265 + Mcqs in Heat Transfer, Refrigeration and Air Conditioning Page 3 McqOptions

101.	The rate of heat flow through a body is . The term is known as temperature gradient.
A.	Yes
B.	No
Answer» B. No

Discussion

102.	Oil separator in a refrigeration cycle is installed
A.	before compressor
B.	between compressor and condenser
C.	between condenser and evaporator
D.	between condenser and expansion valve
Answer» C. between condenser and evaporator

Discussion

103.	In larger industrial and commercial reciprocating compression systems, refrigerent widely used is
A.	ammonia
B.	carbon dioxide
C.	sulphur dioxide
D.	R-12
Answer» B. carbon dioxide

Discussion

104.	In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
A.	1
B.	1.25
C.	2.15
D.	5.12
Answer» C. 2.15

Discussion

105.	The undesireable property of a refrigerant is
A.	non-toxic
B.	non-flammable
C.	non-explosive
D.	high boiling point
Answer» E.

Discussion

106.	The dry bulb temperature during sensible heating of air
A.	remains constant
B.	increases
C.	decreases
Answer» C. decreases

Discussion

107.	Radiation is the process of heat transfer in which heat flows from a __________ , in a straight line, without affecting the intervening medium.
A.	cold body to hot body
B.	hot body to cold body
C.	smaller body to larger body
D.	larger body to smaller body
Answer» C. smaller body to larger body

Discussion

108.	The heating of air, without any change in its specific humidity, is known as sensible heating.
A.	True
B.	False
Answer» B. False

Discussion

109.	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

110.	The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called
A.	wet bulb temperature
B.	dry bulb temperature
C.	dew point temperature
D.	none of these
Answer» B. dry bulb temperature

Discussion

111.	During sub-cooling, sensible heat from a liquid refrigerant is removed.
A.	Yes
B.	No
Answer» B. No

Discussion

112.	The expression is used for calculating relative humidity.
A.	Yes
B.	No
Answer» C.

Discussion

113.	If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + λ is represented by (λ.λ), then λ is called
A.	absorptive power
B.	emissive power
C.	emissivity
D.	none of these
Answer» C. emissivity

Discussion

114.	The highest temperature during the cycle in a vapour compression system occurs after evaporation.
A.	True
B.	False
Answer» C.

Discussion

115.	Which of the following refrigerant has the maximum ozone depletion potential in the stratophere?
A.	Ammonia
B.	Carbon dioxide
C.	Sulphur dioxide
D.	Flourine
Answer» E.

Discussion

116.	According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.
A.	Correct
B.	Incorrect
Answer» B. Incorrect

Discussion

117.	In electrolux refrigerator
A.	ammonia is absorbed in hydrogen
B.	ammonia is absorbed in water
C.	ammonia evaporates in hydrogen
D.	hydrogen evaporates in ammonia
Answer» D. hydrogen evaporates in ammonia

Discussion

118.	The water, alcohol and ammonia have same refrigerating effect at different altitudes.
A.	Yes
B.	No
Answer» C.

Discussion

119.	The automobile radiator is a heat exchanger of
A.	parallel flow type
B.	counter flow type
C.	cross flow type
D.	regenerator type
Answer» D. regenerator type

Discussion

120.	In mechanical refrigeration system, the refrigerant occurs as liquid between condenser and expansion valve.
A.	True
B.	False
Answer» B. False

Discussion

121.	The wet bulb temperature at 100% relative humidity is __________ dew point temperature.
A.	same as
B.	lower than
C.	higher than
Answer» B. lower than

Discussion

122.	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

123.	The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity.
A.	Correct
B.	Incorrect
Answer» C.

Discussion

124.	The sensible heat gain is due to the __________ difference between the fresh air and the air in space.
A.	temperature
B.	humidity
Answer» B. humidity

Discussion

125.	The coefficient of performance of electrolux refrigerator is the ratio of
A.	heat supplied by the gas burner to the heat absorbed by the evaporator
B.	heat absorbed by the evaporator to the heat supplied by the gas burner
C.	heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner
D.	heat absorbed by the evaporator minus the heat supplied by the gas burner to the heat absorbed by the evaporator
Answer» C. heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner

Discussion

126.	The sulphur sticks, in case of leakage of ammonia refrigerant, gives white smoke.
A.	True
B.	False
Answer» B. False

Discussion

127.	During gas charging in an ammonia vapour compression system, the connection is made at the compressor outlet.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

128.	Thermal conductivity of a material may be defined as the
A.	quantity of heat flowing in one second through a slab of the material of area 1 cm
B.	and thickness 1 cm when its faces differ in temperature by 1° C
C.	quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C
D.	heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
E.	all of the above
Answer» E. all of the above

Discussion

129.	During sensible heating of air, specific humidity remains constant.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

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

Discussion

131.	The wet bulb depression is zero when relative humidity is
A.	zero
B.	0.5
C.	0.75
D.	1.0
Answer» E.

Discussion

132.	The superheated vapour region, in a pressure enthalpy chart, is represented by the space
A.	to the left of saturated liquid line
B.	to the right of saturated liquid line
C.	between the saturated liquid line and saturated vapour line
D.	none of the above
Answer» D. none of the above

Discussion

133.	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

134.	The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
A.	mean radiant temperature
B.	effective temperature
C.	dew point temperature
D.	none of these
Answer» C. dew point temperature

Discussion

135.	The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
A.	Stanton number
B.	Biot number
C.	Peclet number
D.	Grashoff number
Answer» B. Biot number

Discussion

136.	In a shell and coil condenser, water flows in the shell and the refrigerant in the coil.
A.	True
B.	False
Answer» C.

Discussion

137.	Dew point temperature corresponds to the saturation temperature of vapour at its partial pressure.
A.	True
B.	False
Answer» B. False

Discussion

138.	The capillary tube is not used in large capacity refrigeration systems because
A.	cost is too high
B.	capacity control is not possible
C.	it is made of copper
D.	required pressure drop can not be achieved
Answer» C. it is made of copper

Discussion

139.	The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

140.	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

141.	The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
A.	high pressure saturated liquid
B.	wet vapour
C.	very wet vapour
D.	dry vapour
Answer» D. dry vapour

Discussion

142.	The process of adding moisture to the air, without change in its dry bulb temperature, is known as humidification.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

143.	In case of liquids and gases, the heat transfer takes place according to
A.	conduction
B.	convection
C.	radiation
D.	none of these
Answer» C. radiation

Discussion

144.	The sensible heat during humidification process decreases.
A.	True
B.	False
Answer» C.

Discussion

145.	According to Newton's law of cooling, the heat transfer from a hot body to a cold body is
A.	directly proportional to the surface area
B.	directly proportional to the difference of temperatures between the two bodies
C.	either (a) or (b)
D.	both (a) and (b)
Answer» E.

Discussion

146.	The freezing point of carbon dioxide is equal to boiling point of R-12.
A.	Correct
B.	Incorrect
Answer» C.

Discussion

147.	The super-heating in a refrigeration cycle
A.	does not alter C.O.P.
B.	increases C.O.P.
C.	decreases C.O.P.
D.	none of these
Answer» D. none of these

Discussion

148.	Sulphur dioxide is extremely toxic and non-flammable.
A.	True
B.	False
Answer» B. False

Discussion

149.	The transfer of heat from one body to another takes place only when there is a temperature difference between the bodies.
A.	Yes
B.	No
Answer» B. No

Discussion

150.	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

Explore topic-wise MCQs in Mechanical Engineering.

The rate of heat flow through a body is . The term is known as temperature gradient.

Oil separator in a refrigeration cycle is installed

In larger industrial and commercial reciprocating compression systems, refrigerent widely used is

In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about

The undesireable property of a refrigerant is

The dry bulb temperature during sensible heating of air

Radiation is the process of heat transfer in which heat flows from a __________ , in a straight line, without affecting the intervening medium.

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

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

The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called

During sub-cooling, sensible heat from a liquid refrigerant is removed.

The expression is used for calculating relative humidity.

If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + λ is represented by (λ.λ), then λ is called

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

Which of the following refrigerant has the maximum ozone depletion potential in the stratophere?

According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.

In electrolux refrigerator

The water, alcohol and ammonia have same refrigerating effect at different altitudes.

The automobile radiator is a heat exchanger of

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

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

The use of heat exchangers is made in

The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity.

The sensible heat gain is due to the __________ difference between the fresh air and the air in space.

The coefficient of performance of electrolux refrigerator is the ratio of

The sulphur sticks, in case of leakage of ammonia refrigerant, gives white smoke.

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

Thermal conductivity of a material may be defined as the

During sensible heating of air, specific humidity remains constant.

Air refrigeration cycle is used in

The wet bulb depression is zero when relative humidity is

The superheated vapour region, in a pressure enthalpy chart, is represented by the space

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

The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as

The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to

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

Dew point temperature corresponds to the saturation temperature of vapour at its partial pressure.

The capillary tube is not used in large capacity refrigeration systems because

The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.

Which of the following refrigerant has the highest freezing point.

The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is

The process of adding moisture to the air, without change in its dry bulb temperature, is known as humidification.

In case of liquids and gases, the heat transfer takes place according to

The sensible heat during humidification process decreases.

According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

The freezing point of carbon dioxide is equal to boiling point of R-12.

The super-heating in a refrigeration cycle

Sulphur dioxide is extremely toxic and non-flammable.

The transfer of heat from one body to another takes place only when there is a temperature difference between the bodies.

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