Free Printable MCQ on RAC Section 1

1.

A reversible Carnot cycle used for refrigeration

comprises

a)

Two isentropic and two adiabatic processes

b)

Two isentropic and two constant volume processes

c)

Two isentropic and two constant pressure process

d)

Two isentropic and two isothermal processes

2.

In a typical system, within which component would the evaporation of refrigerant take place?

a)

Condenser

b)

Receiver dryer

c)

Evaporator

d)

Compressor

3.

Where does the low pressure liquid become a gas (vapour)?

a)

Evaporator

b)

Condenser

c)

TX valve

d)

Compressor

4.

In what state is the refrigerant when it exits the condenser?

a)

High pressure gas

b)

Low pressure gas

c)

High pressure liquid

d)

Low pressure liquid

5.

The two major functions of the compressor are to circulate refrigerant and to compress ____________.

a)

Low-pressure refrigerant vapor into hot, high temperature vapor

b)

High-pressure refrigerant vapor into high-temperature, low temperature liquid

c)

Low-pressure refrigerant liquid into hot, high temperature vapor

d)

Low-pressure refrigerant liquid into hot, high temperature liquid

6.

As refrigerant moves through the condenser it goes from _____ to ________

a)

a Vapor to a Liquid

b)

a Liquid to a Vapor

c)

Low pressure Vapor to a low pressure vapor

d)

High pressure liquid to a low pressure liquid

7.

_______ decrease the pressure inside the system.

a)

compressor

b)

condenser

c)

capillary tube

d)

evaporator

8.

In which type of air refrigeration system a secondary compressor is used?

a)

Reduced ambient type air refrigeration System

b)

Regenerative type air refrigeration System

c)

Simple air refrigeration System

d)

Boot strap air refrigeration System

9.

WHICH TYPE OF AIR COOLING SYSTEM IS USED FOR TRANSPORTATION?

a)

Boot strap air cooling system

b)

Reduced ambient air cooling system,

c)

Reduced aircraft air cooling system,

d)

Regenerative air cooling system.

10.

The COP of a refrigerator is 4. What will be the COP of a heat pump if it is working between same source and sink temperature ?

a)

2

b)

3

c)

4

d)

5

11.

The simple air cooling system is good for ---- flight speeds

a)

low

b)

high

c)

ground level

d)

sliding

12.

One tonne of refrigeration is equal to

a)

21 KJ/min

b)

210 KJ/min

c)

420 KJ/min

d)

620 KJ/min

13.

One tonne of refrigerating machine means that,

a)

One tonne is the total mass of the machine

b)

One tonne of refrigerant is used

c)

One tonne of water can be converted into ice.

d)

One tonne of ice when melts from and at 0^oC in 24 hours, the refrigerating effect produced is equivalent to 210 KJ/min

14.

In a refrigerating machine, heat rejected is ............ heat absorbed.

a)

Equal to

b)

Less than

c)

Greater than

d)

partially less than

15.

In air conditioning of aeroplanes, using air as refrigerant, the cycle used is

a)

Reversed Carnot cycle

b)

Reversed Joule cycle

c)

Reversed Brayton cycle

d)

Reversed Otto cycle

16.

The coefficient of performance is always.......one

a)

Equal to

b)

less than

c)

Greater than

d)

None of the above

17.

The sub-cooling in a refrigeration cycle ....

a)

Does not alter C.O.P.

b)

Increases C.O.P.

c)

Decreases C.O.P.

d)

None of the above

18.

In a refrigeration system, the expansion device is connected to

a)

(A) Compressor and condenser

b)

(B) Condenser and receiver

c)

(C) Receiver and evaporator

d)

(D) Evaporator and compressor

19.

The condition of refrigerant after passing through the condenser in a vapour compression system is

a)

(A) Saturated liquid

b)

(B) Wet vapour

c)

(C) Dry saturated vapour

d)

(D) Superheated vapour

20.

When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

a)

(A) Operating the machine at higher speeds

b)

(B) Operating the machine at lower speeds

c)

(C) Raising the higher temperature

d)

(D) Lowering the higher temperature

21.

The C.O.P. of a heat pump working on a reversed Carnot cycle is ( T₂- high temperature, T₁ - Low Temperature)

a)

(A) T₁/(T₂ - T₁)

b)

(B) (T₂ - T₁)/T₁

c)

(C) (T₁ - T₂)/T₁

d)

(D) T₂/(T₂ - T₁)

22.

A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)

a)

(A) 25 kJ/kg

b)

(B) 50 kJ/kg

c)

(C) 100 kJ/kg

d)

(D) 125 kJ/kg

23.

If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be

a)

(A) 0.2

b)

(B) 1.2

c)

(C) 5

d)

(D) 6

24.

A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be

a)

(A) 1 kW

b)

(B) 4 kW

c)

(C) 3 kW

d)

(D) 2 kW

25.

The highest temperature during the cycle,in a vapour compression system,occures after .......

a)

A.Compression

b)

B.Condensation

c)

C.Expansion

d)

C.Evaporation

26.

A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be

a)

(A) 1.33

b)

(B) 2.33

c)

(C) 3.33

d)

(D) 4.33

27.

Effect of superheating on COP is

a)

remains the same

b)

increases

c)

decreases

28.

What is Pressure and state of the refrigerant in the suction pipe?

a)

High pressure vapor

b)

Low pressure vapor

c)

Low pressure liquid

d)

High pressure liquid

29.

What are the 4 basic components of all refrigeration system?

a)

Fan motor, compressor, drain pan and condensor

b)

Condensor, compressor, metering device and filter dryer

c)

Evaporator, condensor, compressor and disconnect

d)

Evaporator, condenser, compressor and metering device

30.

In a typical system, within which component would the evaporation of refrigerant take place?

a)

Condenser

b)

Receiver dryer

c)

Evaporator

d)

Compressor

31.

In what part of a refrigeration system does the refrigerant change from a hot high pressure vapor to a hot high pressure liquid?

a)

Evaporator

b)

Condenser

c)

Liquid line

d)

Suction line

32.

A capillary tube serves the same purpose as a?

a)

small water line

b)

pressure relief line

c)

expansion valve

d)

bypass line

33.

In which direction does refrigerant flow during a normal cooling cycle?

a. compressor to condenser

b. compressor to evaporator

c. compressor to filter drier

d. compressor to exit of evaporator

a)

compressor to evaporator

b)

compressor to filter drier

c)

compressor to exit of evaporator

d)

compressor to condenser

34.

Below is the main component of refrigeration system EXCEPT:

a)

Compressor

b)

Evaporator

c)

Condenser

d)

Pump

35.

Below are the process in refrigeration system EXCEPT

a)

Compression

b)

Condensation

c)

Power

d)

Evaporation

36.

The Lowest temperature during the cycle,in a vapour compression system,occures after .......

a)

A.Compression

b)

B.Condensation

c)

C.Expansion valve

d)

C.Evaporation

37.

A boot-strap air cooling system has

a)

One heat exchanger

b)

Two heat exchanger

c)

Three heat exchanger

d)

Four heat exchanger

38.

ODP stands for

a)

Outdoor Dangerous Pollution

b)

Over Demanding Protocol

c)

Ozone Depletion Protocol

d)

Ozone Depletion Potential

39.

Which of the following refrigerants are phased-out due to Montreal protocol on ozone layer depletion-

a)

R11

b)

R21

c)

R12

d)

R32

40.

TEWI stands for

a)

Total Energy Work Interaction

b)

Total Equivalent Warming Index

c)

Total Equivalent Work Index

d)

Transfer of Energy With Intensity

41.

A refrigerant should have

a)

High ODP

b)

High GWP

c)

Low ODP

d)

Low GWP

42.

The chemical formula of refrigerant R11 is:

a)

CCl3F

b)

CClF3

c)

CClHF

d)

CHF

43.

The chemical formula of R141 is:

a)

C2H3ClF3

b)

C2H2Cl3F

c)

C2H3Cl2F

d)

C2H2ClF3

44.

Secondary refrigerants are also called as

a)

Coolers

b)

Brines

c)

Wines

d)

Synthetic Solutions

45.

Azeotropic mixtures are

a)

100 series

b)

500 series

c)

400 series

d)

1000 series

46.

Inorganic compounds are

a)

500 series

b)

200 series

c)

700 series

d)

1000 series

47.

The reference gas used in calculation of ODP is:

a)

CO2

b)

CFC

c)

NO2

d)

Hydrocarbons

48.

The reference gas used in calculation of GWP is:

a)

CFC

b)

Bromine

c)

CO2

d)

NH3

49.

R717 is refrigerant name for

a)

Water

b)

Carbon dioxide

c)

Ammonia

d)

Air

50.

For the refrigernat R134a, 'a' stands for:

a)

isomers

b)

Epimers

c)

isotopes

d)

Derivation

51.

Which of the following refrigerants is a blend?

a)

R-134a

b)

R-22

c)

R-410a

d)

none of the above

52.

Which of the following describes an azeotropic blend best?

a)

A mixture of two or more refrigerants that act as a single refrigerant.

b)

A mixture of three refrigerants that have a temperature glide.

c)

A mixture of compounds that result in fractionation.

d)

A single compound, HCFC refrigerant.

53.

In multi-stage systems

a)

The refrigerant used should have high critical temperature and low freezing point

b)

There is a possibility of migration of lubricating oil from one compressor to other

c)

Operating pressures can be too high or too low

d)

All of the above

54.

Refrigeration system with liquid subcooler is used to

a)

Prevent the entry of liquid into compressor

b)

Prevent flashing of refrigerant liquid ahead of low stage expansion device

c)

Reduce work of compression

d)

None of the above

55.

Ammonia is one of the oldest refrigerants, which is still used widely, because

a)

It offers excellent performance

b)

It is a natural refrigerant

c)

It is inexpensive

d)

All of the above

56.

CFC based refrigerants are being replaced as they are found to

a)

Cause ozone layer depletion

b)

Consume more energy

c)

React with several materials of construction

d)

Expensive

57.

Which of the following refrigerants replace R12 in domestic refrigerators?

a)

R22

b)

R11

c)

R134a

d)

R141b

58.

For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of

a)

copper

b)

aluminum

c)

steel

d)

brass

59.

The freon group of refrigerants are

a)

halo-carbon refrigerants

b)

azeotrope refrigerants

c)

inorganic refrigerants

d)

hydro-carbon refrigerants

60.

ODP value of R11 is

a)

0

b)

1

c)

2

d)

3

61.

In absorption refrigeration systems, the compressor of vapour compression systems is replaced by

a)

Absorber

b)

Generator

c)

Pump

d)

All of the above

62.

Which is the three fluid vapour absorption system ?

a)

Aqua-Ammonia

b)

LiBr-Aqua

c)

Electrolux

d)

Kelvinator

63.

In the Aqua-Ammonia vapour absorption system, which is used as absorbent

a)

Aqua

b)

Ammonia

c)

Air

d)

None of above

64.

In a three fluid vapour absorption refrigeration system, the hydrogen gas is used to

a)

Improve system performance

b)

Reduce the partial pressure of refrigerant in evaporator

c)

Circulate the refrigerant

d)

Provide a vapour seal

65.

In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively

a)

water and water

b)

water and lithium bromide

c)

ammonia and water

d)

ammonia and lithium bromide

66.

Compared to compression systems, absorption systems offer the benefits of

a)

Higher COPs

b)

Lower refrigeration temperatures

c)

Possibility of using low-grade energy sources

d)

All of the above

67.

Absorption of the refrigerant by the absorbent in a vapour absorption refrigeration system is accompanied by

a)

Absorption of heat

b)

Release of heat

c)

No thermal effects

d)

Reduction in volume

68.

Compared to compression systems, the performance of absorption systems

a)

Is very sensitive to evaporator temperature

b)

Is not sensitive to load variations

c)

Does depend very much on evaporator superheat

d)

All of the above

69.

Compared to compression systems, absorption systems

a)

Contain very few moving parts

b)

Offer less noise and vibration

c)

Are compact for large capacities

d)

All of above

70.

The ODP Value for R134a is

a)

0

b)

1

c)

2

d)

3

71.

Identify odd word

a)

R11

b)

R12

c)

R21

d)

R134a

72.

Identyfy odd word

a)

R500

b)

R717

c)

R118

d)

R744

73.

The refrigerant, commonly used in vapour absorption system is

a)

Ammonia

b)

Water

c)

Halocarbon

d)

Hydrocarbon

e)

Ammonia & Water

74.

When different temperatures are to be maintained at different points then_______evaporator system may be used

a)

Single

b)

Multiple

c)

Both

d)

None

75.

In a compound compression refrigeration system, the compression of refrigerant is carried out in ____ compressor

a)

Single

b)

Multiple

c)

Both

d)

None

76.

What is correct formula for calculating COP of heat pump?

a)

[COP]_{H. P.} = Q_H / W

b)

[COP]_{H. P.} = Q_L / W

c)

[COP]_{H. P.} = W / Q_H

d)

[COP]_{H. P.} = W / Q_L

77.

Co-efficient of performance of a Reversed Carnot cycle refrigerator working between higher temperature T2 and lower temperature T1

a)

(a) will increase with increase in T1 keeping T2 fixed

b)

(b) will decrease with increase in T1 keeping T2 fixed

c)

(c) will first increase with increase in T1 and then decrease with increase T1 keeping T2 fixed

d)

(d) None of the above

78.

Bell-Colemann cycle comprises

a)

(a) two isentropic processes and two adiabatic processes

b)

(b) two isentropic processes and two isothermal processes

c)

(c) two isentropic processes and two isobaric processes

d)

(d) two isentropic processes and two isochoric processes

79.

A Bell-Colemann cycle is

a)

(a) reversed Carnot Cycle

b)

(b) reversed Joule Cycle

c)

(c) reversed Rankine cycle

d)

(d) None of the above

80.

A reversible refrigerator working between two fixed temperatures

a)

(a) has the same COP whatever the working substance

b)

(b) has its COP increased for working substance with high enthalpy of evaporation

c)

(c) has its COP increased for working substance with higher specific heats

d)

(d) none of the above

81.

In a simple saturated vapour compression cycle, the refrigerant is in superheated condition

a)

(a) before entering compressor

b)

(b) before entering condenser

c)

(c) before entering throttle valve

d)

(d) before entering evaporator

82.

In vapour compression refrigeration cycle the following data is available Heat rejected in condenser = 65 KW Work done in compressor = 10 kw, then COP( refrigerator) is

a)

(a) 4.5

b)

(b) 5.5

c)

(c) 6.5

d)

(d) not possible to find with the given data

83.

During compression in a vapour compression cycle the refrigerant is super heated

a)

(a) C.O.P is reduced

b)

(b) C.O.P is increased

c)

(c) Work done is reduced

d)

(d) Refrigerating effect is reduced

84.

Heat is absorbed by a refrigerant, during a refrigeration cycle in a

a)

a) condenser

b)

b) evaporator

c)

c) compressor

d)

d) throttle valve

85.

The relative coefficient of performance is

a)

(a) actual COP/fheoretical COP

b)

(b) theoretical COP/actual COP

c)

(c) actual COP x theoretical COP

d)

(d) 1-actual COP x theoretical COP

e)

(e) 1-actual COP/fheoretical COP.

86.

In vapour compression cycle, the condition of refrigerant is saturated liquid

a)

(a) after passing through the condenser

b)

(b) before passing through the condenser

c)

(c) after passing through the expansion throttle valve

d)

(d) before entering the expansion valve

e)

(e) before entering the compressor.

87.

In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid

a)

(a) after passing through the condenser

b)

(b) before passing through the condenser

c)

(c) after passing through the expansion or throttle valve

d)

(d) before entering the expansion valve

e)

(e) before entering the compressor.

88.

Which component causes a pressure drop in the system?

a)

Condenser

b)

Suction Line

c)

Evaporator

d)

Metering Device

89.

What type of refrigerant is R134a?

a)

CFC

b)

HCFC

c)

HSBC

d)

HFC

90.

Air refrigerator works on......

a)

A. Carnot cycle

b)

B.Rankine cycle

c)

C.Reversed carnot cycle

d)

D.Bell-Coleman cycle

e)

E.Both C and D

91.

Which of the following refrigerants is a CFC-type refrigerant?

a)

R-22

b)

R-123

c)

R-134a

d)

R-12

92.

Which of the following refers to the term C.O.P. of refrigeration?

a)

a) Cooling for Performance

b)

b) Coefficient of Performance

c)

c) Capacity of Performance

d)

d) Co-efficient of Plant

93.

In lithium bromide absorption refrigeration system it is not necessary to keep the refrigeration temperature above 0°C.

a)

False

b)

True

94.

Which of the following is the common application of Air standard refrigeration system?

a)

Cold storage

b)

Car air conditioning system

c)

Domestic refrigerators

d)

Aircraft air conditioning

95.

Which of the following type of refrigerants take a direct part in the refrigeration system?

a)

Primary

b)

Secondary

c)

Tertiary

d)

Mixed

96.

Which of these refrigerants is highly flammable and toxic?

a)

R-12

b)

Sulphur dioxide

c)

Carbon dioxide

d)

Ammonia

97.

Freon group of refrigerants are

a)

Inflammable

b)

Toxic

c)

Non-inflammable and toxic

d)

Nontoxic and non-inflammable

98.

The boiling point of ammonia is

a)

-10.5°C

b)

-50°C

c)

-33.3°C

d)

-77.7°C

99.

For obtaining high COP, the pressure range of compressor should be

a)

High

b)

Low

c)

Optimum

d)

Any value

100.

The COP of a vapour compression plant in comparison to vapour absorption plant is

a)

More

b)

Less

c)

Same

d)

More/less depending on size of plant

101.

The fluids used in Electrolux refrigerator are

a)

Water and hydrogen

b)

Ammonia and hydrogen

c)

Ammonia, water and hydrogen

d)

None of these

102.

The moisture in a refrigerant is removed by

a)

Evaporator

b)

Safety relief valve

c)

Dehumidifier

d)

Driers

103.

At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant

a)

Decreases

b)

Increases

c)

Remain same

d)

Depends on other factors

104.

The reduced ambient air cooling system has

a)

One cooling turbine and one heat exchanger

b)

One cooling turbine and two heat exchangers

c)

Two cooling turbines and one heat exchanger

d)

Two cooling turbines and two heat exchangers

105.

Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.

a)

Equalize

b)

Reduce

c)

Increase

d)

None of these

106.

Pick up the wrong statement. A refrigerant should have

a)

Low specific heat of liquid

b)

High boiling point

c)

High latent heat of vaporisation

d)

Higher critical temperatur

107.

In a pressure enthalpy chart, the space to the left of the saturated liquid line represents

a)

Wet vapour region

b)

Superheated vapour region

c)

Sub-cooled liquid region

d)

None of these

108.

In a bootstrap air evaporative cooling system, the evaporator is provided

a)

Between the combustion chamber and the first heat exchanger

b)

Between the first heat exchanger and the secondary compressor

c)

Between the secondary compressor and the second heat exchanger

d)

Between the second heat exchanger and the cooling turbine

109.

Carbon dioxide is

a)

Colourless

b)

Odourless

c)

Non-flammable

d)

All of these

110.

On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process

a)

Involves no change in volume

b)

Takes place at constant temperature

c)

Takes place at constant entropy

d)

Takes place at constant pressure

111.

Most thermostatic expansion valves are set for a superheat of

a)

5°C

b)

10°C

c)

15°C

d)

20°C

MCQ on RAC Section 1

Total questions: 111

Worksheet time: 4hrs 42mins

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