Time
Allowed: Three Hours maximum Marks: 200
Candidates should attempt Questions 1 and 5
which are compulsory and any THREE of the remaining questions, selecting at
least ONE question form each section. If any data is considered insufficient,
assume suitable values.
SECTION
– A
1.
Answer any four of the following:
(a)
(i) What is the time dependent flow? With the
help of this phenomenon, explain the meaning of Thyrotrophic liquid and
Rheopeptic substances.
(ii) Write the power law equation
for dilatants and pseudo plastic fluids, and explain the terms ‘flow
consistency index’ and ‘flow behavior index’.
(b)
Derive an equation for steady conduction in the
radial direction of a hollow cylinder. From the equation, explain the term
log-mean radius. Under what condition, can the log-mean radius be replaced by
arithmetic mean radius?
(c)
In a double pipe heat exchanger, an hour fluid
is cooled from 150 to 100˚C by using cold water, which is heated form 30 to 50˚C.
Derive a suitable expression to prove that there is a distinct advantage of
using it in parallel flow.
(d)
Explain how thermal condition of feed influences
the column. What common factor can be used for characterizing five different
feed conditions? From the value of this common factor, explain the meaning of
horizontal & vertical feed lines.
(e)
Explain the phenomenon of primary nucleation in
the process of crystallization, and illustrate the difference between
homogeneous and heterogeneous nucleation.
2.
(a) For an incompressible fluid, write the
Bernoulli equation for frictionless flow. What correction would you apply for
incorporating fluid friction? Explain the difference between skin friction and
form friction.
(b) What is terminal velocity? Write the equation for terminal velocity
for the flow of a single particle through a fluid under the action of (i)
gravity and (ii) centrifugal force.
How is the equation for terminal velocity under free setting condition
modified for hindered setting conditions?
(c) What is a ball mill? Derive an equation for the critical speed of a
ball mill.
(d) What is a venturimeter? Describe the principle of working of a
venturimeter and write an expression for the venture coefficient.
3.
(a) An
air water system has a dry bulb temperature of 65.5˚C and a wet bulb
temperature of 54.5˚C.
(i)
If the air cooled to 37.8˚C, what per cent of
the moisture will condense?
(ii)
If the air is again heated to 65.5˚C, how much
heat will be required per kg of dry air? Specific heat of air= 0.23 kcal/
(kg˚C)
(b) A spherical particle of ethanol of 10mm diameter is evaporating in an
air stream at 26˚ C. The thickness of the stagnant air surrounding the particle
is 1.5 mm. Vapour pressure of ethanol at 26 ˚C is 60 mm Hg and the mole
fraction of ethanol in the main stream of the air is 0.005. The diffusion coefficient of ethanol in air
is 1.04 x 10ˉ⁵ m² /sec and the value of R is 82.06 x 10ˉ³ m³ atm/kg moles.
Determine
(i) The mole fraction of ethanol at different positions across the
stagnant layer.
(ii) Rate of evaporation of the particle per second.
(c) What are different types of
pickings that are used in an absorption tower? Explain a simple procedure for
calculating the height of a packed tower for absorption of a single component
form a gas mixture.
(d) What is critical moisture content? Describe the method for drying of
a wet solid before it reaches the critical moisture content.
4.
(a) Develop a relation between heat transfer and
fluid friction by using the Reynold’s Analogy.
(b) (i) What is a radiation shield? How does it help in reducing radiant
heat loss?
(ii) A double walled spherical
container is used for storing liquid oxygen. The diameter of the inner and
outer walls of the container is 30 cm 36 cm, respectively. The surfaces of both
the spheres are plated, so that their emissivity is 0.05. Determine the rate at
which oxygen will evaporate at -183˚ C, when the outer wall of the sphere is
maintained at 20˚C. Latent heat of evaporation of oxygen is 57.2 kcal/ kg
(C) What are drop wise and film wise condensation? Mention the conditions
that favour drop wise condensation. Describe how the heat transfer coefficient
in a vertical condenser is influenced by the height of the condenser.
(d) What is effectiveness of a heat exchanger? Derive a relation between
the effectiveness and number of transfer units for a counter- current heat
exchanger.
