Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as (A) D0.5 (B) D (C) 1/D (D) D1.5

Mass transfer co-efficient 'K' according to penetration theory varies

with mass diffusivity as

(A) D0.5

(B) D

(C) 1/D

(D) D1.5

by

1 Answer

Answer :

(A) D0.5

by

Related questions

Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as (A) K ∝ D (B) K ∝√D (C) K ∝ D1.5 (D) K ∝ D

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Last Answer : (A) K ∝ D

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

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Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as (A) K ∝D (B) K ∝√D (C) K ∝D1.5 (D) K ∝D

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According to the film theory of mass transfer, the mass transfer co￾efficient is proportional to (where, D = molecular diffusivity). (A) D (B) D2 (C) D0.5 (D) 1/D

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Mass transfer co-efficient is directly proportional to DAB 0.5 , according to __________ theory. (A) Penetration (B) Surface renewal (C) Film (D) None of these

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Last Answer : (C) Mass transfer co-efficient

Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the (A) Mass transfer co-efficient (B) Thermal diffusivity (C) Kinematic viscosity (D) Volumetric diffusivity

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Last Answer : (A) Mass transfer co-efficient

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Last Answer : (D) Dependent on the Reynolds number

Which of the following is not a dimension-less group used in catalysis? (Where, D = dispersion co-efficient, cm2 /sec.D1 = diffusion co-efficient; cm2 /sec L = length of the reactor, cm t = time, sec, v = volumetric flow rate, cm3 /sec. V = volume, cm3 .) (A) Reactor dispersion number (D/vL) (B) Reduced time (vt/V) (C) Thiele modulus L √(k/D1 ) (D) None of these

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The effectiveness factor for large value of Thiele modulus [L√(K/D1 )] of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D1 = diffusion co-efficient, cm2 /second). (A) L √(K/D1 ) (B) 1/[L√(K/D1 )] (C) 1 (D) ∞

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Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

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In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

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The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is(A) 100(B) 10(C) 5(D) 1.

Description : The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is. (A) 100 (B) 10 (C) 5 (D) 1

Last Answer : (B) 10

Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

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Penetration model (theory) for mass transfer was enunciated by (A) Danckwerts (B) Toor and Marcello (C) Higbie (D) Kissinevskii

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Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is ‘3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?(A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Description : Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l'. If the wall temperature ... wall temperature in degree centigrade? (A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Last Answer : (C) 81.25

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/µ) 0.8 (CP .µ/k) 0.4 . This is valid for the value of NRe equal to (A) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

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Last Answer : (D) > 10000

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Description : The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the ... temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Last Answer : (D) 48.7

The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year ofoperation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co￾efficient at this time is(A) 1200 W/m2.K(B) 894 W/m2.K(C) 333 W/m2.K(D) 287 W/m2.K

Description : The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2 .K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2 .K. The overall heat transfer co￾efficient ... 1200 W/m2 .K (B) 894 W/m2 .K (C) 333 W/m2 .K (D) 287 W/m2 .K

Last Answer : (C) 333 W/m2 .K

In case of non-ideal gases and liquids, the molal diffusivity (A) Varies inversely as the pressure (B) Varies directly as the pressure (C) Is independent of pressure (D) Is equal to the volumetric diffusivity

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. (NSh /NRe .NSc ) is termed in mass transfer operation as the (A) Stanton number (B) Peclet number (C) Thermal diffusivity (D) Momentum diffusivity

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Last Answer : (A) Stanton number

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of (A) Mass diffusivity to momentum diffusivity (B) Thermal diffusivity to mass diffusivity (C) Momentum diffusivity to thermal diffusivity (D) None of these

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Last Answer : (B) Thermal diffusivity to mass diffusivity

In fluid flow, and heat and mass transfer, one encounters (i) kinematic velocity (μ), (ii) molecular diffusivity (θ) and thermal diffusivity (α). The units of these quantities are. (A) μ , α and θ all have units of m/s (B) μ , α and θ all have units of m2/s (C) α and θ have units of m2/s, while μ has unit of m/s (D) α and θ have units of m/s, while μ has unit of m2/s

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Last Answer : Option C

Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s (D) The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Description : Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In ... layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

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The wetted wall tower is used to determine (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system (B) M.T.C. of individual components in a liquid-liquid system (C) M.T.C. of liquid in liquid-gas system (D) The overall M.T.C. of the system

Description : The wetted wall tower is used to determine (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system (B) M.T.C. of individual components in a liquid-liquid system (C) M.T.C. of liquid in liquid-gas system (D) The overall M.T.C. of the system

Last Answer : (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system

For absorbing a sparingly soluble gas in a liquid (A) Gas side mass transfer co-efficient should be increased (B) Liquid side mass transfer co-efficient should be increased (C) Liquid side mass transfer co-efficient should be decreased (D) Mass transfer co-efficient must be kept constant

Description : For absorbing a sparingly soluble gas in a liquid (A) Gas side mass transfer co-efficient should be increased (B) Liquid side mass transfer co-efficient should be increased (C) Liquid side mass transfer co-efficient should be decreased (D) Mass transfer co-efficient must be kept constant

Last Answer : (B) Liquid side mass transfer co-efficient should be increased

Mass transfer co-efficient of liquid is (A) Affected more by temperature than that for gases (B) Affected much less by temperature than that for gases

Description : Mass transfer co-efficient of liquid is (A) Affected more by temperature than that for gases (B) Affected much less by temperature than that for gases

Last Answer : (A) Affected more by temperature than that for gases

The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by (A) Increasing the gas film co-efficient(B) Increasing the liquid film co-efficient(C) Increasing the total pressure(D) Decreasing the total pressure

Description : The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by (A) Increasing the gas film co-efficient (B) Increasing the liquid film co-efficient (C) Increasing the total pressure (D) Decreasing the total pressure

Last Answer : (A) Increasing the gas film co-efficient

Which of the following is not a unit of mass transfer co-efficient? (A) Moles transferred/ [(time) (area) (mole fraction)] (B) Moles transferred/ [(time) (area) (mass A/mass B)] (C) Moles transferred/ [(time) (area) (pressure)] (D) None of these

Description : Which of the following is not a unit of mass transfer co-efficient? (A) Moles transferred/ [(time) (area) (mole fraction)] (B) Moles transferred/ [(time) (area) (mass A/mass B)] (C) Moles transferred/ [(time) (area) (pressure)] (D) None of these

Last Answer : (D) None of these

For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is (A) Calculated (B) Unknown (C) Known (D) Not required

Description : For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is (A) Calculated (B) Unknown (C) Known (D) Not required

Last Answer : (C) Known

Experimental determination of __________ is done by wetted wall column method. (A) Diffusion co-efficient (B) Mass transfer co-efficient (C) NTU (D) None of these

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Last Answer : (B) Mass transfer co-efficient

Pick out the wrong statement. (A) Mass transfer co-efficient does not account for gas-liquid diffusion (B) Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation

Description : Pick out the wrong statement. (A) Mass transfer co-efficient does not account for gas-liquid diffusion (B) Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation

Last Answer : (A) Mass transfer co-efficient does not account for gas-liquid diffusion

In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL ) as (A) KG = 1/KG + m/KL (B) 1/KG = 1/KG + m/KL (C) 1/KG = 1/KL + m/KG (D) KG = 1/KL + m/KG

Description : In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL ) as (A) KG = 1/KG + m/KL (B) 1/KG = 1/KG + m/KL (C) 1/KG = 1/KL + m/KG (D) KG = 1/KL + m/KG

Last Answer : (B) 1/KG = 1/KG + m/KL

Mass transfer co-efficient is defined as (A) Flux = Co-efficient/concentration difference (B) Co-efficient = Flux/concentration difference (C) Flux=concentration difference/coefficient (D) None of these

Description : Mass transfer co-efficient is defined as (A) Flux = Co-efficient/concentration difference (B) Co-efficient = Flux/concentration difference (C) Flux=concentration difference/coefficient (D) None of these

Last Answer : (B) Co-efficient = Flux/concentration difference

The film penetration model of mass transfer was enunciated by (A) Gilliland (B) Toor and Marcello (C) Stefan (D) Fick

Description : The film penetration model of mass transfer was enunciated by (A) Gilliland (B) Toor and Marcello (C) Stefan (D) Fick

Last Answer : (B) Toor and Marcello

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Last Answer : (D) 1/ke ff = 1/k + 1/kg

Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 (D) The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

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Last Answer : (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2

Pick out the wrong statement. (A) The binary diffusivity in liquids is of the order of 10 -5 cm2 /sec (B) Molecular diffusion in solid is much faster than that in liquids (C) Particles movement from higher concentration to lower concentration takes place in diffusion process (D) According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary

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Last Answer : (B) Molecular diffusion in solid is much faster than that in liquids

Thermal diffusivity of a material (A) Has the unit m2 /sec (B) Is defined as K/ρ . Cp (C) Is the ratio of thermal conductivity to thermal capacity (D) All (A), (B) and (C)

Description : Thermal diffusivity of a material (A) Has the unit m2 /sec (B) Is defined as K/ρ . Cp (C) Is the ratio of thermal conductivity to thermal capacity (D) All (A), (B) and (C)

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Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) (A) 1/k (B) k (C) k2 (D) 1/k2

Description : Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) (A) 1/k (B) k (C) k2 (D) 1/k2

Last Answer : (B) k

Which is the correct relationship for a centrifugal pump? (Where, D = Impeller diameter, inches H = Head developed, ft of liquid pumped N = Speed of pump, rpm) (A) D = 1840 H0.5 /N (B) D = 1840 N/H0.5 (C) H = 1840 D0.5 /N (D) D = 1840 H/N

Description : Which is the correct relationship for a centrifugal pump? (Where, D = Impeller diameter, inches H = Head developed, ft of liquid pumped N = Speed of pump, rpm) (A) D = 1840 H0.5 /N (B) D = 1840 N/H0.5 (C) H = 1840 D0.5 /N (D) D = 1840 H/N

Last Answer : (A) D = 1840 H0.5 /N

Thermal diffusivity is the most important in heat transfer by (A) Conduction (B) Radiation

Description : Thermal diffusivity is the most important in heat transfer by (A) Conduction (B) Radiation

Last Answer : (A) Conduction

Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is (A) Vertical heat exchanger with steam on tube side (B) Vertical heat exchanger with steam on shell side (C) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

Description : Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient ... ) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

Last Answer : (B) Vertical heat exchanger with steam on shell side

. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Description : . The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C ... from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Last Answer : (A) 165.4

What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Last Answer : (A) 2

Pick out the wrong statement. (A) The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonian fluids is (D/4L). ∆p (B) In the equation, T. gc = k. (du/dy) n the value of 'n' for pseudoplastic and Dilatant fluid are < 1 and >1 respectively (C) Shear stress for Newtonian fluid is proportional to the rate of shear in the direction perpendicular to motion (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

Description : Pick out the wrong statement. (A) The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonian fluids is (D/4L). ∆p (B) In the equation, T. gc = k. ... to motion (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

Last Answer : (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids