Other Bachelor Degree- THERMAL ENGINEERING (Karunya University, Coimbatore-2012)
Saturday, 24 August 2013 10:31anudouglas
Karunya University
(Karunya Institute of Technology and Sciences)
(Declared as Deemed to be University under Sec.3 of the UGC Act, 1956)
Supplementary Examination – June 2012
Subject Title: THERMAL ENGINEERING Time: 3 hours
Subject Code: 09ME203 Maximum Marks: 100
Answer ALL questions
PART – A (10 x 1 = 10 MARKS)1. What are the four strokes in an IC Engine?
2. The internal diameter of engine cylinder is called ________.
3. What is heat rate?
4. Define diffuser.
5. Mach number is the ratio of fluid velocity to ________.
6. Express the major two classification of air compressor.
7. One ton of refrigeration = ________.
8. What is meant by refrigeration system?
9. The psychrometric properties are presented in the form of ________.
10. The ratio of actual humidity to specific humidity is ________.
PART – B (5 x 3 = 15 MARKS)
11. Define knocking.
12. Define and give the expression for efficiency of diffuser.
13. Draw the schematic diagram of centrifugal compressor with parts. Give its advantages.
14. Compare the vapor compression and absorption system.
15. Define humidification and dehumidification.
PART – C (5 x 15 = 75 MARKS)
16. Briefly explain the valve timing and port timing diagrams for two stroke and four stroke engines.
(OR)
17. What are the types of fuel ignition system? Discuss any one in detail with neat diagram. Mention the advantages and disadvantages.
18. Steam at 7 bar and supplied 200°C is supplied to a nozzle which expands it to 1.2 bar. Determine the throat and exit areas for a steam of 2.5 kg/s assuming that isentropic efficiency for the flow from throat to exit is 0.9.
(OR)
19. A steam turbine plant employing regenerative feed heating cycle has the following data.
Steam condition at inlet p = 82.75 bar, t = 510°C, Condenser pressure = 42 mbar
Bleed points are at pressure 22.75, 10.65, 4.35. 1.25 and 0.60 bar.
The efficiencies of expansion between various pressure are 85%, 85%, 80%, 79%, 70% and 70% respectively.
Construct the condition line for this turbine and determine:
a. Final state of steam after expansion
b. Mass of steam raised in the boiler per kg of steam condensed in the condenser,
c. Improvement in the thermal efficiency and heat rates due to feed heating and
d. Decrease of steam flow to the condenser per kWh due to feed heating.
[P.T.O]
20. In a rotary air compressor, the air is compressed from 1 bar to 6 bar, initial air temperature being 17°C. Calculate, per kg of air delivered, the work required to drive the compressor and the heat exchanged with the jacket water, in each of the following cases: (a) isothermal compression, (b) reversible and adiabatic compression, (c) adiabatic but not frictionless compression, the end states being defined by the relation pV1.6 = C, (d) reversible compression according to the law of pV1.6 = C.
(OR)
21. Explain with neat sketch of single stage reciprocating compressor and derive the expressions for volumetric efficiency, isothermal efficiency, isentropic efficiency.
22. An ammonia vapor compression refrigeration plant operates between an evaporator Pressure of 1.907 bar and a condenser pressure of 15.57 bar. From the given data, calculate the COP and the refrigeration effect produced for a work input of 1 kW for the following cycles.
a. The vapour has a dryness of 0.8642 at entry to the compressor.
b. The vapour is dry saturated at entry to the compressor.
c. The vapour has 5K of superheat at entry to the compressor. In each case there is no under cooling in the condenser.
At 1.907 bar: ts = -20°C; hfg = 1328.6 kJ/kg
At 15.57 bar : ts = 40°C ; hfg =1099.8 kJ/kg
The specific heat of liquid is 4.815 kJ/kg and that of superheated vapour is 2.897 kJ/kg K at high pressure and 2.282 kJ/kg K at low pressure.
(OR)
23. Briefly explain the working principle of vapour absorption system with neat sketch and mention the advantages.
24. A room is to be kept at temperature of 20°C and a pressure of 1.03 bar. The air which is drawn from A supply at 5°C, 1.03 bar and 70% relative humidity, is saturated with water vapour in a sprayer and then blown through a heater by a fan which absorbs 0.5 kW. 430 m3 of air is drawn from the supply every hour. Calculate:
a. Amount of water at 5°C added per hour,
b. The heat supplied to the heater in kJ,
c. The final relative humidity.
(OR)
25. Air at 20°C, 40% RH is mixed adiabatically with air at 40°C, 40% RH in the ratio of 1 kg of the latter (On dry basis). Find the final condition of air. Plot the results on psychrometric chart.
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