387 + Mcqs in Heat Transfer Refrigeration and Air Conditioning Page 4 McqOptions

151.	During dehumidification process, __________ remains constant.
A.	wet bulb temperature
B.	relative humidity
C.	dry bulb temperature
D.	specific humidity
Answer» D. specific humidity

Discussion

152.	The vertical and uniformly spaced lines on a psychrometric chart indicates
A.	dry bulb temperature
B.	wet bulb temperature
C.	dew point temperature
D.	specific humidity
Answer» B. wet bulb temperature

Discussion

153.	Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference.
A.	Agree
B.	Disagree
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

154.	The ratio of surface convection resistance to the internal conduction resistance is known as
A.	Grashoff number
B.	Biot number
C.	Stanton number
D.	Prandtl number
Answer» C. Stanton number

Discussion

155.	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
Answer» D. specific humidity

Discussion

156.	The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h0).
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

157.	At 100% relative humidity, wet bulb temperature, dry bulb temperature, dew point temperature and saturation temperature are equal.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

158.	The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.
A.	low
B.	high
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

159.	The critical temperature is the temperature
A.	below which a gas does not obey gas laws
B.	above which a gas may explode
C.	below which a gas is always liquified
D.	above which a gas will never liquified
Answer» E.

Discussion

160.	Kirchhoff's law states that
A.	the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
B.	the wave length corresponding to the maximum energy is proportional to the absolute temperature
C.	the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
D.	none of the above
Answer» D. none of the above

Discussion

161.	Upto the critical radius of insulation,
A.	added insulation will increase heat loss
B.	added insulation will decrease heat loss
C.	convective heat loss will be less than conductive heat loss
D.	heat flux will decrease
Answer» B. added insulation will decrease heat loss

Discussion

162.	In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature
A.	which lies between the dry bulb and wet bulb temperatures of the incoming stream
B.	which lies between the wet bulb and dew point temperatures of the incoming stream
C.	which is lower than the dew point temperature of the incoming stream
D.	of adiabatic saturation of incoming stream
Answer» D. of adiabatic saturation of incoming stream

Discussion

163.	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

164.	Air conditioning means
A.	cooling
B.	heating
C.	dehumidifying
D.	all of these
Answer» E.

Discussion

165.	The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
A.	sub-cooling or under-cooling
B.	super-cooling
C.	normal cooling
D.	none of these
Answer» B. super-cooling

Discussion

166.	The rate of heat flow through a body is . The term is known as temperature gradient.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» B. No

Discussion

167.	The centrifugal compressors are generally used for refrigerants that require
A.	small displacements and low condensing pressures
B.	large displacements and high condensing pressures
C.	small displacements and high condensing pressures
D.	large displacements and low condensing pressures
Answer» E.

Discussion

168.	If a gas is to be liquified, its temperature must be
A.	increased to a value above its critical temperature
B.	reduced to a value below its critical temperature
C.	equal to critical temperature
D.	none of the above
Answer» D. none of the above

Discussion

169.	The product of Reynolds number and Prandtl number is known as
A.	Stanton number
B.	Biot number
C.	Peclet number
D.	Grashoff number
Answer» D. Grashoff number

Discussion

170.	An ordinary passenger aircraft requires a cooling system of capacity.
A.	2 TR
B.	4 TR
C.	8 TR
D.	10 TR
Answer» D. 10 TR

Discussion

171.	The thermostatic expansion valve operates on the changes in the
A.	degree of superheat at exit from the evaporator
B.	temperature of the evaporator
C.	pressure in the evaporator
D.	none of the above
Answer» B. temperature of the evaporator

Discussion

172.	For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is __________ that for counter flow.
A.	equal to
B.	less than
C.	greater than
D.	None of these
Answer» B. less than

Discussion

173.	Prandtl number (PN) is given by PN = μ.cp/k.
A.	Yes
B.	No
C.	Can't say
D.	None of these
Answer» B. No

Discussion

174.	A condenser is used in the __________ pressure side of a refrigerating system.
A.	low
B.	high
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

175.	Wet bulb temperature is the temperature of air recorded by a thermometer, when
A.	it is not effected 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
Answer» C. the moisture present in it begins to condense

Discussion

176.	For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» B. Incorrect

Discussion

177.	A vapour absorption refrigeration system
A.	gives noisy operation
B.	gives quiet operation
C.	requires little power consumption
D.	cools below 0° C
Answer» C. requires little power consumption

Discussion

178.	In aircraft, air refrigeration Cycle is used because of
A.	low weight per tonne of refrigeration
B.	high heat transfer rate
C.	low temperature at high altitudes
D.	higher coefficient of performance
Answer» B. high heat transfer rate

Discussion

179.	In case ofsensible cooling of air, the coil efficiency is given by
A.	B.P.F. - 1
B.	1 - B.P.F.
C.	1 + B.P.F.
D.	None of these
Answer» C. 1 + B.P.F.

Discussion

180.	The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as
A.	conduction
B.	free convection
C.	forced convection
D.	radiation
Answer» C. forced convection

Discussion

181.	The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity.
A.	Correct
B.	Incorrect
C.	Can't say
D.	None of these
Answer» C. Can't say

Discussion

182.	The evaporator used in house-hold refrigerators is
A.	frosting evaporator
B.	non-frosting evaporator
C.	defrosting evaporator
D.	none of these
Answer» B. non-frosting evaporator

Discussion

183.	The specific humidity during heating and humidification process.
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» C. decreases

Discussion

184.	Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)
A.	S.H/(S.H + L.H)
B.	(S.H + L.H) /S.H
C.	(L.H - S.H)/S.H
D.	S.H/(L.H - S.H)
Answer» B. (S.H + L.H) /S.H

Discussion

185.	A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature drop, this can be replaced by a layer of diatomite earth of conductivity 0.14 W/mK and thickness
A.	0.5 m
B.	0.1 m
C.	0.2 m
D.	0.5 m
Answer» C. 0.2 m

Discussion

186.	A good refrigerant should have
A.	high latent heat of vaporisation and low freezing point
B.	high operating pressures and low freezing point
C.	high specific volume and high latent heat of vaporisation
D.	low C.O.P. and low freezing point
Answer» B. high operating pressures and low freezing point

Discussion

187.	The freon group of refrigerants are
A.	halo-carbon refrigerants
B.	azeotrope refrigerants
C.	inorganic refrigerants
D.	hydro-carbon refrigerants
Answer» B. azeotrope refrigerants

Discussion

188.	The boiling point of carbon dioxide is
A.	-20.5°C
B.	-50°C
C.	-63.3°C
D.	-78.3°C
Answer» E.

Discussion

189.	During cooling and dehumidification, dry bulb temperature
A.	remains constant
B.	increases
C.	decreases
D.	None of these
Answer» D. None of these

Discussion

190.	The absolute humidity is the mass of water vapour present in 1 m³ of dry air.
A.	Agree
B.	Disagree
C.	Can't say
D.	None of these
Answer» B. Disagree

Discussion

191.	The unit of overall coefficient of heat transfer is
A.	W/m²K
B.	W/m²
C.	W/mK
D.	W/m
Answer» B. W/m²

Discussion

192.	The C.O.P. of a Carnot refrigerator in winter will be __________ as compared to C.O.P. in summer.
A.	same
B.	lower
C.	higher
D.	None of these
Answer» D. None of these

Discussion

193.	The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body
A.	move actually
B.	do not move actually
C.	affect the intervening medium
D.	does not affect the intervening medium
Answer» C. affect the intervening medium

Discussion

194.	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
Answer» D. dry bulb temperature is higher than dew point temperature

Discussion

195.	A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in __________ power per tonne of refrigeration.
A.	same
B.	lower
C.	higher
D.	None of these
Answer» C. higher

Discussion

196.	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
C.	Can't say
D.	None of these
Answer» B. No

Discussion

197.	The average value of thermal conductivity for water at 20° C saturate is about 0.51.
A.	True
B.	False
C.	Can't say
D.	None of these
Answer» B. False

Discussion

198.	The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called
A.	coefficient of performance of refrigeration
B.	coefficient of performance of heat pump
C.	relative coefficient of performance
D.	refrigerating efficiency
Answer» B. coefficient of performance of heat pump

Discussion

199.	The critical thickness of insulation for a sphere is
A.	k/h0
B.	2k/h0
C.	h0/k
D.	h0/2k
Answer» C. h0/k

Discussion

200.	During heating and humidification, the final relative humidity of air
A.	is higher than that of the entering air
B.	is lower than that of the entering air
C.	can be lower or higher than that of the entering air
D.	none of the above
Answer» D. none of the above

Discussion

Explore topic-wise MCQs in Automobile Engineering.

During dehumidification process, __________ remains constant.

The vertical and uniformly spaced lines on a psychrometric chart indicates

Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference.

The ratio of surface convection resistance to the internal conduction resistance is known as

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

The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h0).

At 100% relative humidity, wet bulb temperature, dry bulb temperature, dew point temperature and saturation temperature are equal.

The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.

The critical temperature is the temperature

Kirchhoff's law states that

Upto the critical radius of insulation,

In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature

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

Air conditioning means

The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called

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

The centrifugal compressors are generally used for refrigerants that require

If a gas is to be liquified, its temperature must be

The product of Reynolds number and Prandtl number is known as

An ordinary passenger aircraft requires a cooling system of capacity.

The thermostatic expansion valve operates on the changes in the

For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is __________ that for counter flow.

Prandtl number (PN) is given by PN = μ.cp/k.

A condenser is used in the __________ pressure side of a refrigerating system.

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

For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0.

A vapour absorption refrigeration system

In aircraft, air refrigeration Cycle is used because of

In case ofsensible cooling of air, the coil efficiency is given by

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

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

The evaporator used in house-hold refrigerators is

The specific humidity during heating and humidification process.

Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)

A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature drop, this can be replaced by a layer of diatomite earth of conductivity 0.14 W/mK and thickness

A good refrigerant should have

The freon group of refrigerants are

The boiling point of carbon dioxide is

During cooling and dehumidification, dry bulb temperature

The absolute humidity is the mass of water vapour present in 1 m³ of dry air.

The unit of overall coefficient of heat transfer is

The C.O.P. of a Carnot refrigerator in winter will be __________ as compared to C.O.P. in summer.

The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

In a saturated air-water vapour mixture, the

A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in __________ power per tonne of refrigeration.

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

The average value of thermal conductivity for water at 20° C saturate is about 0.51.

The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called

The critical thickness of insulation for a sphere is

During heating and humidification, the final relative humidity of air