-Hill Book company, New york, _1929, p. 10.

{ ^From

E

Schmidt and

w.

Seilschopp, Forsch. Geb- Ingenieurw.,3z277 (rg32).

$ Calculated from J. H- Kecnan

"nd

F.

G. Keyes, Thermodyumic properties ol steam,John wilcy

&

Sons-. Inc.. New york. _1937.

-8-

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