REFRIGERATION AND AIR CONDITIONING THEORY SEMESTER-II JULY2016

REFRIGERATION AND AIR CONDITIONING THEORY SEMESTER-II JULY2016

1. The compressor motor in

a hermetically sealed compressor

 is cooled by ............

a) Water

b) Air

c) Refrigerant

d) Nitrogen

Answer:- b) Air

2. The screw compressors can be

used for wet compression with

refrigerant -
a)  R134a

b)  R12

c)  NH3

d)  Water

Answer:- c)  NH3

3. For large capacity and high

volume flow rate the suitable

compressor is ............
a)  Centrifugal

b)  Reciprocating      

c)  Screw

d)   Scroll

Answer:- a)  Centrifugal

4. The main components of a

centrifugal compressor are .....

a)  Eye

b)  Impeller

c)  Diffuser

d)  Both (a) & (b)

Answer:- d)  Both (a) & (b)

5. The slip in case of three

phase induction motor is in

the range of.........

a) 0.5% to 5%

b) 2% to 10%

c) 10% to 15%

d) 15% to 20%

Answer:- a) 0.5% to 5%

6. High starling torque induction

motors for compressors are

used with .............

a)  Capillary tube      

b)  Condenser

c)  Float valves

d)  None of these

Answer:- d) None of these

7. The relationship between

rotor speed 'N' frequency 'F'and no.

of poles 'P' is given by
the relation ...........

a)  N=120t7P

b)  PN=120/f

c)  f=120N/P

d)  N=l20P/f

Answer:- a)  N=120t7P

8. The function of condenser

 in a refrigeration system is ..........

a) To cool surrounding air

b) To cool products or space

c) To condense the superheated

vapor refrigerant discharged by

the compressor

d) To condense the refrigerant

vapour entering the compressor

Answer:- c) To condense the superheated

vapor refrigerant discharged by

the compressor

9. Domestic refrigeration work on .....

a) Vapour compression cycle

b) Vapour absorption

c) Otto cycle

d) None of these

Answer:- a) Vapour compression cycle

10. Liquid receiver is installed in -

a) Suction line

b) Discharge line

c) Liquid line

d) Expansion line

Answer:- c) Liquid line

11. The efficiency of a water cooled

condenser is ......

a) Lower than the air cooled condenser

b) Same as that of air cooled condenser
c) Higher than the air cooled condenser     

d) None of these

Answer:- c) Higher than the air cooled condenser

12. The function of drier in a refrigeration

system is to ............
a) Separate lubricant from the refrigerant
b) Remove the moisture from the refrigerant

c) To maintain the level of the liquid

     refrigerant in the system

d) Help in dry compression of the refrigerant

Answer:- b) Remove the moisture from the refrigerant

13.     The dry compression can be

avoided by installing -

a) Liquid suction heat exchanger

b) Accumulator

c) Thermostatic expansion valve

d) All of these methods can be used

Answer:- d) All of these methods can be used

14.     The length and diameter of

           capillary tube are -

a) Small

b) Large

c) Small and large respectively

d) Long and small

Answer:- d) Long and small

15. The expansion valve used in

central air-conditioning plant

should be

a) Capillary tube

b) Thermostatic expansion valv

c) Automatic expansion valve

d) Low side float valve

Answer:- b) Thermostatic expansion valv

16. The drawback of automatic

expansion valve is ............

a) Increase in load increases the

mass flow rate

b) Increase in load decreases

mass flow rate

c) Not suitable for varying load

d) Both (a) and (c)

Answer:- d) Both (a) and (c)

17. During expansion in capillary tube

enthalpy ........

a) Increase

b) Decrease

c) Not change

d)  None of these

Answer:- c) Not change

18. Temporary fastening done by

help of..............

a) Welding

b) Brazing

c) Soldering

d) Rivet

Answer:- d) Rivet

19. The power consumption of a

1TR window AC is in the

range of..........

a)   1 to 1.5 kW

b)  1.5 to 2 kW

c)  2kW to2.5kW

d)  3to3.5kW

Answer:- c)2kW to2.5kW

20. Superheating in evaporator

causes ...........

a) Capacity to increase

b) Compressor power consumption to

c) COP to increase only

d) Both (a) and (b)

Answer:- b) Compressor power consumption to

21. The HFC refrigerants have ........

a)  Low ODP value

b)  High OPD

c)  Low GWP

d)  Zero ODP

Answer:- d)  Zero ODP

22. The HCFC refrigerant is -

a)  R12

b)  R22

c)  R134a

d)  R600

Answer:- b)  R22

23. The HFC refrigerant is -

a) RH

b) R22

c) R134a

d)  R290

Answer:- c) R!34a

24. The main drawback of HC

refrigerants is their

a) High ODP

b) High GWP

c) Flammability

d) High GWP and Flammability

Answer:- c) Flammability

25. The alternate refrigerant for

R l 1 is ...........

a)  R22

b)  R123

c)  R134a

d)  R125

Answer:- b)  R123

26. Window AC for cooling can be

easily converted to heating mode

by installing a .........
a) Two way reversing valve

b) Four way reversing valve

c) Throttle valve

d) Three way valve

Answer:- b) Four way reversing valve

27. Brine is a solution of .........

a) Ice and water

b) water and sodium chloride

c) Water and acid

d) None of these

Answer:- b) water and sodium chloride

28. In the condenser, the

refrigerant first loses its ........

a) Latent heat

b) Sensible heat

c) Sometimes sensible and

sometimes latent heat

d) None of these

Answer:- b) Sensible heat

29. The pipe line pressure drops

 in split AC are more compared to

window AC because of-

a) Long length of suction and

discharge lines

b) Two units i.e. indoor and

    outdoor units

c) Long length of discharge and

     liquid line

d) Long lengths of suction and

     liquid lines

Answer:- d) Long lengths of suction and

     liquid lines

30. The lubricating oil used with

     R134a is ..........

a) Mineral Oil

b) Polyol Ester

c) Polyglycol

d) None of these

Answer:- b) Polyol Ester

31. PUF stands ior ...........

a) Poly user foam

b) Poly urea foam

c) Polyurethane foam

d) Polyurea urethane foam

Answer:- c) Polyurethane foam

32. Refrigerant R134a..........

a) Is Non flammable

b) is Flammable      

c) Has Low GWP    

d) Low ODP

Answer:- a) Is Non flammable

33. In a split AC the indoor

unit comprises of .......

a) Evaporator and blower

b) Evaporator coil, blower and

    capillary tube

c) Evaporator coil, blower and motor,

    air filter, control panel, supply and

     return air grills

d) Evaporator coil, air filter, control

     panel, supply and return air grills,

     capillary tube

Answer:- c) Evaporator coil, blower and motor,

    air filter, control panel, supply and

     return air grills

34. Hissing or gurgling noise is

produced from at the exit of-

a) Evaporator

b) Compressor

c) Capillary tube     

d) Condenser

Answer:- c) Capillary tube

35. The compressor of the car

Air-conditioning system gets

the drive from ............

a) Solar panels

 b) Car battery

c) Generator of car   

d)  l.C. engine shaft

Answer:- d)  l.C. engine shaft

36. The condenser of a car AC is .......

a) Water cooled       

b) Air cooled

c) Evaporative type  

d) None of these

Answer:- b) Air cooled

37. The drier filter of a window

AC is installed in ........

a) Suction line

b) Discharge line     

c) Liquid line

d) Expansion

Answer:- c) Liquid line

38. The heal rejection capacity

of the condenser should be .........

a) Same as that of cooling capacity

b)  Higher than cooling capacity

c) Lower than cooling capacity

d) Same that of compressor cooling

capacity

Answer:- b)  Higher than cooling capacity

39. The upcoming alternative

refrigerant to be used in car air-

conditioning system is...........
a) R134a

b) RI234yf

c) R1234ze

d) R764

Answer:- b) RI234yf

40. The pressure testing of the

following equipment in the

plant is not necessary ............

a) Compressor

b) Evaporator

c) Condenser

d) None of these

Answer:- a) Compressor

41. The azeotropic refrigerant  is ......

at R407C

b) R410A

c) R7I7

d) R502

Answer:- d) R502

42. The refrigerant leaves the

condenser as ............

a) High pressure saturated liquid

b) Low pressure saturated liquid

c) High pressure high temperature  

    saturated liquid

d) Low pressure high temperature

    saturated liquid

Answer:- c) High pressure high temperature  

    saturated liquid

43. The thickness of fins used on

condenser coil of a window AC

 is about ..........
a) 0.5 cm

b) 0.2 nun

c) 0.2 cm

d) 0.5

Answer:- b) 0.2 nun

44. A loss in vacuum after 24 hours

in standing vacuum test indicates
a) The presence of moisture

b) Leak in the system

c) Both (a) & (b)

d) None of these

Answer:- c) Both (a) & (b)

 45.High pressure cut out is used

with......

a) Condenser

b) Evaporator

c) Compressor

d) Expansion valve

Answer:- c) Compressor

46. The lowest temperature with

liquid refrigerant in a vapour

compression refrigeration
system occurs after -

a) Compression     

 b) Condensation     

c) Evaporation       

d) Expansion

Answer:- d) Expansion

47. A thermostatic expansion

valve is used with

a) Window air-conditioner

 b) Split Air-conditioner

C) Central Air-conditioning plant

d) None of these

Answer:- C) Central Air-conditioning plant

48. The capacity of a refrigeration

plant is measured in .........
a) Litres

b) Metric     

c) TR

d) Tonnes

Answer:- c) TR

49. This is a pari of Vapour compression

system ......

a) Absorber

b) Pump

c) Compressor       

d) Turbine

Answer:- c) Compressor

50. Undercharging a system ........

a) Increases COP

b) Reduces COP

C) COP remains constant

d) None ol these

Answer:- b) Reduces COP