Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping

the top tube sheet floating and bottom tube sheet fixed.

the top tube sheet fixed and the bottom tube-sheet floating.

If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

increases or decreases depending on number of shell passes.

Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?

Area of the wall perpendicular to heat flow.

Temperature difference between the two surfaces of the wall.

Shell side pressure drop in a shell and tube heat exchanger does not depend upon the

baffle spacing & shell diameter.

viscosity, density & mass velocity of shell side fluid.

The Grashoff number is defined as the ratio of the

buoyancy to surface tension forces.

Air is best heated with steam in a heat exchanger of

double pipe type with fin on steam side.

double pipe type with fin on air side.

In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

directly proportional to LMTD and inversely proportional to the area.

varies directly as the area and the LMTD.

directly proportional to LMTD and inversely proportional to the area.

does not provide a safety factor for design.

accounts for additional resistances to heat flow.

Black liquor generated during paper manufacture is concentrated in a

multiple effect evaporators followed by a crystalliser.

single effect evaporator followed by a crystalliser.

multiple effect evaporators followed by a crystalliser.

640 + Mcqs in Heat Transfer in Chemical Engineering Page 13 McqOptions

601.	Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
A.	laminar
B.	transition
C.	both 'a' & 'b'
D.	highly turbulent
Answer» E.

Discussion

602.	In Joule's experiment, an insulated container contains 20 kg of water initially at 25¬∞C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in ¬∞C) is
A.	40.5
B.	34.4
C.	26.8
D.	25
Answer» C. 26.8

Discussion

603.	In case of evaporators, liquid entrainment results primarily due to
A.	high vacuum in the evaporator.
B.	high evaporation rate.
C.	foaming of the solution.
D.	high heat transfer rate.
Answer» D. high heat transfer rate.

Discussion

604.	The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ŒîT) between wall and outside bulk. The proportionality is given as
A.	(ŒîT)1/4
B.	ŒîT1/2
C.	(ŒîT)5/4
D.	(ŒîT)3/4
Answer» E.

Discussion

605.	For heat flow through very thick walled cylinder, use____mean radius.
A.	arithmetic
B.	logarithmic
C.	geometric
D.	either (a) or (c)
Answer» C. geometric

Discussion

606.	Fourier's law applies to the heat transfer by
A.	convection
B.	radiation
C.	conduction
D.	all (a), (b) & (c)
Answer» D. all (a), (b) & (c)

Discussion

607.	A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is
A.	0
B.	R2/(R1+R2)
C.	1
D.	(R1/R2)2
Answer» C. 1

Discussion

608.	Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping
A.	both the tube sheets fixed.
B.	both the tube sheets floating.
C.	the top tube sheet floating and bottom tube sheet fixed.
D.	the top tube sheet fixed and the bottom tube-sheet floating.
Answer» B. both the tube sheets floating.

Discussion

609.	Mode of heat transfer involved in the cooling of air cooled internal combustion engine is
A.	conduction
B.	natural convection
C.	forced convection
D.	none of these
Answer» C. forced convection

Discussion

610.	The number of kg vaporised per kg of steam fed to the evaporator is defined as
A.	capacity
B.	rate of evaporation
C.	economy
D.	rate of vaporisation
Answer» D. rate of vaporisation

Discussion

611.	__________ paint has the maximum absorption coefficient.
A.	Black
B.	Yellow
C.	White
D.	Grey
Answer» B. Yellow

Discussion

612.	If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
A.	remains unchanged.
B.	increases.
C.	increases or decreases depending on number of shell passes.
D.	decreases.
Answer» E.

Discussion

613.	Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.
A.	Grashoff
B.	Reynolds
C.	both 'a' & 'b'
D.	Prandtl & Grashoff
Answer» E.

Discussion

614.	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

615.	Thermal conductivity of a conducting solid material depends upon its
A.	temperature
B.	porosity
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

616.	Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?
A.	Thickness of the wall.
B.	Area of the wall perpendicular to heat flow.
C.	Material of the wall.
D.	Temperature difference between the two surfaces of the wall.
Answer» E.

Discussion

617.	Thermal diffusivity is the most important in heat transfer by
A.	conduction
B.	radiation
C.	condensation
D.	natural convection
Answer» B. radiation

Discussion

618.	The type of liquor circulation system to be ' employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid.
A.	viscosity
B.	density
C.	thermal conductivity
D.	corrosive nature
Answer» B. density

Discussion

619.	Shell side pressure drop in a shell and tube heat exchanger does not depend upon the
A.	baffle spacing & shell diameter.
B.	tube diameter & pitch.
C.	viscosity, density & mass velocity of shell side fluid.
D.	none of these.
Answer» E.

Discussion

620.	Heat waves
A.	can not pass through vacuum.
B.	travel in straight line.
C.	can be reflected by a mirror.
D.	both (b) and (c).
Answer» E.

Discussion

621.	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

622.	Kirchoff s law applies to __________ radiation.
A.	total
B.	monochromatic
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

623.	What is the steam economy in case of a single effect evaporator system ?
A.	1
B.	>1
C.	< 1
D.	0.1
Answer» D. 0.1

Discussion

624.	A __________ evaporator employs an annular downtake.
A.	basket type
B.	horizontal
C.	long tube vertical
D.	none of these
Answer» B. horizontal

Discussion

625.	When vaporisation takes place directly at the heating surface, it is called
A.	film boiling
B.	nucleate boiling
C.	vapour binding
D.	none of these
Answer» C. vapour binding

Discussion

626.	The Grashoff number is defined as the ratio of the
A.	buoyancy to inertial forces.
B.	buoyancy to viscous forces.
C.	inertial to viscous forces.
D.	buoyancy to surface tension forces.
Answer» C. inertial to viscous forces.

Discussion

627.	Which of the following is generally considered as opaque surface towards radiations?
A.	Gases
B.	Solids
C.	Liquids
D.	Both (b) and (c)
Answer» E.

Discussion

628.	Intermittant tube cleaning is possible to be done in case of a __________ evaporator.
A.	basket type
B.	horizontal tube
C.	calendria
D.	none of these
Answer» B. horizontal tube

Discussion

629.	Air is best heated with steam in a heat exchanger of
A.	plate type.
B.	double pipe type with fin on steam side.
C.	double pipe type with fin on air side.
D.	shell and tube type.
Answer» D. shell and tube type.

Discussion

630.	Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80¬∞C and leaves at 50¬∞C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20¬∞C. The log mean temperature difference in ¬∞C is approximately
A.	32
B.	37
C.	45
D.	50
Answer» B. 37

Discussion

631.	In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid
A.	varies directly as the area and the LMTD.
B.	directly proportional to LMTD and inversely proportional to the area.
C.	varies as square of the area.
D.	none of these.
Answer» B. directly proportional to LMTD and inversely proportional to the area.

Discussion

632.	The equivalent diameter for pressure drop is __________ that for heat transfer.
A.	smaller than
B.	greater than
C.	equal to
D.	not related with
Answer» B. greater than

Discussion

633.	The critical radius 'r' of insulation on a pipe is given by
A.	r = 2k/h
B.	r = k/h
C.	r = k/2h
D.	r = h/k
Answer» C. r = k/2h

Discussion

634.	Reason for operating an evaporator in multiple effect is to secure
A.	increased steam economy.
B.	decreased steam consumption.
C.	both (a) and (b).
D.	increased capacity.
Answer» D. increased capacity.

Discussion

635.	Fouling factor
A.	is a dimensionless quantity.
B.	does not provide a safety factor for design.
C.	accounts for additional resistances to heat flow.
D.	none of these.
Answer» D. none of these.

Discussion

636.	Black liquor generated during paper manufacture is concentrated in a
A.	single effect evaporator.
B.	single effect evaporator followed by a crystalliser.
C.	multiple effect evaporator.
D.	multiple effect evaporators followed by a crystalliser.
Answer» D. multiple effect evaporators followed by a crystalliser.

Discussion

637.	The unit of heat transfer co-efficient in SI unit is
A.	J/M2¬∞K
B.	W/m2¬∞K
C.	W/m¬∞K
D.	J/m¬∞K
Answer» C. W/m¬∞K

Discussion

638.	Choose the correct equation.
A.	Nu = (Re) (Pr) (Gz)
B.	Nu = (Re) (Pr) (St)
C.	Nu = (Re)(Pr)
D.	Nu = (Pr)(St)
Answer» C. Nu = (Re)(Pr)

Discussion

639.	The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ŒîT = Temperature drop across condensate film )
A.	(ŒîT)2
B.	ŒîT
C.	(ŒîT)1/4
D.	(ŒîT)3/2
Answer» D. (ŒîT)3/2

Discussion

640.	Crystal size in a continuous crystalliser depends upon the
A.	rate of heat transfer.
B.	degree of turbulence.
C.	degree of supersaturation.
D.	all (a), (b) and (c).
Answer» E.

Discussion

Explore topic-wise MCQs in Chemical Engineering.

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.

In case of evaporators, liquid entrainment results primarily due to

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ŒîT) between wall and outside bulk. The proportionality is given as

For heat flow through very thick walled cylinder, use____mean radius.

Fourier's law applies to the heat transfer by

A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is

Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping

Mode of heat transfer involved in the cooling of air cooled internal combustion engine is

The number of kg vaporised per kg of steam fed to the evaporator is defined as

__________ paint has the maximum absorption coefficient.

If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.

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

Thermal conductivity of a conducting solid material depends upon its

Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?

Thermal diffusivity is the most important in heat transfer by

The type of liquor circulation system to be ' employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid.

Shell side pressure drop in a shell and tube heat exchanger does not depend upon the

Heat waves

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

Kirchoff s law applies to __________ radiation.

What is the steam economy in case of a single effect evaporator system ?

A __________ evaporator employs an annular downtake.

When vaporisation takes place directly at the heating surface, it is called

The Grashoff number is defined as the ratio of the

Which of the following is generally considered as opaque surface towards radiations?

Intermittant tube cleaning is possible to be done in case of a __________ evaporator.

Air is best heated with steam in a heat exchanger of

Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80¬∞C and leaves at 50¬∞C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20¬∞C. The log mean temperature difference in ¬∞C is approximately

In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

The equivalent diameter for pressure drop is __________ that for heat transfer.

The critical radius 'r' of insulation on a pipe is given by

Reason for operating an evaporator in multiple effect is to secure

Fouling factor

Black liquor generated during paper manufacture is concentrated in a

The unit of heat transfer co-efficient in SI unit is

Choose the correct equation.

The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ŒîT = Temperature drop across condensate film )

Crystal size in a continuous crystalliser depends upon the