Tuesday, November 8, 2016

ME6301 Engineering Thermodynamics Nov Dec 2016 Important Questions

Anna University Important Questions
Third Semester
Mechanical Engineering Important Questions
ME6301 Engineering Thermodynamics
Nov Dec 2016 Important Questions
(Regulation 2013)

1. A turbine operating under steady flow conditions receives steam at the following state: pressure 13.8 bar, specific volume 0.143 m^3 /kg, internal energy 2590 KJ/Kg, velocity 30 m/s. The state of the stream leaving turbine is turbine is; pressure 0.35 bar, specific volume 4.37 m^3 /Kg, internal energy 2360 KJ/Kg, velocity 90 m/s. Heat is lost to the surroundings at the rate of 0.25 KJ/s. If the rate of steam flow is 0.38 Kg/s, what is the power developed by the turbine?

2. Derive the general steady flow energy equation and deduce SFEE for (i) Boiler (ii) Condenser and evaporator (iii) Nozzle (iv) Turbine and compressor

3. In a gas turbine installation air is heated inside the heat exchanger up to 750○C from the ambient temperature of 27○C. hot air then enters into the gas turbine with a velocity of 50 m/s and leaves at 600○C. Air leaving the turbine enters a nozzle at 60m/s velocity and leaves the nozzle at the temperature of 500○C. for unit mass of the flow rate of air, Examine the following assuming the adiabatic expansion in the turbine and nozzle.
(i) Heat transfer to air in heat exchanger
(ii) Power output from turbine
(iii) Velocity at the exit of the nozzle. Take Cp of air as 1.005 kJ/Kg K

4. A vessel of constant volume 0.3 m^3 contains air at 1.5 bar and is connected via a valve to a large main carrying air at a temperature of 38 deg C and high pressure. The valve is opened allowing air to enter the vessel and raising the pressure therein to 7.5 bar. Assuming the vessel and valve to be thermally insulated, predict the mass of the air entering the vessel.

5. A fluid is confined in a cylinder by a spring-loaded, frictionless piston so that the pressure in the fluid is a linear function of the volume (p = a + bV). The internal energy of the fluid is given by the following equation U = 34 + 3.15 pV where, U is in KJ, p in KPa, and V in cubic meter. If the fluid changes from an initial state of 170 KPa, 0.03 m^3 to a final state of 400 KPa, 0.06 m^3 ,with no work other than that done on the piston, find the direction and magnitude of the work and heat transfer.

6. Derive the efficiency of Carnot cycle and Explain with neat the help of p-v and t-s diagram

7. Explain and derive Isothermal process & Isobaric process.

8. A reversible heat engine operates between two reservoirs a temperature of 600 deg C and 40 deg C. the engine drives a reversible refrigerator which operates between the reservoirs at temperatures of 40 deg C and -20 deg C. the heat transfer to the heat engine is 2000 KJ and the network output for the combined engine refrigerator is 30 KJ. Evaluate the heat transfer to the refrigerant and the net heat transfer to the reservoir at 40 deg C.

9. Three Carnot engines A, B and C working between the temperature of 1000 K and 300 K are in a series combination. The works produced by these engines are in the ratios 5:4:3. Make calculations of temperature for the intermediate reservoirs

10. Helium enters an actual turbine at 300 KPa and expands to 100 KPa, 150 deg C. Heat transfer to atmosphere at 101.325 KPa, 25 deg C amounts to 7KJ/Kg. Calculate the entering stream availability, leaving stream availability and the maximum work. For helium, Cp=5.2 KJ/Kg and molecular weight= 4.003 Kg/Kg-mol

11. A steam power plant operates on a theoretical reheat cycle. Steam at 25 bar pressure and 400 deg C is supplied to a high pressure turbine. After its expansion to dry state the steam is reheated to a constant pressure to its original temperature. Subsequent expansion occurs in the low pressure turbine to a condenser pressure of 0.04 bar. Considering feed pump work, make calculation to determine (i) quality of steam at the entry to the condenser (ii) thermal efficiency (iii) specific steam consumption.

12. Consider a steam power plant that operates on a reheat Rankine cycle and has a net power output of 80 MW. Steam enters the high pressure turbine at 10 MPa and 500˚C and the low pressure turbine at 1 MPa and 500˚C. Steam leaves the condenser as a saturated liquid at a pressure of 10 KPa. The isentropic efficiency of the turbine is 80 percent, and that of the pump is 95 percent. Show the cycle on a T-s diagram with respect to saturation lines, and determine, (i) The quality (or temperature, if superheated) of the steam at the turbine exit, (ii) The thermal efficiency of the cycle, and (iii) The mass flow rate of the steam.

13. Draw P-V-T surface for any substance that contracts on freezing and get P-T pot out of them.(b) 3 kg of steam at 18 bar occupy a volume of 0.2550 m^3 . During a constant volume process, the heat rejected is 1320 KJ. Determine final internal energy. Find dryness fraction and pressure, change in entropy and work.

14. Derive Vandar Waals AND Maxwell’s equation

15. Derive Dalton’s law of partial pressure. Define Amagats law of partial volume

16. Determine the specific volume of water vapour at 110 bar and 841 K by (i) the ideal gas equation of state, (ii) the principle of corresponding state and (iii) the super heat steam table. (iv) Also calculate the % of error in the volume obtained by ideal gas equation and that by the principle of corresponding state. Take, pc = 221.2 bar and Tc = 647 C. Use generalized compressibility chart.

17. The gas neon has a molecular weight of 20.183 and its critical temperature pressure and volume are 44.5 K, 2.73 MPa and 0.0416 m 3 /Kg mol. Reading from a compressibility chart for a reduced pressure of 1.3, the compressibility factor Z is 0.7. What are the corresponding specific volume, pressure, temperature and reduced volume?

18. A tank of 0.2 m^3 capacity contains O2 at 15 bar and 400 deg C. A second tank 0.5 m^3 contains N2 at 20 and 300 deg C. the two tans are connected together and allowed to mix. The heat lost during mixing is 50 KJ. Determine the final pressure, final temperature of the mixture and net entropy change due to mixing.

19. Atmospheric air at 1 bar pressure has 2.5°0 DBT and 75% RH using psychometric chart, calculate DBT, enthalpy, vapour pressure.

20. Show that slope of the sublimation curve at the triple point is greater than that of vaporization curve on P-T diagram, using (i) latent heat and (ii) entropy change.
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