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Name
Reg No
C
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
07 THRISSUR CLUSTER
SECOND SEMESTER M.TECH. DEGREE EXAMINATION APRIL 2018
Chemical Engineering
Process Control
07CH6106 ADVANCED HEAT AND MASS TRANSFER
Time:3 hours Max.Marks: 60
Answer all six questions. Part of each question is compulsory.
Answer either part or part of each question
(Use of standard heat and mass transfer data book may be permitted)
Q.no. Module 1 Marks
1a Derive the general three dimensional heat conduction equation in Cartesian
coordinates and write down its special forms
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Answer b or c
b A hollow sphere of pure iron contains a liquid chemical mixture which releases
30 kW of energy. The I.D and O.D of the sphere are 15 cm and 30 cm
respectively. If the outside surface temperature of the sphere is 400
determine the temperature at a location 2.5 cm from the outer surface. Take k
70 W/mK.
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c Derive the expression for temperature distribution and rate of heat transferred
through a plane wall of thickness 2L with internal generation q° W/m3. Assume
one dimensional steady state conduction.
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Q.no. Module 2 Marks
2a What are Biot and Fourier numbers. Explain their physical significance. 4
Answer b or c
b An aluminium fin 200 3 mm thick and 7.5 cm long protrudes from a
wall at 300 0C. The ambient temperature is 50 0C with 10 W/m2 K. Compute
the heat loss from the fin. Also calculate its efficiency.
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c Describe lumped heat capacity analysis. Obtain the expression for
temperature distribution for a solid initially at a temperature T0, which is
suddenly placed in a convective atmosphere of Temperature T∞, using lumped
capacity analysis.
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Q.no. Module 3 Marks
3a Explain the development of hydrodynamic and thermal boundary layer for
laminar flow over a flat plate
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Answer b or c
b Air at 270 C flows over a flat plate at a velocity of 2 m/s. The plate is heated
over its entire length to a temperature of 60 0 C. Calculate the heat transfer for
the first 20 cms of the plate.
The properties of air at 43.5 0 C are kinematic viscosity 17.36 x 10
thermal conductivity 0.0275 W/mK., Prandtl No. 0.7 and specific heat
capacity 1.006kJ/kg 0 C
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c Explain heat transfer in fluidized beds. 5
Q.no. Module 4 Marks
4a Explain different types of fluxes used in molecular diffusion. 4
Answer b or c
b For the diffusion of A through a binary mixture of components A and B derive
the following relations, stating the assumptions made:
A AB A A A B n w n n
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c Using equations of change, derive Fick's second law of diffusion for a multicomponent
system.
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Q.no. Module 5 Marks
5a Define effectiveness factor and explain its significance. 5
Answer b or c
b Linton and Sherwood conducted experiments on the dissolving of cast tubes of
cinnamic acid into water flowing through the tubes in turbulent flow. In
one run, with a tube of 5.23 cm internal diameter, Re 35800 and Sc 1450,
they measured a Stanton number for mass transfer, StD, of 0.0000351.
Compare this experimental value with predictions by the Reynolds and
Chilton-Colburn analogies. The following correlation may be used for Fanning
friction factor
f 0.00140 0.125(Re)-0.32
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c Species A undergoes the irreversible chemical reaction A C while diffusing
through a homogeneous phase B. Assuming concentration of A to be very low
in the mixture with obtain expression for steady state concentration profile
of A. Choose appropriate boundary conditions.
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Q.no. Module 6 Marks
6a Overall resistance to mass transfer in a typical experiment is observed to be a
strong function of temperature. Is mass transfer in this case gas phase
controlled or liquid phase controlled? Explain.
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Answer b or c
b Compare film theory and penetration theory of interphase mass transfer, listing
the assumptions involved, advantages and limitations.
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c For a system in which component A is transferring from the gas phase to the
liquid phase, the equilibrium relation is given by PA,i 0.8XAi where PA,i is the
equilibrium partial pressure in atm. and XA,i is the equilibrium liquid
concentration in mole fraction. At one point in the apparatus, the liquid stream
contains 4.5 mole and the gas stream contains 9.0 mole A. The total
pressure is 1 atm. The individual gas-film coefficient at this point is kG 3.0
mole/m2-s-atm. Fifty per cent of the overall resistance to mass transfer is
known to be encountered in the gas phase. Evaluate The overall masstransfer
coefficient and individual liquid-film coefficient ii) The molar flux of A
iv) The interfacial concentrations of A.
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