Cochin University of Science and Techology (CUST) 2007-3rd Sem B.Tech fluid mechanics and heat engines - Question Paper

BTECH DEGREE 3rd SEMESTER exam NOVEMBER 2007
FLUID MECHANICS AND HEAT ENGINES
Time:3 Hrs Max maks:100
PART A

1. a) discuss how fluids are classified. Using stress-strain diagram discuss the behaviour
of fluids.

b) define differential manometer.

c) Differentiate the subsequent 1) steady and unsteady flow 2) uniform and non
uniform flow.

d) discuss Froude and Reynolds laws.Give suitable examples where these no.s can be
used.

e) Derive Darcy Weisbach formula for the loss of head due to friction in a pipe.

f) What is a draft tube? Why is it used in a reaction turbine?

g) What is specific speed of a turbine? Derive an expression for the identical.

h) What is priming? Why is it necessary?

PART B

2. a) describe the terms: 1) velocity potential function 2) stream function

b) If for a 2 dimensional potential flow, the velocity potential = x(2y-1). Determine
also the value of stream function at the point.
OR

3. a) discuss the principle of venturimeter with a neat sketch. Derive the expression for
the rate of flow of fluid through it.

b) A horizontal venturimeter with inlet diameter 20cm and throat diameter 10cm is
used to measure the flow of oil of specific gravity 0.8. The discharge of oil through
venturimeter is 60litres/sec. obtain the studying of the oil mercury differential
manometer. Take Cd = 0.98.

4. a) Derive the Hagen- Poiseuille formula.

b) An oil of viscosity 0.1NS/sq.m and relative density 0.9 is flowing through a circular
pipe of diameter 5cm and of length 300m. The rate of flow of liquid through the
pipe is 3.5litres/sec. obtain the pressure drop in a length of 300m and also the shear
stress at the pipe wall.

5. The Pen Stock supplies water from a reservoir to the pelton wheel with a gross head of
500m. 1 3rd of the gross head is lost in friction in the Penstock. The rate of flow of
water through the nozzle fitted at the end of the penstock is 2.0meter cube/s. The angle
of deflection of the jet is 165 degree. Determine the power provided by the water to the
turbine and also hydraulic efficiency of the Pelton wheel. Take speed ratio = 0.4S and
Cv =1.0.
OR

6. A Kaplan turbine working under a head of 20m develops 1172kw shaft power. The
outer diameter of the runner is 3.5m and hub diameter 1.75m. The guide blade angle at
the extreme edge of the runner is 35 degree. The hydraulic and overall efficiencies of
the turbines are 88% and 84% respectively. If the velocity of whirl is zero at outlet.
Determine 1) runner vane angles at inlet and outlet at the extreme edge of the runner
and 2) speed of turbine.

7. a) discuss with neat sketches the working of a single stage centrifugal pump.

b) The internal and external diameters of the impeller of a centrifugal pump are 20cm
and 40cm respectively. The pump is running at 1200r.p.m. the vane angles of the
impeller at inlet and outlet are 20 and 30 degrees respectively. The water enters the
impeller radially and velocity of flow is constant. Determine the work done by the
impeller per unit weight of water.
OR

8. A single-acting reciprocating pump has a plunger diameter of 250mm and stroke of
450mm and it is driven with SHM at 60r.p.m. The length and diameter of delivery pipe
are 60m and 100mm respectively. Determine the power saved in overcoming friction
in the delivery pipe by fitting an air vessel on the delivery side of the pump. presume
friction factor = 0.01.

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Earning:   Approval pending.