JNTU Previous Question Papers-B.Tech II Semester Regular Examinations-November 2008

JNTU  B.Tech

 Semester Regular Examinations

November 2008

 

 

1. (a) State whether the following quantities are point functions or path function?

Explain briefly:

i. Integral p dv

ii. inter v dp

iii. ????R p dv + R v dp_ and

iv. R dv

(b) Compare the state function and path function.

 

2. (a) Name and state the property introduced by first law of thermodynamics.

(b) For what temperature is the Fahrenheit value two times the centigrade value?

 

3. (a) What is the absolute thermodynamic temperature scale? Why is it called absolute?

(b) Using an engine of 30% thermal efficiency to derive a refrigerator having a

COP of 5. What is the heat input into the engine for each MJ removed from the cold body by refrigerator. If this system is used as heat pump how many MJ of heat would be available for heating for each MJ of heat input to the engine.

 

 

4. (a) Draw the otto cycle on P-V and T-S diagrams marking the various processes.

(b) In an otto cycle air at 17 0C and 1 bar is compressed adiabatically until the pressure is 15 bar. Heat is added at constant volume until the pressure rises to 40 bar. Calculate the air-standard efficiency, the compression ratio and the mean effective pressure for the cycle. Assume CV = 0.717 KJ/kg K and R =8.314 KJ/kg mol-K.

 

5. In an open cycle air refrigeration machine, air is drawn from a cold chamber at-2o C

and 1 bar and compressed to 11 bar. It is then cooled at this pressure, to the cooler temperature of 200 C and then expanded in expansion cylinder and returned to the cold room. The compression and expansion are isentropic, and follow the low pv1.3 =constant. Sketch the p-v and T-s diagrams of the cycle and the for a refrigerationof 15 tonnes, find: 1. theoretical C.O.P; 2. rate of the air in kg/min ; 3. piston displacement per minute in the compressor and expander ; and 4. theoretical power per tonne of refrigeration.

 

 

6. (a) With help of a neat sketch, explain the working of a two stroke C.I engine.

(b) Compare four stroke and two stroke cycle engines. Bring out clearly their

relative merits and demerits.

 

7. (a) What is abnormal combustion in S.I. Engine? Compare the abnormal combustion with normal combustion.

(b) What are different stages of combustion in C.I. Engine? Explain with p-? diagram.

 

8. (a) What are the major applications of gas turbine cycle? Explain

(b) What are the advantages and limitations of reheating gas turbine cycle with multistage expansion

 

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