JNTU
JNTU B.Tech II THERMODYNAMICS Previous Question Paper (February - 2024 - R13)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions. iv) Use of steam tables, Mollier chart and psychrometric chart is permitted.
PART - A
With example differentiate intensive and extensive properties.
Answer
Intensive properties are independent of the mass of the system (e.g., pressure, temperature), while extensive properties depend on the mass or size of the system (e.g., total volume, total internal energy).
Write the steady flow energy equation and reduce it for a nozzle and a turbine.
Answer
The steady flow energy equation is: h1 + (v1^2)/2 + gz1 + Q = h2 + (v2^2)/2 + gz2 + W. For a nozzle (adiabatic, no work): h1 + (v1^2)/2 = h2 + (v2^2)/2. For a turbine (adiabatic, negligible kinetic/potential energy changes): W = h1 - h2.
List any two limitations of first law of thermodynamics.
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Determine the efficiency of a Carnot engine and the COP of a Carnot refrigerator, when both are working between the same temperature limits of 150K and 300K.
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Relate gas constant and universal gas constant and hence find the value of gas constant for CO2.
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Write a brief note on critical point and triple point of water.
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State Dalton’s law of partial pressure.
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A sling psychrometer reads 40°C dry bulb temperature and 36°C wet bulb temperature. Find the humidity ratio and relative humidity.
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Represent Otto cycle on P-V and T-S coordinates.
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What is refrigeration effect? Define a tonne of refrigeration.
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PART - B
Derive an expression for the work done in a non-flow reversible isothermal process.
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A mixture of gases expands at constant pressure from 1 MPa, 0.03 m3 to 0.06 m3 with 84 kJ of positive heat transfer. There is no work other than that done on a piston. Find the change in stored energy for the mixture. If the same mixture expands through the same state path, while a stirring device does 21 kJ of work on the system, find the work and heat transfer for the process.
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Compare and contrast work and heat. Also provide sign convention for them.
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A blower handles 1 kg/s of air at 20°C and consumes a power of 15 kW. The inlet and outlet velocities of air are 100 m/s and 150 m/s respectively. Find the exit air temperature, assuming adiabatic conditions. Take Cp for air as 1.005 kJ/kgK.
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Prove the equivalence of Kelvin Planck and Clausius statements of second law of thermodynamics.
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Define: entropy, availability, irreversibility.
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What is Clausius inequality? Highlight its significance.
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A domestic food freezer maintains a temperature of -12°C, the ambient temperature is 35°C. If heat leaks into the freezer at the rate of 2 kJ/s, determine the least power necessary to pump this heat out continuously. Also find the COP of this system and the COP if the system works as a heat pump, between the same temperature limits.
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A cylinder contains 1 m3 of air at 100 kPa and 100°C. This air is compressed to a volume of 0.25 m3, the final pressure being 600 kPa. Determine: mass of the gas, polytropic index 'n' for the compression, work transfer, heat transfer and change in internal energy.
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Write short note on steam turbines and Mollier chart.
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Draw and explain P-T diagram for water.
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Atmospheric air is a mixture of 6 kg of O2 and 9 kg of N2, existing at 300 kPa pressure and temperature of 25°C. Determine for the mixture: (a) the mole fraction of each constituent, (b) the equivalent molecular weight, (c) the equivalent gas constant, (d) the values of Cp and Cv. If the mixture is heated at constant volume to 40°C, find the changes in internal energy, enthalpy and entropy of the mixture. Take γ for O2 and N2 to be 1.286 and 1.4 respectively.
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Write a brief note on psychrometric chart and its use.
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A sling psychrometer reads 40°C DBT and 35°C WBT. Find the humidity ratio, relative humidity, dew point temperature, specific volume and enthalpy of air.
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Derive an expression for the efficiency of air standard Otto cycle.
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With a simple layout explain the Bell-Colleman refrigeration cycle.
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Write a brief note on the commonly used refrigerants and the essential properties of a good refrigerant.
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