Thermodynamics - Dec 2013
Mechanical Engg (Semester 3)
TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
Answer any one question from Q1 and Q2
1 (a) Define any three and give suitable example wherever necessary:
ii) Intensive and extensive properties
iii) Quasi-static Process
iv) Zeroth law of thermodynamics
v) Heat Sink and Heat Source(6 marks) 1 (b) A reversible heat engine operates between three isothermal heat reservoirs. The engine receives 4000 kW heat from reservoir A at 1000 K produces work output of 1600 kW. Heat source reservoir B and Heat sink reservoir C are at 300 K and 400 K respectively. Calculate the heat transfer with the reservoir B and C using Clausius inequality theorem. Also estimate the thermal efficiency of the heat engine.(6 marks) 2 (a) State and explain Clausius inequality. Explain law of increase of entropy principle and change in entropy for reversible, irreversible and impossible process.(6 marks) 2 (b) During a Thermodynamic cycle of processes (A-B-C-D-A), the heat transferred during each process are: 120 kJ, -16 kJ, -48 kJ and 12 kJ respectively. Estimate net work transferred during the Thermodynamic cycle, direction of work transfer, Change in Internal energy and Total energy during the cycle using the first law for Thermodynamic cycle.(6 marks)
Answer any one question from Q3 and Q4
3 (a) For Dual Cycle define the following by using P-V diagram: i) Clearance Volume
ii) Swept Volume
iii) Compression ratio
iv) Cut off ratio
v) Expansion ratio
vi) Pressure ratio(6 marks) 3 (b) Determine the total enthalpy and total Internal energy for the following cases:
i) 3kg of steam at 11 bar and 60% dry.
ii) 5kg of steam at l0 bar and 250°C.(6 marks) 4 (a) Explain heating of ice from -107deg;C to Super heated steam at 150°C and 1 atmospheric pressure on T-h Diagram (Show sensible heating and latent heating regions clearly).(6 marks) 4 (b) A system at 400 K receives 150 kJ of heat from a heat source at 1200 K. Atmospheric temperature is 300 K. The temperature of both the system and the source are assumed to be constant during the heat transfer process, find the net change in the entropy, available energy of the heat source, available energy of system.(6 marks)
Answer any one question from Q5 and Q6
5 (a) Explain the Classification of boilers with example.(6 marks) 5 (b) In a boiler test 1250 kg of coal is consumed in 24 hours, mass of water evaporated is 13000 kg and boiler pressure of 7 bar. Feed water temperature was 40°C and heating value of coal is 30000 kJ/kg. Find equivalent evaporation per kg of coal and boiler efficiency. (Take enthalpy of 1 kg of steam at boiler exit as 2570 kJ/kg).(7 marks) 6 (a) What are the desirable characteristics of a good boiler (6 valid points).(6 marks) 6 (b) A boiler uses 1000 kg of coal per hour. The temperature of the hot gases inside the chimney is 650 K and outside air temperature is 300 K. The draught produced by the chimney of 25 m of height is 15 mm of water column. Determine the air supplied per kg of fuel burnt, draught in terms of hot gases, mass flow rate of hot gases and the area of the chimney required if the coefficient of the velocity is 0.4.(7 marks)
Answer any one question from Q7 and Q8
7 (a) Define and explain following terms,
i) Mass fraction.
ii) Mole fraction.
iii) Stoichiometric or Theoretical air.
iv) Excess Air.(6 marks) 7 (b) A sample of coal has the following composition by mass: C = 90 %, H2 = 3 %, O2 = 2.5 %, N2 = 1 %, S = 0.05 %, Ash = 3 %. Calculate: i) Stoichiometric A/F ratio & Actual A:F ratio if 20% excess air is supplied , ii) Analysis of products of combustion by mass.(7 marks) 8 (a) Explain working of Bomb Calorimeter with neat sketch.(6 marks) 8 (b) During Bomb Calorimeter test on diesel oil, the following data were recorded,
|Room Temperature (R.T)||=25oC|
|Weight of the crucible||=8.116 gm|
|Weight of the crucible and oil||=8.702 gm|
|Weight of can||=1.051kg|
|Weight of can and water||=3.492kg|
|Water equivalent of can||=0.559kg|
|Rise in temperature of can and water||=2.305oC|
Find the HCV of the fuel.(7 marks)