8/12/2019 MID SEM 2012-13

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Birla Institute of Technology and Science, Pilani

BITS F111/ES C112 THERMODYNAMICS

Second Semester, 2012 2013 MID SEM (Open Book)Date : 02/03/2013 Max. Marks: 100 Max. Time: 90 min.

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The Question paper has two parts: Part A and Part B

Answer Part A in question paper itself in the space provided.

Answer Part B in the answer book.

Attach part A to the answer book (length wise) just under the cover page before submission.

ID No. Name Tut. Sec.No.PART-A

Q.1a An ideal gas is expanded adiabatically from the initial state to final state. Will the final gas

pressure be the same in the case of (a) Free expansion, as compared to (b) a very slow

expansion? Justify [4M]

Q.1b An ideal gas undergoes throttling across an adiabatic valve. Which, if any, of the followingquantities is non-zero for the process? U, H, T, P, W? Justify. [4M]

Q.2a A rigid adiabatic container contains a mixture of hydrogen and oxygen gases. The mixture

undergoes an explosive reaction. Is U for the process positive, negative, or zero? Justify. [4M]

Q.2b What will be the value of specific volume of water at 300 kPa and at 25 OC, and why? [4M]

Q.3a At 1 atm., for which of the following processes, the change in internal energy is less than theheat transfer? (i) the melting of ice to liquid water; (ii) the evaporation of liquid water to

vapor. Justify your answer. [4M]

Q.3b In an isothermal process, 2257 kJ of work is done by an ideal gas. Is this enough information to

tell how much heat has been added to the system? If so, how much? [4M]

8/12/2019 MID SEM 2012-13

2/2

Birla Institute of Technology and Science, Pilani

BITS F111/ES C112 THERMODYNAMICS

Second Semester, 2012 2013 MID SEM (Open Book)Date : 02/03/2013 Max. Marks: 100 Max. Time: 90 min.

Page 2 of 2

Q.4a The volume of an ideal gas increases at constant pressure. Does the internal energy increase or

decrease during this process? Justify your answer. [4M]

Q.4b If a reversible heat pump operates between the exterior at 270K and the interior of a room at

300 K, for every kJ of work input, how much heat is transferred to the room? [4M]

PART-B

Q.5. The rigid tank of volume 80 liters initially contains water at a pressure 1500 kPa such that it

contains 5% of liquid and 95% of vapour by volume. Now the tank is heated and simultaneously

a valve at the top of the tank is opened to allow the vapour to escape such that constant pressure

is maintained. The process continues till the volume of liquid in the tank reaches to 400ml.

Determine (a) initial mass, (b) the final mass in the tank, (c) the heat transfer, and (d) work done

during the process. (e) Show the process on P-v diagram. [20M]

Q.6. A cylinder contains chlorine at 800 kPa and 292 K, and quality 0.80. The gas leaks slowly from

the top of the cylinder. If the volume of the tank is 1 m3, using compressibility factor chart,

estimate the mass of chlorine in the tank (i) at the beginning, and (ii) when the pressure hasdropped to 400 kPa. [13M]

Q.7. A gas within a pistoncylinder assembly undergoes a thermodynamic cycle consisting of three

processes:

Process 12: Constant volume,V= 0.028 m3, U2 - U1 = 26.4 kJ.

Process 23: Expansion withPV= constant,U3 = U2.

Process 31: Constant pressure,P =1.4 bar, W31 = -10.5 kJ.

There are no significant changes in kinetic or potential energy. Show the cycle on a PVdiagram

and calculate a) the net work done b) the heat transfer for process 23 and c) the heat transfer

for process 31. [15M]

Q.8. A piston-cylinder device that has stops and a linear spring (spring constant 500 kN/m) as shownin figure, contains 1 kg of water initially at 60 C. Water is stirred by a paddle wheel while a

current of 8 A at 50 V flows for 60 min through a resistor

placed in the water. The piston (cross-section 1 m2), whose

thickness is negligible, requires pressure of 300 kPa to float.

The entire arrangement is adiabatic and the process is

assumed to be quasi-equilibrium. In the final state, the

pressure is 600 kPa.

a) In the final state, is the piston pressed against the

upper stops?

b) Represent the process on P-v diagram.c) Find the paddle work.

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