A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below: Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

A bed of spherical particles (specific gravity 2.5) of uniform size 1500
μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity
may be taken as 0.4. Ergun's equation for the above fluid-particle system (in
SI units) is given below:
Δ P/L = 375 × 10
3 VOM + 10.94 × 10
6 V2
OM (SI units)
If water is to be used as the fluidising medium, in actual operation, the
above bed has a height = 1 m. What is the porosity of the fluidised bed?
(A) 0.2
(B) 0.5
(C) 0.7
(D) 0.8
by

1 Answer

Answer :

(C) 0.7
by

Related questions

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below : Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle ... fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Last Answer : (B) 16 mm/s

A gas (density = 1.5 kg/m3 , viscosity = 2 × 10 ‒5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5 kg/m3and viscosity of 3 × 10 ‒5kg/m.s flowing at 3 m/s will be (A) 8400 Pa/m (B) 12600 Pa/m (C) 18900 Pa/m (D) 16800 Pa/m

Description : A gas (density = 1.5 kg/m3 , viscosity = 2 10 -5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The ... flowing at 3 m/s will be (A) 8400 Pa/m (B) 12600 Pa/m (C) 18900 Pa/m (D) 16800 Pa/m

Last Answer : (B) 12600 Pa/m

If dry density, water density and specific gravity of solids of a given soil sample are 1.6 g/cc, 1.84 g/cc and 2.56 respectively, the porosity of the soil sample, is (A) 0.375 (B) 0.370 (C) 0.380 (D) 0.390

Description : If dry density, water density and specific gravity of solids of a given soil sample are 1.6 g/cc, 1.84 g/cc and 2.56 respectively, the porosity of the soil sample, is (A) 0.375 (B) 0.370 (C) 0.380 (D) 0.390

Last Answer : (A) 0.375

. A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Description : . A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Last Answer : (A) 4.4 KPa

Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Description : Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Last Answer : (B) 60

The specific surface of spherical particles is given by (where D and ρ are diameter and density of particle). (A) 6/D.ρ(B) 2/D.ρ (C) 4/D.ρ (D) 12/D.ρ

Description : The specific surface of spherical particles is given by (where D and ρ are diameter and density of particle). (A) 6/D.ρ (B) 2/D.ρ (C) 4/D.ρ (D) 12/D.ρ

Last Answer : (A) 6/D.ρ

The specific surface of spherical particles is proportional to (where, Dp = diameter of particle). (A) D2 p (B) Dp (C) 1/Dp (D) 1/D2p

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Last Answer : (C) 1/Dp

Brunauer, Emmet and Teller (BET) equation is used to determine the specific surface area of a porous particle but not the pore volume & the porosity of the catalyst bed. Which of the following postulates is not used to derive BET equation? (A) Langmuir's assumption applies to every adsorbed layer (B) There is no dynamic equilibrium between successive layer (C) The adsorbed layer may be polymolecular in thickness and the heat of adsorption in each layer (except the first one) is involved in each of the evaporation process (D) None of these

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Slugging in a fluidised bed can be avoided by using (A) Tall narrow vessel (B) Deep bed of solids (C) Shallow beds of solids and proper choice of particle size (D) Very large particles

Description : Slugging in a fluidised bed can be avoided by using (A) Tall narrow vessel (B) Deep bed of solids (C) Shallow beds of solids and proper choice of particle size (D) Very large particles

Last Answer : (C) Shallow beds of solids and proper choice of particle size

A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is (A) 0.90 μm/s (B) 1 μm/s (C) 22.1 μm/s (D) 0.02 μm/s

Description : A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is (A) 0.90 μm/s (B) 1 μm/s (C) 22.1 μm/s (D) 0.02 μm/s

Last Answer : (B) 1 μm/s

A bed consists of particles of density 2000 kg/m3 . If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is (A) 25.61 kPa (B) 11.77 kPa (C) 14.86 kPa (D) 21.13 kPa

Description : A bed consists of particles of density 2000 kg/m3 . If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is (A) 25.61 kPa (B) 11.77 kPa (C) 14.86 kPa (D) 21.13 kPa

Last Answer : (B) 11.77 kPa

The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond's law) of the energy to grind the particles from a very large size to 50 μm is (A) 6.35 kWh/ton (B) 9.0 kWh/ton (C) 18 kWh/ton (D) 25.4 kWh/ton

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Last Answer : (C) 18 kWh/ton

Particles having diameter greater than 75 μm (micrometer = 10 -6 mm) are called (A) Grit (B) Dust (C) Powder (D) Smoke

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A suspended particle falls through a height minutes. If the viscosity of water is and specific gravity of the particle is , the diameter of the particle is (where M is a constant factor) (A) 103M (H/t) (B) 104M (H/t) (C) 105M (H/t) (D) 102M (H/t)

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BET apparatus is used to determine the (A) Specific surface of a porous catalyst (B) Pore size distribution (C) Pore diameter (D) Porosity of the catalyst bed

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Minimum porosity for fluidisation is(A) That corresponding to static bed (B) That corresponding to completely fluidised bed (C) The porosity of the bed when true fluidisation begins (D) Less than that of the' static bed

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With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity (A) Widens (B) Squeezes (C) Does not change (D) Unpredictable from the data

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The main factor on which the behaviour of a mass of fluidised solid depends mainly is the (A) Fluid characteristics (B) Particle size (C) Both (A) and (B) (D) Neither (A) nor (B)

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Last Answer : (C) Both (A) and (B)

. The most widely used crude topping column in refineries is the__________ column.(A) Bubble-cap(B) Packed bed(C) Fluidised bed(D) Perforated plate

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Last Answer : (A) Bubble-cap

Pressure drop in a fluidised bed reactor is __________ that in a similar packed bed reactor. (A) Less than (B) Greater than (C) Same as (D) None of these

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The uniformity of a gas fluidised bed depends upon the __________ of the solid particles. (A) Size (B) Surface properties (C) Both (A) and (B) (D) Neither (A) nor (B)

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For motion of spherical particles in a stationary fluid, the drag co￾efficient in hindered settling compared to that in free settling is (A) More (B) Less (C) Equal (D) More or less, depending on the type of particle

Description : For motion of spherical particles in a stationary fluid, the drag co￾efficient in hindered settling compared to that in free settling is (A) More (B) Less (C) Equal (D) More or less, depending on the type of particle

Last Answer : (A) More

Internal energy of a gas obeying Van-Der-Waals equation of state, [p + (a/v2)] (V - b) = RT, depends upon its (A) Pressure & temperature (B) Pressure & specific volume (C) Temperature & specific volume (D) Temperature only

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Last Answer : (A) Pressure & temperature

In Newton's law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass varies as the __________ of its diameter. (A) Inverse (B) Square root (C) Second power (D) First power

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For laminar flow of a fluid through a packed bed of spheres of diameter d, the pressure drop per unit length of bed depends upon the sphere diameter as (A) d (B) d 2 (C) d 4 (D) d

Description : For laminar flow of a fluid through a packed bed of spheres of diameter d, the pressure drop per unit length of bed depends upon the sphere diameter as (A) d (B) d 2 (C) d 4 (D) d

Last Answer : (D) d

A 3.2 m diameter balloon is filled with Helium. The total weight of balloon, gas and pay load is 10 kg kg. In an isothermal atmosphere having conditions identical to N.T.P. the balloon will rise to a height of about a.6000 m b.1500 m c.3000 m d.2000 m e.1000 m

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Last Answer : a. 6000 m

For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is (A) More (B) Less (C) Equal (D) Independent of porosity

Description : For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is (A) More (B) Less (C) Equal (D) Independent of porosity

Last Answer : (B) Less

In a fluidised bed reactor (A) Temperature gradients are very high (B) Temperature is more or less uniform (C) Hot spots are formed (D) Segregation of the solids occurs

Description : In a fluidised bed reactor (A) Temperature gradients are very high (B) Temperature is more or less uniform (C) Hot spots are formed (D) Segregation of the solids occurs

Last Answer : (B) Temperature is more or less uniform

If is specific gravity of sand particles, is porosity, the critically hydraulic gradient (A) ic = (G + 1)/(1 - e) (B) ic = (G + 1)/(1 + e) (C) ic = (G - 1)/(1 + e) (D) ic = (G - 1)/(1 - e)

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Last Answer : Answer: Option C

Which of the following equations applies to the fluid flow through a packed bed for very large Reynolds number? (A) Fanning equation (B) Blake-Plummer equation (C) Hagen-Poiseuille equation (D) Kozeny-Carman equation

Description : Which of the following equations applies to the fluid flow through a packed bed for very large Reynolds number? (A) Fanning equation (B) Blake-Plummer equation (C) Hagen-Poiseuille equation (D) Kozeny-Carman equation

Last Answer : (B) Blake-Plummer equation

Which of the following equations is valid for laminar flow of a fluid through packed bed? (A) Fanning equation (B) Kozeny - Karman equation (C) Hagen-Poiseuille equation (D) Blake-Plummer equation

Description : Which of the following equations is valid for laminar flow of a fluid through packed bed? (A) Fanning equation (B) Kozeny - Karman equation (C) Hagen-Poiseuille equation (D) Blake-Plummer equation

Last Answer : (B) Kozeny - Karman equation

A certain fluid is flowing in a 0.5m x 0.3 channel at the rate of 3 m/s and has a specific volume of 0.012 m³/kg. Determined the mass of water flowing in kg/s.  a. 267 kg/s  b. 378 kg/s  c. 375 kg/s  d. 456.5 kg/s m = Aν/V

Description : A certain fluid is flowing in a 0.5m x 0.3 channel at the rate of 3 m/s and has a specific volume of 0.012 m³/kg. Determined the mass of water flowing in kg/s.  a. 267 kg/s  b. 378 kg/s  c. 375 kg/s  d. 456.5 kg/s m = Aν/V

Last Answer : 375 kg/s

A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke's law. A particle B with diameter 20microns settling in the same oil will have a settling velocity (A) Same as that of A (B) One fourth as that of A (C) Twice as that of A (D) Four times as that of A

Description : A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke's law. A particle B with diameter 20microns settling in the same oil will have a settling velocity (A) ... ) One fourth as that of A (C) Twice as that of A (D) Four times as that of A

Last Answer : (B) One fourth as that of A

Two particles are called to be equal settling, if they are having the same. (A) Size (B) Specific gravity (C) Terminal velocities in the same fluid & in the same field of force (D) None of these

Description : Two particles are called to be equal settling, if they are having the same. (A) Size (B) Specific gravity (C) Terminal velocities in the same fluid & in the same field of force (D) None of these

Last Answer : (C) Terminal velocities in the same fluid & in the same field of force

5-200 μm size particles are called (A) Colloids or aerosols (B) Powder (C) Dust (D) Smoke

Description : 5-200 μm size particles are called (A) Colloids or aerosols (B) Powder (C) Dust (D) Smoke

Last Answer : (A) Colloids or aerosols

Sphericity for a non-spherical particle is given by (where, V and S are volume and surface area respectively of one particle. and, D = equivalent diameter of particle). (A) 6.V/D.S(B) V/6D.S (C) D.S/V (D) V/D.S

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Last Answer : (B) V/6D.S (C) D.S/V (D) V/D.S

The R.L. of ground water table on the sides of a valley is 1505 m whereas R.L. of the stream water is 1475 m. If 60° slope consists of pervious soil between R.L. 1485 m to 1500 m, the gravity spring may be expected at the point of reduced level (A) 1500 m (B) 1505 m (C) 1475 m (D) 1485 m

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Last Answer : (D) 1485 m 

Carbonaceous particles having size less than 1 μm are called (A) Grit (B) Aggregates (C) Aerosols (D) Smoke

Description : Carbonaceous particles having size less than 1 μm are called (A) Grit (B) Aggregates (C) Aerosols (D) Smoke

Last Answer : (D) Smoke

Drag co-efficient for motion of spherical particles in a stationary fluid in the stoke's law range is (A) 24/NRe,P (B) 16/NRe,P (C) 64/NRe,P (D) 48/NRe,P

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Last Answer : (A) 24/NRe,P

A rectangular tank 10 m x 5 m in plan and 3 m deep is divided by a partition wall parallel to the shorter wall of the tank. One of the compartments contains water to a depth of 3 m, and the other a lighter liquid of specific gravity 0.75 to a depth of 2 m. The resultant pressure thrust on the partition wall is (a) 1000 kg (b) 1500 kg (c) 2000 kg (d) 2500 kg

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Last Answer : Correct Answer is 15000 kg

The terminal velocity of a solid spherical particle falling through a stationary fluid mass in the Stoke's law range is proportional to the (A) Inverse of fluid viscosity (B) Square of particle size (C) Difference in the densities of the particle & fluid (D) All (A), (B) and (C)

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Last Answer : (D) All (A), (B) and (C)

For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (C) Chemical reaction

For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (B) Diffusion through ash layer

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0for the cubic to spherical tablet is: (A) 0.54 (B) 1.04 (C) 1.24 (D) 1.94

Description : A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t ... tablet is: (A) 0.54 (B) 1.04 (C) 1.24 (D) 1.94

Last Answer : (C) 1.24

essure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as (A) V1.8 (B) V-0.2 (C) V2.7 (D) V

Description : essure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as (A) V1.8 (B) V-0.2 (C) V2.7 (D) V

Last Answer : (D) V

Gas is enclosed in a cylinder with a weighted piston as the stop boundary. The gas is heated and expands from a volume of 0.04 m^3 to 0.10 m^3 at a constant pressure of 200kPa.Calculate the work done by the system.  A. 8 kJ  B. 10 kJ  C.12 kJ  D.14 kJ Formula: W = p(V2-V1)

Description : Gas is enclosed in a cylinder with a weighted piston as the stop boundary. The gas is heated and expands from a volume of 0.04 m^3 to 0.10 m^3 at a constant pressure of 200kPa.Calculate the work done by the system.  A. 8 kJ  B. 10 kJ  C.12 kJ  D.14 kJ Formula: W = p(V2-V1)

Last Answer : 12 kJ

Fluidised beds are formed, when the (A) Fluid friction is zero (B) Gravity force is less than the fluid friction (C) Pressure forces equal gravity forces (D) Sum of the fluid friction and pressure forces is equal and opposite to gravity forces

Description : Fluidised beds are formed, when the (A) Fluid friction is zero (B) Gravity force is less than the fluid friction (C) Pressure forces equal gravity forces (D) Sum of the fluid friction and pressure forces is equal and opposite to gravity forces

Last Answer : (B) Gravity force is less than the fluid friction

The porosity of a certain soil sample was found to be 80% and its specific gravity was 2:7; the critical hydraulic gradient will be estimated as (a) 0.34 (b) 0.92 (c) 1.0 (d) 1.5

Description : The porosity of a certain soil sample was found to be 80% and its specific gravity was 2:7; the critical hydraulic gradient will be estimated as (a) 0.34 (b) 0.92 (c) 1.0 (d) 1.5

Last Answer : (a) 0.34

Packed column distillation is limited to the column __________ metres. (A) Height < 6 (B) Diameter < 0.6 (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : Packed column distillation is limited to the column __________ metres. (A) Height < 6 (B) Diameter < 0.6 (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is (A) 0.5 (B) 1 (C) √2 (D) √3

Description : Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is (A) 0.5 (B) 1 (C) √2 (D) √3

Last Answer : (B) 1