In a forward feed multiple effect, the pressure build up will be

highest at the inlet of the last effect.

least at the inlet of the first effect.

least at the outlet of the last effect.

highest at the inlet of the last effect.

highest at the outlet of the last effect.

Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

average temperature of the fin.

constant temperature equal to that of the base

In a forward feed multiple effect evaporator, the pressure is

dependent on the number of effects

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is

entry length problem in laminar forced conduction (developing thermal boundary layer)

mixed convection (both free and forced)

Analogy between mass and heat transfer is not applicable in case of

same velocity profile or equal eddy diffusivities.

thermal or pressure mass diffusion.

viscous heating or chemical reaction.

In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is

equal to the difference between hot and cold fluids inlet temperature.

equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature.

In a heat exchanger, one transfer unit means

the size of the exchanger in which heat transfer rate is 1 kcal/hr.

a section of the exchanger in which change in temperature of one stream equals the average driving force in the section.

the size of the exchanger in which heat transfer rate is 1 kcal/hr.

is not the same as baffle pitch.

should be less than one fifth the diameter of the shell.

should be less than the inside diameter of the shell.

Boiling point elevation of an ideal solution

decreases rapidly with temperature rise

increases rapidly with temperature rise.

decreases rapidly with temperature rise

A multiple effect evaporator as compared to a single effect evaporator of the same capacity has

higher solute concentration in the product.

The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the

evaporators operate under vacuum.

solution has an elevation of boiling point.

evaporators operate under vacuum.

evaporators opreate at atmospheric pressure.

The thickness of condensate layer in filmwise condensation depends on the

liquid flow rate from the surface

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

increase the condensing film co-efficient as well as

LMTD for counterflow and prallel flow heat exchanger will be the same, when the

outlent temperature of both the hot and cold fluid are same.

cold fluid is heated to a certain temperature by condensing steam (isothermal fluid).

outlent temperature of both the hot and cold fluid are same.

outlet temperature of hot fluid is less than the outlet temperature of the cold fluid.

In pipe flow, heat is transferred from hot wall to the liquid by

forced convection and conduction.

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?

Calenderia vertical tube evaporator

Multipass heat exchangers are used

because of simplicity of fabrication.

to obtain higher heat transfer co-efficient and shorter tube.

Which of the following situations can be approximated to a steady state heat transfer system ?

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬∞C.

A red hot steel slab (having outside surface temperature as 1300¬∞C) exposed to the atmosheric air at 35¬∞C.

10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35¬∞C.

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬∞C.

A sub-cooled refrigerant liquid at 8¬∞C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35¬∞C.

The main function of baffles provided in a shell and tube heat exchanger is to

facilitate the cleaning of outer tube surface.

Prandtl number is the ratio of

thermal diffusivity to mass diffusivity.

momentum diffusivity to mass diffusivity.

momentum diffusivity to thermal diffusivity.

thermal diffusivity to mass diffusivity.

thermal diffusivity to momentum diffusivity.

Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube

exit-fluid temperature > wall temperature.

exit fluid temperature < wall temperature.

exit fluid temperature = wall temperature.

The actual temperature drop across the heating surface of an evaporator depends on the

liquid depth over the heating surface.

pressure difference between the steam chest and the vapor space above the boiling liquid.

640 + Mcqs in Heat Transfer in Chemical Engineering Page 7 McqOptions

301.	In a forward feed multiple effect, the pressure build up will be
A.	least at the inlet of the first effect.
B.	least at the outlet of the last effect.
C.	highest at the inlet of the last effect.
D.	highest at the outlet of the last effect.
Answer» C. highest at the inlet of the last effect.

Discussion

302.	__________ equation relates the thermal conductivity of a solid to its temperature.
A.	Antonie
B.	Kopp's
C.	Lee's
D.	Kistyakowski
Answer» D. Kistyakowski

Discussion

303.	Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
A.	surrounding temperature.
B.	average temperature of the fin.
C.	temperature of the fin end.
D.	constant temperature equal to that of the base
Answer» E.

Discussion

304.	In a forward feed multiple effect evaporator, the pressure is
A.	highest in last effect
B.	lowest in last effect
C.	same in all effects
D.	dependent on the number of effects
Answer» C. same in all effects

Discussion

305.	When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is
A.	free convection
B.	entry length problem in laminar forced conduction (developing thermal boundary layer)
C.	mixed convection (both free and forced)
D.	forced convection
Answer» D. forced convection

Discussion

306.	Analogy between mass and heat transfer is not applicable in case of
A.	same velocity profile or equal eddy diffusivities.
B.	thermal or pressure mass diffusion.
C.	viscous heating or chemical reaction.
D.	both (b) and (c).
Answer» E.

Discussion

307.	In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is
A.	‚àû
B.	0
C.	equal to the difference between hot and cold fluids inlet temperature.
D.	equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature.
Answer» C. equal to the difference between hot and cold fluids inlet temperature.

Discussion

308.	A hot body will radiate heat most rapidly, if its surface is
A.	white & rough
B.	black & rough
C.	white & polished
D.	black & polished
Answer» C. white & polished

Discussion

309.	In a heat exchanger, one transfer unit means
A.	a section of the exchanger in which change in temperature of one stream equals the average driving force in the section.
B.	the size of the exchanger in which heat transfer rate is 1 kcal/hr.
C.	both (a) and (b)
D.	none of these
Answer» B. the size of the exchanger in which heat transfer rate is 1 kcal/hr.

Discussion

310.	Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface)
A.	U1 - U2
B.
Answer» C.

Discussion

311.	Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)
A.	d
B.	d
C.	d2
D.	d1.5
Answer» D. d1.5

Discussion

312.	Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)
A.	x/KA
B.	KA/x
C.	K/Ax
D.	A/Kx
Answer» C. K/Ax

Discussion

313.	Agitated film evaporator is suitable for concentrating __________ liquids.
A.	foaming
B.	viscous
C.	very thin
D.	corrosive
Answer» C. very thin

Discussion

314.	Baffle spacing
A.	is not the same as baffle pitch.
B.	should be less than one fifth the diameter of the shell.
C.	should be less than the inside diameter of the shell.
D.	none of these.
Answer» D. none of these.

Discussion

315.	Maximum heat transfer rate is achieved in __________ flow.
A.	co-current
B.	counter-current
C.	turbulent
D.	laminar
Answer» D. laminar

Discussion

316.	The Dietus-Boelter equation for convective leat transfercannot be used for
A.	low Reynold's number
B.	very low Grashoff number
C.	molten metals
D.	all (a), (b) and (c)
Answer» E.

Discussion

317.	Dropwise condensation is promoted on a/an __________ surface.
A.	glazed
B.	oily
C.	coated
D.	smooth
Answer» C. coated

Discussion

318.	Boiling point elevation of an ideal solution
A.	increases rapidly with temperature rise.
B.	decreases rapidly with temperature rise
C.	in independent of pressure.
D.	both (b) and (c).
Answer» B. decreases rapidly with temperature rise

Discussion

319.	Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer.
A.	Grashoff
B.	Biot
C.	Stantan
D.	Reynolds
Answer» B. Biot

Discussion

320.	A multiple effect evaporator as compared to a single effect evaporator of the same capacity has
A.	lower heat transfer area.
B.	lower steam economy.
C.	higher steam economy.
D.	higher solute concentration in the product.
Answer» D. higher solute concentration in the product.

Discussion

321.	The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the
A.	solution has an elevation of boiling point.
B.	evaporators operate under vacuum.
C.	evaporators opreate at atmospheric pressure.
D.	none of these.
Answer» B. evaporators operate under vacuum.

Discussion

322.	The ratio of momentum diffusivity to thermal diffusivity is the __________ number.
A.	Prandtl
B.	Nusselt
C.	Stanton
D.	Grashoff
Answer» B. Nusselt

Discussion

323.	A __________ surface has the maximum thermal emissivity out of the following.
A.	black & smooth
B.	black & rough
C.	white & smooth
D.	white & rough
Answer» C. white & smooth

Discussion

324.	The thickness of condensate layer in filmwise condensation depends on the
A.	condensation rate
B.	surface configuration
C.	liquid flow rate from the surface
D.	all (a), (b) and (c)
Answer» E.

Discussion

325.	If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
A.	increase
B.	decrease
C.	not affect
D.	increase the condensing film co-efficient as well as
Answer» C. not affect

Discussion

326.	LMTD for counterflow and prallel flow heat exchanger will be the same, when the
A.	cold fluid is heated to a certain temperature by condensing steam (isothermal fluid).
B.	outlent temperature of both the hot and cold fluid are same.
C.	outlet temperature of hot fluid is less than the outlet temperature of the cold fluid.
D.	none of these.
Answer» B. outlent temperature of both the hot and cold fluid are same.

Discussion

327.	LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.
A.	parallel
B.	mixed
C.	counterflow
D.	same in either 'a', b' or 'c'
Answer» E.

Discussion

328.	In pipe flow, heat is transferred from hot wall to the liquid by
A.	conduction only.
B.	forced convection only.
C.	forced convection and conduction.
D.	free and forced convection.
Answer» D. free and forced convection.

Discussion

329.	Which is the most suitable for the concentration of foamy & frothy liquors ?
A.	Agitated film evaporator
B.	Long tube vertical evaporator
C.	Open pan evaporator
D.	None of these
Answer» C. Open pan evaporator

Discussion

330.	Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
A.	Long vertical evaporator
B.	Horizontal tube evaporator
C.	Agitated film evaporator
D.	Calenderia vertical tube evaporator
Answer» D. Calenderia vertical tube evaporator

Discussion

331.	In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell)
A.	0.25 D
B.	0.75 D
C.	0.50 D
D.	none of these
Answer» C. 0.50 D

Discussion

332.	Multipass heat exchangers are used
A.	because of simplicity of fabrication.
B.	for low heat load.
C.	to obtain higher heat transfer co-efficient and shorter tube.
D.	to reduce the pressure drop.
Answer» D. to reduce the pressure drop.

Discussion

333.	is termed as the __________ number.
A.	Grashoff
B.	Nusselt
C.	Prandtl
D.	Stanton
Answer» D. Stanton

Discussion

334.	The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
A.	‚àù t
B.	‚àù 1/t
C.	‚àù t
D.	independent of 't'
Answer» C. ‚àù t

Discussion

335.	A black body does not __________ radiation.
A.	absorb or emit
B.	refract
C.	reflect
D.	both(b) & (c)
Answer» E.

Discussion

336.	Which of the following situations can be approximated to a steady state heat transfer system ?
A.	A red hot steel slab (having outside surface temperature as 1300¬∞C) exposed to the atmosheric air at 35¬∞C.
B.	10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35¬∞C.
C.	Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬∞C.
D.	A sub-cooled refrigerant liquid at 8¬∞C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35¬∞C.
Answer» C. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬∞C.

Discussion

337.	A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300¬∞C and allowed to cool in natural air. Which one will cool the slowest ?$
A.	Cube
B.	Plate
C.	Sphere
D.	All will cool at the same rate
Answer» D. All will cool at the same rate

Discussion

338.	The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns.
A.	0.38-0.78
B.	0.5-50
C.	100-1000
D.	18384
Answer» C. 100-1000

Discussion

339.	During crystallisation, formation of crystal can occur in __________ solution only.
A.	saturated
B.	supersaturated
C.	undersaturated
D.	all (a), (b) and (c)
Answer» C. undersaturated

Discussion

340.	The main function of baffles provided in a shell and tube heat exchanger is to
A.	facilitate the cleaning of outer tube surface.
B.	enhance turbulence.
C.	hold the tubes in position.
D.	all 'a', 'b' & 'c'.
Answer» C. hold the tubes in position.

Discussion

341.	Corrosiveness of steam condensate is due to the presence of
A.	CO2
B.	dissolved O2
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

342.	Prandtl number is the ratio of
A.	momentum diffusivity to mass diffusivity.
B.	momentum diffusivity to thermal diffusivity.
C.	thermal diffusivity to mass diffusivity.
D.	thermal diffusivity to momentum diffusivity.
Answer» C. thermal diffusivity to mass diffusivity.

Discussion

343.	Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by
A.	eddies current
B.	conduction
C.	convection
D.	none of these
Answer» C. convection

Discussion

344.	Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
A.	exit-fluid temperature > wall temperature.
B.	exit fluid temperature < wall temperature.
C.	exit fluid temperature = wall temperature.
D.	Graetz number > 100.
Answer» D. Graetz number > 100.

Discussion

345.	Heat transfer rate described by Fourier's law will decrease, if the __________ increases.
A.	thermal conductivity
B.	thickness
C.	temperature difference
D.	heat transfer area
Answer» C. temperature difference

Discussion

346.	The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.
A.	average
B.	geometric mean
C.	product
D.	sum
Answer» E.

Discussion

347.	What is the geometric mean of two heat transfer areas A1 and A2 ?
A.	A1 . A2
B.	A1 + A2
C.	A1 . A2
D.	2 A1 . A2
Answer» B. A1 + A2

Discussion

348.	Reynold's analogy states that (where, St = Stanton number f = friction factor)
A.
B.
Answer» B.

Discussion

349.	The actual temperature drop across the heating surface of an evaporator depends on the
A.	liquid depth over the heating surface.
B.	solution being evaporated.
C.	pressure difference between the steam chest and the vapor space above the boiling liquid.
D.	all (a), (b) and (c)
Answer» E.

Discussion

350.	LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is
A.	0
B.	1
C.	>1
D.	<1
Answer» E.

Discussion

Explore topic-wise MCQs in Chemical Engineering.

In a forward feed multiple effect, the pressure build up will be

__________ equation relates the thermal conductivity of a solid to its temperature.

Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

In a forward feed multiple effect evaporator, the pressure is

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is

Analogy between mass and heat transfer is not applicable in case of

In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is

A hot body will radiate heat most rapidly, if its surface is

In a heat exchanger, one transfer unit means

Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface)

Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)

Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)

Agitated film evaporator is suitable for concentrating __________ liquids.

Baffle spacing

Maximum heat transfer rate is achieved in __________ flow.

The Dietus-Boelter equation for convective leat transfercannot be used for

Dropwise condensation is promoted on a/an __________ surface.

Boiling point elevation of an ideal solution

Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer.

A multiple effect evaporator as compared to a single effect evaporator of the same capacity has

The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the

The ratio of momentum diffusivity to thermal diffusivity is the __________ number.

A __________ surface has the maximum thermal emissivity out of the following.

The thickness of condensate layer in filmwise condensation depends on the

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

LMTD for counterflow and prallel flow heat exchanger will be the same, when the

LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.

In pipe flow, heat is transferred from hot wall to the liquid by

Which is the most suitable for the concentration of foamy & frothy liquors ?

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?

In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell)

Multipass heat exchangers are used

is termed as the __________ number.

The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)

A black body does not __________ radiation.

Which of the following situations can be approximated to a steady state heat transfer system ?

A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300¬∞C and allowed to cool in natural air. Which one will cool the slowest ?$

The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns.

During crystallisation, formation of crystal can occur in __________ solution only.

The main function of baffles provided in a shell and tube heat exchanger is to

Corrosiveness of steam condensate is due to the presence of

Prandtl number is the ratio of

Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by

Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube

Heat transfer rate described by Fourier's law will decrease, if the __________ increases.

The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.

What is the geometric mean of two heat transfer areas A1 and A2 ?

Reynold's analogy states that (where, St = Stanton number f = friction factor)

The actual temperature drop across the heating surface of an evaporator depends on the

LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is