Thermal diffusivity of a substance is

directly proportional to the thermal conductivity

inversely proportional to density of substance

inversely proportional to specific heat

The desirable property of a refrigerant is

high latent heat of vaporisation

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

operating the machine at higher speeds

operating the machine at lower speeds

lowering the higher temperature

Which of the following statement is correct for ammonia as a refrigerant?

It is toxic to mucous membranes.

it requires large displacement per TR compared to fluoro carbons.

It reacts with copper and its alloys.

R-12 is generally preferred over R-22 in deep freezers since

it gives higher coefficient of performance

it is miscible with oil over large range of temperatures

During sensible cooling,

relative humidity remains constant

partial pressure of vapour remains constant

Conduction is a process of heat transfer

from one particle of the body to another by the actual motion of the heated particles.

from one particle of the body to another without the actual motion of the particles

from one particle of the body to another by the actual motion of the heated particles.

from a hot body to a cold body, in a straight line, without affecting the intervening medium

The process of undercooling is generally brought about by

circulating more quantity of cooling water through the condenser

using water colder than the main circulating water

A refrigerant compressor is used to

raise the pressure of the refrigerant

raise the temperature of the refrigerant

circulate the refrigerant through the refrigerating system

A human body feels comfortable when the heat produced by the metabolism of human body is equal to the

heat dissipated to the surroundings

A thermostatic expansion valve in a refrigeration system

is suitable only for constant load systems

ensures the evaporator completely filled with refrigerant of the load

is suitable only for constant load systems

maintains different temperatures in evaporator in proportion to load

The use of heat exchangers is made in

condensers and boilers in steam plants

condensers and evaporators in refrigeration and air conditioning units

A one tonne refrigerating machine means that

one tonne is the total mass of machine

one tonne of water can be converted into ice

one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min

387 + Mcqs in Heat Transfer Refrigeration and Air Conditioning in Automobile Engineering Page 3 McqOptions

101.	The freezing point of R-12 is
A.	-86.6°C
B.	-95.2°C
C.	-107.7°C
D.	-135.8°C
Answer» E.

Discussion

102.	One tonne of refrigeration (1TR) means that the heat removing capacity is
A.	21 kJ/min
B.	210 kJ/min
C.	420 kJ/min
D.	620 kJ/min
Answer» C. 420 kJ/min

Discussion

103.	The transfer of heat by molecular collision is smallest in
A.	solids
B.	liquids
C.	gases
D.	none of these
Answer» D. none of these

Discussion

104.	The highest temperature during the cycle in a vapour compression system occurs after evaporation.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

105.	Thermal diffusivity of a substance is
A.	directly proportional to the thermal conductivity
B.	inversely proportional to density of substance
C.	inversely proportional to specific heat
D.	all of the above
Answer» E.

Discussion

106.	The desirable property of a refrigerant is
A.	low boiling point
B.	high critical temperature
C.	high latent heat of vaporisation
D.	all of these
Answer» E.

Discussion

107.	When there is an addition of water vapour to the air of enclosed space, a gain in __________ is said to occur.
A.	sensible heat
B.	latent heat
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

108.	The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to
A.	bright green
B.	yellow
C.	red
D.	orange
Answer» B. yellow

Discussion

109.	In a parallel flow heat exchanger, the rate of flow of heat and the rate of decrease of temperature are maximum.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» B. No

Discussion

110.	Conduction is the process of heat transfer from one particle of the body to another by the actual motion of the heated particles.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

111.	The emissivity for a black body is
A.	0
B.	0.5
C.	0.75
D.	1
Answer» E.

Discussion

112.	When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
A.	operating the machine at higher speeds
B.	operating the machine at lower speeds
C.	raising the higher temperature
D.	lowering the higher temperature
Answer» E.

Discussion

113.	Which of the following statement is correct for ammonia as a refrigerant?
A.	It is toxic to mucous membranes.
B.	it requires large displacement per TR compared to fluoro carbons.
C.	It reacts with copper and its alloys.
D.	all of these
Answer» E.

Discussion

114.	A device used for transfering heat from one fluid to another is called heat exchanger.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

115.	The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.
A.	increases
B.	decreases
C.	Can't say
D.	None of these
Answer» B. decreases

Discussion

116.	R-12 is generally preferred over R-22 in deep freezers since
A.	it has low operating pressures
B.	it gives higher coefficient of performance
C.	it is miscible with oil over large range of temperatures
D.	all of the above
Answer» D. all of the above

Discussion

117.	During sensible cooling,
A.	relative humidity remains constant
B.	wet bulb temperature increases
C.	specific humidity increases
D.	partial pressure of vapour remains constant
Answer» E.

Discussion

118.	Thermal conductivity of air increases with rise in temperature.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

119.	Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)
A.	h = k/ ρS
B.	h = ρS/k
C.	h = S/ρk
D.	h = kρ/S
Answer» B. h = ρS/k

Discussion

120.	Which of the following refrigerant has the highest freezing point.
A.	Ammonia
B.	Carbon dioxide
C.	Sulphur dioxide
D.	R-12
Answer» C. Sulphur dioxide

Discussion

121.	During gas charging in an ammonia vapour compression system, the connection is made at the compressor outlet.
A.	Agree
B.	Disagree
C.	Can't say
D.	None of these
Answer» B. Disagree

Discussion

122.	The cooling of air, without any change in its specific humidity, is known as sensible cooling.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

123.	The process, generally used in winter air-conditioning to warm and humidity the air, is called
A.	humidification.
B.	dehumidification
C.	heating and humidification
D.	cooling and dehumidification
Answer» D. cooling and dehumidification

Discussion

124.	During sensible cooling of air, the relative humidity increases.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» B. No

Discussion

125.	The heat of sun reaches to us according to
A.	conduction
B.	convection
C.	radiation
D.	none of these
Answer» D. none of these

Discussion

126.	In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.
A.	same
B.	less
C.	greater
D.	None of these
Answer» D. None of these

Discussion

127.	Conduction is a process of heat transfer
A.	from one particle of the body to another without the actual motion of the particles
B.	from one particle of the body to another by the actual motion of the heated particles.
C.	from a hot body to a cold body, in a straight line, without affecting the intervening medium
D.	none of the above
Answer» B. from one particle of the body to another by the actual motion of the heated particles.

Discussion

128.	The process of undercooling is generally brought about by
A.	circulating more quantity of cooling water through the condenser
B.	using water colder than the main circulating water
C.	employing a heat exchanger
D.	any one of the above
Answer» E.

Discussion

129.	When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a
A.	black body
B.	grey body
C.	opaque body
D.	white body
Answer» B. grey body

Discussion

130.	In a vapour compression system, the condition of refrigerant before passing through the condenser is
A.	saturated liquid
B.	wet vapour
C.	dry saturated vapour
D.	superheated vapour
Answer» E.

Discussion

131.	Bell-Coleman cycle is a
A.	reversed Carnot cycle
B.	reversed Otto cycle
C.	reversed Joule cycle
D.	reversed Rankine cycle
Answer» D. reversed Rankine cycle

Discussion

132.	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
Answer» C. dry bulb temperature of air

Discussion

133.	A refrigerant compressor is used to
A.	raise the pressure of the refrigerant
B.	raise the temperature of the refrigerant
C.	circulate the refrigerant through the refrigerating system
D.	all of the above
Answer» E.

Discussion

134.	In which of the following refrigeration system, waste heat can be effectively used?
A.	Vapour compression cycle
B.	Vapour absorption cycle
C.	Air refrigeration cycle
D.	none of these
Answer» C. Air refrigeration cycle

Discussion

135.	The material of pipe lines for a system using ammonia as a refrigerant should be copper.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

136.	The value of the wave length for maximum emissive power is given by
A.	Kirchhoff's law
B.	Stefan's law
C.	Wein's law
D.	Planck's law
Answer» D. Planck's law

Discussion

137.	Air refrigeration cycle is used in
A.	commercial refrigerators
B.	domestic refrigerators
C.	air-conditioning
D.	gas liquefaction
Answer» E.

Discussion

138.	A human body feels comfortable when the heat produced by the metabolism of human body is equal to the
A.	heat dissipated to the surroundings
B.	heat stored in the human body
C.	sum of (a) and (b)
D.	difference of (a) and (b)
Answer» D. difference of (a) and (b)

Discussion

139.	The relative humidity __________ as air gets drier.
A.	increases
B.	decreases
C.	Can't say
D.	None of these
Answer» B. decreases

Discussion

140.	A thermostatic expansion valve in a refrigeration system
A.	ensures the evaporator completely filled with refrigerant of the load
B.	is suitable only for constant load systems
C.	maintains different temperatures in evaporator in proportion to load
D.	none of the above
Answer» B. is suitable only for constant load systems

Discussion

141.	The boiling point of ammonia is
A.	-10.5°C
B.	-30°C
C.	-33.3°C
D.	-77.7°C
Answer» D. -77.7°C

Discussion

142.	A boot-strap air cooling system has
A.	one heat exchanger
B.	two heat exchangers
C.	three heat exchangers
D.	four heat exchangers
Answer» C. three heat exchangers

Discussion

143.	In mechanical refrigeration system, the refrigerant occurs as liquid between condenser and expansion valve.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

144.	A low wet bulb temperature indicates very __________ humidity.
A.	low
B.	high
C.	Can't say
D.	None of these
Answer» B. high

Discussion

145.	The drier in a refrigeration system removes moisture in the system.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

146.	The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.
A.	same
B.	less
C.	more
D.	None of these
Answer» C. more

Discussion

147.	Planck's law holds good for all coloured bodies.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

148.	The use of heat exchangers is made in
A.	radiators in automobile
B.	condensers and boilers in steam plants
C.	condensers and evaporators in refrigeration and air conditioning units
D.	all of the above
Answer» E.

Discussion

149.	A one tonne refrigerating machine means that
A.	one tonne is the total mass of machine
B.	one tonne refrigerant is used
C.	one tonne of water can be converted into ice
D.	one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
Answer» E.

Discussion

150.	In a shell and coil condenser, water flows in the shell and the refrigerant in the coil.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

Explore topic-wise MCQs in Automobile Engineering.

The freezing point of R-12 is

One tonne of refrigeration (1TR) means that the heat removing capacity is

The transfer of heat by molecular collision is smallest in

The highest temperature during the cycle in a vapour compression system occurs after evaporation.

Thermal diffusivity of a substance is

The desirable property of a refrigerant is

When there is an addition of water vapour to the air of enclosed space, a gain in __________ is said to occur.

The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to

In a parallel flow heat exchanger, the rate of flow of heat and the rate of decrease of temperature are maximum.

Conduction is the process of heat transfer from one particle of the body to another by the actual motion of the heated particles.

The emissivity for a black body is

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

Which of the following statement is correct for ammonia as a refrigerant?

A device used for transfering heat from one fluid to another is called heat exchanger.

The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.

R-12 is generally preferred over R-22 in deep freezers since

During sensible cooling,

Thermal conductivity of air increases with rise in temperature.

Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)

Which of the following refrigerant has the highest freezing point.

During gas charging in an ammonia vapour compression system, the connection is made at the compressor outlet.

The cooling of air, without any change in its specific humidity, is known as sensible cooling.

The process, generally used in winter air-conditioning to warm and humidity the air, is called

During sensible cooling of air, the relative humidity increases.

The heat of sun reaches to us according to

In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.

Conduction is a process of heat transfer

The process of undercooling is generally brought about by

When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a

In a vapour compression system, the condition of refrigerant before passing through the condenser is

Bell-Coleman cycle is a

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

A refrigerant compressor is used to

In which of the following refrigeration system, waste heat can be effectively used?

The material of pipe lines for a system using ammonia as a refrigerant should be copper.

The value of the wave length for maximum emissive power is given by

Air refrigeration cycle is used in

A human body feels comfortable when the heat produced by the metabolism of human body is equal to the

The relative humidity __________ as air gets drier.

A thermostatic expansion valve in a refrigeration system

The boiling point of ammonia is

A boot-strap air cooling system has

In mechanical refrigeration system, the refrigerant occurs as liquid between condenser and expansion valve.

A low wet bulb temperature indicates very __________ humidity.

The drier in a refrigeration system removes moisture in the system.

The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.

Planck's law holds good for all coloured bodies.

The use of heat exchangers is made in

A one tonne refrigerating machine means that

In a shell and coil condenser, water flows in the shell and the refrigerant in the coil.