An Energy Source must be Bountiful……

P M V SubbaraoProfessor

Mechanical Engineering Department

I I T Delhi

Conversion of A Resource into Useful Form

4th Law & A Two Way implementation

• Conversion of available resource into usable form of resource.– Combustion & Heat Transfer

– Thermodynamics – Carnot & Rankine

• Utilization of usable form into Mechanical Power– Parson’s Approach

– De Laval’s Approach

4th Law of thermodynamics

• Matter cycles in regions of energy flow; such cycles, visible in natural complex structures, including those of life, occur as limited material resources scramble to provide a vehicle for entropy export. {Schneider & Sagan, 2005}

Entropy Vehicles on Earth

• Biomass energy: 4.3 x 103EJ/year

• Wind, waves convection and currents: 11.7 x 103EJ/year• Convection in volcanoes and hot springs: 9.36 EJ/year

• Ocean tides: 93.6 EJ/year

• Direct conversion to heat in air, earth and oceans: 2.55 x 106EJ/year

A tree converts disorder to order with a little help from the Sun

• The building materials are in a highly disordered state - gases, liquids and vapors.

• The tree takes in carbon dioxide from the air, water from the earth as well as a small amount from water vapor in the air.

• From this disordered beginning, it produces the highly ordered and highly constrained sugar molecules, like glucose.

The radiant energy from the Sun gets transferred to the bond energies of the carbons and the other atoms in the glucose molecule.

In addition to making the sugars, the plants also release oxygen which is essential for animal life.

First Law Analysis of Photosynthesis:SSSF

First Laws for furnace in SSSF Mode:

m CO2

m water

m vegetation

Q

Q

W

m Oxygen0dt

dmcv

0dt

dEcv

CV

out

out

in

inCV WgzV

hmgzV

hmQ

22

22

Conservation of Mass:

outin mm

First Law Analysis of Photosynthesis:SSSF

Species Conservation Equation: 26222 666 OOCHOHCO

First Laws for furnace in SSSF Mode:

CV

Oveg

OHCO

CV

WgzV

hmgzV

hm

gzV

hmgzV

hmQ

2

22

2

2

2

2

22

22

Conservation of Mass: 0222

OvegetationOHCO mmmm

Fossilization : Bio - Chemical

• Peat deposition is the first step in the formation of coal.

• The humid climate of the Carboniferous Period (360 to 286 million years ago), which favoured the growth of huge tropical seed ferns and giant nonflowering trees, created the vast swamp areas

• As the plants died and fell into the boggy waters, which excluded oxygen and killed bacteria, they partially decomposed but did not rot away.

• The vegetation was changed into peat, some of which was brown and spongy, some black and compact, depending on the degree of decomposition.

OHCOCHOHCOHC 22451085106 222

First Law Analysis of Formation of Peat :SSSF

Species Conservation Equation:

First Laws for furnace in SSSF Mode:

CV

COCH

peatveg

CV

WgzV

hmgzV

hm

gzV

hmgzV

hmQ

2

2

4

2

22

22

22

Conservation of Mass:

W

m CO2

m vegetation

Q

Q

m Peat

m CH4

024

COCHpeat mmmm vegetation

OHCOCHOHCOHC 22451085106 222

Peat

• Peat is The first stage in the formation of coal from wood (cellulose).

• Rate of reaction : 3cm layer per 100 years.

• Light brown fibrous at the surface and colour becomes darker with depth.

• Typical Composition:

• Moisture : 85%, Volatile Matter : 8 %, Fixed Carbon : 4%, Ash : 3%.

• Calorifica Value : 650 kCal/kg.

• Occurrence of Peat : Niligiri Hills and banks of Hooghly.

• Sun dried Peat is very useful as a fuel with following composition:

• Moisture : 20%, Volatile Matter : 50 %, Fixed Carbon : 25%, Ash : 5%

• Bulk density : 300 kg/m3 and low furnace temperature and efficiency.

• Products from Peat: Charcoal,Producer gas.

Secondary Transformation : Geo-Chemical Stage

• The decayed vegetation was subjected to extreme temperature and crushing pressures.

• It took several hundred million years to transform the soggy Peat into the solid mineral.

• 20 m of compacted vegetation was required to produce 1 m seam of coal.

• This is called as coalification or coal forming.

• The extent to which coalification has progressed determines the rank of coal.

Modeling of Coalification

Peat to Enriched peat: (mostly due to heating)

OHOOHCOHC 22318195108 2324819

lignite to Sub-bituminous: (mostly due to pressure &heating)

OpHzOOHyCOHxC 224163531819 Enriched peat to lignite: (mostly due to pressure &heating)

OpHzOOHyCOHxC 224194941635

Sub-bituminous to High volatile Bituminous:

OpHzOOHyCOHxC 223235741949

High Volatile Bituminous to Medium volatile Bituminous:

4221236432357 qCHOpHzOOHyCOHxC

Medium Volatile Bituminous to Low volatile Bituminous:

4225.0216612364 qCHOpHzOOHyCOHxC

Low Volatile Bituminous to semi Anthracite:

4225.016675.02166 qCHOpHzOOHyCOHxC

Semi Anthracite to Anthracite:

42225.011725.01667 qCHOpHzOOHyCOHxC

Constant Pressure Steam Generation Process

Constant Pressure Steam Generation:

vdpdhq =0

Theory of flowing Steam Generation

vdpdhq

qHVm fuelSG

Knowledge for Use & Conservation

Constant Pressure Steam Generation: dhHVm fuelSG

Practical way of understanding the use of fuel energy:

dTcHVm pfuelSG

Is it possible to get high temperature with same amount of burnt fuel?

What decides the maximum possible increase for same amount of burnt fuel?

Carnot’s View of Rankine Cycle

dss

hTdsq

p

constant

constantps

hT

Creation of Temperature at constant pressure : p

dhTdsq

Steam Generation : Expenditure Vs Wastage

h

s

Liquid

Liquid +Vapour

Vapour

Variable Pressure Steam Gneration

s

h

Specific Specific Specific

Pressure Enthalpy Entropy Temp VolumeMPa kJ/kg kJ/kg/K C m3/kg

1 1 3500 7.79 509.9 0.3588

2 5 3500 7.06 528.4 0.071493 10 3500 6.755 549.6 0.03562

4 15 3500 6.582 569 0.023695 20 3500 6.461 586.7 0.017766 25 3500 6.37 602.9 0.01422

7 30 3500 6.297 617.7 0.011878 35 3500 6.235 631.3 0.0102

Analysis of Steam Generation at Various Pressures

More Availability of Energy

             Specific Specific Specific

Temp Pressure Volume Enthalpy EntropyC MPa m3/kg kJ/kg kJ/kg/K575 5 0.0762 3608 7.191575 10 0.03701 3563 6.831575 12.5 0.02917 3540 6.707575 15 0.02393 3516 6.601575 17.5 0.02019 3492 6.507575 20 0.01738 3467 6.422575 22.5 0.0152 3441 6.344575 25 0.01345 3415 6.271575 30 0.01083 3362 6.138575 35 0.008957 3307 6.015