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THERMAL ENGINEERING II MCQ (MODEL EXAM - 6)

Total questions: 111

Worksheet time: 2hrs 51mins

Name
Class
Date
1.

For unsaturated air, the dew point temperature is __________ wet bulb temperature.

a)

equal to

b)

less than

c)

more than

d)

can’t predict

2.

The wet bulb depression indicates __________ humidity of the air.

a)

absolute

b)

relative

c)

specific

d)

any of the above

3.

The wet-bulb depression is zero when relative humidity is

a)

0%

b)

50%

c)

75%

d)

100%

4.

The minimum temperature to which water can be cooled in a cooling tower is

a)

dew point temperature of air

b)

wet bulb temperature of air

c)

dry bulb temperature of air

d)

ambient air temperature

5.

A low wet bulb temperature indicates very __________ humidity.

a)

low

b)

high

c)

can’t predict

d)

100%

6.

The wet bulb temperature at 100% relative humidity is __________ dew point temperature.

a)

same as

b)

lower than

c)

higher than

d)

may lower or higher

7.

The sensible cooling process on the psychrometric chart is shown by

a)

horizontal line

b)

vertical line

c)

inclined line

d)

curved

8.

During sensible cooling of air __________remains constant.

a)

dew point temperature

b)

specific humidity

c)

dry bulb temperature

d)

both A and B

9.

The dry bulb temperature during sensible cooling of air

a)

remains constant

b)

increases

c)

decreases

d)

first increases then decreases

10.

Which of the following statement is TRUE?

a)

During sensible cooling of the air, both dry bulb and wet bulb temperatures decrease

b)

During sensible cooling of the air, dry bulb temperature decreases but wet bulb temperature remains constant

c)

During sensible cooling of the air, dry and wet bulb temperatures decrease but dew point temperature remains constant

d)

Both A and C

11.

Dry air does NOT contain

a)

krypton

b)

argon

c)

neon

d)

none of the above

12.

The ratio of partial pressure of water vapour in a mixture to the saturation pressure of water at the same temperature of the mixture is called as

a)

humidity

b)

partial humidity

c)

specific humidity

d)

relative humidity

13.

What is the specific humidity?

a)

the ratio of the mass of water vapour to the mass of the total mixture of air and water vapour

b)

the ratio of the mass of dry air to the mass of the total mixture of air and water vapour

c)

the ratio of the mass of dry air to the mass of water vapour in a mixture of air and water vapour

d)

the ratio of the mass of water vapour to the mass of dry air in a mixture of air and water vapour

14.

What is the relative humidity for a saturated air?

a)

0%

b)

50%

c)

100%

d)

cannot say

15.

What is the degree of saturation?

a)

the ratio of the actual relative humidity to the saturated specific humidity at the same temperature

b)

the ratio of the actual specific humidity to the saturated specific humidity at the same temperature

c)

the ratio of the saturated specific humidity to the actual specific humidity at the same temperature

d)

none of the above

16.

The degree of saturation varies between

a)

1 to infinity

b)

0 to infinity

c)

0 to 1

d)

none of the above

17.

What is the temperature at which the water vapour in the mixture of water vapour in air, starts condensing called?

a)

condensation temperature

b)

dew point temperature

c)

vaporization temperature

d)

all of the above

18.

The temperature of air recorded by thermometer when the bulb is covered by a cotton wick saturated by water is called as

a)

dry bulb temperature

b)

wet bulb temperature

c)

stream temperature

d)

psychrometric temperature

19.

Which temperature can be measured by an instrument called psychrometer?

a)

dry bulb temperature

b)

wet bulb temperature

c)

both a. and b.

d)

none of the above

20.

When dry bulb temperature (DBT) and wet bulb temperature (WBT) are measured, greater the difference between DBT and WBT

a)

greater the amount of water vapour held in the mixture

b)

smaller the amount of water vapour held in the mixture

c)

same the amount of water vapour held in the mixture

d)

none of the above

21.

COP of a five star window air conditioner is greater than or equal to

a)

2.7

b)

2.9

c)

3.1

d)

3.3

22.

When dry bulb temperature of air is equal to web bulb temperature

a)

Air is 100% saturated

b)

Air is 50% saturated

c)

Air is completely dry

d)

Air is at dew point temperature

23.

The ration of water vapour to mass of dry air in a given mixture is known as

a)

Relative humidity

b)

Absolute humidity

c)

Humidity ratio

d)

Degree of saturation

24.

During adiabatic saturation process on unsaturated air, the

a)

DBT remains unchanged

b)

WBT remains unchanged

c)

DPT remains unchanged

d)

Saturation temperature remains unchanged

25.

The comfort conditions in the air-conditioning are at

a)

25°DBT & 100% RH

b)

20°DBT & 80% RH

c)

24°DBT & 60% RH

d)

25°DBT & 40% RH

26.

If the specific heats of dry air and water vapour are 1.00 kJ/kg-K and 1.88 kJ/kg-K respectively and the humidity ratio is 0.011, then the specific heat of moist air at 25°C and 50% relative humidity will be

a)

1.869 kJ/kg-K

b)

1.891 kJ/kg-K

c)

0.9793 kJ/kg-K

d)

1.0206 kJ/kg-K

27.

Infiltration of air in the building adds to

a)

Sensible heat load of the building

b)

Does not add any cooling load

c)

Sensible and latent heat load of the building

d)

Latent heat load of the building

28.

Air in which of the following classes is cleaner

a)

Class 10000

b)

Class 1000

c)

Class 100

d)

Class 10

29.

If air at dry-bulb temperature of 35° C and dew point temperature of 20° C passes through a cooling coil which is maintained at 25° C, then the process would be

a)

Sensible cooling

b)

Cooling and dehumidification

c)

Cooling and humidification

d)

Cooling at constant wet bulb temperature

30.

The grill temperature of air is

a)

temperature of air entering the cooling coil

b)

temperature of air leaving the room

c)

temperature of air entering the room

d)

temperature of fresh air after mixing with return air

31.
The air conditioning compressor _____________ vaporized refrigerant and allows it to flow to the condenser. 
a)
pressurizes
b)
cools
c)
supplies
d)
cleans
32.

Where would you expect to find a high pressure liquid within an AC system?

a)

Between the compressor and the Thermal Xpansion Valve

b)

Between the Thermal Xpansion Valve and the Evaporator

c)

Between the compressor and the condenser

d)

Between the Condenser and the Thermal Xpansion Valve

33.
How should R134a be stored to meet safety requirements?
a)
Under pressure as a vapour
b)
Under pressure as a gas
c)
Under no pressure as a vapour
d)
Under no pressure as a gas
34.
Assuming normal atmospheric pressure at what temperature would R134a boil?
a)
-26.3 degrees C
b)
-26.3 degrees Fahrenheit
c)
-103.3 degrees C
d)
-103.3 degrees Fahrenheit
35.
How could you confirm the type of refrigerant present in an air conditioning system?
a)
The odour the refrigerant emits when released to atmosphere
b)
The colour of the refrigerant which is visible through the sight glass in the top of the receiver drier
c)
By checking the identifier label located on the vehicle
d)
It does not matter as R12 and R134a are interchangeable
36.
What are the impacts on the environment of fluorinated greenhouse gases?
a)
Contributes to the formulation of acid rain
b)
Contributes to the global warming
c)
Mixes with the Nitrogen within the atmosphere to create a toxic substance, Nox
d)
Has little or no detrimental effect
37.
If contamination within an air conditioning system is suspected and a flushing procedure is to be carried out what component should also be changed?
a)
Compressor
b)
Receiver Drier
c)
TXV
d)
Condenser
38.
What does a TXV do?
a)
Cleans, dries and filters the refrigerant
b)
It controls the quantity of refrigerant entering the evaporator
c)
Allows for an increase in pressure and temperature prior to entering the condenser
d)
It acts as a safety device if the compressor is over pressuring the system
39.
What does COSHH stand for?
a)
Control of Substances Hazardous to health
b)
Company omissions of safe Health hazards
c)
Control of solutions hazardous to health
d)
Control of Substances which are health hazardous
40.

Air refrigeration operates on

a)

A.Carnot cycle

b)

B.Brayton cycle.

c)

C.Rankine cycle

d)

D.Erricson cycle

41.

Air refrigeration cycle is used in

a)

A.Domestic refrigerators

b)

B.Commercial refrigerators

c)

C.Air conditioning

d)

D.Gas liquefaction

42.

The value of COP in vapour compression cycle is usually

a)

A.Always less than unity

b)

B.Always more than unity

c)

C.Equal to unity

d)

D.Any one of the above

43.

Moisture in a refrigerant system is removed by

a)

A.Driers

b)

B.Filter-driers

c)

C.Dessicants

d)

D.All of the above

44.

The refrigerator which does not require compressor is known as

a)

A.Vapour absorption refrigerator

b)

B.Vapour compression refrigerator

c)

C.Electrolux refrigerator

d)

D.Carnot refrigerator

45.

Chemical formula of Freon-12 is

a)

A.C C12 F2

b)

B.C C12 f3.L.

c)

C.C C13 F2

d)

D.C C13 F3

46.

Air conditioning is concerned with maintaining

a)

A.Temperature

b)

B.Littriudity

c)

C.Cleanliness

d)

D.All the three above

47.

Relative humidity is

a)

A.Something concerned with air conditioning

b)

B.The ratio of moisture present in air to the capability of air to hold maximum moisture

c)

C.The ratio of actual humidity to absolute humidity

d)

D.Representative of amount of moisture held in air

48.

D.Representative of amount of moisture held in air

a)

A.Dry bulb temperature

b)

B.Wet bulb temperature

c)

C.Saturation temperature

d)

D.Dew point temperature

49.

Wet bulb temperature is

a)

A.Indication of amount of moisture in air

b)

B.Measured by wetting the bulb of the thermometer

c)

C.Less than dry-bulb temperature

d)

D.Dependent on the dryness and temperature of air

50.
In a typical system, within which component would the evaporation of refrigerant take place?
a)
Condenser
b)
Receiver dryer
c)
Evaporator
d)
Compressor
51.
What does MAC stand for?
a)
Mobile Air Conditioning
b)
Mechanical Air Conditioning
c)
Mobile Air Compressor
d)
Mechanical Air Compressor
52.
Where would you expect to find a high pressure liquid within an AC system?
a)
Between the compressor and the TXV
b)
Between the TXV and the Evaporator
c)
Between the compressor and the condenser
d)
Between the Condenser and the TXV
53.
How would you know the air con gas has been fully recovered from the system? 
a)
The gauge on the high pressure side reads a positive pressure
b)
The gauge on the low pressure side reads a negative pressure
c)
Both gauges read zero pressure at the end of the recovery process
d)
Both gauges read a positive pressure of 20 Bar at the end of the recovery process
54.
Which of the following would be carried out to confirm a system contained no refrigerant?
a)
Press the service port valve on the low pressure side and listen for a gas leak
b)
Connect the gauges to both high and low pressure ports to confirm a vacuum is present
c)
Connect the Air Conditioning equipment and carry out a full recovery
d)
Connect the gauges to both high and low pressure ports to confirm no pressure is present
55.
What type of refrigerant is R134a?
a)
CFC
b)
HCFC
c)
HSBC
d)
HFC
56.
What does COSHH stand for?
a)
Control of Substances Hazardous to health
b)
Company omissions of safe Health hazards
c)
Control of solutions hazardous to health
d)
Control of Substances which are health hazardous
57.
When did it become a legal requirement to hold certification for the handling of  fluorinated gas?
a)
31st August 2009
b)
6th February 1998
c)
4th July 2010
d)
12th September 2007
58.
What does GWP stand for?
a)
Gross Warming Potential
b)
Global Warming Potential
c)
Gross Warming Possible
d)
Global Warming Possible
59.
What type of service ports would an R134a system generally have?
a)
Each manufacturer have their own style of port and a series of adaptors need to be used
b)
Quick release type adaptors
c)
Schrader Valves with a ¼ BSP Thread
d)
Schrader Valves with 3/8 BSP Thread
60.
Which of the following situations would necessitate a recovery of the refrigerant prior to continuing the task?
a)
When replacing a cylinder head gasket or an engine area job
b)
When carrying out a body repair job that requires welding
c)
When carrying out a paint repair that requires the use of an oven
d)
When carrying out a major trim repair that involves plastic repair
61.
Before removing a major component from an air conditioning system what action must be taken?
a)
Inform all workshop staff of your actions 
b)
Ensure all workshop staff have the appropriate PPE 
c)
No specific actions need to be taken above standard good practice 
d)
Recover the refrigerant from the vehicle’s system
62.
Which of the following agreements would relate to December 1997
a)
Montreal
b)
K7
c)
K8
d)
Kyoto
63.
When leaving the compressor what state is the refrigerant in?
a)
High Pressure, High Temperature vapour
b)
High Pressure, High Temperature liquid
c)
Low Pressure, low Temperature vapour
d)
Low Pressure, low Temperature vapour
64.

Which of the following is true about the optimum effective temperature for human comfort?

a)

Same in winter and summer

b)

Not dependent on season

c)

Lower in winter than in summer

d)

Higher in winter than in summer

65.

The heat production from a normal healthy man when asleep is about _________

a)

50 W

b)

40 W

c)

70 W

d)

60 W

66.

When the heat stored in the body is ________ the human body feels comfortable.

a)

zero

b)

infinite

c)

positive

d)

negative

67.

Which of the following does not mainly a factor of dependency for the degree of warmth or cold?

a)

Relative humidity

b)

WBT

c)

Air velocity

d)

DBT

68.

The effective temperature increases with a decrease in relative humidity at the same DBT.

a)

True

b)

False

69.

What is the value of optimum effective temperature in winter?

a)

17

b)

18

c)

19

d)

20

70.

What is the value of the optimum effective temperature in summer?

a)

23

b)

22

c)

21

d)

24

71.

Which of the following provides the relationship between the optimum indoor effective temperature and optimum outdoor effective temperature?

a)

Clothing

b)

Occupants

c)

Duration of stay

d)

Climatic and seasonal differences

72.

What is sensible cooling of air?

a)

the cooling in which sensible heat of air is removed in order to reduce temperature

b)

the cooling in which temperature of air is reduced without changing in its moisture content

c)

both a. and b.

d)

none of the above

73.

When the humidity ratio of air increases the the air is said to be

a)

dehumidified

b)

humidified

c)

heated

d)

cooled

74.

The temperature at which the air cannot hold all the water vapour mixed in it and some vapour starts condensing is called as

a)

humidification temperature

b)

dehumidification temperature

c)

dew point temperature

d)

none of the above

75.

The formation of fog starts when,

a)

air temperature is equal to the dew point temperature

b)

air temperature is greater than the dew point temperature

c)

both a. and b.

d)

none of the above

76.

When the dew point temperature is equal to the air temperature then the relative humidity is

a)

0%

b)

50%

c)

100%

d)

unpredictable

77.

On psychrometric chart, wet bulb temperature lines are

a)

horizontal with uniformly spaced

b)

horizontal with non-uniformly spaced

c)

inclined with uniformly spaced

d)

inclined with non-uniformly spaced

78.

At any point on the saturation curve in psychometric chart, the dry bulb temperature is always

a)

less than the corresponding wet bulb temperature

b)

more than the corresponding wet bulb temperature

c)

equal to the corresponding wet bulb temperature

d)

cannot predict

79.

The moisture content lines in psychrometric chart are also called as

a)

relative humidity lines

b)

specific humidity lines

c)

both a. and b.

d)

none of the above

80.

The horizontal line in psychrometric chart joining the change of state of air represents

a)

humidification

b)

sensible cooling or heating

c)

sensible cooling or heating with humidification

d)

sensible cooling or heating with dehumidification

81.

Air at dry bulb temperature Td1 is passed through the heating coil and some amount of air is by passed unaffected and leaves with dry bulb temperature Tb2 and the temperature of heated air is Td3 (where Td2 < Td3), what is the correct formula for by pass factor (The amount of air by passed unaffected)?

a)

Bypass Factor = (Td3 – Td2) / (Td3 – Td1)

b)

Bypass Factor = (Td3 – Td1) / (Td3 – Td2)

c)

Bypass Factor = (Td2 – Td1) / (Td2 – Td3)

d)

Bypass Factor = (Td2 – Td3) / (Td2 – Td1)

82.

Humidification is the process of addition moisture in air at

a)

constant wet bulb temperature

b)

constant dry bulb temperature

c)

constant latent heat

d)

none of the above

83.

What is the perfect condition for dehumidification of air?

a)

air is heated above its dew point temperature

b)

air is cooled up to its dew point temperature

c)

air is heated below its dew point temperature

d)

air is cooled below its dew point temperature

84.

At 100% relative humidity, the wet bulb temperature is

a)

lower than the dew point temperature

b)

higher than the dew point temperature

c)

equal to the dew point temperature

d)

none of the above

85.

The dew point temperature is less than the wet bulb temperature for

a)

saturated air

b)

unsaturated air

c)

both saturated and unsaturated air

d)

none of the above

86.

When,

H1 = Total heat of air entering the coil (heating or cooling)

H2 = Total heat of air leaving the coil (heating or cooling)

H3 = Total heat of air at the end of the process (humidification or dehumidification)

then, the sensible heat factor (H2 – H1) / (H3 – H1) represents the process of

a)

cooling and humidification

b)

cooling and dehumidification

c)

heating and humidification

d)

heating and dehumidification

87.

When the rate of evaporation of water is zero, the relative humidity of the air is

a)

0%

b)

100%

c)

50%

d)

unpredictable

88.

What is the perfect condition for dehumidification of air?

a)

air is heated above its dew point temperature

b)

air is cooled up to its dew point temperature

c)

air is heated below its dew point temperature

d)

air is cooled below its dew point temperature

89.

The science of study of the thermodynamic properties of a mixture of dry air and water vapour in the atmosphere is called

a)

Refrigeration

b)

Psychrometry

c)

Air conditioning

d)

None of the above

90.

The mixture of a number of gases by volume in the air is known as

a)

dry air

b)

moist air

c)

saturated air

d)

none of the above

91.

A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

a)

dry air

b)

moist air

c)

saturated air

d)

specific humidity

92.

The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called

a)

Kinetic theory of gases

b)

Newton's law of gases

c)

Dalton's law of partial pressures

d)

Avogadro's hypothesis

93.

Dry bulb temperature is the temperature of air recorded by a thermometer, when

a)

it is not affected by the moisture present in the air

b)

its bulb is surrounded by a wet cloth exposed to the air

c)

the moisture present in it begins to condense

d)

none of the above

94.

Wet bulb temperature is the temperature of air recorded by a thermometer, when

a)

it is not affected by the moisture present in the air

b)

its bulb is surrounded by a wet cloth exposed to the air

c)

the moisture present in it begins to condense

d)

none of the above

95.

The temperature at which moisture present in the air is begins to condense is known as

a)

dry bulb temperature

b)

wet bulb temperature

c)

dew point temperature

d)

wet bulb depression

96.

The difference between dry bulb temperature and wet bulb temperature is called

a)

dry bulb depression

b)

wet bulb depression

c)

dew point depression

d)

degree of saturation

97.

The difference between dry bulb temperature and dew point temperature is called

a)

dry bulb depression

b)

wet bulb depression

c)

dew point depression

d)

degree of saturation

98.

The sling psychrometer is used to measure

a)

dry bulb temperature only

b)

wet bulb temperature only

c)

specific humidity

d)

both A and B

99.

The specific humidity is the mass of water vapour present in

a)

one cubic meter of wet air

b)

one cubic meter of dry air

c)

one kg of wet air

d)

one kg of dry air

100.

The ratio of the actual specific humidity to the specific humidity when the air is saturated at the same dry bulb temperature is called

a)

humidity ratio

b)

relative humidity

c)

absolute humidity

d)

degree of saturation

101.

The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure is called

a)

humidity ratio

b)

relative humidity

c)

absolute humidity

d)

degree of saturation

102.

The instrument used to measure relative humidity of air is

a)

hygrometer

b)

hydrometer

c)

pyrometer

d)

anemometer

103.

The mass of water vapour present in __________ is called absolute humidity.

a)

1 cubic meter of wet air

b)

1 cubic meter of dry air

c)

1 kg of wet air

d)

1 kg of dry air

104.

The dry bulb temperature lines on the psychrometric chart are

a)

vertical and uniformly spaced

b)

horizontal and uniformly spaced

c)

horizontal and non-uniformly spaced

d)

curved lines

105.

In a psychrometric chart, specific humidity (moisture content) lines are

a)

vertical and uniformly spaced

b)

horizontal and uniformly spaced

c)

horizontal and non-uniformly spaced

d)

curved lines

106.

The horizontal and non-uniformly spaced lines on a psychrometric chart indicates

a)

dry bulb temperature

b)

wet bulb temperature

c)

dew point temperature

d)

specific humidity

107.

The inclined straight and non-uniformly spaced lines on a psychrometric chart indicates

a)

dry bulb temperature

b)

wet bulb temperature

c)

dew point temperature

d)

specific humidity

108.

The relative humidity lines on a psychrometric chart are

a)

vertical and uniformly spaced

b)

horizontal and uniformly spaced

c)

horizontal and non-uniformly spaced

d)

curved lines

109.

Which of the following statement is correct?

a)

The constant enthalpy lines are also constant wet bulb temperature lines

b)

The wet bulb and dry bulb temperature are equal at saturation condition

c)

The wet-bulb temperature is a measure of enthalpy of moist air

d)

All of the above

110.

The scale given in mm of Hg on the left side of the psychrometric chart is called

a)

enthalpy scale

b)

sensible heat factor scale

c)

vapour pressure scale

d)

none of the above

111.

In a saturated air-water vapour mixture, the

a)

dry bulb temperature is higher than wet bulb temperature

b)

dew point temperature is lower than wet bulb temperature

c)

dry bulb, wet bulb and dew point temperature are same

d)

dry bulb temperature is higher than dew point temperature

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