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(Pages:

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Name..................................

Reg ••.•..•.••..•...••.•,

.............

.

EIGHTH SEMESTER"B.TECH.

(ENGINEERING)

DEGREE

" "EXAMINATION, APRIL 2013

ME 09

SOl-REFRIGERATION

AND AIR CONDITIONING

(2009

Admissions)·

Three

Hours

Maximum:

70

Marks

Part

A

Short

Answer Questions. (One"! two sentence)

All questioTJ S are compulsory.

1.

Defineatonof

e f r i g e r a t i o n ~

. . ,

2. Whyis

it

necessaryto

p r c s s u r i z ~

the cabin

in

case

of air

refrigeration

system "

3.

What

are the parts

ora

simple

vapour

compressionrefrigeration

system?

4.

What

isdew

point

temperature?

5.

What

is the function

o

ashaft

seal in

a

refrigerant

o m p ~ e s s o r ?

(5

x

2

=10

marks>

Par tB

Analytical Problem solving questions.

Answer four

out of six.

6.

"The

COP ofan air remgeration

cycleisverylow.

but

still

air

refrigeration

system is o s t c o ~ m o n

inaircraft",discussthe statement. .

7.

Witha

neat sketch

1

explain

the

working

of

vortex

tube

refrigeration.system.

8. Withthe helpof aPsychrometr icchart·explainadiaba ticheath-tgand dehumidificationprocess.

9.

What

is.Bypassfactor?

Explain its s e f i I l ~ e s s

10.

What are h e f c t o r

to

be

consideredwhileselecting

the

condenserforarefrigeration

system?

11. Explainwhy a reciprocatingcompressor

cannot

be

u s ~ d

as a

vacuum

pump for

p r o d u ~ i n g

high

vacuum.

4x

5= 20

marks)

"Part C

Descrtptive! Analytical! Problem Solving Questions.

All

questions are compulsory.

MO ULE

I

12. (a)

Thecockpitofajet

plane flyingata

speed

of1200kmlhr. istobecooled

by

asimpleair cooling

system:"The cockpitis

to

be

maintained

at 25°C and pressure

in

the cockpit is 1

bar. The

.ambient

air pressure and temperature are

0.85

bar and

35°C respectively.

The other data

availableisas follows,

Turn" over

•

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2

C41682

·Cockpitcoolingload= 10TN.

MainCompressor

pressure

ratio

=

4;

Temperature

ofair leavingheat exchanger

and entering

coolingturbine:::60°C.

.

·

Pressure

drop

in

heat

exchanger

=

0.5bar.

Pressure

lossbetweencockpit

and

cooling

turbine =

0.2bar.

Assumingisentropicefficiencies of mainair compressor

and

cooler

turbine

as80

  ,

find

quantity

of air

passing

through the

cooling

turbine and .COP of

system.

  r

. .

12. (a) With

neat

sketch,

explain the

working

of

steam

jet

refrigeration

system

.

.MODULE

 

13. (a) BrieflyexplainLithium Bromideabsorptionsystem.

r

'(b) n ammonia

vapour

compressionrefrigeratingmachineworksbetweeD:

25°C and

- 200C. The

ammonia.eavesthe compressorin

dry

and saturated condition.Liquidammoniais.under

cooledto21.5°C,before·passing

through

throttle

valve.

The

averagespecific

heat of

liquid

·ammoniais4.75kJlkg_oC.

Find the

theoreticalCOP

ofthe

machine.

The

followingproperties

of NH3are

given.

Temperatures

iquid

Vapour

D

h

f

(kJlkg.)

  f

(kJlkg-k)

h

f

(kJlkg.)

  f

(kJlkg-k)

25

- 20

537 l>

328.4

4.612

3.854

1708.5

1661.0

H.5 14

9;118

  f

the

net refrigerationrequiredis400 x l0

3

kJlhr.

findthe massof ammoniacirculated/min.

AssumerelativeCOPis75

oftheoretical

COP.

MpDULE III

.14. (a) Onekg. of air at

400C

DBT

and

50 R.H.ismixedwith twokg.of air

at

20

D

CDBT

and

12°C

·dew-pointt e m p e r a t u r e ~ Calculate

the temperature

and specifichumidity ofthe mixture

..

r

(b).With neat sketch explain

summer

air conditioning

y s ~ : n : i

MODULE IV

· l5 .(a) Explainthe construction

and

workingof thermostaticexpansionvalve.

-

r

. (b) Brieflyexplaindifferenttypes

of rotary

compres$Ors.

(4x10'"'40marks)

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