7/21/2019 GE1003

1/3

THE

II\STTTUTION

OF ENGINEERS

SRI

LAI{KA

ENGINEtrRTNG

CERTIFICATE

COURSE

STAGB

I

G81003

-

Thermodynamics

and

Fluid

Mechanics

DATE:

FROM:

0900IIRS

ru 1200HRS

DURATION:

TIIREE

IIOURS

READ

THE

FOLLOWING

INSTRUCTIONS

CAREFULLY

BBFORE

ANSWERING

THE

QUESTION

PAPER

Answer

only five

(05)

questions

and all

questions

carry equal

marks.

Wherever

appropriate,

use

tables and

charts

available

in

the in

the examination

hall.

At

the

end

of

the

examination

return

all

such

material

to

the

exa miner/supervisor.

3 Any missing

data can

be sensibly

and

reasonably

assumed,

but

state such

assumptions

clearly with

justifications.

Any

result

from

calculations

should

have

units,

unless they

are dimensionless.

All answers

to

the

given

questions

should

be underlined

for

the

purpose

of

easy

identification.

write

the

question

Number

to

which

you

answer

on the

cover

page

appropriately.

Assume

density

of water

is

1000kg/m3

and

acceleration

due to

gravity

is 10m/s2

wherever

relavant.

L

2

4

5

7/21/2019 GE1003

2/3

1

a Explain

non

flow

process .

b

Name

three

thermodynamic

non

flow

processes.

c

ln

a

system

executing

a non flow

process,

the

work

and heat

transfer

are

given

by

#

=

*ul

/

C

and#

=

*kl

/ c

respectivety.

The

temperature

of

the system increases

from

150oC

to

300 C.

Find

the

change

in internal

energy.

2

a

State

the

second

law of

thermodynamics.

b

Draw

a

p-v

diagram for

Carnot

cycle and

name

each

process

of the

cycle.

c

A

Carnot

engine works

between

temperature

limits

of

825oC

and

125 C. The

engine

receives

3600kJ of heat

per

minute.

Determine

the

power

of

the

engine

and

the amount of heat

rejected

to the

sink.

Efficiency of Carnot cycle

is

given

as

,-=t-b

T7

where

Tris

the

upper

limit

temperature

and Tris

the lower

limit

temperature.

3 a

Draw

a

p-v

diagram

for Otto

cycle

and identify

each

process.

b

Name

the

four

processes

in

the Otto

cycle.

c

An engine

working

on ideal

Otto cycle has

temperature

and

pressure

at

the beginning

of compression

as 25oC

and

1.Sbar respectively.

-

Find

the

compression

ratio

(r)

if

y

is

7.4 and

thermal efficiency (4)

is

48%. Also

find

the temperature

and

pressure

at,the

end of

compression.

You may

use

the following equation if necessary.

rl

=

L- .l:

r0-r)

4 a

State the

difference

between intensive

properties

and

extensive

properties

of a

pure

substance.

b

Define

the term

specific

heat of

a

substance.

c

A

piece

of iron

ball

of mass

5kg

is heated

to

'105oC

and

dropped into

a

vessel

containing 25kg

of

water

at

20 C.

What

is

the specific

heat of

iron, if

the

rise

in

temperature

of

water be

3.6oC

? Specific

heat of

water

is

4.193 kJ/kg

K,

d Three

pipes

discharge water into

the

same

main,

one supplying

0.75

m'/min

at

82oC, the

second

pipe

1.35m3/min

at 7 C

and

the third

0.06

m3/min

at 100'C.

Find

the final temperature

of

the water

mixture

assuming

specific heat

of

water

to

be constant.

5 a

What

will

be the

gauge

pressure

and

absolute

pressure

of water at

7/21/2019 GE1003

3/3

depth

12m

below

the

surface?

pwarcr

=

1000

kg/m3,

and

atmospheric

pressure

=

101kpa.

A

cube

with

100

mm

each side

is made

of

a rigid

foam

material

and

floats

in water

with

60mm

below

the

free

surface

of water.

calculate

the

magnitude

and

direction

of

the

force

required

to hold

it

completely

submerged

in

glycerine

which

has

a

specific gravity

of

1.26.

Name

the flow

measuring

devices

that

can

be

used

to

measure

velocity, discharge

and

pressure

of a fluid

flow

stream.

A

u

tube mercury

differential

manometer

has

been

used

to

measure

the

pressure

differential

across

the inlet

and

throat

of

a

venturimeter

that

conveys

water

as shown

in

figure

Q6.Calculate

the

pressure

difference

when

manometer

reads

250mm:

Figure

Q6

The

velocity

components

in a

two dimensional

incompressible

flow

field

are

expressed

as

y3

,=T*2x-x,y

^-3

^L

'U=Xyz-2v--

3

Determine

the

velocity

at

point

x=1m,y=3m.

ls

the flow

physically

possible?

lf

so

find

the

stream

function.

Calculate

the discharge

between

the streamlines

passing

through

(1,3)

and

(2,3).

Show

that

the flow is

irrotational

and find

the

potential

function.

State

Darcy

formula

with

usual notations.

Two

pipes

of diameter

50mm and

100mm

,

each of length 100m

are

connected

in

parallel

between

two reservoirs

which have

a

difference

of

level

of 10m.

If

the coetficient

of

friction

(f)

for

each

pipe

is

f

=

0.08,

calculate

the rate

of

flow

for

each

pipe

considering

only

the

friction

loss.

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