JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech IV BASICS OF THERMODYNAMICS Previous Question Paper (July - 2021 - R16)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
Define the following with examples: i) Open system ii) Closed system iii) Isolated system
Answer
An open system is a system where both mass and energy can cross the system boundary. An example is a steam turbine, where steam enters and leaves the control volume while performing work.
A closed system (or control mass) is a system where only energy (heat and work) can cross the boundary, but mass cannot. An example is a gas compressed by a piston in a cylinder where the boundary is fixed or moving but sealed.
An isolated system is a system that exchanges neither mass nor energy with its surroundings. An example is a perfectly insulated, rigid container holding a fluid, representing a universe in miniature.
Distinguish the following terms: i) Thermal and thermodynamic equilibrium ii) Exact and Inexact differentials.
Answer
Thermal vs. Thermodynamic Equilibrium: Thermal equilibrium occurs when the temperature of a system is uniform throughout and does not change with time, implying no heat transfer. Thermodynamic equilibrium is a more comprehensive state where the system is simultaneously in thermal, mechanical, and chemical equilibrium, meaning there are no gradients in temperature, pressure, or chemical potential.
Exact vs. Inexact Differentials: An exact differential (denoted by d) represents a change in a state function, such as pressure (dP) or temperature (dT), where the integral depends only on the end states, not the path taken. An inexact differential (denoted by δ) represents path-dependent quantities like work (δW) or heat (δQ), where the total value depends on the specific process path between two states.
Prove that heat transfer is a path function.
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State Zeroth law of thermodynamics. The readings tA and tB of two Celsius thermometers A and B agree at ice and steam point, but elsewhere are related by the equation
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Define the following: i) Thermal Energy Reservoir(TER) ii) COP of Heat pump.
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A fish freezing plant requires 40 tons of refrigeration. The freezing temperature is -35C, while the ambient temperature is 30C. If the performance of the plant is 20% of the theoretical reversed Carnot cycle working with in the same temperature limits, Calculate power required.
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Write the first law of thermodynamics equation for closed system undergoing a non cyclic process and show that internal energy is property.
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Steam expands through a turbine in a steady flow adiabatic process. The mass flow rate of the steam is 1.36 kg/s. The entering state of steam is 34.48 bar and 538C, while the existing state is 6.896 bar and 294C. Neglecting the changes in kinetic and potential energies, find the power output for the turbine. Assume Cp for steam as 2.01 kJ/kg K.
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Define i) Dry bulb temperature ii) Wet bulb temperature iii) Relative humidity.
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The pressure and temperature of mixture of 4kg of O2 and 6kg of N2 are 4 bar and 27C respectively. For the mixture, determine the mole fraction of each component, specific gas constant and average molecular weight.
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Derive the expression for specific heat at constant pressure and constant volume for mixture of gases.
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A mixture of gases comprises 30% CO, 15% CO2 and 55% H2. Find the gravimetric analysis specific gas constant and molecular weight of the mixture.
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Derive an expression for Otto cycle efficiency with usual notation.
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In a Diesel cycle, air at 0.1 MPa and 300K is compressed adiabatically until the pressure rises to 5 MPa. If 700KJ/Kg of energy in form of heat is supplied at constant pressure, determine compression ratio, cut off ration, thermal efficiency and mean effective pressure.
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Explain the effect of mean effective pressure on thermal efficiency of air standard cycles.
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Explain the working principle of Vapour compression cycle with neat diagram.
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