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Title: Basic Engineering Thermodynamics U3MEA02

1
Basic Engineering Thermodynamics U3MEA02

Prepared by
Mr.N.Dilip Raja, Assistant Professor,
Department of Mechanical Engineering,
VelTech Dr. RR Dr. SR Technical University.

2
UNIT - 1
3
SYSTEM

In thermodynamics system is a closed region in
space or a body upon which experiments or study
is conducted.
Types of system
Open system Energy transfer and mass transfer
take place. Eg Pump, compressor, turbine.
Closed system Only energy transfer take place
but no mass transfer. Eg Earths atmosphere,
inflated baloon
Isolated system Neither energy transfer nor mass
transfer take place. Eg Flask

Surrounding Every thing apart from system is
called as surroundings
Universe Both system and surrounding together is
called as universe
Boundary The invisible layer which separates
system and surrounding is called boundary
Control volume The maximum volume occupied by a
system is called control volume

5
PROPERTIES

In thermodynamics, properties are the quantities
used to determine the state of a system
Types of properties
Intrinsic properties These depend upon mass of
the system. Eg mass, density, specific heat,
etc.
Extrinsic properties These do not depend upon
mass of the system. Eg pressue, temperature,
time, etc.

State In thermodynamics state is the term used
to denote the present conditions of the system
Process If a system experiences changes in
state, then it is called as process
Cycle A series of process in which the initial
and final states are the same is called as a
cycle.
Types of cycle
Open cycle
Closed cycle

Equilibrium In thermodynamics equilibrium is a
term used to determine whether there is a process
taking place in a system. If there is no changes
in states of a system, then it is said to be in
equilibrium
Types of equilibrium
Chemical
Mechanical
Thermodynamic

8
HEAT

Heat is the form of energy transfer taking place
in a system by virtue of temperature difference.
It is denoted by the symbol Q.
Its unit is J (joules). Rate of heat transfer is
W.
Sign conversion
for heat given to a system
- For heat taken from a system

9
WORK

Work is the form of energy transfer taking place
in a system because of change in volume.
It is denoted by the symbol W.
Its unit is J (joules).
Sign conversion
for work taken from a system
- For heat given to a system

10
INTERNAL ENERGY

The energy available within a system is called as
internal energy
It is denoted by the symbol U.
Change in internal energy is denoted by the
symbol ? U.
Its unit is J (joules).

11
ENTHALPY

Enthalpy is a measure of the total energy of a
system. It includes the system's internal energy,
as well as its volume and pressure.
It is denoted by the symbol H.
Change in internal energy is denoted by the
symbol ? H.
Its unit is J (joules).
H U pV

12
LAWS OF THERMODYNAMICS

Zeroth law of thermodynamics
First law of thermodynamics
For open system ?W ?Q
For closed system Q W ?U

13
STEADY FLOW ENERGY EQUATION
14
UNIT - 2
15
SECOND LAW OF THERMODYNAMICS

Kelvin statement It is impossible, by means of
inanimate material agency, to derive mechanical
effect from any portion of matter by cooling it
below the temperature of the coldest of the
surrounding objects.
Clausius statement Heat can never pass from a
colder to a warmer body without some other
change, connected therewith, occurring at the
same time.

16
CARNOT THEOREM

Carnots theorem(1824) is a principle that limits
the maximum efficiency for any possible engine.
The efficiency solely depends on the temperature
difference between the hot and cold thermal
reservoirs. Carnot's theorem states
All irreversible heat engines between two heat
reservoirs are less efficient than a Carnot
engine operating between the same reservoirs.
All reversible heat engines between two heat
reservoirs are equally efficient with a Carnot
engine operating between the same reservoirs.
In his ideal model, the heat of caloric converted
into work could be reinstated by reversing the
motion of the cycle, a concept subsequently known
as thermodynamic reversibility. Carnot however
further postulated that some caloric is lost, not
being converted to mechanical work. Hence no real
heat engine could realise the Carnot
cycle reversibility and was condemned to be less
efficient.

17
CARNOT CYCLE
18

The Carnot cycle when acting as a heat engine
consists of the following steps
Reversible isothermal expansion of the gas at the
"hot" temperature, T1 (isothermal heat addition
or absorption). During this step (1 to 2 on
Figure 1, A to B in Figure 2) the gas is allowed
to expand and it does work on the surroundings.
The temperature of the gas does not change during
the process, and thus the expansion is
isothermal. The gas expansion is propelled by
absorption of heat energy Q1 and of entropy from
the high temperature reservoir.
Isentropic (reversible adiabatic) expansion of
the gas (isentropic work output). For this step
(2 to 3 on Figure 1, B to C in Figure 2) the
piston and cylinder are assumed to be thermally
insulated, thus they neither gain nor lose heat.
The gas continues to expand, doing work on the
surroundings, and losing an equivalent amount of
internal energy. The gas expansion causes it to
cool to the "cold" temperature, T2. The entropy
remains unchanged.
Reversible isothermal compression of the gas at
the "cold" temperature, T2. (isothermal heat
rejection) (3 to 4 on Figure 1, C to D on Figure
2) Now the surroundings do work on the gas,
causing an amount of heat energy Q2 and of
entropy to flow out of the gas to the low
temperature reservoir. (This is the same amount
of entropy absorbed in step 1, as can be seen
from the Clausius inequality).
Isentropic compression of the gas (isentropic
work input). (4 to 1 on Figure 1, D to A on
Figure 2) Once again the piston and cylinder are
assumed to be thermally insulated. During this
step, the surroundings do work on the gas,
increasing its internal energy and compressing
it, causing the temperature to rise to T1. The
entropy remains unchanged. At this point the gas
is in the same state as at the start of step 1.

19
ENTROPY

Entropy is a measure of the number of specific
ways in which a system may be arranged, often
taken to be a measure of disorder, or a measure
of progressing towards thermodynamic equilibrium.
The entropy of an isolated system never
decreases, because isolated systems spontaneously
evolve towards thermodynamic equilibrium, which
is the state of maximum entropy.
Entropy was originally defined as

20
UNIT - 3
21
IDEAL GAS

An ideal gas is a theoretical gas composed of a
set of randomly moving, non-interacting point
particles. The ideal gas concept is useful
because it obeys the ideal gas law, a simplified
equation of state.

22
IDEAL GAS LAW

The ideal gas law is the equation of state of a
hypothetical ideal gas. It is a good
approximation to the behaviour of many
gases under many conditions, although it has
several limitations. It was first stated by Emile
Clapeyron in 1834 as a combination of Boyels law
and Charles law. The ideal gas law is often
introduced in its common form
where P is the absolute pressure of the gas, V is
the volume of the gas, n is the amount if
substance of gas (measured in moles), T is the
absolute temperature of the gas and R is the
ideal, or universal, gas constant.

Boyels law or
Charles law or
Gay Lusacs law or
Daltons law of partial pressure
Amagats law of partial volume

24
REAL GAS

Real gases as opposed to a perfect or ideal
gas exhibit properties that cannot be
explained entirely using the ideal gas law. To
understand the behaviour of real gases, the
following must be taken into account
compressibility effects
Variable specific heat capacity
Van der Waals forces
non-equilibrium thermodynamic effects
issues with molecular dissociation and elementary
reactions with variable composition.

25
Van der Waals equation

The van der Waals equation is an equation of
state for a fluid composed of particles that have
a non-zero volume and a pairwise attractive
inter-particle force (such as the Van der Waals
force).

26
COMPRESSIBILTY FACTORY

The compressibility factor (Z), also known as
the compression factor, is the ratio of the molar
volume of a gas to the molar volume of an ideal
gas at the same temperature and pressure. It is a
useful thermodynamic property for modifying the
ideal gas law to account for the real
gas behaviour.
The compressibility factor is defined as

27
COMPRESSIBILTY CHART
28
UNIT - 4
29
THERMODYNAMIC POTENTIAL
30
MAXWELL EQUATIONS
31
TdS EQUATIONS
32
JOULE THOMSON EFFECT

In thermodynamics, the JouleThomson
effect or JouleKelvin effect or KelvinJoule
effect or JouleThomson expansion describes the
temperature change of a gas or liquid when it is
forced through a valve or porous plug while kept
insulated so that no heat is exchanged with the
environment.This procedure is called
a throttling process or JouleThomson
process. At room temperature, all gases
excepthydrogen, heliun and neon cool upon
expansion by the JouleThomson process.
The effect is named for James Prescott Joule and
William Thomson, 1st Baron Kelvin, who discovered
it in 1852 following earlier work by Joule on
Joule expansion, in which a gas undergoes free
expansion in a vacuum.
In the Joule experiment, the gas expands in a
vacuum and the temperature drop of the system is
zero, if the gas is ideal.
The throttling process is of the highest
technical importance. It is at the heart of
thermal machines such as refrigerators, air
conditioners, heat pumps, and liquefiers.
Furthermore, throttling is a fundamentally
irreversible process. The throttling due to the
flow resistance in supply lines, heat exchangers,
regenerators, and other components of (thermal)
machines is a source of losses that limits the
performance.

33
JOULE THOMSON CO-EFFICIENT

The rate of change of temperature with respect
to pressure in a JouleThomson process (that is,
at constant enthalpy ) is the JouleThomson
(Kelvin) coefficient . This coefficient can be
expressed in terms of the gas's volume , its heat
capacity atr constant pressure, and hat capacity
at constant pressure, and its coefficient of
thermal expansion as

34
ClausiusClapeyron relation

The ClausiusClapeyron relation, named after
Rudolf Clausius and Benoit Paul Emile Clapeyron,
is a way of characterizing a discontinuous phase
transition between two phase of matter a single
constituent. On apressure - temperature (PT)
diagram, the line separating the two phases is
known as the coexistence curve. The
ClausiusClapeyron relation gives the slope of
the tangents to this curve. Mathematically,

35
UNIT - 5
36
STEAM

Steam is the technical term for water vapour ,
the gaseous phase of water, which is formed when
water boils.
Technically speaking, in terms of the chemistry
and physics, steam is invisible and cannot be
seen however, in common language it is often
used to refer to the visible mist of water
droplets formed as this water vapour
condenses in the presence of (cooler) air.
Water boils at a lower temperature than the
nominal 100 C (212 F) at standard temperature
and pressure.
If heated further it becomes superheated steam.

37
FORMATION OF STEAM
38
TYPES OF STEAM

Steam is traditionally created by heating a
boiler via burning coal and other fuels, but it
is also possible to create steam with solar
energy. Water vapour that includes water
droplets is described as wet steam.
As wet steam is heated further, the droplets
evaporate, and at a high enough temperature
(which depends on the pressure) all of the water
evaporates and the system is in vapour-liquid
equilibrium.
Superheated steam is steam at a temperature
higher than its boiling point for the pressure
which only occurs where all the water has
evaporated or has been removed from the system.