'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a

conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient.

For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it

is easy to operate and maintain.

In the equation Q = UAŒît; Œît is

the difference of average bulk temperatures of hot and cold fluids.

geometric mean temperature difference.

arithmetic mean temperature difference.

logarithmic mean temperature difference.

the difference of average bulk temperatures of hot and cold fluids.

Multiple effect evaporators ar used to

decrease the steam economy & the capacity.

increase the steam economy & decrease the capacity.

increase the steam economy & the capacity.

decrease the steam economy & the capacity.

decrease the steam economy & increase the capacity.

The Graetz number is concerned with the

mass transfer between a gas and a liquid.

absorption with chemical reaction.

heat transfer in turbulent flow.

A 2-4 heat exchanger involves

smaller pressure drop compared to 1-2 exchanger.

both counter and parallel-flow of the fluids.

smaller pressure drop compared to 1-2 exchanger.

Presence of a non-condensing gas in a condensing vapour

increases the rate of condensation.

is desirable to increase the film co-efficient.

In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate.

may increase or decrease, depends on the type of baffle

The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

may increase or decrease ; depends on the material

With the increase of temperature, the Col-burn jH factor

may increase or decrease ; depending on temperature.

Film boiling is usually not desired in commercial equipments, because

the heat transfer rate is low in view of the large temperature drop.

The advantage of backward feed multiple effect evaporators over forward feed units is that

equal heat transfer co-efficients exist in various effects.

heat sensitive material can be handled.

there is no additional cost of pumping.

most concentrated liquid is at highest temperature.

equal heat transfer co-efficients exist in various effects.

The purpose of providing expansion bellows in the shell of tubular exchanger is to

facilitate increase of shell length, if needed.

account for the uneven expansion of shell and tube bundles.

facilitate increase of shell length, if needed.

In a heat exchanger, floating head is provided to

increase log mean temperature gradient.

facilitate cleaning of the exchanger.

increase the heat transfer area.

relieve stresses caused by thermal expansion.

increase log mean temperature gradient.

In a forward feed multiple effect evaporator unit

viscosity of liquid is highest in first effect.

transfer from effect to effect is done by pumps.

no pump is required to withdraw the product from the last effect.

Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is

in the central core of the fluid.

uniformly distributed throughout the fluid.

mainly confined to a thin film of fluid near the surface.

Baffles in the shell side of a shell and tube heat exchanger

decrease the shell side heat transfer co-efficient.

increase the cross-section of the shell side liquid.

force the liquid to flow parallel to the bank.

increase the shell side heat transfer co-efficient.

decrease the shell side heat transfer co-efficient.

Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?

Corrosiveness & fouling characteristics

640 + Mcqs in Heat Transfer in Chemical Engineering Page 12 McqOptions

551.	Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is
A.	IR
B.	I2R
C.	IR2
D.	I2R2
Answer» C. IR2

Discussion

552.	Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500¬∞C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for
A.	cube
B.	cylinder
C.	sphere
D.	equal for all the three
Answer» B. cylinder

Discussion

553.	'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a
A.	non-dimensional factor.
B.	factor of safety.
C.	conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient.
D.	none of these.
Answer» C. conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient.

Discussion

554.	jH factor for heat transfer is not a function of the __________ number.
A.	Reynolds
B.	Nusselt
C.	Grashoff
D.	both (b) & (c)
Answer» E.

Discussion

555.	A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides
A.	higher economy
B.	lower capacity
C.	both (a) & (b)
D.	lower economy
Answer» B. lower capacity

Discussion

556.	For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it
A.	occupies smaller space.
B.	is more economical.
C.	is easy to operate and maintain.
D.	all (a), (b) and (c).
Answer» E.

Discussion

557.	In the equation Q = UAŒît; Œît is
A.	geometric mean temperature difference.
B.	arithmetic mean temperature difference.
C.	logarithmic mean temperature difference.
D.	the difference of average bulk temperatures of hot and cold fluids.
Answer» D. the difference of average bulk temperatures of hot and cold fluids.

Discussion

558.	Nucleate boiling is promoted
A.	on polished surfaces
B.	on rough surfaces
C.	in the absence of agitation
D.	none of these
Answer» C. in the absence of agitation

Discussion

559.	Water is normally used as a coolant in the heat exchange equipments mainly because ofits
A.	abundance & high heat capacity
B.	low density
C.	low viscosity
D.	high fluidity
Answer» B. low density

Discussion

560.	Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.
A.	no
B.	the least
C.	the largest
D.	lower
Answer» D. lower

Discussion

561.	If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.
A.	hyperbolic
B.	parabolic
C.	linear
D.	logarithmic
Answer» D. logarithmic

Discussion

562.	Multiple effect evaporators ar used to
A.	increase the steam economy & decrease the capacity.
B.	increase the steam economy & the capacity.
C.	decrease the steam economy & the capacity.
D.	decrease the steam economy & increase the capacity.
Answer» C. decrease the steam economy & the capacity.

Discussion

563.	Kg of liquid evaporated per hour in an evaporator is defined as its
A.	capacity
B.	economy
C.	steam load
D.	none of these
Answer» B. economy

Discussion

564.	The Graetz number is concerned with the
A.	mass transfer between a gas and a liquid.
B.	absorption with chemical reaction.
C.	heat transfer in turbulent flow.
D.	heat transfer in laminar flow.
Answer» E.

Discussion

565.	A 2-4 heat exchanger involves
A.	only counter-flow of fluids.
B.	only parallel-flow of fluids.
C.	both counter and parallel-flow of the fluids.
D.	smaller pressure drop compared to 1-2 exchanger.
Answer» D. smaller pressure drop compared to 1-2 exchanger.

Discussion

566.	Presence of a non-condensing gas in a condensing vapour
A.	increases the rate of condensation.
B.	decreases thermal resistance.
C.	is desirable to increase the film co-efficient.
D.	none of these.
Answer» E.

Discussion

567.	The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.¬∞K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is - 5¬∞C. The outside wall temperature is
A.	25¬∞C
B.	30¬∞C
C.	35¬∞C
D.	40¬∞C
Answer» D. 40¬∞C

Discussion

568.	In SI units, fouling factor is expressed in
A.	m2¬∞K/W
B.	W/m2¬∞K
C.	m2¬∞K
D.	m¬∞K/W
Answer» B. W/m2¬∞K

Discussion

569.	Boiling of milk in an open vessel is an example of __________ boiling.
A.	film
B.	sub-cooled
C.	saturated nucleate
D.	none of these
Answer» B. sub-cooled

Discussion

570.	For an ideal black body
A.	absorptivity = 1
B.	reflectivity = 1
C.	emissivity = 0
D.	transmissivity = 1
Answer» B. reflectivity = 1

Discussion

571.	Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by This is valid for the value of NRe equal to
A.	< 2100
B.	2100-4000
C.	> 4000
D.	> 10000
Answer» E.

Discussion

572.	The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is
A.	Nusselt number.
B.	Sherwood number.
C.	Schmidt number.
D.	Stanton number.
Answer» D. Stanton number.

Discussion

573.	Nusselt number is the ratio of the temperature gradient at the wall to
A.	temperature difference
B.	heat flux
C.	that across the entire pipe
D.	none of these
Answer» D. none of these

Discussion

574.	In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate.
A.	increases
B.	decreases
C.	does not affect
D.	may increase or decrease, depends on the type of baffle
Answer» B. decreases

Discussion

575.	The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.
A.	increases
B.	decreases
C.	remains constant
D.	may increase or decrease ; depends on the material
Answer» E.

Discussion

576.	If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length
A.	ha = hl
B.	ha = 2hl
C.	ha = 0.5 hl
D.	ha = 0.75 hl
Answer» C. ha = 0.5 hl

Discussion

577.	For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
A.	high pressure
B.	vacuum
C.	backward feed
D.	none of these
Answer» C. backward feed

Discussion

578.	The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are
A.	(COP)R = (COP)HP = 0.6
B.	(COP)R = 2.5; (COP)HP = 1.5
C.	(COP)R = 1.5; (COP)HP = 2.5
D.	(COP)R = (COP)HP = 2.5
Answer» D. (COP)R = (COP)HP = 2.5

Discussion

579.	For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are
A.	same
B.	different
C.	never different
D.	linearly related
Answer» C. never different

Discussion

580.	The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is
A.	1.66
B.	88.66
C.	3.66
D.	dependent on NRe only
Answer» D. dependent on NRe only

Discussion

581.	With the increase of temperature, the Col-burn jH factor
A.	increases.
B.	decreases.
C.	remains unchanged.
D.	may increase or decrease ; depending on temperature.
Answer» B. decreases.

Discussion

582.	Film boiling is usually not desired in commercial equipments, because
A.	the heat transfer rate is low in view of the large temperature drop.
B.	it is difficult to maintain.
C.	it is not economic.
D.	none of these.
Answer» B. it is difficult to maintain.

Discussion

583.	A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?
A.	Yellow paint
B.	White paint
C.	Black paint
D.	Grey paint
Answer» D. Grey paint

Discussion

584.	The advantage of backward feed multiple effect evaporators over forward feed units is that
A.	heat sensitive material can be handled.
B.	there is no additional cost of pumping.
C.	most concentrated liquid is at highest temperature.
D.	equal heat transfer co-efficients exist in various effects.
Answer» D. equal heat transfer co-efficients exist in various effects.

Discussion

585.	The purpose of providing expansion bellows in the shell of tubular exchanger is to
A.	increase the heating load.
B.	impart structural strength.
C.	account for the uneven expansion of shell and tube bundles.
D.	facilitate increase of shell length, if needed.
Answer» D. facilitate increase of shell length, if needed.

Discussion

586.	In a heat exchanger, floating head is provided to
A.	facilitate cleaning of the exchanger.
B.	increase the heat transfer area.
C.	relieve stresses caused by thermal expansion.
D.	increase log mean temperature gradient.
Answer» D. increase log mean temperature gradient.

Discussion

587.	In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.
A.	nucleate
B.	pool
C.	low pressure
D.	none of these
Answer» C. low pressure

Discussion

588.	In a forward feed multiple effect evaporator unit
A.	viscosity of liquid is highest in first effect.
B.	transfer from effect to effect is done by pumps.
C.	no pump is required to withdraw the product from the last effect.
D.	none of these.
Answer» E.

Discussion

589.	Film boiling occurs at __________ pressure.
A.	atmospheric
B.	sub-atmospheric
C.	negative
D.	very high
Answer» E.

Discussion

590.	Reynold's analogy states that
A.	Nst Œ± f
B.	Nst Œ± NRe
C.	NNu Œ± f
D.	NRe Œ± f
Answer» B. Nst Œ± NRe

Discussion

591.	Which one gives the monochromatic emissive power for black body radiation ?
A.	Planck's law
B.	Kirchhoffs law
C.	Wien's law
D.	Stefan-Boltzman law
Answer» B. Kirchhoffs law

Discussion

592.	Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is
A.	in the central core of the fluid.
B.	uniformly distributed throughout the fluid.
C.	mainly confined to a thin film of fluid near the surface.
D.	none of these.
Answer» D. none of these.

Discussion

593.	Which is the most suitable for cold viscous feed?
A.	Forward feed
B.	Backward feed
C.	Mixed feed
D.	Parallel feed
Answer» C. Mixed feed

Discussion

594.	The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.
A.	greater than
B.	lower than
C.	is same as
D.	half
Answer» C. is same as

Discussion

595.	Baffles in the shell side of a shell and tube heat exchanger
A.	increase the cross-section of the shell side liquid.
B.	force the liquid to flow parallel to the bank.
C.	increase the shell side heat transfer co-efficient.
D.	decrease the shell side heat transfer co-efficient.
Answer» D. decrease the shell side heat transfer co-efficient.

Discussion

596.	Grashoff number, which is defined as g . Œ≤(Ts - T‚àû) œÅ2. L3/Œº2, is proportional to the ratio of buoyancy force to __________ force.
A.	viscous
B.	elastic
C.	inertial
D.	none of these
Answer» B. elastic

Discussion

597.	According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)
A.	2f
B.	f
C.	f/2
D.	f/4
Answer» D. f/4

Discussion

598.	Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?
A.	Corrosiveness & fouling characteristics
B.	pressure
C.	viscosity
D.	density
Answer» E.

Discussion

599.	For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)
A.	NPr
B.	NPr1/3
C.	NPr-1
D.	NPr-1/3
Answer» C. NPr-1

Discussion

600.	Baffles are provided in heat exchangers to increase the
A.	fouling factor
B.	heat transfer area
C.	heat transfer co-efficient
D.	heat transfer rate
Answer» D. heat transfer rate

Discussion

Explore topic-wise MCQs in Chemical Engineering.

Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is

'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a

jH factor for heat transfer is not a function of the __________ number.

A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides

For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it

In the equation Q = UAŒît; Œît is

Nucleate boiling is promoted

Water is normally used as a coolant in the heat exchange equipments mainly because ofits

Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.

If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.

Multiple effect evaporators ar used to

Kg of liquid evaporated per hour in an evaporator is defined as its

The Graetz number is concerned with the

A 2-4 heat exchanger involves

Presence of a non-condensing gas in a condensing vapour

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.¬∞K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is - 5¬∞C. The outside wall temperature is

In SI units, fouling factor is expressed in

Boiling of milk in an open vessel is an example of __________ boiling.

For an ideal black body

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by This is valid for the value of NRe equal to

The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is

Nusselt number is the ratio of the temperature gradient at the wall to

In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate.

The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length

For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.

For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is

With the increase of temperature, the Col-burn jH factor

Film boiling is usually not desired in commercial equipments, because

A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ?

The advantage of backward feed multiple effect evaporators over forward feed units is that

The purpose of providing expansion bellows in the shell of tubular exchanger is to

In a heat exchanger, floating head is provided to

In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.

In a forward feed multiple effect evaporator unit

Film boiling occurs at __________ pressure.

Reynold's analogy states that

Which one gives the monochromatic emissive power for black body radiation ?

Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is

Which is the most suitable for cold viscous feed?

The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.

Baffles in the shell side of a shell and tube heat exchanger

Grashoff number, which is defined as g . Œ≤(Ts - T‚àû) œÅ2. L3/Œº2, is proportional to the ratio of buoyancy force to __________ force.

According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)

Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

Baffles are provided in heat exchangers to increase the