University of Mumbai 2009-1st Sem M.E Thermal Engineering Advanced Thermodynamics - - Question Paper
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Con. 2989-09. 7 BB-5616
(4 Hours) [Total Marks : 100
N.B.: (1) Question No. 1 is compulsory.
(2) Attempt any four queslions out of remaining six questions.
(3) Answers of all parts of the question should be written together and one below the other.
(4) Assume any suitable data whenever required but justify the same.
(5) Use of thermodynamic table and chart is permitted.
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1. Answer the following questions : A#
(a) Develop the transient form of mass, energy* and entropy equation for an open system , interacting with surrounding in the form of heat and work.
(b) Sate the significance of second law of thermodynamics. How does it help us in the analysis of the thermodynamic system ? Give examples and explain.
(c) 10 kg of water at 273 K is brought into contact with a surrounding at 373 K.
Find the net entropy exchange, when water reaches to 373 K.
(d) What do understand by property relations ? Derive MaxWcll's equations.
(e) Define following terms:
(i) Equivalent ratio. (iii) Complete and incomplete combustion
(ii) IIIIV and LHV (iv) Adiabatic Flame temperature.
2. (a) A rigid vessel containing gas at pressure P, and temperature T1 is charged to a pressure P2, 10
Find the final temperature and the average gas mass flow rate entering the lank.
(b) A I-m\ 40-kg rigid tank contains air at 800 kPa, and both tank and air are at 20C. 10 The tank is connected to a line flowing air at 2 MPa, 20C. The valve is opened, allowing air to flow into the tank until the pressure reaches 1.5 MPa and is then closed.
Assume the air and tank are always at the same temperature and the final temperature is 35C. Find the final air mass and the heat transfer.
3. (a) Explain the principle of increase of entropy ? How does this principle helps in the 10
analysis of a thermodynamic system ?
(b) Two 10 kg blocks ofsteel, one at 400C the other at 50C, come in thermal contact. 10 Find the final temperature and the change in entropy of the steel ? Assume specific heat of steel is 0.46 kJ/kgK.
4. (a) What do you mean by irreversibility of a thermodynamic process ? What is its 10
significance in thermodynamics ? Discuss about the factors which make a process irreversible.
(b) Liquid water at 200 kPa and 20C is healed in a chamber by mixing it with superheated 10 steam at 200 kPa and I 50C. Liquid water enters the mixing chamber at a rate of
2.5 kg/s, and the chamber is estimated to lose heat to the surrounding air at 25C at a rale of 1200 kJ/min. If the mixture leaves the mixing chamber at 200 kPa and 60C, determine (i) the mass flow rate of the superheated steam and (ii) the rate of entropy generation during this mixing process.
5. (a) What is meant by cxergy ? Derive the expression for exergy loss in a process 10
executed by : (i) dosed system, (ii) open system.
(b) A rigid tank initially contains saturated liquid water. A valve at the bottom of 10 the tank is opened, and half of mass in liquid form is withdrawn from the tank.
The temperature in the tank is maintained constant. Determine the amount of heat transfer, the reversible work, and the exergy destruction during this process.
6. (a) What does the Joule-Thomson coefficient represent ? Derive a relation for the 10
Joule-Thomson coefficient and the inversion temperature for a gas whose equation of state is pv = RT.
(b) C4Hi0 (1) enters a combustion chamber at 25C at a rate of 0.05 kg/min where it is 10 mixed and burned with 50 percent excess air that enters the combustion chamber at 7C. An analysis of the combustion gases reveals that all the hydrogen in the fuel bums to HzO but only 90 percent of the carbon bums to C02, with the remaining 10 percent forming CO. If the exit temperature of the combustion gases is 1500 K, determine (i) the mass flow rate of air and (ii) the rate of heat transfer from the combustion chamber.
10
|
Substance |
h* (kJi kmole) |
hw {kJ / kmole) |
hm {kJ I kmole) |
W / kmole) |
|
C4HI0(1) |
-118,910 |
- |
- |
. |
|
Oz |
0 |
8150 |
8682 |
49,292 |
|
n2 |
0 |
8141 |
8669 |
47,073 |
|
h2o |
-241,820 |
- |
9904 |
57,999 |
|
C02 |
-393,520 |
- |
9364 |
71,078 |
|
CO |
-110,530 |
- |
8669 |
47,517 |
|
Prove that for an van der Waals gas | ||||
|
T | ||||
|
p |
v 1 - 2a(v |
- b)2/RTv3 | ||
(b) Over a certain range of pressure and temperature of the equation of a certain substance 10 is given by the following relation
RT C
v = --Tfr were C is a constant.
p TJ
Derive an expression for change of h and s of this substancc in an isothermal proccss.
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Attachment: |
| Earning: Approval pending. |
