### THERMAL ENGINEERING MODEL QUESTION PAPER FOURTH SEMESTER DIPLOMA COURSE IN MECHANICAL ENGINEERING

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