MASS TRANSFER BY DIFFUSION IS ANALOGOUS TO HEAT TRANSFER BY CONDUCT...
4. Mass transfer by diffusion is analogous to heat transfer by
conduction.
Which of the above statements are correct ?
(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 2, 3 and 4 only
(d) 1, 2, 3 and 4
IES-2.
If heat and mass transfer take place simultaneously, the ratio of heat
transfer coefficient to the mass transfer coefficient is a function of the
ratio of:
[IES-2000]
(a) Schmidt and Reynolds numbers
(b) Schmidt and Prandtl numbers
(c) Nusselt and Lewis numbers
(d) Reynolds and Lewis numbers
IES-3.
In case of liquids, what is the binary diffusion coefficient proportional
to?
[IES-2006]
(a) Pressure only
(b) Temperature only
(c) Volume only
(d) All the above
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IES-4.
In a mass transfer process of diffusion of hot smoke in cold air in a
power plant, the temperature profile and the concentration profile will
become identical when:
[IES-2005]
(a) Prandtl No. = 1
(b) Nusselt No. = 1
(c) Lewis No. = 1
(d) Schmilt No. = 1
IES-5. Given
that:
[IES-1997]
N
u
= Nusselt number
R
e
= Reynolds number
P
r
= Prandtl number
S
h
= Sherwood number
S
c
= Schmidt number
G
r
= Grashoff number
The functional relationship for free convective mass transfer is given
as:
( )
a N
u
=
f G P
(
r
,
r
) ( )
b S
h
=
f S G
(
c
,
r
)
( )
c N
u
=
f R P
(
r
,
r
) ( )
d S
h
=
f R S
(
e
,
c
)
IES-6.
Schmidt number is ratio of which of the following?
[IES-2008]
(a) Product of mass transfer coefficient and diameter to diffusivity of fluid
(b) Kinematic viscosity to thermal diffusivity of fluid
(c) Kinematic viscosity to diffusion coefficient of fluid
(d) Thermal diffusivity to diffusion coefficient of fluid
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Answers with Explanation (Objective) Previous 20-Years IES AnswersIES-1. Ans. (d)
IES-2. Ans. (b)
Nu
x
=
(
conct
.
) ( )
1
×
Re
0.8
×
( )
Pr
1
3
0.8
1
3
(
) ( )
( )
=
×
×
.
Re
Sh
conct
Se
x
2
1
3
h
conct
⎛
⎞
.
Pr
(
)
∴
=
⎜
⎝
⎟
⎠
h
Se
3
xm
IES-3. Ans. (b)
IES-4. Ans. (c)
IES-5. Ans. (b)
IES-6. Ans. (c) Schmidt number
μ
υ
Momentum diffusivity
Sc
D
=
ρ
=
=
D
Mass diffusivity
Page 97 of 97