> 02000CH206052001 Pages: 3

Reg No.: Name:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Fourth semester B.Tech examinations (S), September 2020

Course Code: CH206
Course Name: FLUID AND PARTICLE MECHANICS II (CH)
Max. Marks: 100 Duration: 3 Hours

PARTA
Answer any two questions. Each question carries 15 marks.

1 a) What is the difference between streamlined and bluff bodies? Is a tennis ball a 3
streamlined or bluff body?

b) Urea pellets are made by spraying drops of molten urea into cold air ೩! the top ofa 9
tall tower and allowing the material to solidify as it falls. Pellets 6 mm in diameter
are to be made in a tower 25 m high containing air at 20°C. The density of urea is
1330 kg/m? . What would be the terminal velocity of pellets, assuming free settling
conditions?

c) The height of a fluidised bed at incipient fluidisation is 0.015 m, and the 3
corresponding voidage is 0.3. Calculate the bed height, if the voidage of the bed
increases to 0.5 by increasing the empty tower velocity.

2 a) What is the difference between skin friction drag and pressure drag? Which is 5
usually more significant for streamlined bodies such as airfoils? Justify your
answer with mathematical equations.

b) Write the mathematical expression of flow through packed bed. From the base 10
model derive the formulae to obtain minimum fluidization velocity. Derive the
minimum fluidization velocity in case of a low Reynolds number and high
Reynolds number for particulate fluidization separately.

3 ಖ Air (p= 1.22 kg/m’, p= 1.9 x 10° Pas) is flowing in a fixed bed of diameter 0.5 5
m and height 2.5 m. The bed is packed with spherical particles of diameter 10 mm.

The void fraction is 0.38. The air mass flow rate is 0.5 kg/s. Calculate the pressure
drop across the bed of particles

b) Oil, of density 900 kg/m? and viscosity 3 x 107 Ns/m’, is passed vertically upwards 10

through a bed of catalyst consisting of approximately spherical particles of diameter

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