8247 + Mcqs in Chemical Engineering Page 76 McqOptions

3751.	When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
A.	At high fluid velocity
B.	At low velocity
C.	When fluid flows past a smooth surface
D.	None of these
Answer» B. At low velocity

Discussion

3752.	A long iron rod initially at a temperature of 20 C has one end dipped in boiling water (100 C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40 C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time
A.	t = 283 s
B.	t = 356 s
C.	t = 400 s
D.	t = 800 s
Answer» E.

Discussion

3753.	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

3754.	Rate of crystallisation does not depend upon the
A.	extent of supersaturation.
B.	turbulence within the solution.
C.	number and active surface area of the crystals.
D.	none of these.
Answer» E.

Discussion

3755.	Stefen's block body radiation law can also be derived from __________ law.
A.	Kirchoffs
B.	Planck's
C.	Fourier's
D.	none of these
Answer» C. Fourier's

Discussion

3756.	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

3757.	A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,
A.	the cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant.
B.	both the spheres will emit equal amount of radiation per unit time in the beginning.
C.	both will absorb equal amount of radiation from the surrounding in the beginning.
D.	both(b) & (c).
Answer» E.

Discussion

3758.	Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 . C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the
A.	higher condensing film co-efficient is desired.
B.	condensate is corrosive in nature.
C.	lower pressure drop through the exchanger is desired.
D.	temperature of the incoming vapor is very high.
Answer» C. lower pressure drop through the exchanger is desired.

Discussion

3759.	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

3760.	Dropwise condensation is promoted on a/an __________ surface.
A.	glazed
B.	oily
C.	coated
D.	smooth
Answer» C. coated

Discussion

3761.	At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the
A.	buffer zone
B.	turbulent core
C.	both (a) and (b)
D.	viscous sub-layer
Answer» E.

Discussion

3762.	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

3763.	is called the __________ number
A.	Peclet
B.	Stanton
C.	Graetz
D.	none of these
Answer» D. none of these

Discussion

3764.	In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.
A.	once
B.	twice
C.	thrice
D.	four times
Answer» C. thrice

Discussion

3765.	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

3766.	The purpose of providing bleed points in the evaporator is to
A.	admit the feed
B.	remove the product
C.	facilitate removal of non-condensable gases
D.	create vacuum
Answer» D. create vacuum

Discussion

3767.	Water always boils when its
A.	temperature reaches 100 C.
B.	vapour pressure equals 76 cm of Hg.
C.	saturated vapour pressure equals the external pressure on its surface.
D.	saturated vapour pressure is less than the atmospheric pressure.
Answer» D. saturated vapour pressure is less than the atmospheric pressure.

Discussion

3768.	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

3769.	h.D/K is called the __________ number.
A.	Nusselt
B.	Peclet
C.	Rayleigh
D.	Grashoff
Answer» B. Peclet

Discussion

3770.	Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the
A.	existence of thermal boundary layer.
B.	temperature gradient produced due to density difference
C.	buoyancy of the bubbles produced at active nucleation site.
D.	none of these.
Answer» E.

Discussion

3771.	Evaporator tubes are generally
A.	horizontal
B.	vertical
C.	inclined
D.	random
Answer» C. inclined

Discussion

3772.	For a counter current heat exchanger with Tih = 80 C, T c = 60 C, T h = 50 C and Tic = 30 C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy
A.	<img src="/_files/images/chemical-engineering/heat-transfer/271-494-1.png">
B.	<img src="/_files/images/chemical-engineering/heat-transfer/271-494-2.png">
C.	<img src="/_files/images/chemical-engineering/heat-transfer/271-494-3.png">
D.	<img src="/_files/images/chemical-engineering/heat-transfer/271-494-4.png">
Answer» C. <img src="/_files/images/chemical-engineering/heat-transfer/271-494-3.png">

Discussion

3773.	In a boiling curve, the peak heat flux is called the __________ point.
A.	Nusselt
B.	Leidenfrost
C.	boiling
D.	burnout
Answer» E.

Discussion

3774.	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

3775.	What is the logarithmic mean of r1 and r2 ?
A.	<img src="/_files/images/chemical-engineering/heat-transfer/233-14-1.png">
B.	<img src="/_files/images/chemical-engineering/heat-transfer/233-14-2.png">
C.	<img src="/_files/images/chemical-engineering/heat-transfer/233-14-3.png">
D.	<img src="/_files/images/chemical-engineering/heat-transfer/233-14-4.png">
Answer» B. <img src="/_files/images/chemical-engineering/heat-transfer/233-14-2.png">

Discussion

3776.	Maximum heat transfer rate is achieved in __________ flow.
A.	co-current
B.	counter-current
C.	turbulent
D.	laminar
Answer» D. laminar

Discussion

3777.	Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law.
A.	Stefan's
B.	Dalton's
C.	Wien's
D.	Kirchoffs
Answer» D. Kirchoffs

Discussion

3778.	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

3779.	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

3780.	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

3781.	In a shell and tube heat exchanger, floating head is used for
A.	large temperature differentials.
B.	high heat transfer co-efficient.
C.	low pressure drop.
D.	less corrosion of tubes.
Answer» B. high heat transfer co-efficient.

Discussion

3782.	Steam trap is used to
A.	condense the steam flowing in the pipeline.
B.	remove water resulting from partial condensation of steam.
C.	stop the supply of steam.
D.	none of these.
Answer» C. stop the supply of steam.

Discussion

3783.	The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.
A.	Colburn
B.	Reynolds
C.	Prandtl
D.	none of these.
Answer» B. Reynolds

Discussion

3784.	The driving potential for the crystal growth during crystallisation is the __________ of the solution.
A.	concentration
B.	viscosity
C.	super-saturation
D.	density
Answer» D. density

Discussion

3785.	jH factor for heat transfer depends upon the __________ number.
A.	Biot
B.	Nusselt
C.	Reynolds
D.	Prandtl
Answer» D. Prandtl

Discussion

3786.	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

3787.	The separation of liquid droplets from the vapor is done by a/an __________ , in the evaporators.
A.	steam ejector
B.	entrainment separator
C.	compressor
D.	vacuum pump
Answer» C. compressor

Discussion

3788.	A steel sphere of radius 0.1 m at 400 K is immersed in an oil at 300 K. If the centre of the sphere reaches 350 K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
A.	5 minutes
B.	10 minutes
C.	20 minutes
D.	40 minutes
Answer» B. 10 minutes

Discussion

3789.	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

3790.	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

3791.	In forced circulation, the heating element is injected
A.	internally
B.	externally
C.	both (a) and (a)
D.	neither (a) nor (b)
Answer» B. externally

Discussion

3792.	If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is
A.	1
B.	2
C.	1/2
D.	4
Answer» C. 1/2

Discussion

3793.	The equation, Nst = f/2, is the __________ analogy.
A.	Colburn
B.	Reynolds
C.	Prandtl
D.	none of these
Answer» C. Prandtl

Discussion

3794.	Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
A.	boiling point
B.	dynamic viscosity
C.	kinematic viscosity
D.	density
Answer» B. dynamic viscosity

Discussion

3795.	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

3796.	Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?
A.	aluminium foil
B.	refractory bricks
C.	iron plate
D.	coke breeze
Answer» E.

Discussion

3797.	Thermal diffusivity is given by
A.	<img src="/_files/images/chemical-engineering/heat-transfer/233-17-1.png">
B.	<img src="/_files/images/chemical-engineering/heat-transfer/233-17-2.png">
C.	<img src="/_files/images/chemical-engineering/heat-transfer/233-16-1.png">
D.	<img src="/_files/images/chemical-engineering/heat-transfer/233-17-4.png">
Answer» B. <img src="/_files/images/chemical-engineering/heat-transfer/233-17-2.png">

Discussion

3798.	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

3799.	Fourier's law of heat conduction applies to __________ surfaces.
A.	isothermal
B.	non-isothermal
C.	both (a) and (b)
D.	neither (a) and (b)
Answer» D. neither (a) and (b)

Discussion

3800.	__________ chart is known as transient heat conduction chart.
A.	Dirhing's
B.	Heisler's
C.	Mollier's
D.	Cox
Answer» B. Heisler's

Discussion

Explore topic-wise MCQs in Engineering.

When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?

LMTD for evaporators &amp; condensers for a given terminal parameters &amp; 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.

Rate of crystallisation does not depend upon the

Stefen's block body radiation law can also be derived from __________ law.

Multipass heat exchangers are used

A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 . C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

Which is the most suitable for cold viscous feed?

Dropwise condensation is promoted on a/an __________ surface.

At Pr &gt; 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the

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

is called the __________ number

In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.

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

The purpose of providing bleed points in the evaporator is to

Water always boils when its

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

h.D/K is called the __________ number.

Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

Evaporator tubes are generally

For a counter current heat exchanger with Tih = 80 C, T c = 60 C, T h = 50 C and Tic = 30 C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy

In a boiling curve, the peak heat flux is called the __________ point.

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

What is the logarithmic mean of r1 and r2 ?

Maximum heat transfer rate is achieved in __________ flow.

Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law.

Three material A, B and C of equal thick-nes and of thermal conductivity of 20, 40 &amp; 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.

Heat sensitive materials can be concentrated in an evaporator employing

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

In a shell and tube heat exchanger, floating head is used for

Steam trap is used to

The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.

The driving potential for the crystal growth during crystallisation is the __________ of the solution.

jH factor for heat transfer depends upon the __________ number.

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

The separation of liquid droplets from the vapor is done by a/an __________ , in the evaporators.

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

Nucleate boiling is promoted

In forced circulation, the heating element is injected

If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is

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

Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.

In a heat exchanger, one transfer unit means

Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?

Thermal diffusivity is given by

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

Fourier's law of heat conduction applies to __________ surfaces.

__________ chart is known as transient heat conduction chart.

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.

At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the

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.