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Wednesday, 12 December 2012

Applied thermodynamics-Model question paper for B.E/B.Tech/M.E/M.Tech

1 (a) Explain the method to determine air consumption with the help of neat sketch. (6 Marks)
(b) Differentiate between brake power and frictional power. (4 Marks)
(c) Write notes on mechanical efficiency and volumetric efficiency. (6 Marks)
(d) A single cylinder petrol engine working on two-stroke cycle develops indicated power of 5kW. If the mean effective pressure is 7 bar and piston diameter is 100 mm, calculate the average piston speed. (4 Marks)
2(a) What are the advantages and disadvantages of excess air in combustion? (4 Marks)
(b)Explain complete and incomplete combustion. (6 Marks)
(c) Write a note on enthalpy and internal energy of combustion. (6 Marks)
(d) Determine the molal analysis of products of combustion when octane C8H18 is burned with 200% of air. (4 Marks)
3(a) Describe the air standard Otto cycle and derive an expression for efficiency as a function of compression ratio. (8 Marks)
(b) Distinguish between air standard cycle and actual cycle in general. What are the reasons for deviations? (8 Marks)
(c) A reversible engine converts one-sixth of the heat input into work, when the temperature of sink is reduced to 700C, its efficiency is doubled. Find the temperature of source and sink. (4 Marks)
4(a) Obtain an expression for thermal efficiency of dual cycle in terms of compression ratio, cut-off ratio and pressure ratio. (8 Marks)
(b) Explain various methods of improving the specific work output and thermal efficiency of gas turbine cycle. (8 Marks)
(c) A gas turbine set takes air at 270C and 1 atm. The pressure is 4 and the maximum temperature is 5600C. The compressor and turbine efficiencies are 0.83 and 0.85 respectively. Determine the overall efficiency if regenerator efficiency is 0.75. (4 Marks)
5(a) Discuss the effects of exhaust pressure and superheating on Rankine cycle efficiency. (6 Marks)
(b) Draw an ideal regenerative vapour power cycle on temperature entropy diagram. What are its advantages? How is the cycle approximated in practice? (10 Marks)
(c) In a thermal power plant, the saturated liquid water coming out of condenser is at 10 kPa. This liquid is to be recycled by pumping into boiler which is maintained at 2.5 kPa. Determine the work to be done (per kg of water) on the pump if isentropic efficiency of the pump is 0.8. (4 Marks)
6(a) What is multistage compression? Discuss the advantages. (6 Marks)
(b) Explain the need of multi-staging in reciprocating compression. (6 Marks)
(c) Enumerate the applications of compressed air. (4 Marks)
(d) A two stage air compressor receives air at 3 m3/min at 1 bar and delivers it at 10 bar. Assuming perfect intercooling, determine the power required. (4 Marks)
7(a) Write a note on essential properties of a refrigerant material. (4 Marks)
(b) Differentiate between vapour refrigeration system and air refrigeration system. (6 Marks)
(c) With neat sketch explain the working of the steam jet refrigeration. (6 Marks)
(d) Determine the least power of a perfect reversed heat engine that makes 400 kg of ice per hour at -80C from feed water at 180C. Assuming specific heat of ice as 2.09 kJ/kg and latent heat 334 kJ/kg. (4 Marks)
8(a) Sketch and explain various psychrometric processes on psychrometric chart. (6 Marks)
(b) Define the term bypass factor used for cooling or heating coil and find expression for the same. (6 Marks)
(c) Define terms wet bulb temperature and dew point temperature. (4 Marks)
(d)Moist air saturated at 1.70C enters the heating coil at the rate of 600 m3/min. Air leaves the coil at 37.80C. Find the required amount of heat addition per hour. (4 Marks)

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