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Tuesday, 25 February 2014

Basic Thermodynamics- model question paper for B.E/B.Tech Engineering


1 (a) Define thermodynamic system and point out the difference

between closed system, open system and isolated system. 6 Marks)

(b) Describe briefly the working of constant volume gas

 thermometer. (4 Marks)

(c) Explain equality of temperature. (4 Marks)

(d) A Celsius scale and a Fahrenheit scale are immersed in a fluid.

Calculate the temperature of a fluid when,
(a) the numerical reading is identical in both the thermometers.
(b) the Fahrenheit reading is numerically twice that of the Celsius

 reading.
Calculate the values in R and K. (6 Marks)

2 (a) Give the thermodynamic definition of work and heat.

 Establish the relation between the two. (6 Marks)

(b) Differentiate between isochoric and isenthalpic processes. 

(6 Marks)

(c) What is a polytropic process? Explain. (4 Marks)

(d) A shaft rotates at a rate of 100 rpm against a constant torque of 1000 Nm. Calculate the power required to rotate the shaft. Also calculate the work required to rotate the shaft through 50 revolutions. (4 Marks)
3(a) Derive an expression for the first law of thermodynamics applied to a closed system. Show how it gives a conception of internal energy. (6 Marks)
(b)Deduce an expression for the work done when a system undergoes a quasi-static hyperbolic process. (6 Marks)
(c) Explain why Cp is greater than Cv. (4 Marks)
(d) A tank containing a fluid is stirred by a paddle wheel. Heat is transferred from the tank at the rate of 6000 kJ/hr. The work required is 3 kW. Determine the change in internal energy of the system in one hour. (4 Marks)
4 (a) What are the limitations of first law of thermodynamics? (4 Marks)
(b) Write a note on perpetual motion machine. (4 Marks)
(c) Classify reversible process and explain briefly with example and neat sketch. (6 Marks)
(d) Three Carnot engines are connected in series and the combination of these series engines operates between 727oC and 27oC. The work produced by these engines are in the ratio of 5:4:3. Calculate the intermediate temperature. (6 Marks)
5 (a) Define change of entropy. Show that change in entropy is a measure of irreversibility. (6 Marks)
(b) Write a brief note on degradation of entropy. (4 Marks)
(c) Explain the principle of entropy production. (6 Marks)
(d) A heat source at 1000 K transfer heat at the rate of 8373.6 kJ/min to a system at 400 K. The heat sink temperature is 300 K. Assuming that these temperatures remain constant, find the entropy production accompanying the heat transfer. (4 Marks)
6 (a) Define second law efficiency for expansion process or heating. (4 Marks)
(b) Write the expression for irreversibility of closed system and open system. (4 Marks)
(c) Explain the term available and unavailable energy. When does the system become dead state? (6 Marks)
(d) Determine the irreversibility per kg of Freon 12 flow, associated with an expansion valve. Freon = 12 enters at 1.2 MPa, at 30oC and is expanded to 100 kPa. (6 Marks)
7 (a) Draw TV and TP diagrams for a pure substance and indicate all the salient features. (6 Marks)
(b) Describe with a neat sketch how you determine the dryness fraction of wet steam using a throttling calorimeter. (6 Marks)
(c) 0.5 kg of steam with initial dryness of 0.7 is heated at a constant pressure of 8 bar till the volume is tripled. Determine the final temperature, heat and work transfer. (4 Marks)
(d) A closed rigid vessel contains 1.68 kg of liquid water and 1.35 kg of water vapour at a pressure of 300 kPa. Heat transfer to the water causes the water to reach a pressure of 800 kPa. Determine the internal energy change during the process. (4 Marks)
8 (a) State Gibbs Dalton's law. (4 Marks)
(b) Explain Boyle's law and Charle's law and deduce the equation of perfect gases. (6 Marks)
(c) Define critical properties and reduced properties. (4 Marks)
(d) A mixture of 1 kg of Oxygen and 2 kg of Nitrogen occupies volume of i cubic meter at temperature 300 K. Assuming perfect gas behaviour, determine the following properties of the mixture: (a) specific volume, (b) pressure and (c) relative molecular mass. (6 Marks)

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