1.

One ton refrigeration is equal to

210 kJ/minute
2000 kg
3.5 kJ/h
4.186 kJ/h

2.

The ambient air temperature is 10 ºC. Which of the following process is called refrigeration?

Cooling of warm air from 30 ºC to 10 ºC
Cooling of the air from 10 ºC to 5 ºC
Changing the temperature from 10 ºC to 22 ºC
None of the above.

3.

Which of the following statement is true for evaporative cooling of air using water?

It is an adiabatic process.
Enthalpy of air during evaporative cooling of air increases.
The air can be cooled up to dry bulb temperature of the air.
Relative humidity of air does not change during the process

4.

Air conditioning for human comfort refers the

Control of only relative humidity.
Control of dry bulb temperature of the air.
Control of purity of air.
Control of temperature, relative humidity and quality of air along with proper distribution of the air.

5.

The cooling capacity of refrigeration system is expressed as

Ton of refrigeration
kJ of work consumed per hour
Amount of water cooled
Amount of ice produced per hour

6.

The component of vapour compression refrigeration system where the actual cooling takes place is known as

Receiver
Evaporator
Condenser
Expansion valve

7.

The purpose of compressor in vapour compression refrigeration system is

To evaporate the refrigerant.
To increase the pressure of the vapour refrigerant.
To condense the refrigerant.
None of the above.

8.

Heat removed at the condenser of a vapour compression refrigeration system is equal to the

Refrigeration effect produced, R
Work of compression, W
R+W
½ (R+W)

9.

Which of the following is primary refrigerant?

Water
Brine solution
Refrigerant-22
Glycol

10.

The C.O.P. of vapour compression refrigeration system is defined as

Ratio of refrigerating effect produced to the work of compression.
Refrigerating effect plus work of compression.
Ratio of power used to the cooling effect.
Ton of refrigeration produced per day.

11.

The unit of enthalpy in SI system is

kJ/kg K
kJ/h K
kcal/kg
kJ/kg

12.

As the pressure of refrigerant at evaporator increases, the boiling point of the refrigerant

increases
decreases.
remains constant.
none of the above.

13.

As the suction pressure decreases, the specific volume of the refrigerant

increases
decreases
does not change
none of the above.

14.

An Approximate value of suction pressure of vapour compression refrigeration plant to get -18 ºC evaporating temperature in ammonia plant will be

15 bar
7 bar
0 bar
2 bar

15.

Which of the following statement is true for vapour compression refrigeration system?

(A) Refrigerating effect per kg of refrigerant is always equal to latent heat of evaporation.
(B) Refrigerating effect is usually less than the latent heat of evaporation.
Refrigerating effect is equal to work of compression.
Refrigerating effect does not depend on the evaporating temperature of the system.

16.

Which of the following is not desirable for vapour compression refrigeration system?

Sub-cooling of refrigerant
Higher condensing pressure
Higher suction pressure
Lower condensing pressure.

17. Multi-stage vapour compression refrigeration system is employed when
COP is higher.
Compression ration is more than 7.
Compression ratio is less than 4.
Evaporating temperature is higher.

18.

The approximate TR of the refrigeration plant required for milk bulk cooler having capacity of 5000 liter per day is

2.5 TR
3.5 TR
15 TR
50 TR

19.

Excessive super heating of suction vapour is not desirable because

it increases mass flow rate of the refrigerant in the system.
it increases temperature of gas leaving the compressor.
it decreases the specific volume of the refrigerant.
it reduces refrigerating effect.

20. The condensing pressure depends on
Evaporating temperature
Temperature of condensing medium.
Temperature of condensing medium and the rate of heat transfer at the condenser.
Extent of sub-cooling.

21.

Higher evaporating temperature is desirable in vapour compression refrigeration system because

It gives sub-cooling.
It gives higher COP.
It gives lower condensing pressure.
In the system, there is no superheating possible.

22. Which of the following leads to lower suction pressure?
Blockage of expansion valve.
Excessive cooling load on evaporator.
Super heating of suction gas.
High rate of heat transfer in the evaporator.

23.

Which of the following is desirable for the refrigeration plant?

Higher condensing pressure.
Lower condensing pressure.
Excessive super heating of suction gas.
Higher temperature of cooling medium for condenser.

24.

Sub-cooling increases

Refrigerating effect of refrigerant.
Work of compression.
Increases mass flow required in the system.
Volume of the refrigerant.

25. Operation of refrigeration plant during night time is desirable because
It gives higher suction pressure.
It improves COP of the system.
It gives lower suction temperature.
No electricity needed during night time.

26.

Relative COP is defined as the ratio of actual COP to the

Refrigerating effect.
Theoretical COP.
Work of compression.
Carnot COP.

27.

During compression of refrigerant,

Entropy remains constant.
Enthalpy does not change.
Temperature remains constant.
Specific volume remains constant.

28.

Heat removed at the condenser is always

Equal to work of compression.
Equal to refrigerating effect.
Higher than refrigerating effect.
Lower than refrigerating effect.

29.

Carnot COP is always

None of the above.
Double than the actual COP.
Equal to actual COP
Lower than the actual COP.

30. Operation of refrigeration plant during night time is desirable because
It gives higher suction pressure.
It improves COP of the system.
It gives lower suction temperature.
No electricity needed during night time.

31.

Which of the following variable does not change during compression?

(D) temperature
Entropy
Pressure
Enthalpy

32.

What is the work of compression of 35 TR refrigeration plant which operates with COP of 3.5?

3.5 kJ/minute
35 kW
122.5 kJ/minute
2100 kJ/minute

33.

What is the mass flow rate of refrigerant required for 100 TR plant, if the refrigerating effect at the operating evaporating temperature is 1000 kJ/kg?

0.35 kg/s
350 kg/s
100 kg/s
3.5 kg/s

34. Which of the following enthalpy value can not be obtained from refrigerant properties table?
Enthalpy of sub-cooled liquid refrigerant.
Enthalpy of saturated liquid
Enthalpy of saturated vapour
Enthalpy of vapour refrigerant after compression

35.

Which of the following is the unit of specific heat?

kJ/kg K
kJ/h K
kJ/kg
none of the above

36. Example of Secondary Refrigerant is
Water
Halocarbon
Hydrocarbon
Ammonia

37. Dielectric strength is a desirable characteristic in refrigerant for use in
Open type compressor
Screw Compressor
Hermetic compressor
Centrifugal compressor

38. Cylinder color code for Ammonia is
Organge
Silver
Green
White

39. Numbering system for Saturated Hydro-carbon refrigerants is
R( carbon atoms +1)(hydrogen atoms-1)fluorine atoms
R(carbon atoms+1) (hydrogen atoms+1) fluorine atoms
R( hydrogen atoms-1)(Carbon atoms-1) fluorine atoms
R(carbon atoms-1)(hydrogen atoms+1)fluorine atoms

40. Azeotrope refrigerants are
Inorganic refrigerants
Saturated compounds
Mixture of refrigerants which do not separate in to their components
Saturated hydro-carbons

41. Boiling point of Ammonia at atmospheric condition is
Minus 10 ?C
Minus 29.8 ?C
Minus 33 ?C
Minus 41.3 ?C

42. Ammonia can be detected by use of
Halide torch
Burning Halogen stick
Burning Sulphur stick
Soap bubble

43. Boiling point of R-22 at atmospheric condition is
Minus 29.8 ?C
Minus 10 ?C
Minus 33 ?C
Minus 41. ?C

44. As per Montreal Protocol of phasing out of HCFC refrigerants, the phase out year for Developing countries is
2010
2020
2030
2040

45. Refrigerant with highest latent heat/kg among the following is
R-717
R-11
R-22
R-13a

46.

Which of the following method is used for the lubrication of very large capacity reciprocating compressor?

Splash lubrication.
Forced lubrication.
Using grease gun.
Manual lubrication.

47.

Which of the following has adverse effect on the volumetric efficiency of reciprocating compressor?

Lower suction pressure.
Higher suction pressure.
Lower discharge pressure.
Sub-cooling of liquid refrigerant.

48.

Which is the type of compressor used in domestic refrigerator?

Screw compressor.
Hermetically sealed compressor.
Open type reciprocating compressor.
None of the above.

49.

The purpose of shaft seal is to

minimize friction in the shaft.
improve volumetric efficiency
reduce compressor head cooling.
prevent leakage of refrigerant and oil.

50.

Centrifugal compressors are not used in our country because they

handle less quantity of refrigerant.
require heavy maintenance.
can not develop required compression ratio.
consume more power.

51. Which of the following statement it true for the screw compressor?
It consumes slightly less electrical power than the reciprocating compressor.
It consumes more electrical power than the reciprocating compressor.
It requires more maintenance.
Capacity control is difficult.

52.

Which of the following is true for screw compressor?

It is non-positive displacement type.
It is positive displacement type.
It has more spare parts than reciprocating compressor.
It can not be used with ammonia refrigerant.

53.

Compression ratio is equal to

Absolute discharge pressure divided by absolute suction pressure.
discharge pressure minus suction pressure.
Suction pressure divided by discharge pressure.
Absolute suction pressure plus discharge pressure.

54.

Which of the following statement is true for the rotary compressor?

It is used in large capacity plants.
It is non-positive type compressor.
It gives very high COP.
It is positive displacement type compressor.

55.

The capacity of compressor is expressed as

TR
Stoke length
Volume of gas handled
Volumetric efficiency.

56.

The unit to express the capacity of cooling tower is

kJ/h
kg/h
kg/ ºC
kJ/kg K

57.

Which of the following type of condenser is used in domestic refrigerator?

Evaporative condenser
Water cooled condenser
Mechanical draft air cooled condenser
Natural draft air cooled condenser.

58. Which of the following is true for the condenser?
It rejects heat from the system.
The performance of air cooled condenser is better than the water cooled condenser.
Evaporative condenser does not require air.
Higher temperature of water for the condenser is desirable.

59.

Which of the following statement is true for the air when the air passes through the evaporative condenser?

It is an adiabatic process
Enthalpy of the air decreases.
Enthalpy of the air remains constant.
Enthalpy of the air increases.

60.

Soft water is used in the water cooled condenser to

Reduce scale formation on heat transfer area.
Reduce super heating of the refrigerant.
Control suction pressure of the system.
Eliminate the need for oil separator.

61.

The lowest temperature which can be attained in cooling of water in cooling tower is

Equal to dry bulb temperature of the air.
Equal to wet bulb temperature of the air.
Equal to condensing temperature of refrigerant in receiver.
Little less than dry bulb temperature of the air.

62.

The temperature difference between the temperature of water leaving the cooling tower and the wbt of the air is called

Cooling tower approach
Wet bulb depression
Cooling tower range
Cooling tower efficiency.

63.

The efficiency of cooling tower is 100 % when water is cooled to

20 ºC.
dbt of the air.
wbt of the air.
0 ºC

64.

The unit of cooling tower capacity is

kg/h.
kJ/h.
kJ/h ºC.
kJ/h K.

65.

Specific heat of water is

1.0 kJ/kg K.
3.86 kcal/kg ºC.
0.24 kJ/kg K
4.186 kJ/kg K.

66. Capacity of receiver employed in the vapour compression refrigeration system
is three times more than the mass flow rate in the system.
is equal to mass flow rate of refrigerant in the system.
is higher than the total quantity of refrigerant present in the system.
is 1/3 of the mass flow rate of refrigerant in the system.

67.

Dry type evaporator is provided with

high pressure float valve.
low pressure float valve.
hand expansion valve.
thermostatic expansion valve.

68.

The material of pipeline commonly used in small capacity R-22 plant is

copper
stainless steel.
iron
cast iron

69.

Capillary is used as expansion valve in

very small capacity plants.
systems in which cooling load varies heavily.
flooded evaporator.
ammonia plant.

70.

What is the name of expansion valve in which the valve opening varies depending on the super heat at the end of evaporator?

Automatic expansion valve.
Capillary type expansion valve
Thermostatic expansion valve
High pressure float valve.

71.

Which of the following could be the reason for operation of low pressure switch?

Very low rate of heat transfer at condenser
High evaporator load
Lack/insufficient of cooling medium to condenser
Blockage of expansion valve

72.

Which of the following is not the reason for the operation of HP cut out?

Lack of cooling medium at condenser
Presence of non-condensable gases in the system
High level of scale deposit in water cooled condenser of the plant
Low evaporator load

73.

Thermostat is set at cut out temperature of 5 °C and differential setting of 2°C. What is cut in temperature of the plant?

2°C
3°C
7°C
None of the above

74.

The function of permanent magnet provided in thermostat is

To prevent spark problem.
To reduce power requirement.
To work as capacitor.
Increase the range

75.

HP witch is a

Safety device.
An over load protector.
Temperature operated switch
Remote controller of the system.

76.

In which of the following evaporator, defrosting is not required.

Evaporator of ice – cream cold storage
Evaporator of air condition room
Evaporator of milk cold storage
Evaporator of refrigerator

77.

The purpose of defrosting is to

Increase the rate of heat transfer
Achieve sub-cooling
Prevent super heating
Operate solenoid valve

78.

In which of the following, water defrosting can be used?

refrigerator
air conditioner
ice-plant
Butter cold storage

79.

Which of the following is used in hot gas defrosting,

Air
Nitrogen
Refrigerant
Steam

80.

The frequency of defrosting needed for milk cold storage is about

One week
One month.
Every day
Once in year.

81.

One ton refrigeration is equal to

210 kJ/min.
210 kJ/s
12000 kJ/s
50 kJ/h

82.

In multi evaporator system, the mass flow rate of each evaporator

decided by temperature of gas leaving the compressor.
decided by specific volume of suction gas.
depends on capacity of each evaporator.
vary with type of condenser.

83.

Removal of flash vapour by flash chamber

helps in removal of water vapour.
decreases mass flow rate of refrigerant in the evaporator.
helps in sub-cooling.
increases COP

84.

In multi-evaporator with single compressor system, heat and mass balance equation is used to find

enthalpy of liquid entering in the evaporator.
dryness fraction of refrigerant.
enthalpy of gas leaving compressor.
enthalpy of suction vapour.

85.

The temperature of gas leaving the multi-compression system is

equal to evaporating temperature.
higher as compared to single compression system.
equal to condensing temperature.
less as compared to single compression system.

86.

Which of the following is true for dual compressor?

It is centrifugal compressor
It pumps vapour from two different evaporators having different pressure
It pumps vapour from single evaporator.
It pumps vapour from two different evaporators having same pressure.

87.

Which of the following is not commonly used in vapour compression refrigeration system employed in India?

screw compressor
Multi-cylinder reciprocating compressor.
reciprocating compressor
dual compressor

88.

Mass of vapour produced after expansion can be calculated by knowing

Extent of sub-cooling.
COP of the system.
Super heating of suction gas.
Dryness fraction of refrigerant.

89.
zero
1
5
7

90.

Dual compressor is

Rotary compressor
Centrifugal compressor
Reciprocating compressor
Screw compressor.

91.

Flash chamber helps in

Sub-cooling of liquid refrigerant.
Improving COP.
Reducing work of compression
Reducing mass flow rate of refrigerant entering in evaporator.

92.

Which of the following is true for multi-evaporator system?

Control is easier than single evaporator system.
It is required to meet the need of industry.
It improves COP of the system.
It does not need receiver in the system.

93.

Inter-cooling results in

Increasing COP of the plant.
Improving refrigerating effect.
Sub-cooling liquid refrigerant.
Reducing temperature of gas leaving the higher stage compressor.

94.

The amount of refrigerant required for flash inter cooling can be estimated by

Specific volume of refrigerant.
Heat and mass balance equation.
Using second law of thermodynamics.
Dryness fraction of refrigerant.

95.

Which of the following is not true for multi-compression system?

It reduces power input
It does not require compressor head cooling.
It requires when compression ratio is higher.
It improves COP.

96.

Multi-compression system is employed when compression ratio is

> 7
> 100
> 2
> 1

97.

Power requirement for operation of multi-evaporation and individual compressor is

Equal to single compressor system.
Half of the single compressor system.
More than single compressor system.
Less than single compressor system.

98. The enthalpy of mixture of refrigerant after the compressors is
Equal to saturation temperature of vapour.
Less than the compressor of high temperature evaporator compressor.
In between the enthalpy of gas leaving these compressors.
More than the compressor of lower evaporator compressor.

99.

The mass flow rate of refrigerant in expansion valve placed ahead of E₂ (Fig. 20.1) is

None of the above.
Equal to than other expansion valve place on E1.
More than other expansion valve place on E1
Less than other expansion valve place on E1.

100.

Enthalpy per kg of refrigerant in E₁ (Fig. 20.4) is

Higher than E2
Lower than E2
Equal to E2
Decided by condensing pressure.

101.

Flash inter-cooling is done

At condensing pressure.
Using suction vapour
With water
Using refrigerant

102.

Which of the following is true for multi evaporators operating at different temperature with single compressor system?

This system does not require compressor head cooling.
It requires only one expansion valve.
It consumes less power as compared to individual compressor system.
It requires individual expansion valve for each evaporator.

103.

Intermediate pressure to be maintained in multi-compressor system having suction pressure of 1 bar and condensing pressure of 16 bar is about

8.5 bar
4 bar
9 bar
8 bar

104.

The dryness fraction of refrigerant after perfect inter cooling will be

1
0.2
0.5
Zero

105.

Which of the following statement is applicable to inter –cooling?

It is necessary when compression ratio is very low.
It requires insulation of discharge pipeline.
It is not possible to adopt inter cooling in ammonia plant.
It reduces the temperature of refrigerant after second stage compressor.

106. Energy required for pumping is as compared to compressor work is
55%
20%
50%
<5%

107. One of the statement is false with regard to vapour absorption refrigeration system
Liquid refrigerant leaving evaporator has little impact
Efficiency does not change much with load
Only shaft work can be used1
Moving part is only a pump

108. Negative deviation from Raoult’s law by Refrigerant Absorbent combination means
Observes all the Gas laws
Does not observe all the Gas laws
Observed vapour pressure is more than the calculated pressure
Observed vapour pressure is less than the calculated pressure

109. Weak solution in Absorber means
The Absorber pressure is less than that of Generator
The quantity of dissolved ammonia is less
The Absorber pressure is more than that of Generator
The quantity of dissolved ammonia is more

110. Heat source is given in the Vapour Absorption Refrigeration System in
Generator
Absorber
Evaporator
Condensor

111.

Psychrometry deals with

properties of mixture of air and water vapour
Enthalpy of air
Purification of air
Dehumidification of air.

112.

Specific humidity of air is proportional to

Partial pressure of dry air portion of air (Pa).
Wet bulb temperature.
Dry bulb temperature.
Partial pressure of water vapour present in air (Pv).

113.

The difference between dbt and wbt of air is called

Wet bulb depression
Humidity factor.
Relative humidity.
Dew point depression.

114.

The enthalpy of air is sum of enthalpy of dry air

Minus specific weight of air
Plus volume of dry air
Minus enthalpy of water vapour.
Plus enthalpy of water vapour.

115.

The unit of specific humidity is

kJ/kg
kg/unit volume
kg/kg dry air
kg/kg water vapour

116.

Partial pressure of water vapour of saturated (Pvs) air can be obtained from

Specific weight equation
Enthalpy equation on psychrometry
Steam table corresponding to wbt of the air
Steam table corresponding to dbt of the air

117.

Enthalpy line and dbt lines are

Parallel
At right angle to each other.
At 450 angle to each other.
Vertical lines

118.

Relative humidity is the ratio of partial pressure of water vapour (Pv) to

Pvs
Specific humidity
Absolute humidity
Degree of saturation

119.

Which of the following is true for specific humidity

It depends on Pv.
It is equal to Pv.
It can not be obtained from psychrometry chart
It is measured in %

120.

Enthalpy of air depends on

dbt
dbt & wbt
wbt
dew point temperature

121.

Sensible heating of air

Increases specific humidity of air.
Decreases relative humidity of air.
Decreases partial pressure of water vapour of the air.
Increases relative humidity of air.

122. During adiabatic humidification
Enthalpy of air remains constant.
Wet Bulb temperature decreases.
RH remains constant.
RH decreases.

123.

For large scale dehumidification of air requires

Cooling below dew point temperature.
Heating of the air.
Cooling of the air to wet bulb temperature.
Increase of partial pressure.

124.

Sensible heat factor of sensible cooling process is

One
Zero
0.5
0.75

125. Chemical dehumidification
Increases dbt
Decreases dbt.
Increases wbt
Decreases wbt.

126.

Aspirating psychrometer in addition to dry and wet bulb thermometer consists of

Fan
Humidity recorder
Dehumidifier
Humidifier

127.

Which of the following parameter can not be obtained by measurement of dry bulb and wet bulb temperature?

Relative humidity of air
Specific humidity
Enthalpy of air.
Air quantity

128.

What is the velocity of air required for the measurement of wbt using sling psychrometer?

100 m/s
5-10 m/s
1-2 m/s
50 m/s

129.

Which of the following measures % RH of air directly?

Laboratory psychrometer
Hair hygrometer
Sling psychrometer
Digital temperature sensor

130.

The level of RH necessary in comfort air conditioning is around

22 %.
160 %.
90 %
0 %.

131.

Apjohn equation is used for calculating

Pv
Pvs
Specific humidity
Relative humidity

132.

Which of the following equation represents Dalton’s law?

Pt = Pa + Pv
Pv = Pvs
?=P_v/P_vs
Qs+Ql = m (hb-ha)

133.

What is the volume of oxygen required per person per hour under normal conditions?

0.65 m3
5.00 m3
10.00 m3
1.5 m3

134. Capacity of humidifier is expressed as
kg/h
kJ/h.
kg dry air/h.
kJ/kg dry air

135.

In air conditioning system, in which sensible heat removed is 10 kJ/kg dry air and latent heat removed is 10 kJ/kg dry air, what is SHF of the process?

2.00.
Zero.
0.5
10

136.

Air change load is due to

Freezing of products
Door opening of cold storage
Respiration of products
Lack of insulation

137.

Air change factor does not depend on

Size of cold storage.
Frequency of door opening.
Temperature of cold storage.
Type of insulation used in cold storage.

138.

Which of the following is true for the product load?

It depends on specific heat of the product.
It is always fixed as per the size of cold storage.
It depends on U-value of wall.
It does not depend on the temperature of the product to be stored.

139.

Radiation heat load is not applied to dairy plant cold storages because

PUF is used as insulation.
There are no glass windows in dairy cold store.
U-value of cold storage is very high.
Temperature of cold storage is below 0o C.

140.

Which of the following cold storage may have higher air change load?

Cheese
butter
Milk
Ice-cream

141.

Heat gain through wall

Is called sensible heat load
Does not exist in milk cold store.
Does not exist in butter cold store.
Depends on infiltration of air.

142.

Which of the following is used as insulating materials in ready to use insulating panels?

Poly Urethane Foam
Thermocol
Glass wool
Wood

143.

Product load of cold storage is due to

Higher temperature of the product than the cold storage temperature.
Lower temperature of the product than the cold storage temperature.
Large size of cold storage.
Large size evaporator fan.

144.

In majority of dairy cold storages, heat load due to solar radiation is absent because

These cold storages are well insulated.
These cold storages are maintained at lower temperature.
There is no glass windows in these cold storages.
Artificial lights are used in these cold storages.

145.

Structural heat gain is kept minimum by

Employing efficient insulation
Constructing the cold storage using only steel material.
Improving U-value of the structure
Constructing RCC walls.

146.

The temperature of milk cold storage is maintained at

- 20 ºC
3 to 4 ºC
10 ºC
2 ºC

147.

Which of the following vapour compression refrigeration system is expected to give lower COP?

Ice-bank refrigeration system
Ice-cream hardening cold storage system
Vapour compression refrigeration of air conditioning
Cheese cold storage vapour compression refrigeration system.

148.

In insulation of cold storage, water vapour barrier is provided

On warmer side of cold storage.
On colder side of cold storage.
Between two layers of Thermocol.
On inner surface of cold storage wall.

149. Bitumen is a
Insulating material
Vapour barrier.
Dehydrator
Mortar

150.

Which of the following is being recently used for insulation of cold storages?

Thermocol
Cork
Glass wool
PUF