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Posted Date: 26 Jan 2009 Posted By: A santhosh Member Level: Diamond
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2008 Jawaharlal Nehru Technological University Mechanical Engineering Code No: R05 II B.Tech I Semester Supplimentary Examinations, November 2008 THERMODYNAMICS Question paper
Code No: R05210304 Set No. 1
II B.Tech I Semester Supplimentary Examinations, November 2008
THERMODYNAMICS
( Common to Mechanical Engineering and Automobile Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. A gas undergoes two processes that are in series. The first process is an expansion
that is carried out according to the law PV = constant, and the second process
is a Constant pressure process that returns the gas to the initial volume of the
first process. The start of the first process is at 400 KPa and 0.025 m3 with the
expansion to 200 KPa. Sketch the process on a P-V diagram, and determine the
work of the combined process. [16]
2. (a) List any five physical properties of matter which can be used for the measure-
ment of temperature
(b) State the concept of temperature and quality of temperature
(c) In a general compression process, 2 kJ of mechanical work is supplied to 5
kg of working substance, and 800 J of heat is rejected to the cooling jacket.
Calculate the change in specific internal energy. [5+5+6]
3. Two kg of air at 500 KPa, 800C expands adiabatically in a closed system until its
volume is doubled and its temperature becomes equal to that of the surroundings
which is at 100 KPa, 50C. For this process, determine
(a) the maximum work
(b) the change in availability and
(c) the irreversibility for air,
take Cv = 0.718 KJ/Kg-K and R = 0.287 KJ/Kg-K. [16]
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. [7+9]
5. (a) Write down the Vander Waal’s equation of state. How does it differ from the
ideal gas equation of state?
(b) A mass of air is initially at 2600C and 700 Kpa and occupies 0.028m
3. The
air is expanded at constant pressure to 0.084m
3.Apolytropic process with n
= 1.5 is then carried out, followed by a constant temperature process, which
completes a cycle. All the processes are reversible
i. Sketch the cycle in the P-V &T-S planes
ii. Find heat received & rejected in the cycle
iii. Find ? of the cycle. [7+9]
6. (a) Define
i. Humidification
ii. Dehumidification
iii. sensible heating
(b) Avessel of 6m
3 capacity contains two gases ?A? and ?B? in proportion of 45%
respectively at 300C.If the value of ?R? for the gases is 0.288 Kj /kg. k and
0.295 Kj /kg. K and if the total weight of the mixture is 2 kg, calculate
i. Partial presser
ii. The mean value of ?R? for the mixture. [6+10]
7. (a) Explain the dual combustion cycle. Derive an expression for the efficiency of
dual cycle.
(b) Which air-standard cycle is used in I.C. Engines? Explain the differences
between Otto cycle and Dual cycle. [8+8]
8. (a) Explain the important components of a simple vapour compression refrigera-
tion system. Also discuss the functions of each component.
(b) Discuss the effect of sub cooling on C.O.P.of the vapour compression refriger-
ation cycle. Would you derive large sub cooling and why?
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