MECHANICAL ENGINEERING SHORT NOTES [ POWER PLANT ] ~ MECHANICAL ENGINEERING SHORT NOTES

MECHANICAL ENGINEERING SHORT NOTES

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Subject- Power Plant

Topic covered-

Basic terms
Gas Turbine
Rankine cycle
Compressor
Steam Turbines
Boiler and its components

And many more terms, key points, and concepts.

Electricity is the only form of energy that is easy to generate, transport, use, and control. Electricity in bulk quantities is generated in power plants. Nuclear and Thermal power plant has steam as working fluid and have many similarities in construction and layout whereas Gas turbine uses air as working fluid.

The thermal power plant is the major source of electricity production as it generates around 65% of the world's total electricity.

Gas Turbine-

It works on the Brayton Cycle. It has two reversible adiabatic processes and two reversible isobar processes.

The working fluid is air and it doesn't go under phase change like in the Rankine cycle.

Gas Turbine has certain advantages-

Less installation cost
Quick start and stop
Less installation Cost
Quick response to load variation

Rankine Cycle-

The working fluid is water and undergoes phase change during the cycle. Two reversible isentropic and two constant pressure processes. The pump work is small as compared to the turbine work and often it is neglected because of pump handles water in a liquid state.

Economizer-

An economizer is a heat exchanger which raises the temperature of the feedwater leaving the highest pressure feedwater heater to about the saturation temperature corresponding to the boiler pressure. By utilizing these gases in heating feedwater, higher efficiency and better economy were achieved, and hence the heat exchanger was called “economizer”. The economizer is generally placed between the convective superheater and the air preheater.

Superheater-

The superheater is a heat exchanger in which heat is transferred to the saturated steam to increase its temperature. It raises the overall cycle efficiency. In addition, it reduces the moisture content in the last stages of the turbine and thus increases the turbine internal efficiency.

Reheater-

The design considerations for reheaters are similar to those for superheaters. Although the steam outlet temperatures are about the same, the overall temperatures are lower and the steam pressures are about 20−25% of those in the superheaters.

The pressure stresses are, therefore, lower and a lower grade steel alloy is tolerated. In addition, a larger tube diameter with higher stresses may be used to reduce the pressure losses in the reheater. The reheater is usually located above the primary or convective superheater in the convective zone of utility boilers.

COCHRAN BOILER

This is a fire tube boiler of vertical type, capable of generating steam up to a pressure of 20 bar. The efficiency of such boilers ranges between 70 and 75%.

LANCASHIRE BOILER

It is a horizontal fire tube boiler, Two fire tubes run throughout the length of the boiler. Working pressure in these boilers is in the range of 0.7 MPa to 2 MPa and the efficiency of the boiler is about 65% to 70%.

CORNISH BOILER

This is a horizontal fire tube boiler having a single flue gas tube. The general arrangement is very similar to the Lancashire boiler. These boilers are generally capable of producing steam up to the rate of 1350 kgƒhr and maximum steam pressure up to 12 bar.

LOCOMOTIVE BOILERS

These boilers were invented for getting steam to run a steam engine used in locomotives. These are fire-tube type of boilers. It has basically three parts i.e. smoke box, shell, and firebox.

VELOX BOILER

Velox boiler is a fire tube boiler having forced circulation.

BABCOCK AND WILCOX BOILER

It is a water tube boiler suitable for meeting the demand for increased pressure and large evaporation capacity or large-sized boiler units.

STIRLING BOILER

This is a water tube boiler in which bent tubes are connected to three or four drums together. Such boilers are capable of generating steam up to maximum pressure of 60 bar.

HIGH-PRESSURE BOILER

High-pressure boilers generally operate in the supercritical range. The need for such boilers is felt because high pressure and temperature of the steam generated in the boiler improves plant efficiency. forced circulation is maintained by employing a suitable pump.

BENSON BOILER

It is a water tube boiler capable of generating steam at supercritical pressure.

Power Plant is one of the important subjects in terms of marks in different examinations. By putting some extra effort it is easily possible to solve all the problems related to it.

All important concepts and formulas are also present there. It will help you in steady quick revision and save your precious time so that you can practice more problems related to Power Plant.

Always refer to standard textbooks for doubt.

Here are some sample snaps for the Power Plant. The pdf contains a total 18 no. of pages that cover every aspect of the Power Plant.

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