8247 + Mcqs in Chemical Engineering Page 64 McqOptions

3151.	The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.
A.	Peclet
B.	Prandtl
C.	Stanton
D.	Nusselt
Answer» C. Stanton

Discussion

3152.	Mechanical recompression evaporation is used in the production of
A.	alcohol
B.	distilled water
C.	salt
D.	fruits jam
Answer» C. salt

Discussion

3153.	A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
A.	Condensation
B.	Grashoff
C.	Stantan
D.	Brinkman
Answer» E.

Discussion

3154.	Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
A.	0.35
B.	0.45
C.	0.55
D.	0.85
Answer» C. 0.55

Discussion

3155.	The purpose of providing a 'catchall' in the vapor line of an evaporator is to
A.	create vacuum
B.	regulate the vapor flow
C.	vent the non-condensible gases
D.	arrest the entrained liquid
Answer» E.

Discussion

3156.	What is the thermal conductivity of a perfect heat insulator ?
A.	zero
B.	one
C.
D.	between 0 and
Answer» B. one

Discussion

3157.	Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam.
A.	0.4 - 0.6
B.	1-1.3
C.	1.8-2
D.	2 - 2.4
Answer» C. 1.8-2

Discussion

3158.	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

3159.	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

3160.	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

3161.	Among liquids, water has a comparatively high value of thermal conductivity, due to its
A.	low density
B.	high viscosity
C.	partial ionisation
D.	dense structure
Answer» D. dense structure

Discussion

3162.	For evaporation of viscous solution in a multiple effect evaporator, the prefered feeding scheme is
A.	forward
B.	backward
C.	parallel
D.	none of these
Answer» C. parallel

Discussion

3163.	The film thickness for laminar film condensation on vertical surface __________ from top to bottom.
A.	cummulatively increases
B.	cummulatively decreases
C.	remains constant
D.	and the surface conductance increase
Answer» B. cummulatively decreases

Discussion

3164.	The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67xl0-8 W/m2.K4)
A.	1000
B.	727
C.	800
D.	1200
Answer» B. 727

Discussion

3165.	Crystallisation of solids from a homogeneous solution is a/an __________ process.
A.	exothermic
B.	mildly endothermic
C.	highly endothermic
D.	none of these
Answer» B. mildly endothermic

Discussion

3166.	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

3167.	A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is
A.	6000
B.	24000
C.	60000
D.	48000
Answer» C. 60000

Discussion

3168.	Value of Prandtl number for water ranges from
A.	l to 2
B.	5 to 10
C.	100 to 500
D.	1000 to 2000
Answer» C. 100 to 500

Discussion

3169.	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

3170.	A diathermaneous substance __________ the thermal radiation completely.
A.	absorbs
B.	reflects
C.	transmits
D.	none of these
Answer» D. none of these

Discussion

3171.	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

3172.	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

3173.	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

3174.	Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because
A.	convection becomes important
B.	conduction becomes important
C.	radiation becomes important
D.	sub-cooled boiling occurs
Answer» D. sub-cooled boiling occurs

Discussion

3175.	Resistance to heat flow by conduction is proportional to (where, t & are thickness & density of the material respectively and A = area normal to the direction of heat flow. )
A.	<i>t</i>
B.	1/
C.	1/
D.	<i>A</i>
E.	all (a), (b) & (c)
Answer» E. all (a), (b) & (c)

Discussion

3176.	Temperature profile in steady state heat transfer is
A.	asymptotic
B.	hyperbolic
C.	parabolic
D.	linear
Answer» E.

Discussion

3177.	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

3178.	For what value of Prandtl number, St = f/2?
A.	1.5
B.	1
C.	> 1
D.	< 1
Answer» C. > 1

Discussion

3179.	In a shell and tube heat exchanger,
A.	the temperature drops in the two fluids and the wall are proportional to individual resistances.
B.	the temperature drop is inversely proportional to the resistance across which the drop occurs.
C.	there is no relationship between temperature drop and resistance.
D.	the relationship is not generalised.
Answer» B. the temperature drop is inversely proportional to the resistance across which the drop occurs.

Discussion

3180.	Dietus-Boelter equation used for the determination of heat transfer co-efficient is valid
A.	for fluids in laminar flow.
B.	for fluids in tubulent flow.
C.	when Grashhoff number is very important.
D.	for liquid metals.
Answer» C. when Grashhoff number is very important.

Discussion

3181.	The equation, , corrosponds to __________ analogy.
A.	Von-Karmann
B.	Reynolds
C.	Colburn
D.	Prandtl
Answer» E.

Discussion

3182.	In forced convection, the heat transfer depends on
A.	Re, Pr
B.	Re, Gr
C.	mainly Gr
D.	Re only
Answer» B. Re, Gr

Discussion

3183.	With increase in temperature, the thermal conductivity of most liquids
A.	increases
B.	decreases
C.	remains same
D.	first increases upto a certain temperature and then becomes constant
Answer» C. remains same

Discussion

3184.	A perfect black body is a perfect __________ of radiation.
A.	absorber
B.	emitter
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

3185.	In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid.
A.	equal to
B.	more than
C.	less than
D.	either more or less than (depending upon the fluid)
Answer» B. more than

Discussion

3186.	An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a
A.	boiler
B.	heat exchanger
C.	recuperator
D.	regenerator
Answer» C. recuperator

Discussion

3187.	Which of the following is directly concerned with the heat transfer ?
A.	Strouhal number
B.	Sherwood number
C.	Euler number
D.	Grashoff number
Answer» E.

Discussion

3188.	For multicomponent multiple phases to be in equilibrium at the same pressure and temperature, the __________ of each component must be same in all phases.
A.	chemical potential
B.	fugacity
C.	both (a) and (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

3189.	The efficiency of an Otto engine compared to that of a diesel engine, for the same compression ratio will be
A.	more
B.	less
C.	same
D.	data insufficient to predict
Answer» B. less

Discussion

3190.	Mollier chart is a __________ plot.
A.	pressure vs enthalpy
B.	pressure vs volume
C.	enthalpy vs entropy
D.	temperature vs entropy
Answer» D. temperature vs entropy

Discussion

3191.	Heat evolved/absorbed during conversion of a substance from one allotropic form to another is termed as the heat of
A.	fusion
B.	vaporisation
C.	transition
D.	none of these
Answer» D. none of these

Discussion

3192.	What happens in a reversible adiabatic compression ?
A.	Heating occurs
B.	Cooling occurs
C.	Pressure is constant
D.	Temperature is constant
Answer» B. Cooling occurs

Discussion

3193.	Sublimation temperature of dry ice (solid CO2) is __________ C.
A.	-273
B.	0
C.	-78
D.	5
Answer» D. 5

Discussion

3194.	If atmospheric temperature and dew point are nearly equal, then the relative humidity is
A.	zero
B.	50%
C.	almost 100%
D.	unpredictable
Answer» D. unpredictable

Discussion

3195.	The internal energy of an incompressible fluid depends upon its
A.	pressure
B.	temperature
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» C. both (a) & (b)

Discussion

3196.	Which area is used in case of heat flow by conduction through a cylinder ?
A.	Logarithmic mean area
B.	Arithmetic mean area
C.	Geometric mean area
D.	None of these
Answer» B. Arithmetic mean area

Discussion

3197.	Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place
A.	between two bodies in physical contact with each other.
B.	between two bodies not in physical contact with each other.
C.	from one part of a body to the another part of the same body.
D.	both 'b' & 'c'
Answer» C. from one part of a body to the another part of the same body.

Discussion

3198.	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

3199.	Finned tube heat exchangers
A.	give larger area per tube.
B.	use metal fins of low thermal conductivity.
C.	facilitate very large temperature drop through tube wall.
D.	are used for smaller heat load.
Answer» B. use metal fins of low thermal conductivity.

Discussion

3200.	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

Explore topic-wise MCQs in Engineering.

The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.

Mechanical recompression evaporation is used in the production of

A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.

Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be

The purpose of providing a 'catchall' in the vapor line of an evaporator is to

What is the thermal conductivity of a perfect heat insulator ?

Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam.

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

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

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

Among liquids, water has a comparatively high value of thermal conductivity, due to its

For evaporation of viscous solution in a multiple effect evaporator, the prefered feeding scheme is

The film thickness for laminar film condensation on vertical surface __________ from top to bottom.

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67xl0-8 W/m2.K4)

Crystallisation of solids from a homogeneous solution is a/an __________ process.

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

A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is

Value of Prandtl number for water ranges from

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

A diathermaneous substance __________ the thermal radiation completely.

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

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

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

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because

Resistance to heat flow by conduction is proportional to (where, t &amp; are thickness &amp; density of the material respectively and A = area normal to the direction of heat flow. )

Temperature profile in steady state heat transfer is

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

For what value of Prandtl number, St = f/2?

In a shell and tube heat exchanger,

Dietus-Boelter equation used for the determination of heat transfer co-efficient is valid

The equation, , corrosponds to __________ analogy.

In forced convection, the heat transfer depends on

With increase in temperature, the thermal conductivity of most liquids

A perfect black body is a perfect __________ of radiation.

In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid.

An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a

Which of the following is directly concerned with the heat transfer ?

For multicomponent multiple phases to be in equilibrium at the same pressure and temperature, the __________ of each component must be same in all phases.

The efficiency of an Otto engine compared to that of a diesel engine, for the same compression ratio will be

Mollier chart is a __________ plot.

Heat evolved/absorbed during conversion of a substance from one allotropic form to another is termed as the heat of

What happens in a reversible adiabatic compression ?

Sublimation temperature of dry ice (solid CO2) is __________ C.

If atmospheric temperature and dew point are nearly equal, then the relative humidity is

The internal energy of an incompressible fluid depends upon its

Which area is used in case of heat flow by conduction through a cylinder ?

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy &amp; vibrational energy from one molecule to another. Conduction heat transfer can not take place

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

Finned tube heat exchangers

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

Resistance to heat flow by conduction is proportional to (where, t & are thickness & density of the material respectively and A = area normal to the direction of heat flow. )

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place