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Unit 1 - How to
access the portal

Course
outline
Assesment 00
The due date for submitting this assignment has passed. Due on 2018-01-19, 17:00 IST.
How to access
the portal Submitted assignment

Lesson 1: How Fluidization Engineering

to access the
home page? Assesment 00
Lesson 2: How Each question has only one correct answers and carries one mark. (1x10)
to access the
course page?
1) Sphericity of a cubic particle of side ‘a’ is 1 point
Lesson 3: How
to access the
MCQ, MSQ
fs = 1
and fs = 0.75
Programming
assignments? fs = 0.67
Quiz : fs = 0.806
Assesment 00
No, the answer is incorrect.
New Lesson Score: 0

Introduction and Accepted Answers:

Particle fs = 0.806
Properties
2) Drag coefficient for laminar region 1 point
Minimum
Fluidization Cd = 1/Re
Cd = 16/Re
Flow Regime and
its Map Cd = 24/Re

Frictional Cd = 2/Re
Pressure Drop
No, the answer is incorrect.
Characteristics
Score: 0
Gas Distribution Accepted Answers:
Cd = 24/Re
Bubbling
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and Entrainment
Characteristics NonePowered
of theseby
No, the answer is incorrect.
Entrainment, Score: 0
Elutriation and
Attrition Accepted Answers:
Lower than the bed density
Attrition, mixing
and Segregation 4) Median is defined as 1 point

Phase Dispersion Size of the highest frequency

None of these
Mass Transfer
and Heat Transfer Size where 50% of the population is below/above
Average size of population
No, the answer is incorrect.
Score: 0
Accepted Answers:
Size where 50% of the population is below/above
5) Ergun equation is used to calculate the pressure drop in 1 point

Straight pipeline
Packed tower
Plate tower
Cooling tower
No, the answer is incorrect.
Score: 0
Accepted Answers:
Packed tower
6) The pressure drop across the bed remains …………even with the further 1 point
increase in fluid velocity at the particular regime.

Increase then decrease

Decrease
Increase
Constant
No, the answer is incorrect.
Score: 0
Accepted Answers:
Constant
7) In stokes flow, the terminal velocity of the particle falling in fluid is 2.58 m/s, 1 point
calculate the diameter of particle in mm (Fluid: density = 996.2 kg/m3, viscosity = 6.80 ×
10-4 Pa.s, Solid: density= 1633 kg/m3, g = 9.81 m/s2).

4.98 mm
5.20 mm
7.27 mm
2.24 mm
No, the answer is incorrect.
Score: 0
Accepted Answers:

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2.24 mm
8) Pressure drop across the distributor is 1 point

Equal to the pressure drop across the bed

None of these
Greater than pressure drop across the bed
Less than across the bed
No, the answer is incorrect.
Score: 0
Accepted Answers:
Less than across the bed
9) On comparison with Fluidized bed and packed bed, which has the highest 1 point
voidage

Packed bed
Both are equal
Fluidized bed
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Fluidized bed
10)Fluidization occurs when drag force by the upward moving fluid is equal to the 1 point

Volume of the bed

Weight of the particle
Pressure drop across bed
Weight of the fluid
No, the answer is incorrect.
Score: 0
Accepted Answers:
Weight of the particle

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Unit 2 -
Introduction and Particle Properties

Course
outline
Assignment: Module 1
The due date for submitting this assignment has passed. Due on 2018-02-05, 17:00 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle Assignment 01
Properties
Module 1: Introduction and Particle Properties
Introduction of
Fluidization Each question has only one correct answers and carries one mark. (1x25)
Engineering
1) In a highly endothermic or exothermic reactions in a fluidized bed reactor the 1 point
Particle circulation rate of solid particles is chosen in such a way that
Properties and
Its
All of these
Classifications
Improves automatic control of the system
Particle-
Powder Avoiding sintering of catalyst particles
Classifications
To maintain the optimum temperature
Quiz :
Assignment: No, the answer is incorrect.
Module 1 Score: 0
Assignment Accepted Answers:
solutions All of these
Minimum 2) Backmixing of the particles occurs in the fluidized bed reactor which 1 point
Fluidization
Decrease the efficiency of the system
Flow Regime and
its Map No effect on the efficiency
Efficiency of the system first reach to minima then maxima
Frictional
Pressure Drop Increases the efficiency of the system
Characteristics
No, the answer is incorrect.
Gas Distribution Score: 0
Accepted Answers:
Bubbling Decrease the efficiency of the system
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and Entrainment
Characteristics RapidPowered by
reaction
No, the answer is incorrect.
Entrainment, Score: 0
Elutriation and
Attrition Accepted Answers:
Rapid reaction
Attrition, mixing
and Segregation 4) Dust extinction moisture is defined as 1 point

Phase Dispersion Both (a) and (b)

Moisture at which material emit dust
Mass Transfer
and Heat Transfer None of the above
Moisture at which material does not emit dust
No, the answer is incorrect.
Score: 0
Accepted Answers:
Moisture at which material does not emit dust
5) Circularity is defined as 1 point

Actual area/area of an equivalent perimeter circle

Actual diameter/ diameter of an equivalent area circle
Actual perimeter/perimeter of an equivalent area circle
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Actual perimeter/perimeter of an equivalent area circle
6) Convexity is defined as 1 point

Area bound by actual perimeter/area bound by convex hull perimeter

Actual perimeter/convex hull perimeter
Convex hull perimeter/actual perimeter
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Convex hull perimeter/actual perimeter
7) For the catalysts, reactivity changes with the concentration and particle size 1 point

Reactivity inversely proportional to concentration and particle size

None of the above
Reactivity directly proportional to concentration and particle size
Reactivity exponentially proportional to concentration and particle size
No, the answer is incorrect.
Score: 0
Accepted Answers:
Reactivity directly proportional to concentration and particle size
8) Attraction between particles in a liquid suspension is better expressed in terms 1 point
of

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None of the above

Dimension of the particle
Concentration of the particle
Zeta potential
No, the answer is incorrect.
Score: 0
Accepted Answers:
Zeta potential
9) Calculate the sphericity of a cylinder of diameter 1 cm and height 3 cm. 1 point

0.586
0.685
0.779
0.977
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.779
10)Density of a solid particle used in fluidization is 1 point

Both (a) and (b)

Bulk density of solid
Flowing fluid density
True solid density
No, the answer is incorrect.
Score: 0
Accepted Answers:
True solid density
11)Freeboard region in fluidized bed reactor is known as 1 point

Distributor region
Feed inlet region
Region extending from top of the bed surface to the top of reactor vessel

Only present in the pneumatic fluidization

No, the answer is incorrect.
Score: 0
Accepted Answers:
Region extending from top of the bed surface to the top of reactor vessel
12)Which of the flowing is undesirable in the fluidized bed reactor 1 point

High mass transfer coefficient

Attrition of the particles
High heat transfer coefficient
Enhanced contact efficiency
No, the answer is incorrect.

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Score: 0
Accepted Answers:
Attrition of the particles
13)The condition at which packed bed considered to be incipiently fluidized 1 point

Pressure drop through any section of the bed equals the weight of fluid and
particles in that section
Frictional force between particle and fluid just counterbalances the weight of the
particles
All of these
Incipiently fluidized can be termed as minimum fluidization
No, the answer is incorrect.
Score: 0
Accepted Answers:
All of these
14)Aspect ratio is defined as 1 point

Both (a) and (b)

Width/length
Length/width
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Width/length
15)Highest size distribution variance is observed in what type of fluidization 1 point
mechanism

Segregation fluidization
Both (a) and (b)
Sluggish fluidization
Particle and powder fluidization
No, the answer is incorrect.
Score: 0
Accepted Answers:
Segregation fluidization
16)For mass transfer and gas-liquid reaction d32 is 1 point

Volume diameter mean

Volume diameter mean
Volume mean
Sauter mean
No, the answer is incorrect.
Score: 0
Accepted Answers:
Sauter mean
17)The sphericity of a cubical particle is 1 point

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Less than or equal to 1

Greater than or equal to 1
>1
<1
No, the answer is incorrect.
Score: 0
Accepted Answers:
<1
18)Choose the correct sequence of fluidization according to increasing flow rate 1 point

Bubbling-slugging-turbulent-lean fluidization
Bubbling- turbulent - slugging -lean fluidization
Bubbling - pneumatic- turbulent-slugging
Bubbling - pneumatic- slugging- turbulent
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubbling-slugging-turbulent-lean fluidization
19)For a spherical particle of diameter D, sphericity is equal to 1 point

0.806
1.25
0.75
1

No, the answer is incorrect.

Score: 0
Accepted Answers:
1

20)Drag coefficient for turbulent region 1 point

0.67
0.44
16/Re
24/Re
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.44
21)Weber number is defined as 1 point

Surface force/ Inertial force

Pressure/ Inertial force
Viscous force/ Inertial force
Inertial force/Surface tension
No, the answer is incorrect.
Score: 0

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Accepted Answers:
Inertial force/Surface tension
22)A powder is having particle size between 50-80 µm, the nature of force exhibit 1 point
by this powder

Cohesive
Spoutable
Areatable
Bubbling
No, the answer is incorrect.
Score: 0
Accepted Answers:
Areatable
23)Calculate
terminal velocity for laminar region dp = 1 mm, ρp = 7830 kg/m3, ρf = 1 point
800 kg/m and µ = 0.1277 Ns/m2
3

ut = 0.029 m/s
ut = 0.3×10-3 m/s
ut = 0.078 m/s
ut = 0.78×10-3 m/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
ut = 0.029 m/s
24)Terminal velocity is the function of 1 point

Both (a) and (b)

Friction force
Surface tension
Drag force
No, the answer is incorrect.
Score: 0
Accepted Answers:
Drag force
25)When net force acting on a droplet becomes zero, it falls with 1 point

Zero speed
Constant velocity
Increasing speed
Decreasing speed
No, the answer is incorrect.
Score: 0
Accepted Answers:
Constant velocity
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Unit 3 - Minimum
Fluidization

Course
outline
Assignment: Module 2
The due date for submitting this assignment has passed. Due on 2018-02-10, 17:00 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization

Particle Engineering
Properties
Assignment 2
Minimum
Fluidization Module 2: Minimum Fluidization
Each question has only one correct answers and carries one mark. (1x30)
Minimum
Fluidization 1) A conical fluidized bed is operated with cubical catalyst particle of size 2 mm 1 point
Velocity: operating with hot air as the fluidizing gas, estimate the effective diameter of the particle?
fluid-solid
System
dp = 0.87 m
Minimum
Fluidization dp = 1.052×10-5 m
Velocity:
dp = 2.481×10-3 m
Liquid-solid &
gas-liquid-solid dp = 0.5 m
System
No, the answer is incorrect.
Quiz :
Score: 0
Assignment:
Module 2 Accepted Answers:

Assignment dp = 2.481×10-3 m
Solution
2) A fluidized bed is used for drying of coffee beans with hot air as the fluidizing 1 point
Flow Regime and medium working at minimum fluidizing condition. Calculate the void fraction at
its Map minimum fluidizing condition when the sphericity of the coffee beans are 0.88?

Frictional 0.69
Pressure Drop
Characteristics 0.99
0.39
Gas Distribution
0.43

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and Entrainment 0.5 mm and density by kg/m3. The air properties are: density= 1.2 kg/m3 and viscosity
Powered1400
Characteristics
= 1.3´10 pa.s. The bulk density of the fluidized bed with air is 1092 kg/m3. Find the
–5

Entrainment, void fraction of the fluidized bed.

Elutriation and
Attrition 0.22

Attrition, mixing
0.37
and Segregation 0.01

Phase Dispersion 0.41

No, the answer is incorrect.
Mass Transfer
Score: 0
and Heat Transfer
Accepted Answers:
0.22

4) The gas holdup can be experimentally estimated by phase-isolation technique 1 point

where HM and HL represents the gas-liquid mixture height and clear liquid height in
presence of aeration and without aeration. Data: HM = 0.39 m, HL = 0.36 m. Determine
the gas holdup in percentage?

7.692

10.00

18.07

12.05

No, the answer is incorrect.

Score: 0
Accepted Answers:
7.692

5) A fluidized bed of length 1.5 m is being used to reduce the moisture from the 1 point
polymeric particle (density= 1050 kg/m3) in presence of the hot air. Calculate the
frictional pressure drop in the fluidized? Data: Air density= 1.2 kg/m3, bed void fraction
= 0.23, g = 10 m/s2.

25.12 KPa
20.92 KPa
12.11 KPa
15.25 KPa
No, the answer is incorrect.
Score: 0
Accepted Answers:
12.11 KPa
6) A fluidized bed reactor is being used to regenerate the aluminum catalyst 1 point
particle (diameter = 5 mm) in presence of air as the fluidizing medium. The density of the
catalyst particle is 1350 kg/m3. The density and viscosity of the air is 1.2 kg/m and
9´10-5 Pa.s respectively. Estimate the minimum fluidization velocity of the system.

25.983 m/s
1.275 m/s
5.275 m/s
4.263 m/s
No, the answer is incorrect.

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Score: 0
Accepted Answers:
1.275 m/s
7) A fluidized bed is working at minimum fluidization condition in presence of 1 point
water as the fluid medium. The sphericity of the glass particle is 0.88 and the void
fraction at minimum fluidization condition is 0.55. The Archimedes number of the
particle is given as 20000. Estimate the Reynolds number of particle at the minimum
fluidization condition.

Rep,mf = 24.49
Rep,mf = 105.49
Rep,mf = 22.78
Rep,mf = 29.55
No, the answer is incorrect.
Score: 0
Accepted Answers:
Rep,mf = 24.49
8) Ina gas-liquid-solid system, the density of the gas, liquid and solid are 1.1, 1 point
3
997.89 and 1395 kg/m respectively. The gas holdup of gas and liquid are 0.22 and 0.62
respectively. Determine the density of the mixture in the system.

rm = 900 kg/m3
rm = 842.13 kg/m3
rm = 800 kg/m3
rm = 921.55 kg/m3
No, the answer is incorrect.
Score: 0
Accepted Answers:
rm = 842.13 kg/m3
9) The superficial fluid velocity of homogeneous gas-liquid mixture is 0.5 m/s. 1 point
3
The volumetric flow rate of the gas and liquid velocity is 1 and 0.75 m /s. Estimate the
Cross-sectional area of the bed.

2.5 m2
1.5 m2
8.5 m2
3.5 m2
No, the answer is incorrect.
Score: 0
Accepted Answers:
3.5 m2
10)Calculate the solid phase friction factor for three-phase homogeneous flow 1 point
system. Data given: Rea = 889.

fs = 0.456
fs = 0.258
fs = 0.412
fs = 0.88

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No, the answer is incorrect.

Score: 0
Accepted Answers:
fs = 0.456
11)At terminal velocity 1 point

Weight of the object = Sum of buoyancy and drag force

Weight of the object = Multiplication of buoyancy and drag force
Weight of the object = Difference of buoyancy and drag force
None of the these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Weight of the object = Sum of buoyancy and drag force
12)According to stokes law, terminal velocity is expressed as: 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

13)For the Stokes law region, the Reynolds number of the particle is 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

14)Buoyancy force is given by 1 point

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None of these

No, the answer is incorrect.

Score: 0
Accepted Answers:

15)For Rep £ 1, drag force (FD) is expressed as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

16)Terminal velocity for turbulent flow (0.1 < Rep £ 500) is 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

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17) 1 point
The value of drag coefficient for the turbulent flow Rep > 500

0.64
1.0

0.44

0.24

No, the answer is incorrect.

Score: 0
Accepted Answers:
0.44

18)According to Zhou et al. (2009) model minimum fluidization velocity in conical 1 point
fluidized bed with solid-fluid system is

No, the answer is incorrect.

Score: 0
Accepted Answers:

19) 1 point
Void fraction for the spherical particle during minimum fluidization is usually

0.4 - 0.45
0.3 - 0.35
0.5 - 0.55
0.6 - 0.65
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.4 - 0.45
20)The frictional pressure drop at minimum fluidization can be estimated with the help of 1 point

Stokes law
Ergun equation

Archimedes law
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Ergun equation

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21)The drag coefficient (CD) value for a cube of side ‘D’ and Reynolds number 1 point
>104 is

<1
1.05
2.05
1.15
No, the answer is incorrect.
Score: 0
Accepted Answers:
1.05
22) 1 point
At the Stokes law region (Rep £ 0.1), the drag coefficient is expressed as

1.0

No, the answer is incorrect.

Score: 0
Accepted Answers:

23) 1 point
Turbulent drag is expressed by the equation

No, the answer is incorrect.

Score: 0
Accepted Answers:

24) 1 point
Relation between dimensionless particle diameter and the Archimedes number
(Ar)

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No, the answer is incorrect.

Score: 0
Accepted Answers:

25)At the onset of fluidization 1 point

Drag force by upward moving gas > Apparent weight of particle

Drag force by upward moving gas = Apparent weight of particle
Drag force by upward moving gas < Apparent weight of particle
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Drag force by upward moving gas = Apparent weight of particle
26)Archimedes number is same as 1 point

Galileo number
Reynolds number
Capillary number
Bond number
No, the answer is incorrect.
Score: 0
Accepted Answers:
Galileo number
27)According to Wen and Yu (1966), the correlation for the minimum voidage is 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

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28)Calculate the minimum fluidized bed height when the mass of the bed (M bed) is 15 kg 1 point
and cross sectional area of the bed (Abed) is 20 m2. Minimum void fraction (emf) of the bed is
0.45 and the density of the particle (rp) is 1.2×10-3 kg/m3.

0.152 m
0.132 m
0.251 m
0.231 m
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.152 m
29)Calculate the K1 and K2 values for a minimum fluidized bed having minimum void 1 point
fraction (emf) is 0.45 and the sphericity of the particle (Fs) is 0.67.

26.66 and 2010.81

66.28 and 2061.81
66.26 and 2001.81
28.66 and 2016.81
No, the answer is incorrect.
Score: 0
Accepted Answers:
28.66 and 2016.81
30)Calculate the minimum void fraction (emf) at minimum fluidized condition. The bed is 1 point
packed with the cubic particle of sphericity (Fs) 0.81.

0.445
0.544
0.454
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.445

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Unit 4 - Flow
Regime and its Map

Course
outline
Assignment: Module 3
The due date for submitting this assignment has passed. Due on 2018-02-14, 17:00 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 3: Flow Regime and its Map

Fluidization Each question has only one correct answers and carries one mark. (1x30)
Assignment 03
Flow Regime and
1) In a fluidized bed, the flow regime of the system is influenced by 1 point
its Map

Flow regime Physical properties of the system

and its map:
Gas-solid All of these
Fluidization
Dynamic variable
Flow regime Geometric variable
and its map:
Liquid-solid & No, the answer is incorrect.
Gas-liquid-solid Score: 0
Fluidization
Accepted Answers:
Quiz : All of these
Assignment:
Module 3 2) Taylor bubble (bullet shape) bubble occurs in 1 point
Assignment
Solution Slug flow
Annular flow
Frictional
Pressure Drop Bridging flow
Characteristics
None of these
Gas Distribution No, the answer is incorrect.
Score: 0
Bubbling
Fluidization Accepted Answers:
Slug flow
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Entrainment, 10-6 by
Rep =Powered
Elutriation and
Attrition Rep > 10-5
Rep < 10-6
Attrition, mixing
and Segregation No, the answer is incorrect.
Score: 0
Phase Dispersion Accepted Answers:
Rep < 10-6
Mass Transfer
and Heat Transfer 4) Match the following 1 point
(p) Pseudo-homogeneous flow regime (I)10-6< Rep< 0.1
(q) homogeneous flow regime (II) Rep > 2
(r) Heterogeneous flow regime (III) 0.1 < Rep < 2

(P)-(III); (Q)- (II); (r)-(I)

(P)-(III); (Q)- (I); (r)-(II)
(P)-(II); (Q)- (I); (r)-(III)
(P)-(I); (Q)- (II); (r)-(III)
No, the answer is incorrect.
Score: 0
Accepted Answers:
(P)-(III); (Q)- (I); (r)-(II)
5) The solid concentration by volume is considered to be 0, under these condition 1 point
the relation between the hindered settling velocity (us) and single particle settling
velocity (uset)

us = uset
us > uset
us = (uset)0.5
us < uset
No, the answer is incorrect.
Score: 0
Accepted Answers:
us = uset
6) Uniformity of the bubble size distribution is higher in 1 point

Dispersed bubble flow

None of these
Discrete bubble flow
Bubble size distribution is same in both disperse and discrete bubble flow
No, the answer is incorrect.
Score: 0
Accepted Answers:
Dispersed bubble flow
7) Bubble coalescence phenomena is more intensive in air-water systems 1 point
containing glass beads less than 2.5 mm in diameter than in the corresponding gas-liquid
system due to

Coalescence phenomena has nothing to do with viscosity or density

Decrease of phase viscosity and density

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Fluidization Engineering - - Unit 4 - Flow Regim... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

None of these
Increase of phase viscosity and density
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increase of phase viscosity and density
8) The dispersed bubble flow pattern is encountered at 1 point

Lower liquid velocities

When gas and liquid velocity are equal
Higher gas velocities
Higher liquid velocities
No, the answer is incorrect.
Score: 0
Accepted Answers:
Higher gas velocities
9) The churn turbulent flow regime can be characterized by 1 point

Taylor bubbles are distorted

All of these
The distorted Taylor bubbles became elongated
Encounter after Slug flow/plug flow when further gas velocity increases
No, the answer is incorrect.
Score: 0
Accepted Answers:
All of these
10)Estimate the hindered settling velocity in a fluidized bed, data: Re p = 500, solid 1 point
concentration by volume (es)= 0.17, single particle settling velocity (uset) = 0.35 m/s

0.07 m/s
1.207 m/s
0.207 m/s
0.05 m/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.207 m/s
11)Powder belongs to group A or C, if 1 point

None of these

No, the answer is incorrect.

Score: 0

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Accepted Answers:

12)The particulate fluidization occurs in the range of gas velocity 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

13)In case of bubbling fluidization, the change in bubble size with the increasing 1 point
gas velocity

Remains constant
Increases
None of these

Decreases
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
14)In what type of fluidization the particles are transported out the top 1 point

Bubbling fluidization
Slugging fluidization
Particulate fluidization
Fast fluidization
No, the answer is incorrect.
Score: 0
Accepted Answers:
Fast fluidization
15)In what type of fluidization all the particle fed in are transported out the top as a 1 point
lean phase

Pneumatic conveying fluidization

All the above
Fast fluidization
Turbulent fluidization
No, the answer is incorrect.
Score: 0
Accepted Answers:
Pneumatic conveying fluidization

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Fluidization Engineering - - Unit 4 - Flow Regim... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

16)Powder belongs to group B or D, if 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

17)The solid in the fast fluidized bed may typically occupy up to 1 point

55% of the bed volume

25% of the bed volume
35% of the bed volume
45% of the bed volume
No, the answer is incorrect.
Score: 0
Accepted Answers:
25% of the bed volume
18)For group D powders 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

19)Dense phase plug transport occurs in pneumatic conveying fluidization 1 point

At very high velocities of airflow

All the above
At very low velocities of airflow
Intermediate velocities of airflow

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Fluidization Engineering - - Unit 4 - Flow Regim... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

No, the answer is incorrect.

Score: 0
Accepted Answers:
At very low velocities of airflow
20)The principle features of flow regimes in the slug flow regime 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

21)Transition from slugging to churn-turbulent fluidization occurs when the 1 point

standard deviation of pressure fluctuations reaches

Zero (no fluctuation)

Maximum
None of the above
Minimum
No, the answer is incorrect.
Score: 0
Accepted Answers:
Maximum
22)The transition velocity for churn-turbulent to fast fluidization can be calculated 1 point
by

No, the answer is incorrect.

Score: 0
Accepted Answers:

23)In case of batch-operated fluidized bed 1 point

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Fluidization Engineering - - Unit 4 - Flow Regim... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

No, the answer is incorrect.

Score: 0
Accepted Answers:

24)The principle features of flow regimes in the bubbling flow regime 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

25)The minimum bubbling pneumatic velocity is calculated by the equation 1 point

None of these

No, the answer is incorrect.

Score: 0
Accepted Answers:

26) 1 point
A minimum slugging velocity ( ) for the transition from bubbly to slugging
fluidization can be expressed as

No, the answer is incorrect.

Score: 0
Accepted Answers:

27)The minimum bubbling velocity for group ‘A’ particles can be estimated from 1 point
the equation

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Fluidization Engineering - - Unit 4 - Flow Regim... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

No, the answer is incorrect.

Score: 0
Accepted Answers:

28)According to Geldart particle classification, in case of the group ‘A’ powders 1 point

None of these

No, the answer is incorrect.

Score: 0
Accepted Answers:

29)According to Geldart particle classification, in case of the group ‘B’ powders 1 point

None of these

No, the answer is incorrect.

Score: 0

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Accepted Answers:

30)The classical choking in case of batch operated bed depends on 1 point

None of these

Both (a) and (b)

The bubble size
The superficial gas velocity
No, the answer is incorrect.
Score: 0
Accepted Answers:
The superficial gas velocity

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Courses » Fluidization Engineering

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Unit 5 - Frictional
Pressure Drop Characteristics

Course
outline
Assignment: Module 4
The due date for submitting this assignment has passed. Due on 2018-02-21, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 4: Frictional Pressure Drop

Fluidization Characteristics
Each question has only one correct answers and carries one mark. (1x30)
Flow Regime and
its Map 1) Lockhart and Martinelli correlations can be used to estimate the frictional 1 point
pressure drop in
Frictional
Pressure Drop Two-phase flow
Characteristics
Three-phase flow
Frictional
pressure drop
Both (a) and (b)
in fluidized bed: Single - phase flow
fluid-solid
system No, the answer is incorrect.
Score: 0
Frictional
pressure drop Accepted Answers:
in fluidized Both (a) and (b)
Bed:
Gas-liquid-solid 2) Slurry of a system can be defined as 1 point
system

Analysis of Liquid + Solid

Frictional Gas + Solid
Pressure Drop
in Fluidized Liquid+ Gas
Bed By
Different Liquid + Liquid
Models
No, the answer is incorrect.
Quiz : Score: 0
Assignment:
Accepted Answers:
Module 4 © 2014 NPTEL - Privacy & Terms - Honor Code - FAQs -
Liquid + Solid
Assignment
A project of In association with
Solution 3) The property index (Ip) in Baroczy (1966) model is based on the 1 point

Gas Distribution Surface tension

Funded by
Bubbling
Interfacial area

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Fluidization Powered by of the phases

Shear stress
Interaction of Viscosity and density of the phases
Phases
No, the answer is incorrect.
Phase Movement Score: 0
and Entrainment Accepted Answers:
Characteristics
Viscosity and density of the phases
Entrainment, 4) Which model is suitable for estimation of frictional pressure gradient in 1 point
Elutriation and annular flow map
Attrition
Friedel (1980) model
Attrition, mixing
and Segregation Wallis (1969) model
Baroczy (1966) model
Phase Dispersion
None of these
Mass Transfer
No, the answer is incorrect.
and Heat Transfer
Score: 0
Accepted Answers:
Wallis (1969) model
5) Friedel (1980) can be applied to estimate the frictional pressure drop in 1 point
multiphase flow system, this model can be applied when the ratio of density of
liquid to gas is

(rl/rg) < 1000

(rl/rg) >1000
(rl/rg) < 0.1
(rl/rg) = 1000
No, the answer is incorrect.
Score: 0
Accepted Answers:
(rl/rg) < 1000
6) The role of pressure drop in fluidization 1 point

Governs the patterns of energy dissipation

Change the fractional holdup of the phase
Helps in modeling the system and forms the basis of assessment of performance
of the fluidized bed
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
7) The overall volumetric mass transfer coefficient with pressure at constant mass 1 point
flow rate

Decreases
Increases
Remains constant
None of the above
No, the answer is incorrect.

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

Score: 0
Accepted Answers:
Decreases
8) The liquid axial dispersion coefficient with an increase of pressure in a wide 1 point
range of superficial gas and liquid velocity

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
9) The bubble size in bubbling fluidized bed with the increase in pressure 1 point

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
10)The minimum fluidization velocity with the increase of particle diameter 1 point

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
11)The voidage at minimum bubbling with the increase in particle diameter 1 point

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
12)The pressure drop inside the bed may be due to 1 point

Friction
Head

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

Acceleration of the solids and gas

All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
13)Mixture density of a fluid-solid suspension can be expressed as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

14)Maximum pressure contribution to the total pressure is 1 point

Hydrostatic
Accelerative
Frictional
Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Hydrostatic
15)Pressure drop between the particle and wall can be expressed as 1 point

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

16)The terminal velocity (ut) of a particle inside a fluidized bed can be expressed 1 point
as

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

Noe of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

17)The friction factor of a mixture (fm) at turbulent flow condition (Rem>2300) can 1 point
be calculated by

No, the answer is incorrect.

Score: 0
Accepted Answers:

18)The particle diameters almost have no influence on the frictional-pressure 1 point

losses for the gas superficial velocities

< 10 m/s
< 7 m/s
> 10 m/s
> 7 m/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
< 7 m/s
19)The changes in frictional-pressure differences with the increase of gas 1 point

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

superficial velocities

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
20)The frictional-pressure losses with the increase of solid concentration if the 1 point
other operating conditions remain same

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
21)Static pressure drop due to change in potential energy of the gas and solids can 1 point
be expressed as

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

22)According to Blasius empirical formula, the fluids friction factor (ff) for 1 point
Ref<2300 is calculated by

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

No, the answer is incorrect.

Score: 0
Accepted Answers:

23)Hydrostatic pressure drop is defined as 1 point

ρlg

ρmg+ ρlg

ρmg
ρsg
No, the answer is incorrect.
Score: 0
Accepted Answers:
ρm g
24)A gas liquid fluidized bed of cross sectional area of 50.26 cm2 is operating with air flowrate of 1 point
5 lphand water flowrate of 500 lph with catalyst particle size of 100 µm and of sphericity of 0.97. Mass of the solid
intake in the bed is 2.855 Kg. Density of the particle is 3950 Kg/m3. Calculate volume fraction of gas

0.667

0.081

0.056

0.077

No, the answer is incorrect.

Score: 0
Accepted Answers:
0.056

25)The property index (Ip) in terms of viscosity and density of the phases is 1 point
expressed as

None of these

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Fluidization Engineering - - Unit 5 - Frictional P... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

No, the answer is incorrect.

Score: 0
Accepted Answers:

26)The parameter (X) is called Lockhart-Martinelli’s parameter which is defined as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

27)Thepressure drop multiplier for the liquid is related to the Lochart-Martinelli’s 1 point
parameter (X) as

None of the above

Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:

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28)The frictional pressure drop is due to the types of frictional forces 1 point

Frictional force between gas and solid

Frictional force between the solid and the walls of the bed
Frictional force between the gas and the wall of the bed
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
29)If G-L-S mixing height is 20 cm and clean liquid height is 12 cm, then calculate gas 1 point
hold up

0.73

0.667

1.4

No, the answer is incorrect.

Score: 0
Accepted Answers:
0.667

30)If Reynolds number is greater than 2300 then, fm= 1 point

None of these

No, the answer is incorrect.

Score: 0
Accepted Answers:

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You were allowed to submit this assignment only once.

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Unit 6 - Gas
Distribution

Course
outline
Assignment: Module 5
The due date for submitting this assignment has passed. Due on 2018-02-28, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 5: Gas Distribution

Fluidization Each question has only one correct answers and carries one mark. (1x25)

1) The shortcoming of laboratory scale distributors for small scale fluidization 1 point
Flow Regime and
its Map
Increased pumping power
Frictional Clogging by fine particles
Pressure Drop
Characteristics Low resistivity against thermal stresses
All of the above
Gas Distribution
No, the answer is incorrect.
Gas Score: 0
Distribution
Through Accepted Answers:
Distributor All of the above

Calculation of 2) Perforated or multiporous plate distributors are used as 1 point

gas pumping
power
consumption in
Industrial scale distributors
fluidized bed Laboratory scale distributors
Quiz : Both (a) and (b)
Assignment:
Module 5 None of the above
Week 5: No, the answer is incorrect.
Assignment Score: 0
Solutions
Accepted Answers:
Bubbling Industrial scale distributors

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Funded by

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Characteristics Powered by without screen

Perforated plate
Entrainment, No, the answer is incorrect.
Elutriation and Score: 0
Attrition
Accepted Answers:
Attrition, mixing Perforated plate without screen
and Segregation
4) The type of perforated plate distributor which can withstand heavy loads and 1 point

Phase Dispersion thermal stresses

Mass Transfer Curved plate type

and Heat Transfer Grate bars type
Straight plate type
Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Curved plate type
5) What type of distributors is used for high-temperature operations and in highly 1 point
reactive environment?

Tuyers type distributor

Pipe grides and sparger
None of the above
Perforated plate distributor
No, the answer is incorrect.
Score: 0
Accepted Answers:
Tuyers type distributor
6) The main disadvantages of bubble cap distributor are 1 point

Difficult to avoid stagnant regions

Not suitable for sticky solids
Lower pressure drop
Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Difficult to avoid stagnant regions
7) For the same bed height and same ‘U’ 1 point

∆Pd/∆Pb – porous plate > ∆Pd/∆Pb – orifice plate

∆Pd/∆Pb – porous plate < ∆Pd/∆Pb – orifice plate
∆Pd/∆Pb – porous plate = ∆Pd/∆Pb – orifice plate
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
∆Pd/∆Pb – porous plate > ∆Pd/∆Pb – orifice plate

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8) The main advantages of bubble cap distributor are 1 point

Minimizes weeping
Good turndown ratio
Lower pressure drop
All of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:
All of the above

9) The change of ∆Pd/∆Pb with the increase of U/Umf 1 point

Decreases
Increases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
10)For even distribution of fluidizing gas to a bed where ‘U’ is close to ‘Umf’ 1 point

∆Pd/∆Pb ≥ 0.05
∆Pd/∆Pb ≤ 0.05
∆Pd/∆Pb ≥ 0.15
∆Pd/∆Pb ≤ 0.15
No, the answer is incorrect.
Score: 0
Accepted Answers:
∆Pd/∆Pb ≥ 0.15
11)The stirring effect measuring factor is defined as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

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12)The jets will not contribute much to bed stirring and bubble rising when 1 point

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

13)The effect of excessive distributor pressure drop is 1 point

Power consumption at the blower or compressor increases

Design cost of blower or compressor increases
Total pressure drop increases
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
14)For porous plate distributor the pressure is related to fluid velocity as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

15)The thumb rule for the pressure drop across distributors is 1 point

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No, the answer is incorrect.

Score: 0
Accepted Answers:

16)The jet penetration length (Lj) for the horizontal jet (dor = 2.1 mm) is 1 point

Lj = 10-15 cm for many small holes

Lj = 15-20 cm for many small holes
None of the above
Lj = 5-10 cm for many small holes
No, the answer is incorrect.
Score: 0
Accepted Answers:
Lj = 5-10 cm for many small holes
17)At higher flow rate, the jet penetration length (Lj) 1 point

Decreases
None of these

Remains constant
Increases
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
18)Above a perforated plate, the dead zone shrinks when 1 point

The gas velocity increases

The particle size increases
The spacing of orifices decreased
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
The gas velocity increases
19)The change in bubble size with the increase of orifice flow 1 point

Increases
None of the above
Remains constant
Decreases
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases

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20)At a bubble cap tuyer 1 point

At higher flow rate jet forms

At low gas flow rate bubbles form and detach in orderly procession
Prevents solids from falling through the distributor
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Prevents solids from falling through the distributor
21)The ideal shaft work (-ws,ideal) for an axial blower which is being used to 1 point
supply the hot air in a fluidized bed reactor is 100 kJ. The efficiency of the blower is
0.85. The actual shaft work is as

-ws,actual = 300.98 KJ
-ws,actual = 130.64 KJ
-ws,actual = 150.23 KJ
-ws,actual = 117.64 KJ
No, the answer is incorrect.
Score: 0
Accepted Answers:
-ws,actual = 117.64 KJ
22)The outlet temperature of the air when it is compressed in a compressor in 1 point
reversible adiabatic compression? Data: Inlet pressure of air (P1) = 1 atm, Outlet pressure
of air (P2) = 10 atm, Inlet temp of air (T1) = 298 k, g = 1.33

900.59 K
827.52 K
300.56 K
527.64 K
No, the answer is incorrect.
Score: 0
Accepted Answers:
527.64 K
23)A real operation conditions two-stage compressor with frictional losses 1 point

None of these
-ws,actual < -ws,ideal
-ws,actual = -ws,ideal
-ws,actual > -ws,ideal
No, the answer is incorrect.
Score: 0
Accepted Answers:
-ws,actual > -ws,ideal
24)What is the ideal power consumption of the compressor to deliver the hot 1 point
reacting gas to the fluidized bed reactor in the petrochemical plant. The volumetric flow
rate of the reacting gas is 25 m3/s. The Inlet pressure at the compressor is 101 kPa while
the outlet pressure is 500 kPa. Specific heat capacity ratio is 2.4

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6675.57 kW
9000.89 kW
9567.78 kW
2375.50 kW
No, the answer is incorrect.
Score: 0
Accepted Answers:
6675.57 kW
25)A fluidized bed reactor in a polymer processing plant is attached with a 1 point
compressor to transport the reacting fluid to the catalyst bed. What is the outlet pressure?
The inlet pressure and temperature at the compressor is 101 ´ 10 3 Pa and 27 0C. System
parameter are as follows: Δpbed = 18´ 10 3 Pa, Δpgrid distributor = 10´ 10 3 Pa,
Δpcyclone+filters = 20´ 10 3 Pa, Δpfilter exit = 399´ 10 3 Pa

P2 = 458´ 10 2 kPa
P2 = 447´ 10 3 kPa
P2 = 358´ 10 2 kPa
P2 = 799´ 10 4 kPa
No, the answer is incorrect.
Score: 0
Accepted Answers:
P2 = 447´ 10 3 kPa

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Courses » Fluidization Engineering

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Unit 7 - Bubbling
Fluidization

Course
outline
Assignment: Module 6
The due date for submitting this assignment has passed. Due on 2018-03-07, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 6: Bubbling Fluidization

Fluidization Each question has only one correct answers and carries one mark. (1x25)

1) The inertia of the liquid moved by the rising bubbles becomes more important 1 point
Flow Regime and
its Map than the surface tension at

Frictional Higher gas flow rate

Pressure Drop
Independent of gas flow rate
Characteristics
Lower gas flow rate
Gas Distribution
None of the above
Bubbling No, the answer is incorrect.
Fluidization Score: 0

Bubbling Accepted Answers:

Fluidization-Part Higher gas flow rate
1: Bubble
Characteristics 2) Under the aggregative fluidization condition, the bed consists the phase(s) 1 point

Bubbling
Fluidization
Bubble phase
-Part 2: Bubble Emulsion phase
characteristics
Both (a) and (b)
Quiz :
Assignment: None of the above
Module 6
No, the answer is incorrect.
Assignment Score: 0
Solutions
Accepted Answers:

© 2014 NPTEL - Privacy & Terms - Honor Code - FAQs -

A project of In association with

Funded by

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Powered by
Entrainment,
Elutriation and
Attrition

Attrition, mixing
and Segregation

Phase Dispersion

Mass Transfer
and Heat Transfer

No, the answer is incorrect.

Score: 0
Accepted Answers:

4) The gas jet issuing from the orifice or the nozzle tends to be truncated into 1 point
bubbles right at the orifice when

The gas velocity is low

The bed material is dense
The particle size is small
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
5) According to Davidson and Harrison (1963), the bubble volume at high gas 1 point
flow rate can be expressed as

None of these

No, the answer is incorrect.

Score: 0
Accepted Answers:

6) With the increase of u0/umf, the bubble size (db) 1 point

Increases

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Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
7) With the increase of pressure, the bubble size 1 point

Decreases
Remains constant
Increases
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
8) Hydraulic diameter of the bed can be calculated by using the equation 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

9) The bubble velocity is affected by the presence of the vessel wall, when the 1 point
bubbles are large enough

Exceed approximately 35% of the column diameter

Exceed approximately 45% of the column diameter
Exceed approximately 15% of the column diameter
Exceed approximately 25% of the column diameter
No, the answer is incorrect.
Score: 0
Accepted Answers:
Exceed approximately 25% of the column diameter
10)The rising velocity of a single bubble in a quiescent bed can be expressed as 1 point

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No, the answer is incorrect.

Score: 0
Accepted Answers:

11)The absolute bubble velocity from the material balance can be expressed as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

12)The wall effect predominates when the equivalent bubble diameter (dbe) is 1 point

More than 1/3 of the bed diameter

More than ¼ of the bed diameter
Less than 1/3 of the bed diameter
Equivalent to the bed diameter
No, the answer is incorrect.
Score: 0
Accepted Answers:
More than 1/3 of the bed diameter
13)The initial bubble size formed at the end of the jet is expressed as 1 point

Both (a) and (b)

None of the above

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No, the answer is incorrect.

Score: 0
Accepted Answers:

14)According to Kunii and Levenspiel, at higher orifice flows, the bubble 1 point
frequency just above the orifice should be

No, the answer is incorrect.

Score: 0
Accepted Answers:

15)The wall effect becomes negligible only when the equivalent bubble diameter 1 point
(dbe) is

> 0.1
= 0.1
< 0.1
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
< 0.1
16)When the level above the distributor increases, the bubble frequency 1 point

None of the above

Decreases
Increases
Remains constant
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
17)The wall effect is dominant in case of 1 point

Bubbling regime

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Slugging regime
Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Slugging regime
18)The bubbles in fluidized beds increase in size primarily due to 1 point

Reduction in effective hydrostatic pressure toward the top section

Bubble coalesce in the horizontal direction with the neighbouring bubbles
Bubble coalesce in the vertical direction with the trailing bubble
All of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
All of these
19)According to Mori and Wen, 1975 Model, the initial bubble size (db0) through 1 point
the porous plate is directly proportional to

(u - umf)
(umf - u)2
(u - umf)2
(u - umf)2/3
No, the answer is incorrect.
Score: 0
Accepted Answers:
(u - umf)2
20)Fluidized bed reactor is packed with aluminium catalyst of uniform size is 1 point
working with air as the fluidizing medium. The diameter of the reactor is 0.5 m. Estimate
the bubble size at a distance H from the air distributor. The maximum size of the bubble
observed is 4.5 mm. The ignition bubble size nearby distributor is 1 mm. Take H = 0.3 m.
(Use mori and Wen 1975 correlation)

db = 1.57 mm
db = 3.55 mm
db = 1.57 cm
db = 5.39 mm
No, the answer is incorrect.
Score: 0
Accepted Answers:
db = 1.57 mm
21)Calculate the bubble coalescence frequency per unit volume in a fluidized bed. 1 point
The rise velocity and bubble diameter are 3 mm/s and 1 mm. The number of bubbles per
unit volume are 10

5.34 ´ 10 -8 m-3s-1
5.34 ´ 10 -3 m-3s-1

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9.87 ´ 10 -2 m-3s-1
6.34 ´ 10 -5 m-3s-1
No, the answer is incorrect.
Score: 0
Accepted Answers:
5.34 ´ 10 -3 m-3s-1
22)A fluidized bed reactor is operating with nitrogen as the fluidizing medium. The 1 point
area of the reactor is 0.1 m2 and the relative velocity of the nitrogen with respect to the
minimum fluidization is 0.25 mm/s. Determine the maximum bubble size produced in the
reactor. (Use Mori and Wen 1975 model)

9.40 mm
3.45 mm
5.87 mm
2.22 mm
No, the answer is incorrect.
Score: 0
Accepted Answers:
9.40 mm
23)Determine the rise velocity of air bubble in a fluidized bed where the equivalent 1 point
bubble diameter is 3.25 mm

0.95 m/s
1.50 m/s
0.128 m/s
1.128 m/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
1.128 m/s
24)Fluidized bed reactor is used to process the sulphur removal from the coal 1 point
particle. In order to perform this operation, ozone gas is used to pass through the gas
distributor. The mean bubble diameter and ozone bubble voidage in the reactor is 2.55
mm and 0.25 respectively. Calculate the number of bubble per unit volume in the system

74598854.81 m-3
99809854.81 m-3
28809854.81 m-3
65809854.81 m-3
No, the answer is incorrect.
Score: 0
Accepted Answers:
28809854.81 m-3
25)The number of orifices per unit area (Nor) for a equilateral triangle array of 1 point
holes is expressed as

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No, the answer is incorrect.

Score: 0
Accepted Answers:

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Announcements Course Ask a Question Progress Mentor

Unit 8 - Interaction
of Phases

Course
outline
Assignment: Module 7
The due date for submitting this assignment has passed. Due on 2018-03-14, 17:00 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 7: Interaction of Phases

Fluidization Each question has only one correct answers and carries one mark. (1x20)

1) The coalescence of two bubbles in turbulent flow in a three-phase fluidized bed 1 point
Flow Regime and
its Map occurs through the step(s)

Frictional The bubbles collide

Pressure Drop
The surface of the colliding bubbles flattens against each other
Characteristics
Trapping a small amount of liquid between colliding bubbles
Gas Distribution
All the above
Bubbling No, the answer is incorrect.
Fluidization Score: 0
Accepted Answers:
Interaction of
Phases All the above
2) The collision of three or more bubbles at the same time has 1 point
Bubbling
Fluidization
Part 3 : Bubble None of the above
coalescence in
three-phase Very small probability
fluidization
Moderate probability
Bubbling
Very high probability
Fluidization
Part 4: Bubble No, the answer is incorrect.
breakup in Score: 0
three-phase
fluidization Accepted Answers:
Very small probability
Quiz : © 2014 NPTEL - Privacy & Terms - Honor Code - FAQs -
Assignment: 3) According to the film thinning model, thewith
bubbles
approach faster is bounce 1 point
A project of In association
Module 7
back without coalescence due to the limitation of the film drainage rate governed by
Assignment
Solution Density
Funded by
Phase Movement Surface tension

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and Entrainment Powered by

Characteristics Viscosity
None of the above
Entrainment,
Elutriation and No, the answer is incorrect.
Attrition Score: 0
Accepted Answers:
Attrition, mixing
Surface tension
and Segregation
4) According to collision frequency model (only takes turbulent collision into 1 point
Phase Dispersion account), collision frequency depends on
Mass Transfer Bubbles diameter
and Heat Transfer
Bubble number density
All the above
Turbulent dissipation rate
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubbles diameter
5) The buoyancy driven flow of a larger and a smaller bubble from the same depth 1 point
of a liquid column having velocities ur2 and ur1 respectively. What is the correct relation
between bubble rise the velocities under buoyancy

ur2 = ur1
ur2 > ur1
None of the above
ur2 < ur1
No, the answer is incorrect.
Score: 0
Accepted Answers:
ur2 > ur1
6) According to Hibiki and Ishii (2000), coalescence efficiency is mainly the 1 point

Wake-induced coalescence efficiency

Turbulence-induced coalescence efficiency
Sum of (a) and (b)
Either (a) or (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Sum of (a) and (b)
7) Which one among the interaction time (t1) and coalescence time (tc) depends on 1 point
the surface tension (σ)

Coalescence time
Interaction time
None of the above
Both (a) and (b)
No, the answer is incorrect.

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Score: 0
Accepted Answers:
Coalescence time
8) Higher coalescence efficiency results in case of 1 point

Small bubbles and small approach velocities

Large bubbles and small approach velocities
Large bubbles and high approach velocities
Small bubbles and high approach velocities
No, the answer is incorrect.
Score: 0
Accepted Answers:
Small bubbles and small approach velocities
9) Turbulent induced Coalescence efficiency model may not be applied to 1 point

Buoyancy driven collision events

Laminar shear collision events
Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Buoyancy driven collision events
10)The coalescence time (tC) decreased with increasing the volume concentration 1 point
(CS) of particles. What about bubble coalescence with increasing volume concentration
(CS)

Bubble coalescence remains constant

None of the above
Bubble coalescence is enhanced
Bubble coalescence is diminished
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubble coalescence is enhanced
11)The coalescence time (tC) decreased with increasing the volume concentration 1 point
(CS) of particles. What about bubble coalescence with increasing volume concentration
(CS)

Bubble coalescence is diminished

None of the above
Bubble coalescence is enhanced
Bubble coalescence remains constant
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubble coalescence is enhanced
12)At the approach phase, which bubble is faster 1 point

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Both have the same velocity

Leading bubble
Trailing bubble
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Trailing bubble
13)At the coalescence phase, before the liquid film rupture the distance between 1 point
the contracting bubbles is

None of the above

Increasing
Almost constant
Decreasing
No, the answer is incorrect.
Score: 0
Accepted Answers:
Almost constant
14)In an air-water system, the decrease in surface tension of the system causes 1 point
bubble size to

Increase
None of the above option
Decreases

Decrease then increase

No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases

15)The most important interfacial force which required to stabilize the bubble is 1 point

Shear force
Pressure force
Surface Tension

Viscous force
No, the answer is incorrect.
Score: 0
Accepted Answers:
Surface Tension

16)Bubble breakup is common phenomena in the turbulent multiphase flow 1 point

system. Bubble breakup takes place due to the

Bubble coalescence in the radial direction

Bubble coalescence in the axial direction
Pressure variation along the surface of the bubble
Laminar movement of bubble velocity

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No, the answer is incorrect.

Score: 0
Accepted Answers:
Pressure variation along the surface of the bubble
17)Estimate the maximum stable bubble size an air-water system where air is being 1 point
sparged from the air distributor. The system is in turbulent flow condition. The surface
tension of the water is reduced using suitable surfactant. The reduced surface tension of
the water is 55 mN/m at 25 0C. The density of the air is 1.2 kg/m3. The bubble voidage
and density of the water are 0.10 and 1000 kg/m3 respectively. (use Luo et al. 1999
model, b = 8.2)

2.55 mm
7.36 mm
8.77 mm
3.55 mm
No, the answer is incorrect.
Score: 0
Accepted Answers:
8.77 mm
18)For any universal bubble breakup model which important information required 1 point

breakup rate
daughter bubble size probability density
Both (b) and (c)
Coalescence rate
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (b) and (c)
19)Martínez-Bazánet al.’s (1999) deduce bubble breakup rate based on the 1 point
turbulence stress and surface tension analysis for daughter bubbles distribution. Which
condition is correct according to the model

None of the above option

Bubble breakup rate is zero for bubbles of size d < = dmax
Bubble breakup rate is maximum for bubbles of size d < = dmax
Bubble breakup rate is zero for bubbles of size d > = dmax
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubble breakup rate is zero for bubbles of size d < = dmax
20)Bubble break is common phenomena in a multiphase flow system, which 1 point
criteria is responsible for bubble breakup

Velocity fluctuation around the particle surface greater than a critical value
Turbulent kinetic energy of the bubble greater than a critical value
Both (a) and (b)
Turbulent kinetic energy of the bubble smaller than a critical value

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No, the answer is incorrect.

Score: 0
Accepted Answers:
Both (a) and (b)
21)Turbulent fluctuation plays a significant role in a bubble breakup process. The 1 point
bubble breakup rate in a multiphase flow system depends on imbalance between

Potential energy and surface energy

Kinetic energy and surface energy
Surface energy and shear dissipation
kinetic energy and potential energy
No, the answer is incorrect.
Score: 0
Accepted Answers:
Kinetic energy and surface energy

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Unit 9 - Phase
Movement and Entrainment Characteristics

Course
outline
Assignment: Module 8
The due date for submitting this assignment has passed. Due on 2018-03-21, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 8: Phase Movement and Entrainment

Fluidization Characteristics
Each question has only one correct answers and carries one mark. (1x25)
Flow Regime and
its Map 1) According to Davidson model, the relation between the pressure gradient and 1 point
the relative velocity of the particles and the fluidizing medium is
Frictional
Pressure Drop Proportional
Characteristics
Inversely proportional
Gas Distribution Exponential function

Bubbling None of the above

Fluidization
No, the answer is incorrect.
Score: 0
Interaction of
Phases Accepted Answers:
Proportional
Phase Movement
and Entrainment 2) The bed should be considered as slugging when 1 point
Characteristics

Bubbling
Fluidization
Part 5: Gas and
solid
movements at
bubble
None of the above
Bubbling
Fluidization No, the answer is incorrect.
Part 6: Score: 0
Slugging Bed © 2014 NPTEL - Privacy & Terms - Honor Code - FAQs -
Accepted Answers:
A project of In association with
Entrainment
Characteristics
Part 1
3) According to the assumption of Davidson model, the pressure throughout the 1 point
Funded by
Quiz : bubble is
Assignment:

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Module 8 Powered by
Variable
Assignment
Solution
Unpredictable
None of the above
Entrainment,
Elutriation and Constant
Attrition
No, the answer is incorrect.
Attrition, mixing Score: 0
and Segregation Accepted Answers:
Constant
Phase Dispersion
4) In case of flat-nose slug, the gas slugs occupy 1 point
Mass Transfer
and Heat Transfer The complete bed cross section
One third of the bed cross section
One fourth of the bed cross section
Half of the bed cross section
No, the answer is incorrect.
Score: 0
Accepted Answers:
The complete bed cross section
5) Slow bubbles regime is usual for beds of 1 point

Large particles and large bubbles

Small particles and large bubbles
Large particles and small bubbles
Small particles and small bubbles
No, the answer is incorrect.
Score: 0
Accepted Answers:
Large particles and small bubbles
6) The types of slugging are generally seen 1 point

Round-nose slug
Wall slugs
Flat-nose slug
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
7) In case of fast bubble regime the following condition is applicable 1 point

No, the answer is incorrect.

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Score: 0
Accepted Answers:

8) Inthe fast bubble regime, the fluid moves in which direction relative to the 1 point
bubble motion

Upward direction
Downward direction
Radial direction
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Downward direction
9) The bubbles in the fluidized bed are accompanied by a ‘cloud’ while rising 1 point
through the bed. The cloud is usually

Very thin
Very thick
Moderately thick
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Very thin
10)A gas is distributed into a bubbling fluidized bed (diameter 0.6 m) operated at a 1 point
minimum bubbling fluidization velocity. It is seen that the mean diameter of the bubble is
5 cm. Calculate the bubble rise velocity (Ubr)

49.8 cm/s
59.2 cm/s
None of the above
39.6 cm/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
49.8 cm/s
11)When the bubble velocity increases, the cloud thickness 1 point

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases

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12)In small particle bed, the bubbles are flatter. So, with the smaller particles, the 1 point
wake angle

Decreases

Remains constant
Increases
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases

13)The wake fraction is defined as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

14)The cloud is infinite in thickness, when 1 point

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

15)According to Davidson, for three dimensional bed the upward flow rate of gas 1 point
into and out of the bubble is

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No, the answer is incorrect.

Score: 0
Accepted Answers:

16)In the fluidized bed a section of the bed between the surface of the dense phase 1 point
and the exit of the gas stream, is known as

Freeboard height
Bed diameter
Elutriation
Transport disengaging height
No, the answer is incorrect.
Score: 0
Accepted Answers:
Freeboard height
17)In a fluidized bed reactor the entrainment significantly affected by the 1 point

High or low gas velocity

Horizontal or vertical internal
Design of stirrer
All of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
All of the above option
18)A fluidized be is operated with four three different solid particles. The weight 1 point
of aluminium, nickel and vanadium are 300 g, 450 g and 570 g respectively. The total
volume of the bed is 1 m3. The bulk density of the system is

6.89 kg/m3
4.12 kg/m3
7.32 kg/m3
1.32 kg/m3
No, the answer is incorrect.
Score: 0
Accepted Answers:
1.32 kg/m3
19)The physical properties of the multiphase system like bulk density of the solid 1 point
and density of the gas have potential impact on the entrainment of the particles. The
entrainment of the system can be reduced by

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Decreasing the bulk density of solid and Decreasing in density of the gas
Decreasing the bulk density of solid and increasing in density of the gas
Increasing the bulk density of solid and decreasing in density of the gas
Increasing the bulk density of solid and increasing in density of the gas
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increasing the bulk density of solid and increasing in density of the gas
20)A fluidized bed reactor is being used to roast coffee beans by hot air. The 1 point
change of temperature may affect the entrainment characteristics of the reactor. Choose
the correct answer about the temperature effect on the entrainment

Increase in temperature significantly decrease the entrainment

There is no significant effect of temperature on entrainment
Increase in temperature significantly increase the entrainment
Decrease in temperature significantly increase the entrainment
No, the answer is incorrect.
Score: 0
Accepted Answers:
There is no significant effect of temperature on entrainment
21)Motion of wall slugs is defined by 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

22)The wall effect predominant in slug flow based fluidized bed, when 1 point

Bubble diameter is more than 1/3 of bed diameter

Bubble diameter is equal to 1/3 of bed diameter
Bubble diameter is less than 1/3 of bed diameter
Bubble diameter is equal to bed diameter
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubble diameter is more than 1/3 of bed diameter
23)If the ratio of bubble diameter and bed diameter is greater than 0.6, then 1 point

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Bed is considered slugging

Bed is considered bubbling
Bed is considered slugging and bubbling both
None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bed is considered slugging
24)According to Stewart and Davidson criterion 1 point

The height of the slugs is greater than the diameter of bed

The height of the slugs is equivalent to the diameter of bed
The distance between two slugs is equal to the bed diameter
None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
The height of the slugs is equivalent to the diameter of bed
25)Cohesive particles form generally 1 point

Flat-nose slug
Wall slug
Round nose slug
None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Flat-nose slug

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Unit 10 - Entrainment, Elutriation and Attrition

Course
outline
Assignment: Module 9
The due date for submitting this assignment has passed. Due on 2018-03-28, 17:00 IST.
How to access the
portal Submitted assignment

Introduction and Fluidization Engineering

Particle Properties

Minimum
Fluidization Module 9: Entrainment, Elutriation, and Attrition
Each question has only one correct answers and carries one mark. (1x25)
Flow Regime and its 1) In the fast fluidization regime, the carryover of the solids is 1 point
Map

Frictional Pressure
Very small
Drop Very large
Characteristics
Moderate
Gas Distribution None of the above
Bubbling No, the answer is incorrect.
Fluidization Score: 0
Accepted Answers:
Interaction of
Very large
Phases
2) Appropriate conditions to run a fast fluidized circulation system 1 point
Phase Movement
and Entrainment Keep a constant inventory of solids in the bed, even though ‘U’ may change
Characteristics
Keep a constant through flow of solids ‘Gs’, even though ‘U’ may change
Entrainment,
Elutriation and
Keep a constant gas flow rate ‘U’ while changing the solid through flow ‘Gs’
Attrition All the above
Entrainment No, the answer is incorrect.
Characteristics Score: 0
Part 2: Fast
fluidization Accepted Answers:
condition All the above
Elutriation 3) For the fine (Geldart A) particles, ‘U/Ut’ range is 1 point
Characteristics

Attrition in 34 – 42
Fluidized Bed
(Part 1) 25 – 32
Quiz : 2 – 11
Assignment:
15 - 24
Module 9
© 2014
No, the NPTEL
answer - Privacy & Terms - Honor Code - FAQs -
is incorrect.
Assignmnet
A project of
Solution Score: 0 In association with
Accepted Answers:
Attrition, mixing
2 – 11
and Segregation
Funded by Powered by
4) The bed voidage is increased by adding 1 point

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Phase Dispersion Horizontal baffles

Vertical baffles
Mass Transfer and
Heat Transfer Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Horizontal baffles
5) In fast fluidization there is a portion of the vessel of almost constant solid fraction is 1 point
called the dense region. Dense region generally remains at

The top of the vessel

Middle of the vessel
Bottom of the vessel
Not sure
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bottom of the vessel
6) When all the solids are entrainable in the flow regime then 1 point

x>1
x<1
x=1
x=0
No, the answer is incorrect.
Score: 0
Accepted Answers:
x=1
7) The solid distribution fraction ranges 0.55 – 0.40 applicable for the 1 point

Bubbling bed
Turbulent bed
Fast fluidization bed
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bubbling bed
8) For the larger particles, ‘U/Ut’ 1 point

Increases
Decreases
Remains constant
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreases
9) Solid flux at the exit is higher at 1 point

Low ‘U’

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High ‘U’
Moderate ‘U’
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Low ‘U’
10)Theslip velocity ‘us’ is considered as the mean velocity of solids at the exit level of the 1 point
column which is expressed as

No, the answer is incorrect.

Score: 0
Accepted Answers:

11)For fine particles at high ‘U’, the fraction of solids at the exit justify 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

12)The free-board entrainment model of Kunii and Levenspiel, the solid distribution can be 1 point
written as

None of these

No, the answer is incorrect.

Score: 0

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Accepted Answers:

13)During fluidization some solid particles break and form fine particles which required to 1 point
avoid to have the smooth processing of the material. Such phenomena are known as attrition.
Which statement is true about attrition

It severely affects the product quality and equipment

Attrition characteristics need to be studied before handling particulate material
Both (a) and (b)
None of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
14)Attrition mechanism of the particular solid be subject to 1 point

Shear force
Breaking force
Particle strength
both (b) and (c)
No, the answer is incorrect.
Score: 0
Accepted Answers:
both (b) and (c)
15) 1 point

(p) - (n); (q) – (m); (r)- (l)

(p) - (m); (q) – (n); (r)- (o)
(p) - (m); (q) – (n); (r) - (l)
(p) - (r); (q) – (n); (r)- (l)
No, the answer is incorrect.
Score: 0
Accepted Answers:
(p) - (m); (q) – (n); (r) - (l)
16)Hardgrove index (HGI), known as the grindablity index required to understand the 1 point
attrition characteristics of the particle, which is useful in

Single particle test

Multi-particle test
Both single and multi-particle test
None of the above option
No, the answer is incorrect.

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Score: 0
Accepted Answers:
Multi-particle test
17)In a fluidized bed, reactor attrition is necessary to understand to maintain the product 1 point
quality, avoid surface wear and unnecessary energy consumption. The average attrition rate can be
defined as

None of the above option

Either (a) or (b)

No, the answer is incorrect.

Score: 0
Accepted Answers:
Either (a) or (b)
18)If D and HGI represent the fraction of particle passing through the sieves and hardgrove 1 point
index respectively, choose the correct option

HGI = 6.93 + 13D

HGI = 13 + 6.93D
D = 13 + 6.93HGI
HGI = 13+ 7.93 D
No, the answer is incorrect.
Score: 0
Accepted Answers:
HGI = 13 + 6.93D
19)The unit of the average attrition can be provided as 1 point

m-1s-1
s-1
ms
m/s
No, the answer is incorrect.
Score: 0
Accepted Answers:
s-1
20) 1 point

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(p) – (s); (q) – (v); (r) – (t)

(p) – (v); (q) – (s); (r) – (u)
(p) – (v); (q) – (s); (r) – (t)
(p) – (v); (q) – (t); (r) – (s)
No, the answer is incorrect.
Score: 0
Accepted Answers:
(p) – (v); (q) – (s); (r) – (t)
21)Rate of energy input to the fluidized bed can be defined as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

22)The unit of elutriation rate is 1 point

kg/m4s
kg/ms
kg/m2s2
kg/m2s
No, the answer is incorrect.
Score: 0
Accepted Answers:
kg/m2s
23)A fluidized bed of 6 m diameter is operating with catalyst particle under the following 1 point
operating conditions: ρg =5.51 kg/m3, ρs =1200 kg/m3, and u= 0.61 m/s, dp= 130 µm. Assume that
freeboard > TDH What is the saturation carrying capacity, if

6.11
3.83
12.96
4.03
No, the answer is incorrect.
Score: 0
Accepted Answers:
4.03
24)What is the saturation carrying capacity for bed in which the fine constitute just 20% of 1 point
the bed solid? (Use data of question number 23)

0.0806
8.06
0.806
15.23
No, the answer is incorrect.
Score: 0
Accepted Answers:

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0.806
25)If elutriation rate is large, then it signifies 1 point

Solids are not removed

Rapid removal
They are alone in bed
None of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
Rapid removal

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Unit 11 - Attrition,
mixing and Segregation

Course
outline
Assignment 10
The due date for submitting this assignment has passed. Due on 2018-04-04, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 10: Attrition, Mixing, and Segregation

Fluidization Each question has only one correct answers and carries one mark. (1x25)

1) The breakage model is applicable for breakage occurs due to 1 point

Flow Regime and
its Map
Particle-particle collisions
Frictional Particle-wall collisions
Pressure Drop
Characteristics Both (a) and (b)
None of the above
Gas Distribution
No, the answer is incorrect.
Bubbling Score: 0
Fluidization
Accepted Answers:
Particle-wall collisions
Interaction of
Phases 2) The breakage probability depends on 1 point

Phase Movement The cyclone inlet gas velocity and the solids load
and Entrainment
Characteristics Particle size and a material-specific constant

Entrainment,
Cyclone size
Elutriation and Both (a) and (b)
Attrition
No, the answer is incorrect.
Attrition, mixing Score: 0
and Segregation Accepted Answers:
Attrition in Both (a) and (b)
Fluidized Bed
3)©Under the same
2014 NPTEL magnitude
- Privacy & Terms of breaking
- Honor Code -energy,
the material which has the
FAQs - 1 point
(Part 2)
A project of dominant fraction of the surfaceInarea in a mixture,
association with the attrition rate of this material is
Solid
movement,
Dependent on its particle size
mixing:
Gas-fluidized Independent on its particle size
Funded by
Bed

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Solid May Powered

or may by
not depend on its particle size
segregation:
Gas-fluidized None of the above
bed
No, the answer is incorrect.
Quiz : Score: 0
Assignment 10
Accepted Answers:
Assignment Independent on its particle size
Solution
4) For the same type of particles but of different sizes, the frictional loss due to 1 point
Phase Dispersion
attrition for the smaller particles is
Mass Transfer
and Heat Transfer
Larger
Smaller
Moderate
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Larger
5) The
breakage rate of round particles based on Weibull statistics and breakage 1 point
mechanics can be expressed as

No, the answer is incorrect.

Score: 0
Accepted Answers:

6) The attrition rate of a material with only minute fraction of the total surface 1 point
area is

Inversely proportional to its average particle size

Directly proportional to its average particle size
Exponentially proportional to its average particle size
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Inversely proportional to its average particle size
7) According to Fan and Srivastaba (1981), the relation between the mass attrition 1 point
rate and the volume or mass of the component is

Exponential relationship

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Logarithmic relationship
Inversely proportional
Directly proportional
No, the answer is incorrect.
Score: 0
Accepted Answers:
Directly proportional
8) The reaction rate of an individual component (‘component’ is referred to as 1 point
particles of the same material and size) is proportional to its

Surface area
Selectivity
Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
9) According to surface-reaction model, for a particle of radius (ri), mass (Mi) and 1 point
mass attrition rate (Rti), the fractional attrition rate is defined by

No, the answer is incorrect.

Score: 0
Accepted Answers:

10)The rate of effective breaking energy (Ebi) is proportional to 1 point

Cyclone inlet gas velocity

Total surface area of the component
Number of bends of pipe
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Total surface area of the component
11)Significantly higher attrition rate is found in 1 point

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Long elbow-bend
Miter-bend
Blinded-tee
Short elbow-bend
No, the answer is incorrect.
Score: 0
Accepted Answers:
Blinded-tee
12)Higher attrition in the conveying system is caused by 1 point

Particle degradation
Particle-wall impacts
Particle-particle impacts
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Particle-particle impacts
13)The conveying velocity can be minimized to reduce the attrition by 1 point

Increasing gas density

Decreasing the molecular weight of the gas
Decreasing gas pressure
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increasing gas density
14)The moisture content influences 1 point

The hardness of the material

The elasticity of the material
Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
15)The particles become brittle and easy to break at 1 point

Lower jet momentum

Lower temperature
Lower pressure
Higher temperature
No, the answer is incorrect.
Score: 0
Accepted Answers:

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Lower temperature
16)The attrition can be minimized by 1 point

Proper material selection

Proper design of distributor
Reducing the conveying velocity
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Proper material selection
17)Find the vertical mixing rate in small bed if gas velocity is 5 m/s 1 point

11.2
0.56
0.056
5.6
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.56
18)Vertical mixing is _____ than horizontal mixing 1 point

Faster
Slower
Same
None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Faster
19)How does horizontal mixing vary with bed width 1 point

Increases
Decreases
Remains same
None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increases
20)The mean square horizontal shift of a particle passing through the bubble wake 1 point
is directly proportional to

(Bubble diameter)2
Bubble diameter
(Effective diameter of the wake)2

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None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
(Effective diameter of the wake)2
21)In segregation, the term “Flotsam” represents 1 point

Component that ultimately sinks

Component that floats to the top of the bed
Component that clusters together
None of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
Component that floats to the top of the bed
22)In a segregating gas fluidized bed, the mixing index can be represented as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

23)In segregation index, choose the correct option 1 point

s = 1, represents a state of perfect mixing

s = 0, represents a state of perfect mixing
s = 1, represents a state of complete segregation
None of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
s = 1, represents a state of perfect mixing
24)The solid mixing in the fluidized bed and the amount of solids induced upward 1 point
by a single gas bubble is due to the action of

Drift
Wake

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Both (a) and (b)

None of these
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
25)In actual practice where particles are continuously introduced and withdrawn, 1 point
the bed turnover time and particle residence time play important role in governing the
mixing characteristics of the fluidized bed. Choose the correct option

Bed turnover time should be as greater than particle residence time

Bed turnover time should be as short as compared to the particle residence time
Bed turnover time should be equal to the particle residence time
None of the above option
No, the answer is incorrect.
Score: 0
Accepted Answers:
Bed turnover time should be as short as compared to the particle residence time

You were allowed to submit this assignment only once.

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Unit 12 - Phase Dispersion

Course outline Assignment 11

How to access the portal The due date for submitting this assignment has passed. Due on 2018-04-11, 23:59 IST.

Introduction and Particle

Submitted assignment
Properties
Fluidization Engineering
Minimum Fluidization

Flow Regime and its Map

Module 11: Phase Dispersion
Each question has only one correct answers and carries one mark. (1x25)
Frictional Pressure Drop
Characteristics 1) A constant axial pressure gradient throughout the bed denotes 1 point

Gas Distribution Partial mixing of the particles

Bubbling Fluidization Perfect mixing of the particles

Perfect segregation of the particles
Interaction of Phases
None of the above
Phase Movement and No, the answer is incorrect.
Entrainment Characteristics
Score: 0

Entrainment, Elutriation and Accepted Answers:

Attrition Perfect mixing of the particles
2) When the variation of pressure gradient is larger, the degree of segregation is 1 point
Attrition, mixing and
Segregation
Larger
Phase Dispersion Moderate
Solid mixing and Smaller
segregation: Liquid-solid
fluidized bed Independent
Gas Dispersion and No, the answer is incorrect.
Interchange Score: 0

Mass transfer in fluidized Accepted Answers:

Bed-Gas-solid system Larger
Quiz : Assignment 11 3) The changing composition with bed level of two spherical particles differing in both diameter and density can be 1 point

Assignment Solution determined by means of the volume-average density which is expressed as

Mass Transfer and Heat

Transfer

Both (a) and (b)

None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:

4) Particle mixing and segregation depends on 1 point

Shape difference
Particle density difference
Size difference

© 2014 NPTEL - Privacy & Terms - Honor Code - FAQs -

A project of In association with Funded by Powered by

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No, the answer is incorrect.

Score: 0
Accepted Answers:

6) Neglecting the bulk circulation and hydrodynamic instability, the degree of segregation decreases when the 1 point

Inertial effects increases

Inertial effects decreases
Turbulence decreases
Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Inertial effects increases
7) Clean-cut segregation with sharp interface and little intermixing is observed when 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

8) The relation of segregation velocity (Upi) with the local interstitial velocity or slip velocity and the interstitial velocity 1 point
(Ui)

No, the answer is incorrect.

Score: 0
Accepted Answers:

9) For a mono-component system or for the fully segregated regions of either a partially or fully segregated bed, the 1 point
value of segregated velocity (Upi) is

Upi = 0
Upi < 1
Upi = 1
Upi > 1
No, the answer is incorrect.

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Score: 0
Accepted Answers:
Upi = 0
10) The inversion condition is taken as 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

11) At any bed level within the partially mixed region, the relation between the volumetric particle mixing flux of a 1 point
species and the particle segregation flux for that species is

First one is greater than the second one

Second one is greater than the first one
Both are equal
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both are equal
12) At the inversion velocity, the entire bed attains a uniform composition equal to that of the overall solid composition. 1 point
This condition satisfies the value of

No, the answer is incorrect.

Score: 0
Accepted Answers:

13) The relation between PeL and PeS is 1 point

No, the answer is incorrect.

Score: 0
Accepted Answers:

14) In accord with Di Felice et al. (1987), CL and CS are linearly related and expressed as 1 point

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No, the answer is incorrect.

Score: 0
Accepted Answers:

15) Decrease in bubble size causes 1 point

Increase in interchange coefficient of bubble-cloud

Decrease in interchange coefficient of bubble-cloud
No effect on interchange coefficient of bubble cloud
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increase in interchange coefficient of bubble-cloud
16) Calculate the interchange coefficient for the bubble-cloud interface (Kbc.). Data given: 1 point

0.833
0.1677
1.677
0.0833
No, the answer is incorrect.
Score: 0
Accepted Answers:
0.833
17) Calculate interchange coefficient for cloud-emulsion interface (Kce). Use the data of question number 16. 1 point

1.01
1.21
0.121
0.11
No, the answer is incorrect.
Score: 0
Accepted Answers:
1.21
18) Calculate interchange coefficient for bubble-emulsion interface (Kbe). Use the data of question number 16. 1 point

1.866
1.667
1.776
1.11
No, the answer is incorrect.
Score: 0
Accepted Answers:
1.866
19) The unit of bubble-cloud interchange coefficient 1 point

s
m-1s-1
m-1s
s-1
No, the answer is incorrect.
Score: 0

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Accepted Answers:

s-1
20) The area under the pulse-response curve is 1 point

Greater than 1
Unity
None of the above
Less than 1
No, the answer is incorrect.
Score: 0
Accepted Answers:
Unity
21) The relation between mass transfer coefficient (kg;single) and diffusion coefficient of gas (D) under single-sphere1 point
condition can be represented as

No, the answer is incorrect.

Score: 0
Accepted Answers:

22) Fluidized bed operating with hydrogen as the fluid medium is used in petroleum industry for cracking operation. 1 point
Determine the total exterior surface of the catalyst particle? Data: V seg = 0.1 m3, ebed = 0.10, sphericity of the particle (fs) =1,
diameter of sphere (dsph) = 0.001 m.

540 m
2700 m
1000 m
1563 m
No, the answer is incorrect.
Score: 0
Accepted Answers:
540 m
23) According to Behie and Kehoe (1973), the mass transfer coefficient relation between the grid region (k je) and bubble 1 point
region (kbe) can be represented as

kje = 10-50 kbe

kje = 40-60 kbe
kje = 0.5 kbe
kje = 40-100 kbe
No, the answer is incorrect.
Score: 0
Accepted Answers:
kje = 40-60 kbe
24) Choose the correct expression for Sherwood number for particle size of 711 mm in diameter. The Reynold number of 1 point
the particle is 15 < Rep < 30, use Resnick and White ,1949 correlation).

No, the answer is incorrect.

Score: 0
Accepted Answers:

25) What theoretical value can Sherwood number have when the solid particle is exposed to the station gas medium or 1 point
zero Reynold number?

Sh = 1.0

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Sh = 2.0
Sh = 0.1
Sh = 5.0
No, the answer is incorrect.
Score: 0
Accepted Answers:
Sh = 2.0

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Unit 13 - Mass
Transfer and Heat Transfer

Course
outline
Assignment 12
The due date for submitting this assignment has passed. Due on 2018-04-18, 23:59 IST.
How to access
the portal Submitted assignment

Introduction and Fluidization Engineering

Particle
Properties

Minimum Module 12: Mass Transfer and Heat Transfer

Fluidization Each question has only one correct answers and carries one mark. (1x25)

1) The conversion determines the performance of the reactor with the 1 point
Flow Regime and
its Map
Efficiency
Frictional Operating variables
Pressure Drop
Characteristics Lag of the system
None of the above
Gas Distribution
No, the answer is incorrect.
Bubbling Score: 0
Fluidization
Accepted Answers:
Operating variables
Interaction of
Phases 2) The resistance to reaction at the external catalyst surface is expressed as 1 point

Phase Movement
and Entrainment
Characteristics

Entrainment,
Elutriation and
Attrition

Attrition, mixing
and Segregation

Phase Dispersion
© 2014
No, NPTEL -isPrivacy
the answer & Terms - Honor Code - FAQs -
incorrect.
Mass Transfer
A project of Score: 0 In association with
and Heat Transfer
Accepted Answers:
Mass transfer
in fluidized
Bed-Gas- Funded by

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liquid-solid 3) Thiele modulus

Poweredisby
defined as 1 point
system
(Contd.)

Heat transfer
Characteristics

Fluidized bed
reactor design
and its
performance

Quiz :
Assignment 12

Assignment
Solution

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

4) For a first-order reaction in porous particles, the resistance to reaction is 1 point

expressed as

No, the answer is incorrect.

Score: 0
Accepted Answers:

5) One may assume that the solids do not affect the value of kLa when 1 point

The solids concentration is very high

The solids concentration is very low
The solids concentration is moderate
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
The solids concentration is very low
6) The slurry behaves as a pseudo-homogeneous phase, if 1 point

The density difference between the solids and liquids are small

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The liquid viscosity is high

The liquid viscosity is low
Both (a) and (b)
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
7) The unit of fluid consistency index (k) 1 point

m.s-1
Pa.s
m-1
µm
No, the answer is incorrect.
Score: 0
Accepted Answers:
Pa.s
8) With the addition of non-wettable particles in the aqueous solution, the value of 1 point
kL a

Increases
Decreases
Remains constant
None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:
Decreases
9) The gas-to-liquid mass transfer rate of a component ‘A’ can be enhanced by the 1 point
presence of particles due to

Adsorption on the particles

Catalysis by the particles
Reaction with the particles
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
10)According to the film theory of mass transfer, the relation between the mass 1 point
transfer coefficient and the film thickness for the mass transfer

Exponential relationship
Inversely proportional
Logarithmic relationship
Directly proportional
No, the answer is incorrect.

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Score: 0
Accepted Answers:
Inversely proportional
11)According to the penetration theory of mass transfer, the relation between the 1 point
mass transfer coefficient (kL) and the effective diffusivity (DA)

No, the answer is incorrect.

Score: 0
Accepted Answers:

12)Heat transfer coefficient increases with 1 point

Increasing thermal conductivity

Decreasing gas density
Increasing gas viscosity
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Increasing thermal conductivity
13)Heat transfer mechanisms contributing to heat transfer at submersed surfaces 1 point
include

Gaseous convection during times of bubble contact

Particle conduction/convection during times of particle contact
Radiation in the case of high-temperature operation
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
14)The wall heat transfer coefficient (hw) decreases with 1 point

Increasing particle size

Decreasing particle size
Independent of particle size
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:

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Increasing particle size

15)To achieve good mixing within the fluidized bed the pitch to diameter ratio for 1 point
tubes in a bundle should be in the range of

1 to 2
2 to 4 or greater
0 to 1
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
2 to 4 or greater
16)According to Yang (2003), for the high temperature beds the radiative heat 1 point
transfer contribution to the total heat transfer ranges from

50% to 80%
2% to 30%
60% to 90%
70% to 100%
No, the answer is incorrect.
Score: 0
Accepted Answers:
2% to 30%
17)According to Yang (2003), the important parametric effects on the heat transfer 1 point
in fast circulating fluidized beds are

Wall heat transfer coefficient (hw) increases with increasing solid mass flux
Wall heat transfer coefficient (hw) is greater for small heat transfer surfaces
Wall heat transfer coefficient (hw) increases with increasing radial position
towards the bed wall
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
18)To estimate the gas-liquid heat transfer in the three phase fluidized bed, the 1 point
assumptions are

The inertia-particle temperature gradient is neglected

The liquid side resistance to heat transfer is neglected
Both (a) and (b)
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
Both (a) and (b)
19)According to the Stefan-Boltzman equation, the increase of radiative heat 1 point
transfer is proportional to

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Fluidization Engineering - - Unit 13 - Mass Tran... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

The fourth power of absolute temperature

The fifth power of absolute temperature
The third power of absolute temperature
None of the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
The fourth power of absolute temperature
20)Consider a first-order catalytic reaction in a circulating fluidized bed, the rate of 1 point
reaction can be expressed as

Either (a) or (b)

No, the answer is incorrect.

Score: 0
Accepted Answers:

21)Choose the correction option 1 point

The fast fluidized reactor has a lower lean region and an upper dense region
The fast fluidized reactor has a smaller dense region and an upper lean region
The fast fluidized reactor has an only lean region in both lower and an upper
region
The fast fluidized reactor has only dense region in both lower and an upper
region
No, the answer is incorrect.
Score: 0
Accepted Answers:
The fast fluidized reactor has a smaller dense region and an upper lean region
22)Circulating fluidized bed (CFB) 1 point

Has dominant role in FCC

Contain very fine particles
Blow out the solids from the bed
All the above
No, the answer is incorrect.
Score: 0
Accepted Answers:
All the above
23)In a two-phase fluidized bed the heat transfer coefficient (h) is expressed as 1 point

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Fluidization Engineering - - Unit 13 - Mass Tran... https://onlinecourses.nptel.ac.in/noc18_ch10/un...

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

24)The unit of the heat transfer coefficient (h) is 1 point

W/m2-K
J/kg-K
W/kg-K
J/kg-s
No, the answer is incorrect.
Score: 0
Accepted Answers:
W/m2-K
25)Forthe pneumatic flow condition when the gas velocity is very high and the 1 point
presence of solid is very lean then

None of the above

No, the answer is incorrect.

Score: 0
Accepted Answers:

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