DERARTMENT OF TECHNICAL EDUCATION
DIPLOMA COURSE IN MECHANICAL ENGINEERING
FOURTH SEMESTER
MODEL QUESTION PAPER
THERMAL ENGINEERING-I
Time: 3Hrs Max marks: 100
Note: 1.Section-I is compulsory
2. Answer any six full questions from Section -II, Section-III, and Section-IV
Choosing at least TWO from each section
SECTION I
1 A) Fill in the blanks with appropriate words:- 1X5
I) The Second law of thermodynamics defines_____________.
ii) The work done in constant volume process is _____________
iii) ______________ calorimeter is used for measuring calorific value of solid fuel
iv) The Value of gas constant(R) is ______________.
v) The enthalpy of dry saturated steam _______________with the increase in pressure
B) Write a note on Junkers gas calorimeter 5
SECTION II
2 a) Define the following properties
i) Specific weight ii) Enthalpy iii) Density 6
b) Explain with Example open and close system. 5
c) State the Zeorth law of thermodynamics 4
3 a) Name the variables which controls the physical properties of perfect gas 5
b) Derive the relation between two specific heats 5
c) A cylinder contain 3 kg of air at pressure of 300 bar and temperature of 27°C.Find
the volume of air occupied by gas Assume R of air 287 J/Kg°K. 5
4 a) How polytrophic process differ from adiabatic process 3
b) Derive an expression for work done during adiabatic process. 5
c) An ideal gas at 30°C and 1 bar is compressed adiabatically from 5m3 to 1m3.
Find the temperature, Pressure and the work done. Take γ-1.4 7
SECTION III
5 a) State the second law of thermodynamics 5
b) What are the limitations of first law of thermodynamics 4
c) A cyclic heat engine operates between a source temperature of 800°C and sink
temperature of 30°C.What is the least rate of heat rejection per KW net out put
of the engine. 6
6 a) State the assumption made in air standard cycles . 4
b) Derive the air standard efficiency of diesel cycle 6
c) A diesel engine has a compression ratio of 14 and cutoff takes place at6 %.find
the air standard efficiency 5
7 a) State the conditions for reversibility 4
b) Derive an expression for external work done during evaporation when the
Steam is wet 5
c) Dry saturated steam at a pressure of 10 bar is expanded isentropically to a pressure of
0.7 bar, Using mollier diagram determine enthalpy drop 6
SECTION IV
8 a) Define the term Entropy 2
b) Determine the entropy of 1 Kg of wet steam at a pressure of 10 bar and of dryness
fraction 0.9 7
c) Explain how wet, dry, superheated steam are produced 6
9 a) Distinguish between Higher calorific value and Lower calorific value
of a fuel . 3
b) Explain modified rankine cycle 5
c) A simple rankine cycle works between boiler pressure of 3Mpa and condenser
Pressure of 4 Kpa.The steam is dry saturated before throttling in the turbine
Determine i) Rankine cycle efficiency ii)Work ratio iii) Specific fuel consumption 7
10 Write short note on any three of the following 5x3=15
i) Rankine cycle
ii) Constant pressure process
iii) Extensive and Intensive properties
iv) Bomb calorimeter
