Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 5th Sem 3153617 Basics Of Mass Transfer Previous Question Paper
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?V (NEW) EXAMINATION ? WINTER 2020
Subject Code:3153617 Date:27/01/2021
Subject Name:Basics of Mass Transfer
Time:10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
1. Attempt any FOUR questions out of EIGHT questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1
(a) Define: (a) HETP (b) Humid Heat (c) Reflux ratio
03
(b) Mention the factors affecting choice of separation method.
04
(c) Explain in detail about various application of mass transfer
07
operation.
Q.2
(a) Explain in brief about Azeotropic distillation.
03
(b) Explain temperature and pressure dependency of diffusivity
04
of gases and liquids.
(c) Derive the relation for steady state molecular diffusion in
07
fluids at rest and in laminar flow.
Q.3
(a) Write short note on Absorption factor.
03
(b) Define Diffusivity and state its assumptions for penetration.
04
(c)
Starting from the basics of diffusion, derive the equation to
07
calculate NA for steady state equimolal counter diffusion of A
through B for unidirectional binary gas phase.
Q.4
(a) Define relative saturation, percentage saturation and
03
enthalpy.
(b) Write down the selection criteria for the solvent in liquid
04
extraction process.
(c)
A gas (B) ? benzene (A) mixture is saturated at 1 std atm,
07
50C. Calculate the absolute humidity if B is (a) nitrogen and
(b) carbon dioxide. Vapor pressure of nitrogen at 50C =
0.362 std atm
Q.5
(a) Discuss Raoult's law for ideal solutions.
03
(b) With respect to interphase mass transfer, explain mass
04
transfer operation between two immiscible phases.
(c)
CO2 and Air are in equimolal counter diffusion with each
07
other in the tube of 50 mm diameter and 1 m length. The total
pressure is 1 atm and the temperature is 25?C. The partial
pressure of CO2 at one end of the tube is 190 mm Hg while
at the other end of the tube is 95 mm Hg. Estimate the mass
transfer rates (in kg/s) of CO2 and air through the tube.
Diffusivity is 0.16 x 10-4m2/s.
Q.6
(a) Explain in brief about Two resistance theory.
03
(b) Explain with neat sketch the rate of drying curve in detail.
04
(c)
Methane diffuses at steady state through a tube containing
07
helium for the case equimolar counter diffusion. At point 1,
the partial pressure of methane is 55 kPa and at point 2, 0.03
m apart is 15 kPa. The total pressure is 101.325 kPa and
1
temperature is 298 k, at this temperature and pressure the
value of diffusivity is 6.75 ? 10-5 m2/s. Calculate the partial
pressure of methane at point 0.02 m apart from point 1 for the
above case.
Q.7
(a) Write down the various applications of liquid-liquid
03
extraction.
(b) Discuss the concept with principle of crystallization.
04
(c)
A continuous rectification column is used to separate a binary
07
mixture of A & B. Distillate is produced at a rate 100 kmol/h,
containing 98 mole% A. In the enriching section the mole
fraction of A in the liquid and vapour from two adjacent
plates are as follows.
x
y
0.65
0.82
0.56
0.76
If the latent heat of vaporization is same for all mixtures and
if the feed is a saturated liquid, calculate i) Reflux ratio ii)
Vapour flow rate in stripping section
Q.8
(a) Write a short note on flash distillation.
03
(b) Explain in brief about Fluidized bed dryer.
04
(c)
Compute the vapor-liquid equilibria at constant pressure of 1
07
standard atmosphere for mixtures of n-heptane (A) with n-
octane (B), which may be expected to form ideal solutions.
Also calculate the relative volatility for each temperature and
its average value.
T (C)
98.4
105
110
115
120
125.6
pA,mm
760
940
1050
1200
1350
1540
Hg
pB, mm 333
417
484
561
650
760
Hg
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This post was last modified on 04 March 2021