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Human Interventions to Cycles of Nature. P M V Subbarao Professor Mechanical Engineering Department I I T Delhi. New Ideas to Generate New Sources of Energy…. Human Beings An Entity in Carbon Cycle. FIRE, FLAME and TORCH . Fire is a discovery rather than an invention.

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Human interventions to cycles of nature l.jpg

Human Interventions to Cycles of Nature

P M V Subbarao

Professor

Mechanical Engineering Department

I I T Delhi

New Ideas to Generate New Sources of Energy…


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Human Beings An Entity in Carbon Cycle


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FIRE, FLAME and TORCH

  • Fire is a discovery rather than an invention.

  • Homo erectus probably discovered fire by accident.

  • Fire was most likely given to man as a 'gift from the heavens' when a bolt of lightning struck a tree or a bush, suddenly starting it on fire.

  • The flaming touch and the campfire probably constituted early man's first use of 'artificial' lighting.

  • As early as 400,000 BC, fire was kindled in the caves of Peking man.

  • Prehistoric man, used primitive lamps to illuminate his cave.

  • Various Oils were used as fuels.


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The Theory of Producing Steam

  • Water and steam are typically used as heat carriers in heating systems.

  • It is well known that water boils and evaporates at 100°C under atmospheric pressure.

  • By higher pressure, water evaporates at higher temperature - e.g. a pressure of 10 bar equals an evaporation temperature of 184°C.

  • During the evaporation process, pressure and temperature are constant, and a substantial amount of heat are use for bringing the water from liquid to vapour phase.

  • When all the water is evaporated, the steam is called dry saturated.

  • In this condition the steam contains a large amount of latent heat.

  • This latent heat in the dry saturated steam can efficiently be utilised to different processes requiring heat.

  • The steam boiler or steam generator is connected to the consumers through the steam and condensate piping.

  • When the steam is provided to the consumers, it condensate.

  • It can then be returned to the feed water tank.


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The Power Gods

~1760 : James Watt

~1820 : Sadi Carnot

George Brayton & W Rankine ~ 1860


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P M V Subbarao

Mechanical Engineering,

IIT Delhi

Actual Development of Power Generation Cycles

All inventions are need driven …..

However, the final they need for which they are in use is quite different from the need for which they are invented…..

A Tour through Power Era (1600 AD to 2100AD)…..


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P M V Subbarao

Mechanical Engineering,

IIT Delhi

1 GW Solar Space Power Station


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Upto 1800 AD :Generation of Power to pump A Fluid…..


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The Aelopile

  • In 130BC. Hero, a Greek mathematician and scientist is credited with inventing the first practical application of steam power, the aelopile.

  • Simply a cauldron with a lid, the aelopile had two pipes that channeled steam into a hollow sphere.

  • The sphere, which pivoted on the steam pipes, had two nozzles situated on opposite sides of its axis.

  • Thus, the cauldron was fired, the water in it boiled, the steam was channeled into the sphere, and as the steam escaped through the nozzles, the sphere would spin.

  • It was a thought the device and a novelty.


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The Savery Engine

  • Water above the 100oCproduces steam at a pressure greater than one atmosphere.

  • If valves A and B are open but C and D closed, then the steam pressure can pump water to height h2.

  • When the cylinder is full of steam, then valves A and B can be closed and D opened.

  • If cooling water is supplied to the cylinder, then the steam will condense, precipitously dropping its vapour pressure.

  • The resulting vacuum causes water to rise height h1 from the mine shaft provided that height is less than 34 ft.

  • The process can be repeated to pump water from the mine.

  • Thomas Savery patented his mine pump in 1698


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Newcomen Engine

  • In 1712 Thomas Newcomen developed a Steam engine called Atmospheric engine.

  • Steam produced in (a) was conducted through a hand valve (b) to the piston cylinder (C).

  • The steam would push push the piston up to the position shown, allowing the pump rod (d) to descend into a water supply.

  • The valve (e) was then opened to allow a spray of water to condense the steam in the cylinder, causing a vacum to be created.

  • The piston was then pushed down by atmospheric pressure, the pump rod raised, and water pumped up out of the water supply (f).

  • Valve (e) was closed, valve (b) opened, and the process repeated.

  • Line (g) was opened intermittently to allow the condensed steam to flow out of cylinder.

d

©

e

b

f

a


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James Watt

  • The Watt engine worked in 1778, and it consumed 1/3 of the steam that the Newcomen engine used.

  • This engine worked a crossbeam for pumping. The cylinder was closed (by a cap) and heated by a warm steam jacket.

  • The condenser, positioned underground, was cooled and vacuum operated (by a pump).

  • When the piston reached the top of its stroke the exhaust-valve opened and a partial vacuum was produced below the piston

  • Above the piston, at the same time, the entrance of steam helped the atmospheric pressure to drive the piston down.

  • On this stroke the crossbeam raised water in the pump.


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  • When the piston reached the bottom of the stroke the inlet valve closed and an equilibrium valve opened to allow steam to pass from above to below the piston.

  • The engine piston (now with the same pressure above and below) was driven up by the crossbeam and the descent of the very, very heavy pump piston and rod.

  • Note the presence of the condenser and the warm steam jacket that surrounds the cylinder.


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The Steam Engine

  • Huyghens, in l680 : Piston Cylinder Engine -- Gun Powder.

  • Savery's Engine, 1698 -- Atmospheric Steam engine.

  • Denis Papin, 1695 -- invented furnace -- rate of four strokes per minute.

  • Newcomen's Engine, A. D. 1705 -- to drive a separate pump.

  • James Watt, 1765 -- Modern engine.


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James Watt

  • The Watt engine worked in 1778, and it consumed 1/3 of the steam that the Newcomen engine used.

  • This engine worked a crossbeam for pumping. The cylinder was closed (by a cap) and heated by a warm steam jacket.

  • The condenser, positioned underground, was cooled and vacuum operated (by a pump).

  • When the piston reached the top of its stroke the exhaust-valve opened and a partial vacuum was produced below the piston

  • Above the piston, at the same time, the entrance of steam helped the atmospheric pressure to drive the piston down.

  • On this stroke the crossbeam raised water in the pump.


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James WattEngine

  • Watt's Double-Acting Engine, 1784.

  • The Watt Hammer, 1784.

  • Trevithick's Locomotive, 1804

  • The " Atlantlc," 1832.

  • Steam Engine Reached its pinnacle in size when it was called to drive 5 MW electric generator.

Power Generation As A Alternate to Horse or Cattle…..


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Sadi Nicolas Léonard Carnot

  • 1814: After graduating, Carnot went to the École du Génie at Metz to take the two year course in military engineering.

  • 1819: Carnot began to attend courses at various institutions in Paris.

  • 1821: Carnot began the work which led to the mathematical theory of heat and helped start the modern theory of thermodynamics.

  • The problem occupying Carnot was how to design good steam engines.


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The Carnot Cycle

T

s


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All Substance Give the Same Efficiency

  • Carnot knows that the maximum work obtainable from a falling fluid is independent of the substance and depends only on mass flow rate and height through which the fluid falling.

  • He argued by analogy that the maximum work a heat engine can do must also be expressed in terms independent of the working substance.

  • Engines had been proposed and constructed using working substances other than water, with no dramatic improvement in efficiency.

  • Carnot reasoning implies that : to the extent that is it possible to eliminate frictional losses and other sources of inefficient operation, all substances will do the same work for the same temperatures of operation.

  • Carnot believed that heat was an indestructible substance, the heat extracted from the high-temperature source must eventually all be delivered to low temperature condenser.

  • All these situations led to the development of Ideal model for engine using Adiabatic and isothermal processes.

  • He could get an expression for efficiency independent of substance only through this model.


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Realization of Carnot Theorem.

T

Heater

Turbine

Compressor

Cooler

s


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The Carnot Cycle Vs The Natural Cycles

Ability to Perform

Ecological Nuisance


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