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 operate at atmospheric pressure

The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?

Higher shell side heat transfer co-efficient

Higher tube side heat transfer co-efficient

Higher shell side heat transfer co-efficient

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 actual temperature drop across the heating surface in an evaporator depends on the_________________?

Depth of liquid over heating surface

Pressure difference between steam chest and vapour space

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

The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?

May increase or decrease; depends on the material

Rate of heat transfer by vaporisation from pools of water is affected by the ____________________?

Nature of heating surface and distribution of bubbles

Radiation heat transfer rates does not depend upon the_________________?

Distance between the heat source and the object receiving the heat

Surface area and temperature of the heat source

Presence of a non-condensing gas in a condensing vapour___________________?

Increases the rate of condensation

Is desirable to increase the film co-efficient

Prandtl number is the reciprocal of____________________?

Thermal diffusivity × Momentum

Thermal diffusivity/Momentum diffusivity

Thermal diffusivity × Momentum

Thermal diffusivity × Mass diffusivity

Mass diffusivity × Momentum diffusivity

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

Pick out the wrong statement/

The emissivity of a surface increases with increase in surface roughness

The emissivity of a surface decreases, if it gets corroded by atmospheric environment

The emissivity of a surface increases with increase in surface roughness

The emissivity of a polished surface is quite low

The emissivity of a non-metallic surface decreases with increase in the temperature

Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the____________________?

Maximum resistance in the series

Minimum resistance presents in the series

Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (Δt1 – Δt2)/ln(Δt1/Δt2)], which one is subject to the largest deviation in practice ?

Constant overall heat transfer co-efficient

No partial phase change in the system

One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________?

Heat the water from 0°C to 100°C

Data insufficient, can’t be predicted

425 + Mcqs in Chemical Heat Transfer in Chemical Engineering Page 3 McqOptions

101.	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

102.	The equation, (NSt × N2/3 Pr) = f/2, is the ____________ analogy ?
A.	Colburn
B.	Reynolds
C.	Prandtl
D.	None of these
Answer» B. Reynolds

Discussion

103.	The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy?
A.	Von-Karman
B.	Reynolds
C.	Colburn
D.	Prandtl
Answer» E.

Discussion

104.	The equation, Nst = f/2, is the _____________ analogy?
A.	Colburn
B.	Reynolds
C.	Prandtl
D.	None of these
Answer» C. Prandtl

Discussion

105.	The energy radiated from a surface Q at absolute temperature T is related as__________________?
A.	Q ∝ T2
B.	Q ∝ T4
C.	Q ∝ T3
D.	None of these
Answer» C. Q ∝ T3

Discussion

106.	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

107.	The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re)0.8 (Pr)0.4] cannot 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

108.	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

109.	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

110.	The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?
A.	K/h0
B.	2K/h0
C.	hi/K
D.	2hi/K
Answer» B. 2K/h0

Discussion

111.	The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
A.	K/h0
B.	2K/h0
C.	h0/K
D.	h0/2K
Answer» C. h0/K

Discussion

112.	The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?
A.	Re.Gz
B.	Nu, Pr
C.	Nu, Pr, Re
D.	Nu, Gz
Answer» E.

Discussion

113.	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 operate at atmospheric pressure
D.	None of these
Answer» B. Evaporators operate under vacuum

Discussion

114.	The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?
A.	Lower tube side pressure drop
B.	Lower shell side pressure drop
C.	Higher tube side heat transfer co-efficient
D.	Higher shell side heat transfer co-efficient
Answer» D. Higher shell side heat transfer co-efficient

Discussion

115.	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

116.	The actual temperature drop across the heating surface in an evaporator depends on the_________________?
A.	Feed
B.	Depth of liquid over heating surface
C.	Pressure difference between steam chest and vapour space
D.	All A., B. and C.
Answer» E.

Discussion

117.	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

118.	The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?
A.	Increases
B.	Decreases
C.	Remain constant
D.	May increase or decrease; depends on the material
Answer» E.

Discussion

119.	The absorptivity of a body is equal to its emissivity _________________?
A.	At a particular temperature
B.	For circular bodies
C.	Under thermal equilibrium
D.	None of these
Answer» D. None of these

Discussion

120.	Reynold’s analogy states that_________________?
A.	Nst α f
B.	Nst α NRe
C.	NNu α f
D.	NRe α f
Answer» B. Nst α NRe

Discussion

121.	Reynold’s analogy states that (where, St = Stanton number f = friction factor) ?
A.	St = f/2
B.	St = f/4
C.	St = 4f
D.	St = f1/2
Answer» B. St = f/4

Discussion

122.	Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow.) ?
A.	t
B.	1/ρ
C.	1/A
D.	All A., B. & C.
Answer» E.

Discussion

123.	Removal of ______________ heat is involved in the condensation of a vapor under saturated conditions?
A.	Super
B.	Sensible
C.	Latent
D.	Both B. & C.
Answer» C. Latent

Discussion

124.	Reason for operating an evaporator in multiple effects is to secure ___________________?
A.	Increased steam economy
B.	Decreased steam consumption
C.	Both A. and B.
D.	Increased capacity
Answer» D. Increased capacity

Discussion

125.	Rate of heat transfer by vaporisation from pools of water is affected by the ____________________?
A.	Nature of heating surface and distribution of bubbles
B.	Surface tension of water
C.	Viscosity of water
D.	All A., B. and C.
Answer» E.

Discussion

126.	Radiator of an automobile engine is a ______________ type of heat exchanger?
A.	Co-current
B.	Cross-current
C.	Counter-current
D.	Direct contact
Answer» E.

Discussion

127.	Radiation heat losses from satisfactorily insulated high pressure boiler may be about _____________ percent?
A.	1
B.	7
C.	18
D.	26
Answer» C. 18

Discussion

128.	Radiation energy is emitted by all the substances, which are above____________________?
A.	0°K
B.	0°C
C.	100°C
D.	Room temperature
Answer» B. 0°C

Discussion

129.	Radiation heat transfer rates does not depend upon the_________________?
A.	Type of absorbing surface
B.	Distance between the heat source and the object receiving the heat
C.	Surface area and temperature of the heat source
D.	None of these
Answer» E.

Discussion

130.	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

131.	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

132.	Prandtl number is the reciprocal of____________________?
A.	Thermal diffusivity/Momentum diffusivity
B.	Thermal diffusivity × Momentum
C.	Thermal diffusivity × Mass diffusivity
D.	Mass diffusivity × Momentum diffusivity
Answer» B. Thermal diffusivity × Momentum

Discussion

133.	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

134.	Prandtl number is given by__________________?
A.	CP μ/a
B.	hD/k
C.	CP μ/k
D.	μ/h CP
Answer» D. μ/h CP

Discussion

135.	Prandtl and Reynolds analogy are same, when Prandtl number is____________________?
A.	0.5
B.	1
C.	> 2
D.	1.5
Answer» C. > 2

Discussion

136.	Prandtl number for most of dry gases is about________________?
A.	0.001
B.	0.72
C.	70
D.	150
Answer» C. 70

Discussion

137.	Prandtl and Reynold’s analogies are identical for Prandtl number value of__________________?
A.	0
B.	0.5
C.	1
D.	5
Answer» D. 5

Discussion

138.	Planck’s distribution law is valid for _____________ bodies?
A.	Black
B.	White
C.	Coloured
D.	All A., B. & C.
Answer» D. All A., B. & C.

Discussion

139.	Pick out the wrong statement/
A.	The emissivity of a surface decreases, if it gets corroded by atmospheric environment
B.	The emissivity of a surface increases with increase in surface roughness
C.	The emissivity of a polished surface is quite low
D.	The emissivity of a non-metallic surface decreases with increase in the temperature
Answer» B. The emissivity of a surface increases with increase in surface roughness

Discussion

140.	Pick out the correct equation ?
A.	jH = (St)(Pr)2/3 = f/2
B.	jH = (St)(Pr)1/3 = f/2
C.	jH = (St)2/3(Pr) = f/2
D.	jH = (St)1/3(Pr) = f/2
Answer» B. jH = (St)(Pr)1/3 = f/2

Discussion

141.	Peclet number (Pe) is given by____________________?
A.	Pe = Re.Pr
B.	Pe = Re/Pr
C.	Pe = Pr/Re
D.	Pe = Nu.Re
Answer» B. Pe = Re/Pr

Discussion

142.	_____________ paint has the minimum absorption co-efficient?
A.	Black
B.	White lead
C.	Grey
D.	Light cream
Answer» C. Grey

Discussion

143.	_______________ paint has the maximum absorption coefficient ?
A.	Black
B.	Yellow
C.	White
D.	Grey
Answer» B. Yellow

Discussion

144.	Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the____________________?
A.	Maximum resistance in the series
B.	Sum of all resistances
C.	Average of all resistances
D.	Minimum resistance presents in the series
Answer» C. Average of all resistances

Discussion

145.	Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then_________________?
A.	U1 = U2
B.	U2 > U1
C.	U1 > U2
D.	U1 = dirt factor – U2
Answer» B. U2 > U1

Discussion

146.	Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?
A.	50 -100 Kcal/hr.m2.°C
B.	50 -100 W/m2.°K
C.	50 -100 BTU/hr. ft.2°F
D.	1000 – 1500 BTU/hr. ft.2°F
Answer» D. 1000 – 1500 BTU/hr. ft.2°F

Discussion

147.	Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (Δt1 – Δt2)/ln(Δt1/Δt2)], which one is subject to the largest deviation in practice ?
A.	Constant overall heat transfer co-efficient
B.	Constant rate of fluid flow
C.	Constant specific heat
D.	No partial phase change in the system
Answer» C. Constant specific heat

Discussion

148.	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

149.	Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?
A.	Scaling
B.	Highly viscous
C.	Corrosive
D.	Salty
Answer» C. Corrosive

Discussion

150.	One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________?
A.	Heat the water from 0°C to 100°C
B.	Evaporate the water
C.	To superheat the steam
D.	Data insufficient, can’t be predicted
Answer» C. To superheat the steam

Discussion

Explore topic-wise MCQs in Chemical Engineering.

The equivalent diameter for pressure drop is ________________ that for heat transfer?

The equation, (NSt × N2/3 Pr) = f/2, is the ____________ analogy ?

The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy?

The equation, Nst = f/2, is the _____________ analogy?

The energy radiated from a surface Q at absolute temperature T is related as__________________?

The driving potential for the crystal growth during crystallisation is the _______________ of the solution?

The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re)0.8 (Pr)0.4] cannot be used for________________?

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

The critical radius ‘r’ of insulation on a pipe is given by____________________?

The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?

The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?

The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?

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 advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?

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

The actual temperature drop across the heating surface in an evaporator depends on the_________________?

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

The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?

The absorptivity of a body is equal to its emissivity _________________?

Reynold’s analogy states that_________________?

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

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

Removal of ______________ heat is involved in the condensation of a vapor under saturated conditions?

Reason for operating an evaporator in multiple effects is to secure ___________________?

Rate of heat transfer by vaporisation from pools of water is affected by the ____________________?

Radiator of an automobile engine is a ______________ type of heat exchanger?

Radiation heat losses from satisfactorily insulated high pressure boiler may be about _____________ percent?

Radiation energy is emitted by all the substances, which are above____________________?

Radiation heat transfer rates does not depend upon the_________________?

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

Presence of a non-condensing gas in a condensing vapour___________________?

Prandtl number is the reciprocal of____________________?

Prandtl number is the ratio of________________?

Prandtl number is given by__________________?

Prandtl and Reynolds analogy are same, when Prandtl number is____________________?

Prandtl number for most of dry gases is about________________?

Prandtl and Reynold’s analogies are identical for Prandtl number value of__________________?

Planck’s distribution law is valid for _____________ bodies?

Pick out the wrong statement/

Pick out the correct equation ?

Peclet number (Pe) is given by____________________?

_____________ paint has the minimum absorption co-efficient?

_______________ paint has the maximum absorption coefficient ?

Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the____________________?

Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then_________________?

Overall heat transfer co-efficient for cooling of hydrocarbons by water is about_________________?

Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (Δt1 – Δt2)/ln(Δt1/Δt2)], which one is subject to the largest deviation in practice ?

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_________________?

Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?

One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________?