Download Concept of Energy

K.J. INSTITUTE
OF ENGG. &
TECH.
BRANCH=
MECHANICAL(A)
SEM=3
SUBJECT:- ENGINEERING
THERMODYNAMICS
Concept of Energy
energy, in physics, the capacity for doing
work. It may exist in potential, kinetic, thermal,
electrical, chemical, nuclear, or other various
forms. There are, moreover, heat and work—i.e.,
energy in the process of transfer from one body
to another. After it has been transferred, energy
is always designated according to its nature.
Hence, heat transferred may become thermal
energy, while work done may manifest itself in
the form of mechanical energy.
Concept of Energy
Energy can be converted from one form to
another in various ways. Usable mechanical or
electrical energy is, for instance, produced by
many kinds of devices, including fuel-burning
heat engines, generators, batteries, fuel cells,
and magnetohydrodynamic systems.
The SI unit of energy is the joule (J) or
newton-meter (N * m). The joule is also the SI
unit of work
APPLICATION of Energy
Texas Industrial Energy Efficiency: Fifty-three
percent of the energy used in Texas is consumed
by the industrial sector.
Water Energy Uses in California: Water use in
California consumes significant amounts of
electrical energy. Preliminary estimates indicate
that total energy used to pump and treat this
water exceeds 15,000 GWh per year, or at least
6.5 percent of the total electricity used in the
State per year.
APPLICATION of Energy
This energy use is expected to increase due to
a growing population, increasing reuse of
wastewater, the remoteness or lower quality of
alternative water sources, and increasingly
stringent treatment requirements due to a
variety of water quality and environmental
protection concerns.
Natural Gas: Natural gas is the second most
used energy source in industry, trailing only
electricity.
APPLICATION of Energy
Solar Energy and its Uses: Solar Energy
information, news and facts. Freesolaronline
gives user a step by step guide for Solar Energy
Education and it's free uses as a permanent.
How the Body Uses Its Food Energy: The
human body is incredibly complex. Every
second, millions of physiological and chemical
reactions take place in order to maintain good
health.
APPLICATION of Energy
The body both creates things (eg. heat,
muscle, proteins, RNA, hair, nails, enzymes,
fat tissue, bones) and breaks things down
(food, stored fat, etc.). These anabolic and
catabolic processes, along with all organs and
systems, need fuel to enable them to
function. The fuel or energy that the body
uses, comes from the food and drink that we
consume in our diet. In a nutshell, food is
human gasoline.
APPLICATION of Energy
Industrial activity is also more common
place in the North which uses more energy
than the agriculture which takes place in
the South.
However the underlying disparity is the
difference in the standards of livings
between the two areas, with most of the
North making do with cars, televisions
etc… and those in the South having to
make do without.
Concept of Entropy
 Entropy is the quantitative measure of
disorder in a system. The concept comes out
of thermodynamics, which deals with the
transfer of heat energy within a system.
Instead of talking about some form of
"absolute entropy," physicists generally talk
about the change in entropy that takes place
in a specific thermodynamic process.
Concept of Entropy
Calculating Entropy :-
In an isothermal process, the change in
entropy (delta-S) is the change in heat (Q)
divided by the absolute temperature (T):
delta- S = Q/ T In any reversible
thermodynamic process, it can be represented
in calculus as the integral from a processes
initial state to final state of dQ / T .
The SI units of entropy are J/K
(joules/degrees Kelvin).
Concept of Entropy
Entropy & The Second Law of
Thermodynamics :One way of stating the second law of
thermodynamics is: In any closed system, the
entropy of the system will either remain constant or
increase. One way to view this is that adding heat to
a system causes the molecules and atoms to speed
up. It may be possible (though tricky) to reverse the
process in a closed system (i.e. without drawing any
energy from or releasing energy somewhere else) to
reach the initial state, but you can never get the
entire system "less energetic" than it started ... the
energy just doesn't have anyplace to go.
APPLICATION of Entropy
The entropy of a system depends on its internal
energy and the external parameters, such as the
volume.
In the thermodynamic limit this fact leads to an
equation relating the change in the internal energy to
changes in the entropy and the external parameters.
This relation is known as the fundamental
thermodynamic relation.
 If the volume is the only external parameter, this
relation is:-
APPLICATION of Entropy
Since the internal energy is fixed when one
specifies the entropy and the volume, this relation is
valid even if the change from one state of thermal
equilibrium to another with infinitesimally larger
entropy and volume happens in a non-quasistatic
way (so during this change the system may be very
far out of thermal equilibrium and then the entropy,
pressure and temperature may not exist).
The fundamental thermodynamic relation implies
many thermodynamic identities that are valid in
general, independent of the microscopic details of
the system. Important examples are the Maxwell
relations and the relations between heat capacities.
Concept of Exergy
In thermodynamics, the exergy of a system is the
maximum useful work possible during a process that
brings the system into equilibrium with a heat
reservoir.
When the surroundings are the reservoir, exergy is
the potential of a system to cause a change as it
achieves equilibrium with its environment. Exergy is
the energy that is available to be used. After the
system and surroundings reach equilibrium, the
exergy is zero. Determining exergy was also the first
goal of thermodynamics.
Concept of Exergy
The term "exergy" was coined in 1956 by Zoran
Rant (1904–1972) by using the Greek ex and ergon
meaning "from work", but the concept was
developed by J. Willard Gibbs in 1873.
The destroyed exergy has been called anergy.
For an isothermal process, exergy and energy are
interchangeable terms, and there is no anergy.
Application of Exergy
Application of exergy to unit operations in chemical
plants was partially responsible for the huge growth
of the chemical industry during the 20th century.
During this time it was usually called availability or
available work.
As a simple example of exergy, air at atmospheric
conditions of temperature, pressure, and composition
contains energy but no exergy when it is chosen as
the thermodynamic reference state known as
ambient.
Application of Exergy
 Individual processes on Earth like combustion in a
power plant often eventually result in products that
are incorporated into a large atmosphere, so defining
this reference state for exergy is useful even though
the atmosphere itself is not at equilibrium and is full
of long and short term variations.
In recent decades, utilization of exergy has spread
outside of physics and engineering to the fields of
industrial ecology, ecological economics, systems
ecology, and energetics. Defining where one field
ends and the next begins is a matter of semantics,
but applications of exergy can be placed into rigid
categories.
Application of Exergy
EXERGY develop, design and manufacture the
most efficient Organic Rankine Cycle (ORC) biomass
plants, using the innovative and pioneering Radial
Outflow Turbine (ROT).
Industrial Process Heat Recovery is an area ideally
suited to the Organic Rankine Cycle (ORC). As
opposed to steam heat recovery systems, ORC can
give better efficiency for lower temperature
applications, as well as eliminating the requirement
for water treatment and make up.EXERGY use the
innovative and pioneering Radial Outflow Turbine
(ROT) technology in the development of our heat
recovery plants.
Application of Exergy
The Organic Rankine Cycle (ORC) is ideally suited
for exhaust heat recovery from both engines and
small gas turbines. As opposed to steam heat
recovery systems, ORC can give better efficiency for
modern low temperature engines, as well as
eliminating the requirement for water treatment and
make up.
EXERGY use the innovative and pioneering Radial
Outflow Turbine (ROT) technology in the
development of our heat recovery plants.