Friday 10 May 2019

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

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