JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year THERMAL SCIENCE Previous Question Paper (October - 2020 - R13)
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Main
Enumerate the Isothermal process from thermodynamic point of view?
Answer
An isothermal process is a thermodynamic process in which the temperature of the system remains constant throughout the entire operation (dT = 0). For an ideal gas, since the internal energy is a function of temperature only, the change in internal energy (dU) is zero.
Key characteristics include:
- The process follows the relation pV = constant, derived from the ideal gas lawpV = mRTwhere T is constant.
- According to the First Law of Thermodynamics, Q = ΔU + W. Since ΔU = 0, all heat added to the system is converted entirely into work done by the system (Q = W).
- The process must occur very slowly (quasi-statically) to ensure thermal equilibrium with the surroundings at all times, allowing for heat transfer to maintain a constant temperature.
A mass of gas is compressed in a quasi-static process from 80 kPa, 0.1 m3 to 0.4 MPa, 0.03 m3. Assuming that the pressure and volume are related by
Answer
Given data:
Initial state:
Final state:
First, determine the polytropic index
Taking the natural logarithm on both sides:
The work done in a polytropic process is given by:
The work done is
Explain the importance of concept of continuum in thermodynamic approach?
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If a gas of volume 6000 cm3 and at pressure of 100 kPa is compressed quasistatically according to
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Compare the thermal efficiency and mean effective pressure of Otto and dual cycles?
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A piston cylinder device operates 1kg of fluid at 20atm pressure with initial volume is 0.04m3. Fluid is allowed to expand reversibly following
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Explain the Joule’s experiment with a neat sketch?
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0.44kg of air at 180oC, expands adiabatically to 3 times its original volume and during the process there is a fall in temperature to 15oC. The work done during the process is 52.5kJ. Calculate Cp and Cv?
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State the Third law of thermodynamics? Explain the importance.
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0.2 kg of air at 300oC is heated reversibly at constant pressure to 2066 K. Find the available and unavailable energies of the heat added. Take
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What do you understand by entropy principle?
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0.5 kg of air executes a Carnot power cycle having a thermal efficiency of 50%. The heat transfer to the air during isothermal expansion is 40 kJ. At the beginning of the isothermal expansion the pressure is 7 bar and the volume is 0.12 m3. Determine the maximum and minimum temperatures for the cycle in Kelvin, the volume at the end of isothermal expansion in m3 and the work, heat transfer for each of the four processes in kJ.
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Explain the dual cycle working principle with P-V and T-S diagram.
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Compare the thermal efficiency and mean effective pressure of Otto and dual cycles.
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With a neat sketch explain the working principle of a simple carburetor.
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Discuss the various characteristics of an efficient cooling system.
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