THERMODYNAMICS
MODULE 1
Introduction
Thermodynamics is a branch of physics that deals with
the laws governing the energy and work of a system,
which may be described as the exchange of heat energy
to and from other forms of energy within a given
system.
• Careful study of these concept is essential for
good understanding of topics in thermodynamics.
• specifically, it defines macroscopic variables, such as
internal energy, entropy, and pressure.
History
The history of thermodynamics as a scientific
discipline generally begins with Otto von Guericke who,
in 1650, built and designed the world's first vacuum
pump and demonstrated a vacuum using his
Magdeburg hemispheres. Magdeburg hemispheres
Shortly after, the physicist and chemist Robert
Boyle had learned of Guericke's designs and, in
coordination with the scientist Robert Hooke, built an air
pump in 1656. Using this pump, Boyle and Hooke noticed
a correlation between pressure, tempe rature, and
volume. In time, they formulated Boyle's Law.
Based on these concepts, an associate of Boyle's
named Denis Papin built a steam digester, which was a
closed vessel with a tightly fitting lid that confined steam
until a high
pressure
was
generated.
The
first
thermodynamic textbook was written in 1859 by William
Rankine. The first and second laws of thermodynamics
emerged simultaneously in the 1850s, primarily out of
the works of William Rankine, Rudolf Clausius, and
William Thomson (Lord Kelvin).
Etymology
The components of the word thermo- dynamic
are derived from the Greek words therme meaning
"heat," and dynamics meaning “power”. The term
thermo-dynamic was first used in January 1849 by
William Thomson, later Lord Kelvin, in the phrase a
perfect thermo-dynamic engine to describe Sadi Carnot's
heat engine. In April 1849, Thomson added an appendix
to his paper and used the term thermodynamic in the
phrase the object of a thermodynamic engine.
Definition
It can be define as the study of energy, energy
transformations and its relation to matter. The analysis
of thermal systems is achieved through the application of
the governing conservation equations, namely
Conservation of Mass, Conservation of Energy.
In other words, it’s science which deals with the
energies possesed by gases and vapours, that includes
the conservation of these energies in terms of heat and
mechanical work and their relation with properties of
system.
CHAPTER 1: FUNDAMENTALS OF POWER PLANT
ENGINEERING
PART 1A: THERMODYNAMICS
THERMODYNAMICS is a branch of physical sciences that
treats especially phenomena of energy and the related
properties of matter, especially of the laws of
transformation of heat into other forms of energy and
vice-versa.
TEMPERATURE AND PRESSURE
TEMPERATURE is an indication or degree of hotness and
coldness and therefore a measure of intensity of heat.
THE SIX TEMPERATURE SCALES
1. Celsius or Centigrade
2. Fahrenheit
3. Kelvin
4. Rankine
5. Reamur
6. Ligem
ABSOLUTE TEMPERATURE – is the temperature
measured from absolute zero.
ABSOLUTE ZERO – Is the temperature at which the
molecules stop moving.
RELATION BETWEEN TEMPERATURE SCALES:
where: R = Rankine
(absolute temp. scale; English)
K = Kelvin (absolute temp scale; SI)
TEMPERATURE INTERVAL – is the difference between
two temperature readings from the same scale, and the
change in temperature through which the body is
heated.
T – absolute temperature
t - normal temperature
THE TEMPEARATURE INTERVAL/CHANGE:
NOTE: 1 degree Celsius = 9/5 degree Fahrenheit and
degree is to be written after the scale to indicate that it
is temperature change.
ISOLATED SYSTEM – is a system in which neither mass
nor energy cross the boundaries and it is not influenced
by the surroundings. (heat and mass is not include)
INTENSIVE PROPERTY – size independent
EXTENSIVE PROPERTY – size does matter (example: mass,
volume, total energy)
NONFLOW PROCESS – is a process that takes place in a
closed system. EXAMPLE: Compressor
STEADY FLOW PROCESS – is a process that takes place in
an open system in which the quantity of matter within
the system is constant. EXAMPLE: Turbine
NON-FLOW WORK – is the work in a non-flow process
THE ABSOLUTE PRESSURE AND GAGE PRESSURE:
Absolute pressure – is the true pressure measured above
a perfect vacuum.
Gage Pressure – is the pressure measured from the level
of atmospheric pressure by most pressure recording
instrument like pressure gage and open-ended
manometer.
Atmospheric Pressure – is the pressure obtained from
barometric reading.
where:
STEADY FLOW WORK – is the work in a steady flow
process.
where: P = pressure
V = volume
LAW OF CONVERSATION OF MASS
NOTE:
THERMODYNAMIC SYSTEM AND SURROUNDINGS:
SYSTEM – is the term given to the collection of matter
under consideration enclosed within a boundary
SURROUNDING – is the region outside the boundary or
the space and matter external to a system.
CLOSED SYSTEM – is a system in which there is no
transfer of matter across the boundary. (control mass,
have only heat enter)
OPEN SYSTEM – is a
system in which there is
a flow of matter through
the boundary. (control
volume, have mass and
hear)
STEADY FLOW SYSTEM
HEAT and ENTROPY:
HEAT – is a form of energy associated with the kinetic
random motion of large number of molecules.
Sensible heat – is the heat needed to change the
temperature of the body without changing its phase.
Latent Heat – is
the
heat
needed by the body to change its phase without
changing its temperature
Latent Heat of Fusion – solid to fusion
Latent Heat of Vaporization – liquid to gas
ENTROPY – is the measure of the randomness of the
molecules of a substance
ENTHALPY AND INTERNAL ENERGY
ENTHALPY – is the heat energy transferred to a
substance at a constant pressure process.
INTERNAL ENERGY – is the energy stored within the
body. It is the sum of the kinetic energies of all its
constituent plus the sum of all the potential energies of
interaction among these particles.
FIRST LAW OF THERMODYNAMICS
Heat is a form of energy, and as what all other
forms of energy is subject to, it follows the law of
conservation of energy.
It means “Heat energy also cannot be created
nor destroyed and can only be transferred to one form
or another”
APPLICATION OF THIS LAW:
The disco, a type of rock but in scientists this rock
contains an energy that produce heat energy when it
undergoes a complete combustion. Actually, some
power plant utilizes this coal to generate electrical
energy for what we called as electricity . They feed this
coal into a boiler furnace and with an assistance of
oxygen and a little heat this creates a combustion in a
form of heat of energy. The heat energy will transfer its
energy to water above it making it into a steam. The
steam will rotate a turbine and that’s a mechanical
energy. This turbine will detect a generator which
converts that energy into electrical energy.
SECOND LAW OF THERMODYNAMICS
The major of second law:
Clausius Statement
- it is impossible for any
system in such a way that
the sole result would be
and energy transfer by
heat from a cooler to a
hotter body.
Kelvin-Planck Statement
- it is impossible for any
system to operate in a
thermodynamic cycle
and deliver a net
amount of energy by
work
to
its
surroundings
while
receiving energy by
heat transfer from a
single reservoir.
Entropy Statement
- it is impossible for any system to operate in a way
that entropy is destroyed
To make it easy we make two easier statement:
High to Low
For any process a natural flow will always be
from higher energy value to lower energy value
Example:
Coffee, the temperature
of coffee is higher than its cup and
as what it says higher energy
value. The temperature of coffee
transferred to the cup which is
cooler lower energy value. That is
why, the cup gets hotter.
Compressed gas in a
balloon, if you open a small
hole in a balloon that is the
outside air enters the balloon
no instead the gas in the
balloon goes outside transfers
its pressure to the outside air
because the gas in balloon has higher pressure than the
outside air a tank of
water connected to an
empty tank with valve in
the middle. When open
the valve, it happens
that the tank level is
lowered transferring its
level to the empty tank.
Topic being discussed in the classroom, that
transfer of ideas comes from the professor which has
more ideas to its students which is lower ideas. Salary
from employer to employee.
Perfect is Impossible
For every real world process there will always be
losses.
Example:
It means you cannot
convert all of your car’s fuel
into mechanical energy which
can rotate your car’s wheels
proof is the gases you see on
the car muffler.
Try bouncing a ball by
first throwing it up to the air
see that as the number of
buttons increases the level of
bounce decreases because of
the
loss
of energy which is transferred
to the ground.
Our foods that is our
source of energy. We can see
the losses through our sweat
urine and solid waste.
THIRD LAW OF THERMODYNAMICS
“as temperature approaches absolute zero, the
entropy of a system approaches a constant minimum”
ENTROPY
measure of disorder and randomness of a
system
Example:
Bottle of carbonated drink, when you share it
you will see bubbles forming at the top surface and when
you open it, the bottle of coke explodes and forms a lot
of bubbles. That is
entropy. The bottle
coke at rest have a
very low entropy,
but the moment you
share it, you have
introduce
kinetic
energy
in
the
molecules inside the
bottle, increasing
the disorder and randomness of the molecules.
“When a pure crystal is cooled approaching
absolute zero. It becomes highly organized/entropy
approaches to zero.”
- it means that any substance with temperature
greater than absolute zero must have positive
amount of entropy. It indicates that a material or
substance requires certain amount of energy to
raise their temperature this is called SPECIFIC
HEAT CAPACITY.
The energy requirement of one kilogram
substance to raise its temperature by one Kelvin.
Example:
It will take more time to warm a wooden glass
than an aluminum glass because aluminum is a better
conductor than wood. Find how much energy is
required?
If A is thermo equilibrium to B, A is also thermo
equilibrium in another body of C, thus B is thermo
equilibrium to C. A=B=C.
Bodes reaching thermal
equilibrium means that
there is already no heat
transfer. Because these
bodies
have
same
amount of heat.
Example
FUN FACTS:
Did you know that
researchers discovered an
object which eventually reached
a point where it can’t get any
colder this is PIN ICE. In which its
atomic magnetic moments
remain random on its absolute
zero. This makes it hold
properties that most things than such as magnetic balls.
ZEROTH LAW OF THERMODYNAMICS
“If two thermodynamic systems are each in
thermal equilibrium with a third, then they are in thermal
equilibrium with each other.
You place a fresh meat
in refrigerator, the next
morning you assume that
meat already reached the
thermal equilibrium with the
refrigerator because basically
heat will flow if is exposed in
unbalanced system.
Measure
the
temperature of room,
you got 27 degree
Celsius, according to
zero
law
of
thermodynamics you
can assume that your
room and the other
things in your room have the same temperature of 27
degree Celsius.
This
law
is
fundamentally applied
in our thermometers. As
we put thermometer in
a hotter body, as the
temperature increases
the mercury expands
and increases in the
tube. The change of height of mercury in the
thermometer indicates the change in temperature.
BOYLE’S LAW
•
•
•
•
it is concerned in pressure and volume.
it is formulated by the famous scientist Robert
Boyle in 1662.
this law relates the expansion and compression of
the gas at constant temperature.
he has a J shaped tube, with a shorted end closed,
and long end open. He put mercury in the tube
and determines the volume of trapped gas, when
he poured some more mercury he found out the
volume of trapped gas decreases while the
change in height increases. Which indicates the
pressure also increases. He find out that volume
is inversely proportional to pressure.
CHARLE’S LAW
•
•
•
it is concerned in volume and temperature.
it is formulated by the famous scientist Jacque
Charles less than two centuries of Boyle’s law in
1800.
this law describes how gases will expand when
heated in his experiment, he prepared a test tube
with drop air under a small mercury plug. It was
immersed in water but with heating coil for
heating and cooled with ice. Upon changing the
temperature the volume of the gas dropped in
the test also changes. Having all the data he then
found out that volume and pressure in the graph.
NOTE:
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