JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year FUNDAMENTALS OF MECHANICAL ENGINEERING Previous Question Paper (March - 2021 - R16)
Answer any five questions. All questions carry equal marks.
Main
Explain the following:
Fossil fuels
Answer
- Fossil fuels are non-renewable energy sources formed from the remains of ancient plants and animals that were buried under layers of sediment and subjected to intense heat and pressure over millions of years.
- The primary types include coal (solid), petroleum/crude oil (liquid), and natural gas (gaseous).
- These fuels are primarily composed of hydrocarbons. When burned, the chemical energy stored in their molecular bonds is released as heat energy through the process of combustion.
- Advantages: They are currently abundant, relatively easy to transport, and provide a high energy density, making them reliable for base-load power generation and transportation.
- Disadvantages: They are finite resources that cannot be replenished on a human timescale. Their combustion is the leading cause of greenhouse gas emissions (CO2), contributing significantly to global warming, air pollution, and acid rain.
Nuclear fuels
Answer
- Nuclear fuels are materials that can be consumed by nuclear reactors to produce energy through nuclear fission or nuclear fusion. The most common fuel used in commercial power plants is Uranium-235.
- In a fission reaction, a neutron strikes the nucleus of a heavy atom (like Uranium or Plutonium), causing it to split into smaller nuclei. This process releases a massive amount of energy in the form of heat, along with additional neutrons that sustain a chain reaction.
- This heat is transferred to a coolant (usually water) to generate steam, which drives turbines to produce electricity.
- Advantages: Nuclear power is a low-carbon energy source that provides a very high energy output from a small amount of fuel. It is highly efficient and capable of providing continuous, stable baseload power without emitting greenhouse gases during operation.
- Disadvantages: The primary concerns involve the management and long-term storage of radioactive waste, the high capital cost of plant construction, and the potential for catastrophic accidents if safety protocols are breached.
What are the limitations of First law of thermodynamics?
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Compare the first law of thermodynamics with its corollaries.
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At 1.2 MPa, 250°C steam enters into a turbine and expands to 300°C. Determine the work output of turbine for 10 kg/s flow rate steam. [15]
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Explain the function of fusible plug, and where is it located in a Babcock and Wilcox boiler? [15]
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An ideal diesel cycle operates on 1 kg of standard air with an initial pressure of 0.98 bar and a temperature of 35°C. The pressure at the end of compression is 33 bar and the cut-off is 6% of the stroke. Determine: (a) compression ratio, (b) percentage clearance, and (c) heat supplied. [15]
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During testing of single cylinder two-stroke petrol engine, following data were obtained—brake torque = 640 Nm; cylinder diameter = 21 cm, speed = 250 rpm; stroke = 28 cm; m.e.p. = 5.6 bar; oil consumption = 8.16 kg/hr; C.V. = 42,705 kJ/kg. Determine: (a) mechanical efficiency, (b) indicated thermal efficiency, and (c) Brake specific fuel consumption. [15]
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What is multistage compression? What are the advantages of it?
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Derive the expression for work done in multistage compression.
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Explain standard vapor compression refrigeration cycle with T-S and P-H diagram. What is the effect of sub-cooling on the performance of vapor compression refrigeration system? [15]
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