Monday, November 9, 2009

Aeronautical- engineering- thermodynamics-2-1old jntu papers

II B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007 ENGINEERING THERMODYNAMICS (Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????

1. The readings tA and tB of two centigrade thermometers A and B, agree at the ice point (0o C) and the steam point (100o C), but elsewhere are related by the equation tA = l + m tB + n tB 2 where l, m and n are constants. When both the thermometers are immersed in a well stirred oil bath, A registers 510 C while B registers 50o C. (a) Determine the reading on B when A reads 25o C and (b) Discuss which thermometer is correct. [16]

2. One kg of ?uid enters a nozzle with a velocity of 300m/min and enthalpy of 2990 kJ/kg. The enthalpy of the ?uid at exit is 2760 kJ/kg. The nozzle is placed horizontally and neglects the heat loss from the nozzle. Determine (a) The velocity of the ?uid at the exit (b) The mass ?ow rate, if the inlet area of the nozzle is 0.095m2 and the speci?c volume at inlet is 0.19m3 /kg. (c) The exit area of the nozzle if the speci?c volume at exit is 0.5m3 /kg. [16]

3. (a) What is absolute temperature scale? Develop this scale from Carnot theorem (b) A reversible engine during a cycle of operation interacts with three thermal reservoirs maintained at 200K,300K and 400K. It receives 5 MJ of heat from the reservoir at 400K and produces a net positive work of 840 kJ. Find the amount and direction of heat interaction with other reservoirs. [8+8]

4. (a) Deduce an expression for the non-?ow availability for a system. (b) A 2-kg piece of iron is heated from room temperature of 25o C to 400o C by a heat source at 600o C. What is the irreversibility in the process? Assume for iron Cp =0.450kJ/kgK. [6+10]

5. (a) Derive Clausius-Clayperon equation and explain its signi?cance. (b) Find the value of co-e?cient of volume expansion ß and isothermal compressibility k for a Vander Waal’s gas obeying (p + a/v 2 ) (v-b) = RT [8+8]

6. (a) De?ne i. Mole fraction ii. Mass fraction (b) The volumetric analysis of a dry ?ue gas in a boiler trial is given in Percentage as 13% CO2 , 1.5% CO, 3.5% O2 and 82% N2 . Determine the percentage gravimetric analysis. Also ?nd the speci?c gas constant of the mixture.[6+10]

7. (a) Explain with the help of suitable graphs the variation of the e?ciency of the diesel cycle with compression ratio and cut-o? ratio. (b) In an air standard diesel cycle, the compression ratio is 15.Compression begins at 0.1MPa, 400 c. the heat added is 1.675 MJ/Kg. Find i. ii. iii. iv. v. vi. The The The The The The maximum temperature of the cycle. work down per Kg of air. cycle e?ciency. temperature at the end of the isentropic expansion. cut-o? ratio. mean e?ective pressure of the cycle.

8. (a) Sketch the Rankine cycle on P-V and T-S diagram and explain clearly di?erent process of the cycle. State in what respect it di?ers from carnot cycle working between the same temperature limits. (b) Dry and saturated steam at pressure 11 bar is supplied to a turbine and expended isentropicelly to a pressure or 0.07 bar. Calculate the following. i. ii. iii. iv. Heat supplied Total change of entropy Heat rejected Theoretical thermal e?ciency

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