Radiation heat transfer rates does not depend upon the

distance between the heat source and the object receiving the heat.

surface area and temperature of the heat source.

For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would

first decrease and then increase

first increase and then decrease

Evaporation by thermocompression results in the

realisation of multiple effect economy in a single effect.

With increase in temperature, the thermal conductivity of a gas

may increase or decrease depending on the type of gas.

The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is

either more or less ; depends on the nature of vapor

In sub-cooled boiling,

bubbles from heating surface are absorbed by the mass of the liquid.

temperature of the heating surface is less than the boiling point of the liquid.

temperature of the heating surface is more than the boiling point of the liquid.

bubbles from heating surface are absorbed by the mass of the liquid.

very large vapour space is necessary.

Thermal conductivity of a gas at low density, __________ with increase in temperature.

may increase or decrease; depends on the gas

Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212¬∞F may be around __________ BTU.$

data insufficient, can't be predicted

In case of a vertical tube evaporator, with increase in the liquor level, the

capacity of the evaporator is increased.

capacity of the evaporator is decreased.

capacity of the evaporator is increased.

true temperature drop increases.

In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will

either increase or decrease; depends on the coolant flow rate

Rate of heat transfer by vaporisation from pools of water is affected by the

nature of heating surface and distribution of bubbles.

In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.

may increase or decrease, depends on the vacuum

In evaporators, lowering the feed temperature

decreases the heating area required.

increases the heating area required.

decreases the heating area required.

Which of the following has the lowest Prandtl number ?

Molten sodium (a coolant used in fast breeder reactor)

In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used

in low range of temperature differences.

in high range of temperature differences.

to prevent corrosion of the tube bundles.

Boiling point elevation of a solution of NaOH

increases rapidly with temperature rise.

is almost independent of temperature.

is almost independent of pressure.

With increase in temperature, the thermal conductivity of fresh lubricating oil

may increase or decrease; depends on its composition

640 + Mcqs in Heat Transfer in Chemical Engineering Page 5 McqOptions

201.	A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires
A.	less heating surface.
B.	more space.
C.	lower maintenance cost.
D.	none of these.
Answer» C. lower maintenance cost.

Discussion

202.	Radiation heat transfer rates does not depend upon the
A.	type of absorbing surface.
B.	distance between the heat source and the object receiving the heat.
C.	surface area and temperature of the heat source.
D.	none of these.
Answer» E.

Discussion

203.	Which has the lowest Prandtl number ?
A.	Liquid metal
B.	Aqueous solution
C.	Water
D.	Lube oil
Answer» B. Aqueous solution

Discussion

204.	The sum of reflectivity and absorptivity for an opaque body is equal to
A.	0.5
B.	1
C.	0
D.	2
Answer» C. 0

Discussion

205.	Evaporator tubes are generally
A.	horizontal
B.	vertical
C.	inclined
D.	random
Answer» C. inclined

Discussion

206.	A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when
A.	CPA > CPB
B.	CPA < CPB
C.	kA < 0.5kB
D.	kA>2 kB
Answer» D. kA>2 kB

Discussion

207.	Heat transfer co-efficient (h1) for liquids increases with
A.	increasing temperature.
B.	decreasing temperature.
C.	decreasing Reynolds number.
D.	none of these.
Answer» B. decreasing temperature.

Discussion

208.	__________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side.
A.	Single pass, fixed tube sheet
B.	U-tube
C.	Three pass, fixed tube sheet
D.	none of these
Answer» C. Three pass, fixed tube sheet

Discussion

209.	Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?
A.	Bleed point
B.	Vent
C.	Catchall
D.	Baffle
Answer» D. Baffle

Discussion

210.	Heat flux, as defined in heat flow is analogous to __________ in electricity flow.
A.	current
B.	voltage
C.	resistance
D.	none of these
Answer» B. voltage

Discussion

211.	In the free convection regime of pool boiling, the heat flux is proportional to
A.	Œît1/2
B.	Œît2
C.	Œît5/4
D.	Œît
Answer» D. Œît

Discussion

212.	The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
A.	heating volume
B.	heat transfer area
C.	Nusselt number
D.	none of these
Answer» C. Nusselt number

Discussion

213.	For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would
A.	decrease
B.	increase
C.	first decrease and then increase
D.	first increase and then decrease
Answer» E.

Discussion

214.	In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
A.	minimum
B.	maximum
C.	zero
D.	infinity
Answer» D. infinity

Discussion

215.	Evaporation by thermocompression results in the
A.	saving of steam.
B.	realisation of multiple effect economy in a single effect.
C.	both (a) and (b).
D.	none of these.
Answer» D. none of these.

Discussion

216.	Heat sensitive materials can be concentrated in an evaporator employing
A.	vacuum
B.	high pressure
C.	high residence time
D.	none of these
Answer» B. high pressure

Discussion

217.	200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 x 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)
A.	0.5
B.	0.05
C.	0.1
D.	0.15
Answer» D. 0.15

Discussion

218.	With increase in temperature, the thermal conductivity of a gas
A.	increases.
B.	decreases.
C.	remains same.
D.	may increase or decrease depending on the type of gas.
Answer» B. decreases.

Discussion

219.	The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is
A.	more
B.	less
C.	some
D.	either more or less ; depends on the nature of vapor
Answer» D. either more or less ; depends on the nature of vapor

Discussion

220.	In sub-cooled boiling,
A.	temperature of the heating surface is less than the boiling point of the liquid.
B.	temperature of the heating surface is more than the boiling point of the liquid.
C.	bubbles from heating surface are absorbed by the mass of the liquid.
D.	very large vapour space is necessary.
Answer» C. bubbles from heating surface are absorbed by the mass of the liquid.

Discussion

221.	A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is
A.	5.6
B.	0.025
C.	3.5
D.	0.0035
Answer» C. 3.5

Discussion

222.	Natural convection is characterised by
A.	Grashhoff number
B.	Peclet number
C.	Reynolds number
D.	Prandtl number
Answer» B. Peclet number

Discussion

223.	Thermal conductivity of a gas at low density, __________ with increase in temperature.
A.	decreases
B.	increases
C.	remains unchanged
D.	may increase or decrease; depends on the gas
Answer» C. remains unchanged

Discussion

224.	For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
A.	1
B.	1.74
C.	6.1
D.	37
Answer» D. 37

Discussion

225.	When warm and cold liquids are mixed, the heat transfer is mainly by
A.	conduction
B.	convection
C.	radiation
D.	both(a) & (c)
Answer» C. radiation

Discussion

226.	Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212¬∞F may be around __________ BTU.$
A.	180
B.	970
C.	3.97
D.	data insufficient, can't be predicted
Answer» B. 970

Discussion

227.	For a perfectly transparent surface (like gases), the
A.	absorptivity = 0
B.	transmissivity = 1
C.	reflectivity = 0
D.	all (a), (b) & (c)
Answer» C. reflectivity = 0

Discussion

228.	To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is
A.	1-2 heat exchanger
B.	1-1 heat exchanger
C.	3-2 heat exchanger
D.	2-4 heat exchanger
Answer» C. 3-2 heat exchanger

Discussion

229.	1000 Kg of liquid at 30¬∞C in a well stirred vessel has to be heated to 120¬∞C, using immersed coils carrying condensing steam at 150¬∞C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.¬∞C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.¬∞C, the time taken for the liquid to reach desired temperature will be$
A.	15 min
B.	22 min
C.	44 min
D.	51 min
Answer» E.

Discussion

230.	In case of a vertical tube evaporator, with increase in the liquor level, the
A.	capacity of the evaporator is decreased.
B.	capacity of the evaporator is increased.
C.	true temperature drop increases.
D.	both (b) and (c).
Answer» B. capacity of the evaporator is increased.

Discussion

231.	In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will
A.	increase
B.	decrease
C.	remain unchanged
D.	either increase or decrease; depends on the coolant flow rate
Answer» D. either increase or decrease; depends on the coolant flow rate

Discussion

232.	If heat transfer rate varies with the time, it is termed as
A.	forced convection
B.	steady state conduction
C.	monochromatic radiation
D.	none of these
Answer» E.

Discussion

233.	Steam economy in case of a triple effect evaporator will be
A.	1
B.	< 1
C.	> 1
D.	between 0 and 1
Answer» D. between 0 and 1

Discussion

234.	Rate of heat transfer by vaporisation from pools of water is affected by the
A.	nature of heating surface and distribution of bubbles.
B.	surface tension of water.
C.	viscosity of water.
D.	all (a), (b) and (c).
Answer» E.

Discussion

235.	Open pan evaporators are preferred to be used, when the solution to be concentrated is
A.	scaling
B.	highly viscous
C.	corrosive
D.	salty
Answer» C. corrosive

Discussion

236.	Sensible heat of hot industrial flue gases can not be recovered by a/an
A.	economiser
B.	regenerator
C.	ceramic recuperator
D.	none of these
Answer» E.

Discussion

237.	Tube pitch is the __________ of tube diameters and the clearances.
A.	sum
B.	difference
C.	ratio
D.	none of these
Answer» B. difference

Discussion

238.	In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.
A.	increases
B.	decreases
C.	remains constant
D.	may increase or decrease, depends on the vacuum
Answer» B. decreases

Discussion

239.	At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?
A.	1
B.	< 1
C.	> 1
D.	none of these
Answer» B. < 1

Discussion

240.	For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is
A.	1.26 h1
B.	0.794 h1
C.	0.574 h1
D.	1.741 h1
Answer» C. 0.574 h1

Discussion

241.	Dietus-Boelter equation cannot be used for molten metals mainly due to its very low
A.	Prandtl number
B.	Grashoff number
C.	thermal conductivity
D.	viscosity
Answer» B. Grashoff number

Discussion

242.	For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is
A.	3
B.	0.33
C.	1
D.	1.33
Answer» D. 1.33

Discussion

243.	In evaporators, lowering the feed temperature
A.	increases the heating area required.
B.	reduces the economy.
C.	both (a) and (b).
D.	decreases the heating area required.
Answer» D. decreases the heating area required.

Discussion

244.	Which of the following has the lowest Prandtl number ?
A.	Molten sodium (a coolant used in fast breeder reactor)
B.	Water
C.	Transformer oil
D.	Dilute H2SO4
Answer» B. Water

Discussion

245.	In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of
A.	concentrations
B.	chemical potentials
C.	activity co-efficients
D.	mass transfer co-efficients
Answer» B. chemical potentials

Discussion

246.	The equation, Nst = f/2, is the __________ analogy.
A.	Colburn
B.	Reynolds
C.	Prandtl
D.	none of these
Answer» C. Prandtl

Discussion

247.	In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used
A.	in low range of temperature differences.
B.	in high range of temperature differences.
C.	because of its low cost.
D.	to prevent corrosion of the tube bundles.
Answer» C. because of its low cost.

Discussion

248.	Three material A, B and C of equal thick-nes and of thermal conductivity of 20, 40 & 60 kcal/hr. m. ¬∞C respectively are joined together. The temperature outside of A and C are 30¬∞C and 100¬∞C respectively. The interface between B and C will be at a temperature of __________ ¬∞C.$
A.	40
B.	95
C.	70
D.	50
Answer» D. 50

Discussion

249.	Boiling point elevation of a solution of NaOH
A.	increases rapidly with temperature rise.
B.	is almost independent of temperature.
C.	is almost independent of pressure.
D.	both (b) and (c).
Answer» E.

Discussion

250.	With increase in temperature, the thermal conductivity of fresh lubricating oil
A.	increases
B.	decreases
C.	remains unchanged
D.	may increase or decrease; depends on its composition
Answer» C. remains unchanged

Discussion

Explore topic-wise MCQs in Chemical Engineering.

A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires

Radiation heat transfer rates does not depend upon the

Which has the lowest Prandtl number ?

The sum of reflectivity and absorptivity for an opaque body is equal to

Evaporator tubes are generally

Heat transfer co-efficient (h1) for liquids increases with

__________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side.

Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?

Heat flux, as defined in heat flow is analogous to __________ in electricity flow.

In the free convection regime of pool boiling, the heat flux is proportional to

The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the

For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would

In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is

Evaporation by thermocompression results in the

Heat sensitive materials can be concentrated in an evaporator employing

With increase in temperature, the thermal conductivity of a gas

The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is

In sub-cooled boiling,

A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is

Natural convection is characterised by

Thermal conductivity of a gas at low density, __________ with increase in temperature.

For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

When warm and cold liquids are mixed, the heat transfer is mainly by

Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212¬∞F may be around __________ BTU.$

For a perfectly transparent surface (like gases), the

To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is

In case of a vertical tube evaporator, with increase in the liquor level, the

In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will

If heat transfer rate varies with the time, it is termed as

Steam economy in case of a triple effect evaporator will be

Rate of heat transfer by vaporisation from pools of water is affected by the

Open pan evaporators are preferred to be used, when the solution to be concentrated is

Sensible heat of hot industrial flue gases can not be recovered by a/an

Tube pitch is the __________ of tube diameters and the clearances.

In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.

At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?

For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

Dietus-Boelter equation cannot be used for molten metals mainly due to its very low

For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is

In evaporators, lowering the feed temperature

Which of the following has the lowest Prandtl number ?

In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of

The equation, Nst = f/2, is the __________ analogy.

In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used

Three material A, B and C of equal thick-nes and of thermal conductivity of 20, 40 & 60 kcal/hr. m. ¬∞C respectively are joined together. The temperature outside of A and C are 30¬∞C and 100¬∞C respectively. The interface between B and C will be at a temperature of __________ ¬∞C.$

Boiling point elevation of a solution of NaOH

With increase in temperature, the thermal conductivity of fresh lubricating oil