JNTU, B-Tech ,I-Semester Thermodynamics, November 2008

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JNTU, B.Tech ,I-Semester Thermodynamics, November 2008

(Mechanical Engineering and Automobile Engineering)

SET-3

 

1. (a) Explain thermodynamic system, surroundings and universe, illustrate the same

with examples.

(b) Distinguish between closed system, open system and isolated system with suitable examples. [8+8]

 

2. Air at 1.06 bar and 70C is heated at constant volume to a temperature of 8470C. It is then expanded adiabatically until the pressure falls to 1.06bar, following which heat is rejected at constant pressure until the temperature is brought back to 70C. Show that the heat input is equal to work output of the cycle.

 

3. Air is compressed from a pressure of 1 bar and a temperature of 210C to a pressure

of 2 bar and temperature of 380C. For this process determine

(a) determine change in entropy

(b) determine whether heat is added or removed or is it zero

(c) Also calculate the final temperature if the process were isentropic

(d) Sketch process for part (c) on a T-s plane

 

4. (a) Deduce an expression for the non-flow availability for a system.

(b) A 2-kg piece of iron is heated from room temperature of 25oC to 400oC by a

heat source at 600oC. What is the irreversibility in the process? Assume for iron Cp=0.450kJ/kgK.

 

5. (a) Determine the amount of heat, which should be supplied to 2 kg of water at

250C to convert it into steam at 5 bar and 0.9 dry.

(b) A quantity of dry saturated steam occupies 0.395kg/m3 at 1MN/m2. Determine the condition of steam and enthalpy.

i. after isothermal compression to half of its initial volume.

ii. after hyperbolic compression to half its initial volume.

 

6. A rigid tank of volume 1.2m3 is divided into two equal parts by a partition. One

compartment contains neon gas at 200C and 110kPa and other contains argon gas

at 470C and 225kPa. Now partition is removed and the two gases are allowed to mix. If 10kJ of heat is lost to the surroundings at 200C during the mixing process,

determine the final temperature and pressure of the mixture.

 

7. (a) Explain Lenoir cycle with the help of P-V and T-S diagrams.

(b) Derive an expression for its thermal efficiency.

 

8. Explain clearly Rankine cycle and derive on expression for thermal efficiency of the

cycle.

 

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