JNTU,B.Tech,I- Semester, THERMAL SCIENCE, November 2008
( Mechatronics and Production Engineering)
1. (a) State whether the following properties of a system are intensive or extensive.
pressure, temperature, mass, density, volume, specific volume, energy and
(b) A mass of 2.5 kg of air is compressed in a quasi static process from 0.1 MPa to
0.7 MPa for which PV = constant. The initial specific volume is 0.80 m 3/kg.
Find the work done by the piston to compress the air
2. (a) Define enthalpy. How is it related to internal energy?
(b) Name and state the property introduced by first law of thermodynamics
(c) A system undergoes a cycle composed of four processes. The heat transfers in each process are:400KJ, -365KJ, -200KJ and 250KJ. The respetrive work transfers are 140KJ, 0, -55KJ and 0. is the data consistant with first law of thermodynamics?
3. (a) With a schematic representation explain briefly about heat engine, refrigerator and heat pump
(b) Define COP of a refrigerator
(c) A certain machine works on reversed car not cycle between the temperature
limits of -80C and 250C. Find its COP when working as
i. A refrigerating machine
ii. Heat pump and efficiency when working as heat engine.
4. (a) Derive an expression for mean effective pressure of the Otto Cycle?
(b) Show that in an Otto Cycle, the maximum work done per kg of air is obtained when the temperature after isentropic compression equals the temperature after isentropic expansion, each of them being equal to the geometric mean of the product of the maximum and minimum cycle temperatures.
5. A refrigerator working on bell ? Coleman cycle operates between pressure limits of
1.05 bar and 8.5 bar. Air is drawn from the cold chamber at 100 C, compressed and
it is cooled to 300 C before entering the expansion cylinder. The expansion and compression follows the law pv1.3 = constant. Determine the theoretical C.O.P of
6. (a) Explain the different types of fuel injection systems. Why the air injection system is not used now a days?
(b) What are the functions of a fuel nozzle?
7. (a) What are main functions of carburetor in S.I. Engine?
(b) Describe the working principle of simple carburetor with suitable diagram.
8. (a) Explain the operating principle of Brayton cycle with neat diagrams.
(b) Derive the thermal efficiency of Brayton cycle in terms of pressure ratio and polytropic index.