Indian Institute of Technology Kharagpur %28IIT-K%29 2007 B.Tech Chemical Engineering Multiphase aration process - Question Paper

Q.

No.

Question Description

marks

1.

Under what condition are the mass average velocity and molar average velocity of all the components of a mixture are equal?

2

2.

Under what conditions does the diffusivity of the component / (Dj,_m) in a milticomponent gas mixture remain constant over entire the length of the diffusion path?

2

3.

Consider two cases: (i) Diffusion of A through non-diffusing B, and (ii) equimolar counterdiffusion of A and B. The respective fluxes are given by the following equations (in the usual notation):

DP p - p

_{(i) N =} -AJ AL -

^{R 1} ' (^pbl - "J '"("m "J

4

5

D (p - p )

(ii) N = ^{AB V A A1} '

A R 1 L

In which of the above two cases is N_A larger? Explain logically.

4.

Give one example each of: (i) mechanical separation, (ii) diffusional separation.

2

5.

Give two salient characteristics each of: (i) purely diffusional mass transfer, (ii) convective mass transfer.

4

6.

Derive the basic equation for steady state molecular diffusion through a

C . dC

constant area in a binarv 2as mixture: n =-im + n j - d .

* . - ^J A ( V A B / AB

6

7.

Explain the assumptions involved in the film model derivation of flux.

3

8.

D . v

Derive the film model equation: N = (<: - ( I.

A g \ A, A, Bulk/

6

9.

Write the assumptions involved in the derivation of flux using Higbies penetration theory.

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State the governing equation for the flux using Higbies penetration theory, and explain the three initial + boundary conditions needed for the solution.

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11.

Qualitatively explain the concept of surface renewal rate in Danckwerts surface renewal theory.

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12.

What is an operating line ? How does it differ from equilibrium line ?

2

For interphase mass transfer, derive the expression:~ = + .

K k k

4

13.

Qualitatively (in terms of the driving forces) explain the difference between Ky and k_y.

2

14.

What is an Equilibrium / Ideal / Theoretical stage with respect to interphase mass transfer?

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15.

Explain the term stage efficiency with respect to interphase mass transfer.

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