Wednesday 19 December 2012

2009 Kerala University B.Tech Industrial Engineering Fourth Semester B.Tech. Degree Examination, December 2009 Question paper

Fourth Semester B.Tech. Degree Examination, December 2009
(2003 Scheme)
Branch : Industrial
03-406 : THERMAL ENGINEERING (N)
Time : 3 Hours Max. Marks : 100
Instructions : 1) Answer all questions in Part – A.
2) Each question in Part A carries 4 marks.
3) Answer any one full question from each Module in Part – B.
4) Each question in Part B carries 20 marks.
5) Use of Steam Tables, Mollier Chart or Heat Transfer Data
Book is permitted.
PART – A
1. Explain the significance of Mollier chart.
2. With the help of T.S. diagram, explain the modified Rankine cycle.
3. Discuss the effect of friction on the performance of steam nozzles.
4. Explain why compounding is necessary for steam turbines.
5. Discuss the effect of fouling on the performance of heat exchangers.
6. Give a classification of air compressors.
7. What are the characteristics of an ideal fuel ?
8. Sketch an arrangement to measure the fuel consumption of an IC engine.
9. Compare between reciprocating and rotary compressors.
10. What are the different types of combustion chambers for turbines ?

PART – B
Module – I
11. a) Steam at a temperature of 210°C and y bar is expanded by throttling process to
a pressure of 3 bar. It is then expanded isentropically to a pressure of 0.5 bar.
Using Mollier chart determine the change in entropy and enthalpy during the
processes.
b) Steam at a pressure of 10 bar and 200°C enters a group of nozzles. The exit
pressure from the nozzle is 1 base. The throat decimeter of the nozzle is 6.5
mm. Determine the number of nozzles needed to develop 200 kW with a specific
steam consumption of 15 kg/kWh.
12. a) With the help of a neat sketch explain a Benson Boiler.
b) The blade tips of a reaction turbine arc inclined at 35° and 20° in the direction of
motion. The guide blades are similar to moving blades. But reversed in direction
steam got a pressure of 2 bar and dryness fraction 0.9 at a place in turbine where
the drum decimeter is 1 m and blade weight is 100 mm. The turbine runs at 1000
rpm. Determine the mass flow and the power developed.
Module – II
13. a) Distinguish between pre-ignition and detonation.
b) The results of analysis of coal is given below Carbon = 85%, Hydrogen = 5%,
Oxygen = 4%, moisture = 3% and the rest ash.
Theoretically, how much air will be required for complete combustion of 1 kg of
coal ?
If 10% excess air is supplied, obtain the volumetric analysis of dry products of
combustion.
14. The following observations were made during a test of a two-stroke cycle oil engine
Ambient temperature = 30° C
Cylinder diameter = 20 cm.
Stroke length = 30 cm.
Speed = 500 rpm
Brake drum decimeter = 120 cm.
-3- 8064
Net load on the brake drum = 500 N.
Area of indicator diagram = 2.8 cm2.
Length of indicator diagram = 5 cm.
Spring index of the indicator spring = 55 N/cm.
Oil consumption = 3.8 kg/hr.
Calorific value of oil = 40000 kJ/kg.
Determine the brake power, indicated power, mechanical efficiency and the indicated
thermal efficiency.
Module – III
15. a) Prove that for a two stage compressor with perfect intercooling the work input
is minimum when the intermediate pressure is the geometric mean between the
suction and delivery pressures.
b) Describe a closed cycle gas turbine with reheating.
16. a) Explain the working of a centrifugal compressor.
b) In a gas turbine plant working on Brayton cycle, the air at the inlet is at 27°C and
at a pressure of 0.1 MPa. The pressure ratio is 6.25 and the maximum temperature
is 800°C. The turbine and compressor efficiencies are each 80%. Find
i) The compressor work per kg of air.
ii) The turbine work per kg of air
iii) The heat supplied per kg of air.
iv) The cycle efficiency and
v) The turbine exhaust temperature.
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