Process & Cycles

P M V SubbaraoProfessor

Mechanical Engineering Department

I I T Delhi

Mathematical Models for Happening …

Thermodynamic Process

• The path of succession of states through which the system passes is called the process.

• Quasi-equilibrium process is a collection of changes, in which the deviation from thermodynamic equilibrium is infinitesimal.

• All the states the system passes through during a quasi-equilibrium process may be considered as equilibrium states.

Development of Low Emission Diesel Engine

Description of Happening in an Engine Cylinder

Selection of Instrument for Exact Capture of A Happening to A System

The characteristic equation of nth order Pressure Gauge:

)(........... 012

21

1 txyaDyayDayDayDa nn

nn

)(....... 012

2

21

1

1 txyadt

dya

dt

yda

dt

yda

dt

yda

n

n

nn

n

n

Laplace Transformations for Instruments

sXsYasaasasas nn

nn

012

21

1 ...........

012

21

1 ...........

1

asaasasassX

sY

nn

nn

0

1 :

asX

sYOrderZero

01

1 :

asasX

sYOrderFirst

012

2

1 :

asaassX

sYOrderSecond

Diagnosis of The Happening for Better Emissions

Process Executed by A Control Volume

Change of State in A Control Volume

Thermodynamic Process

• During a quasi-equilibrium or quasi-static process, the system remains practically in equilibrium at all times.

• Quasi-equilibrium work-producing devices deliver the maximum work.

• Theoretical description of processes is possible by keeping any one thermodynamic property may be held constant.

• Process Property • isobaric pressure • isothermal temperature • isochoric volume

• Adiabatic No Heat Transfer

Representation of Thermodynamic Processes

Thermodynamic Cycle• A process (series of connected processes) with identical end

states.

• When a system in a given initial state goes through a number of different changes of state or processes and finally returns to its initial state, the system has undergone a cycle.

• At the conclusion of a cycle, all the properties have the same value they had at the beginning.

Cyclic Working of Left Ventrical

Energy Cycles in Nature

• The sun is the source of all that happens on our earth.

• Every form of energy, except for atomic energy, can be traced back to the sun.

• The earth is at the best possible distance from the sun for the sun's heat to provide many systems on earth.

• These systems are atmosphere, hydrosphere, Biosphere etc.

• Energy from sunlight is used by these systems to created many natural cycles.

• This energy is continuously converted/transferred during these cycles.

Various Cycles of Nature

• Water Cycle

• Wind Cycle

• Life Cycles of Animals

• Life Cycles of Plants

• Seasonal Cycles

• Planetary Cycles

• Rock Cycles

• Geo-Physical Cycles

• Chemical Cycles

• Disease Cycles

Water Cycle

• All of the water that is on the earth has always been here.

• Earth never gets water added to it--nor does water disappear from the earth.

• Water is constantly recycled in a process known as the hydrologic or water cycle.

• Why?

• Only 3% is fresh water.

• About 1/2 of 1% of the water on earth is groundwater.

• Only about 1/100 of 1% of the water on earth is in the rivers and lakes.

• Water is essential to life on earth, so it is important to have continuous occurrence of water cycle

Hydrological Cycle

Seasonal Variation of Kinetic Energy of Wind

Rock Cycle

Energy Interaction in Rock Cycle

Rock Cycles

• Rocks are continually circulating in the mantle just below the crust of the earth.

• They are sometimes thrust up into the crust due to convection currents.

• Rocks can also reach the surface when they are spit out by volcanoes.

• Once on the surface of the earth, rocks cool down.

• Over time, they are broken up or worn down by weather, and the fragments are carried back to the ocean by way of wind, rain, and the flow of rivers and streams.

• All of these small pieces of rock collect as sediment at the bottom of seas and oceans.

• The sediment solidifies into rock and is drawn back down in to the mantle at subduction zones or reaches the surface again as sea levels change or plates collide

The Carbon Cycle

CO2 Cycle

Life Cycle an Ozone

New Ozone Cycle

Plastics that never exhaust the resources of the earth

Energy sources such as the fossil fuels of coal, petroleum, and natural gas are really just ancient stockpiles of the sun's energy stored in plants and the animals that ate those plants

that are thousands or millions of years old.

Engineering Cycles

• Carnot Cycle

• Lenoir Cycle

• Otto Cycle

• Sterling Cycle

• Atkinson Cycle

• Diesel Cycle

• Brayton cycle

• Rankine Cycle

• Vapour Compression Refrigeration Cycle

• Vapour Absorption Refrigeration Cycle

The substance contained by the system undergoes a thermodynamic process/cycle

The potential of A Process/Cycle Depends on the substance used by (present in ) the system.

•How to begin the description of A Substance?

•Development of Equation of state…•Is it possible to develop a single EOS model for any substance?