ENGINEERING THERMODYNAMICS ANNA UNIVERSITY QUESTION PAPER DECEMBER 2018

1. Reg. No. : { I J /1 I I 1
'. Question Paper Code~: 23840 I
B.E./B.Tech. DEGREE EXAMINATION, NOVEM.BERIDECEMB.ER 2018.. - . . .
Third Semester
Mechani~al Engineering
ME 2202/AT 2203 ....,._ENGINEERING THERMODYNAMICS
(Common to Automobile Engineering)
(Regulations 2008)
(Also common to PTME 2202- Engin.eering Thermodynamics for B.E.. (Part-Time)
ThirdSein.ester -MechanicalEngineering - Regulations 2009)
Time ; Three hours Maximu:pl : 100 marks
Answer ALL questions.
PART A- (10 x2 := 20 marks)
1. Though.density is depending on mass, itis an intensive property- Justify.
2. Differentiate heat-and work.
3. Define PMM2.
4. State the·Clausius statement of second law.
5. When a liquid is said as compressed liquid and sub Cooled liquid.?
6. State the methods by which the efficiency of rankine cycle ca~ be improved.
7. ·What is an inversion line?
8. Define compressibility factor?
9. · Define degree of saturation.
10. What is cooling ioad in Psychrometry?
BIBIN.C / ASSOCIATE PROFESSOR / MECHANICAL ENGINEERING / RMK COLLEGE OF ENGINEERING AND TECHNOLOGY

2. PART B- (5 x 16= 80 marks)
11. (a) A piston and cylinder machine contains a fluid system which passes
through a complete cycle of four processes During a cycle, the sum of all.·
heat transfers is -170 kJ. The system completes 100 cycle.s per min.
Complete- the following table showing the method for each item and .
compl,lte the· net rate of work output in kW. · . (16)
Process . Q (kJ/min) W (kJ/inin) ~ E (kJ/min) ·
a-b · 0 2170
.b-e
c-d
d-a
21000
-=-2100
. Or
0
-36,600
(b) Air flows steadily at the rate of 0.5 kg/s through an air ~ompressor,
entering at 7 rrlls velocity, 100 kPa pressure, and 0.95 m3/kg volume, a:nd
leaving at 5 m/s, 700 kPa,.and 0.19.m3/kg. The internal energy of the air
leaving·is 90 kJ/Kg greater thah that of the air enteri,ng.. Cooling water in
the compressor jackets absorbs.heat from the air at the rate of 5·8 kW. ·
(i) Compute the rate of shaft workinput to the air in kW. (8)
(ii) Find the ratio of the inlet pipe diameter to outlet pipe diameter. (8).
12. (a) (i) Determine the heat transfer to the refrigerant and the reservoir at ·
500C . A reversible heat engine ·operates between two reservoirs at ·
temperatures 700"C and 50"0. The engine drives a reversible
refrigerator whl~h operates between reservoirs at tell}peratures .of
5000 and -25"C. The heat transfer to the engine is 2500 kJ and the
network output of the combined engine refrigerator plant is 400 kJ.
(ii).. Reconsider (i),_given t~at the efficiemcy of the heat engine and the
.COP of the refrigerator are each 4~% of their maximum possible
values.·
. (10+6)
Or
·(b)· (i) Write the limitations of first law of thermodynamics which gavethe
introduction to·second law. · (8)
(ii) A domestic food refrigerator maintains a temperature of~12"C. The
ambient air temperature is 35"C. If heat leaks into the fr~ezer at
continuous ra:te of 2kJ/s, determine the least power necessary to
pump this heat out contiri.uously. (8)
2
BIBIN.C / ASSOCIATE PROFESSOR / MECHANICAL ENGINEERING / RMK COLLEGE OF ENGINEERING AND TECHNOLOGY

3. 13. (a) A steam· turbine plant operates ori rankine cycle with steam entering
turbine at 40 bar 350°C and leaving at 0.05 bar. Steam leavingturll>ine
condenses to saturated liquid inside Condenser. Feed Pump Pumps
saturated liquid into boiler. De~rmine the network per kg of steam and
.the.cycle effiCiency assuming all processes to be ideal. Also.Show cycle on
T-s diagram and ealc.ulate Pmnp work per kg of steam Considering linear
·variation of specific volume. (16)
Or
(b) .(i)
'(ii)
.Draw the P-T diagram ofwate·r with salient Points and explain. (8)
Draw PVT f!urface of a substance Which contracts on freezing and
~~ . @
14. . (a) · Derive Maxwell relations. (16)
Or
(b) -The Volume ofa high altitude chamber is 40m3 It isput intooperation.
by reducing press~ from 1 bar to 0.4 bar and from 1 bar to 0.4 bar and
temperature from 25°C to 5°C. How many kg of air must be removed
from the chamber during the process?' Express this mass as a ·volume
measured at 1 barand 25°C. Take R ~ 287 J/kg K for air. (16)
15. (a) An air-water vapour mixture is contained in a rigid closed vessel with a
volume of 35m3 at 1.5 bar, 120°C and ¢J = 10% The mixture is Cooled at
constant volume with its temperature decrease to 22°C. Determine (i) the
dew point temperature corresponding to initial state (ii) the temperature
at Which the condensation actually begins and (iii) the amount of water
condensed. •· (16)
Or
(b) It is required to design an air conditioning Plant for a small office room
for following_ Winter conditions :
outdoor conditions = 14°C DBT and 10°C WBT
Requir_ed Conditions =20°C DBT and 60% R.H
Amount of circulation= 0:3 m3/minlperson
Seating capacity ofoffice = 60
.The required condition 1s achiered first by heating and then by adiabatic
humidifying; Deteri:nine the following :
(i) Heating capacity of the coil in kW and surface temperature
required if the by pass factor of coil is 0.4.
··- (ii) The capacity of the humidifier.
Solve.the problem using Psychrometric chart. (16)
23840
BIBIN.C / ASSOCIATE PROFESSOR / MECHANICAL ENGINEERING / RMK COLLEGE OF ENGINEERING AND TECHNOLOGY