OR

Code No.210352 II-B.Tech. I-Semester Examination Nov/Dec 2002

2.a) b)

State the first law of thermodynamics for a closed system and show that internal energy is a property of the system. A closed system of constant volume undergoes a process in which there is a temperature rise of 30oC. There is a heat transfer in the process equal to 80kJ. Cv, the constant volume specific heat, of the working substance is 5 KJ/Kg-oC. If the mass within the system is 2 kg determine the change in the internal energy and the work done. State the process which the system did undergo. Differentiate between heat engine and heat pump. State and prove clausius inequality. Two bodies of the same mass but with different specific heats are at temperature T1 and T2 respectively initially. They are brought into contact with each other and allowed to reach the equilibrium state. Determine the entropy changing the process and show that it is positive.

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3.a) b) c)

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b)

Explain what manoscopic and microscopic view points are when considering a Thermodynamic system. Establish a new temperature scale, say oV, in which the freezing and boiling points of water are assigned as 100oV and 600oV respectively on a mercury-inglass borelate the above scale with celsius temperature scale. How is the asolute temperature expressed in oV?

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1.a)

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THERMO DYNAMICS (Common to Mechanical Engineering, Production Engineering and Mechatronics) Time:3 hours Max.Marks:70 Note:- 1. Answer any FIVE questions 2. All questions carry equal Marks 3. Missing data, if any, may suitably be assumed. 4. Thermodynamic property tables and charts may be used, if needed. ---

Explain availability and irreversibility. An ideal gas is compressed in a reversible process in a cylinder from 1 atmospheric pressure (1.01325bar) and 25oC to 4.5bar pressure according to the law pV1.3 = constant. Determine the work done and heat transferred and also the change in entropy during the process per unit mass of the working substance. Take R1 the characteristic gas constant as 0.298KJ/kg-k and Cp. The specific heat at constant pressure as 1.042 kJ/kg-k.

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4.a) b)

(Contd…2)

Code No.210352

b)

OR

Explain: i) Compressibility factor (ii) Reduced coordinates and iii) Generalized compressibility chart. Air is compressed isentropically from 1 atmospheric pressure and 27oC to 6 atmospheres. Using gas tables determine the final temperature and the changes in enthalpy and internal energy.

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5.a)

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Explain the usefulness of T-s and h-s (Mollies) diagrams in solving problems related to steam. Which one is widely used and why? b) In an adiabatic steady flow process 2kg of hydrogen are mixed with 1 kg of nitrogen. Initially hydrogen is at 1.5bar pressure and 30oC and nitrogen is at 1.5bar pressure and 250oC. The pressure after mixing is 1.4bar. Determine the entropy change per kg of the mixture. Take Cp, the specific heat at constant pressure, for hydrogen as 14.41KJ/Kg-k and for nitrogen 1.042 KJ/Kg-k.

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6.a)

With a simple sketch explain the psychrometric chart. 1 kg of air is taken through a diesel cycle. The air is at 25oC and 1 atmospheric pressure initially. The compression ratio is 15 and the heat added is 1850KJ. Calculate the ideal efficiency and the mean effective pressure.

8.a)

Compare Rankine cycle with bar not cycle and explain why Rankine cycle is best suited to steam power plants. What are the differences between Bell-boleman cycle and vapour compression cycle for refrigeration systems. In a Bell-boleman cycle, air enters the compressor at 1 bar and 10oC and the expender at 5bar and 30oC. Determine the COP of the cycle.

b)

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7.a) b)

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