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Basic Engineering Thermodynamics U3MEA02

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Basic Engineering Thermodynamics U3MEA02 Prepared by Mr.N.Dilip Raja, Assistant Professor, Department of Mechanical Engineering, VelTech Dr. RR & Dr. SR Technical ... – PowerPoint PPT presentation

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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

4
  • 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.

6
  • 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

7
  • 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.

23
  • 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.

39
P V diagram
40
pT diagram
41
TV DIAGRAM
42
hS diagram
43
pVT diagram
44
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