# JNTU II B.Tech I Semester Supplimentary Examinations, November 2008

JNTU II B.Tech I Semester Supplimentary Examinations, November 2008

THERMODYNAMICS

( Common to Mechanical Engineering and Automobile Engineering)

SET-3

1. (a) What are different forms of work energy? Explain each briefly.

(b) Why does free expansion have zero work transfer?

2. A steam turbine operates under steady flow conditions. Steam at inlet to turbine is at 15 bar with internal energy 2700 KJ/kg; specific volume 0.17 m3/kg and velocity 100 m/s. The exhaust of steam from the turbine is at 0.1 bar with internal energy 2175 KJ/kg, specific volume 15 m3/kg and velocity 300 m/s. The intake is 3 meters above the exhaust. The turbine develops 35 kW and heat loss over the surface of the turbine is 20 KJ/kg. Determine the steam flow rate through the turbine.

3. (a) Is it possible for a heat engine to operate without rejecting any heat to a low temperature reservoir.

(b) A heat engine receives 600 KJ of heat from a high temperature source at 1000 K during a cycle. It converts 150 KJ of this heat to net work and rejects the remaining 450 KJ to a low temperature sink at 300 K. determine if this heat engine violates the second law of thermodynamics on the basis of

i. the Carnot principle and

ii. the Clausius inequality.

4. (a) Describe the process of formation of steam and give its graphical representation

(b) Steam enters an engine at a pressure 10 bar absolute and 2500C. It is exhausted at 0.2 bar. The steam at exhaust is 0.9 dry. Find

i. Drop in enthalpy

ii. Change in enthalpy.

5. (a) What is the difference between ideal gas and a perfect gas?

(b) What is equation of state?

(c) 1.kg of CO2 has a volume of 1m3at1000C. Compute the pressure by

i. Vander Waal’s equation

ii. Perfect gas equation.

Take a = 362850Nm4/(kg?mole)2; b = 0.0423m3/kg?mole;R = 8314J/kgmoleK

6. (a) Write short notes on

i. Mole fraction

ii. Volumetric analysis

iii. Dry bulb temperature

(b) An air water vapour mixture has a relative humidity of 60 % at l atmosphere and 300C. Determine per 100m3 of the mixture

i. Mass of water vapour

ii. Mass of dry air

7. A closed cycle ideal gas turbine plant operates between temperature limits of 800C

and 30C and produces a power of 100kW. The plant is designed such that there is

no need for a refrigerator. A fuel of calorific value 45000kJ/kg is used. Calculate

the mass flow rate of air through the plant and rate of fuel consumption. (Take cp = 1.0 kJ/kgK and? =1.4.).

8. (a) Draw the flow diagram of vapour compression refrigeration system and anlyze the thermodynamic cycle applied for it?

(b) Explain the difference between the Bell Coleman and Joule cycle of refrigeration