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

JNTU PAPERS

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

(Mechanical Engineering and Automobile Engineering)

SET-1

1. (a) What do you mean by the system? Discuss types of systems with one example each.

(b) What is the difference between heat and energy.

(c) Explain what do you mean by thermodynamic equilibrium.

2. Calculate the final temperature, pressure, work done and heat transfer if the fluid

is compressed reversibly from volume 6 m3 to 1 m3 when the initial temperature

and pressure of the fluid are 20oC and 1 bar. The index of compression may be

assumed as 1, 1.3 & 1.4 respectively. Take C

p= 1.005 & C

v = 0.718 & R= 0.287

kj / kg K.

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.

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 C

p=0.450kJ/kgK.

5. (a) 2 kg of saturated liquid water at 2 bar is mixed with 1 kg of steam at 2 bar,

3000C in a closed system. The pressure during the mixing process remains at 2 bar and no energy transfer takes place. Determine the quality of steam and the amount of entropy production by the control of mass.

(b) Two streams of steam flow into a main stream. The pressure maintained throughout is 20 bar. The temperature of one stream is 3500C and in the main stream is 2500C. Determine the quality of steam supplied by the second

stream. Take C ps = 2.25kJ/kg K

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) Represent the Otto cycle by P-V and T-S diagram and describe the different

processes with the help of above diagrams.

(b) In an Otto cycle, the pressure limits are 100 kN/m2 and 2000 kN/m2. The compression ratio is 4. Calculate

i. The thermal efficiency

ii. Mean effective pressure.

8. A power plant operating on the Ranking cycle has steam entering the turbine at

37 bar and 4250C. If the turbine output is equivalent to 10,000 Kw, determine the

efficiency of the cycle and the mass flow rate of steam for condenser pressure of

(a) 0.07 bar and

(b) 0.035 bar.