2. ENGINEERING THERMODYNAMICS?
ENGINEERING + THERMODYNAMICS
ENGINEERING-BRANCH OF SCIENCE- ENVIRONMENT
THERMODYNAMICS = THERMAL+ DYNAMICS
HEAT – Kind of energy transfer- Temp. difference
POWER- Capable to work
THERMODYNAMICS- Science of energy and energy transfer
5. • Macroscopic or Classical Approach:
• It is not concerned with the behavior of
• These effects can be perceived by human senses
or measured by instruments
Eg: pressure, temperature
• Microscopic or Statistical Approach:
• Based on the average behavior of large groups
of individual particles.
• the effect of molecular motion is Considered.
6. SYSTEMS AND CONTROL VOLUMES
• A system is defined as a quantity of matter or a region in space chosen for
• Surroundings: The mass or region outside the system boundary.
• Boundary: The real or imaginary surface that separates the system from its
• The boundary of a system can be fixed or movable.
• Systems may be considered to be closed or open.
7. Thermodynamic System and Types
• A specified region in which transfer of mass / energy
takes place is called system.
• To a thermodynamic system two ‘things’ may be
energy (heat, work) matter (mass)
CLASSIFICATION OF THERMODYNAMIC SYSTEM
• Closed or Non-flow
• Open or Flow
• Hetrogeneous 7
13. THERMODYNAMIC PROPERTIES
• MASS – quantity of matter
• WEIGHT - force exerted on a body by gravity
• VOLUME – space occupied by matter
• SPECIFIC VOLUME – volume per unit mass
• SPECIFIC WEIGHT – weight per unit volume
• DENSITY – mass per volume of substance
• TEMPERATURE – degree of hotness or coldness
• PRESSURE - force exerted per unit area
• SPECIFIC HEAT – energy required to raise or lower temp.
of substance about 1 k or 1°C
• INTERNAL ENERGY – energy contain within system
• WORK – kind of energy transfer – acting force- flow
• HEAT- kind of energy transfer – temp difference
• ENTHALPY – total energy of the system (I.E + F.W)
14. INTENSIVE or EXTENSIVE PROPERTY
• Intensive properties: The
property which is
independent of the mass of
a system, such as
temperature, pressure, and
density and specific
• Extensive properties: The
property which depends up
on the mass of a system,
such as volume, internal
energy and enthalpy.
15. DENSITY AND SPECIFIC GRAVITY
The ratio of the density of a substance to the density of some
standard substance at a specified temperature
Density is mass per unit volume; specific volume is volume per unit mass.
The weight of a unit volume of a substance.
The normal stress (or “pressure”) on the feet of a chubby
person is much greater than on the feet of a slim person.
Pressure: A normal force exerted
by a fluid per unit area
68 kg 136 kg
17. • Absolute pressure: The actual pressure at a given position. It is
measured relative to absolute vacuum (i.e., absolute zero pressure).
• Gage pressure: The difference between the absolute pressure and
the local atmospheric pressure. Most pressure-measuring devices are
calibrated to read zero in the atmosphere, and so they indicate gage
• Vacuum pressures: Pressures below atmospheric pressure.
19. Specific Heat Capacity
• Quantity of heat required to raise the
temperature of unit mass of the material
through one degree celsius.
• Specific Heat at constant pressure( Cp)
• Specific Heat at constant volume (Cv)
• Cp=1.003 kJ/kg-K
• Cv= 0.71 kJ/kg-K for air.
UNIVERSAL RU = Cp - Cv
20. STATE, PROCESSES AND CYCLES
It is the condition of a system as
defined by the values of all its
It gives a complete description of
Any change that a system
undergoes from one
equilibrium state to another.
STATE 2- T2,P2,V2
PROCESS - 1 2
21. STATE AND EQUILIBRIUM
• It is the condition of
• the system namely
• In an equilibrium state there are no unbalanced
potentials (or driving forces) within the system.
A system at two different states
22. STATE AND EQUILIBRIUM
• Thermal Equilibrium:
The temperature is the
same throughout the
• Mechanical equilibrium:
There is no change in
pressure at any point
of the system with
A closed system reaching thermal
23. STATE AND EQUILIBRIUM(Con…)
• Phase equilibrium:
• A system which is having two phases and
when the mass of each phase reaches an
• Chemical equilibrium:
• The chemical composition of a system does
not change with time, that is, no chemical
24. Thermodynamic Cycle
• Path: The series of states
through which a system
passes during a process. To
describe a process
completely, one should
specify the initial and final
• Cycle: A number of
processes in sequence
bring back the system to
the original condition.
26. Zeroth Law
• If two bodies A and B are in thermal
equilibrium with a third body C
independently, then these two bodies (A and
B) must be in thermal equilibrium with each
27. Thermodynamic Work
• positive work is done by a
system when the sole effect
external to the system could
be reduced to the rise of a
• Unit of work is N-m or Joule.
• Work flow into the system is
• Work flow out of the system
28. Thermodynamic Heat
• Energy transferred without
mass transfer between the
system and the surroundings
due to difference in
temperature between the
system and the surroundings.
• The unit of heat is Joule or kilo
• Heat flow into the system is
• Heat flow out of the system is
29. Energy and Forms of Energy
• Capacity to do work
• Forms of Energy:
• Stored Energy
• Energy in transition form
30. Stored Energy(Con…)
• Internal Energy(U):It is sum of kinetic energies
of individual atoms or molecules, that kinetic
energy occurred by external heat supplied to
the system it will converted to work.
• Sum energy always stored in the system (U)
not fully converted to work.
• Change in internal energy =mcv (T2-T1) kJ
31. Stored Energy(Con…)
• Kinetic Energy: Energy possessed by a body by
virtue of its motion.
• Change in K.E.=1/2 m(c2
• Flow Energy: Energy required to make the
flow of the system in and out of the device.
• Change in F.E.=( p2v2-p1v1) N-m
• Internal energy and pressure volume product.
• Change in enthalpy= mcp(T2-T1) kJ
• Where m=mass in kg
• cp=sp.heat at const.pressure in kJ/kg
• (T2-T1)= temp. difference in K
33. PATH and POINT FUNCTION
• If cyclic integral of a variable is not equal to
zero, then the variable is said to be a path
• If cyclic integral of a variable is equal to zero,
then the variable is said to be a point
34. The first law of thermodynamics
• Expression of the conservation of energy
• Statement: If a closed system executes a cyclic
process then net heat transfer is equal to net
• Q=W+dU for a process.
35. Laws Of Perfect Gas
• 1) Boyle’s law- “The absolute pressure of a given mass of
perfect gas varies inversely as its volume, when the
temperature remain constant”.
Mathematically pv = constant (T= const.)
• 2) Charles law- “The volume of a given mass of a perfect gas
varies directly as its absolute temperature, when the pressure
Mathematically, V/T = constant (p= const.)
• 3) Gay-lussac law- “The absolute pressure of a given mass of
a perfect gas varies directly as its absolute temperature when
volume is constant.”
Mathematically, P/T = constant (v= const.)
36. THERMODYNAMIC PROCESS
Here is a brief listing of a few kinds of processes, which we will encounter in TD:
Isothermal process → the process takes place at constant temperature
(e.g. freezing of water to ice at –10°C)
Isobaric → constant pressure
(e.g. heating of water in open air→ under atmospheric pressure)
Isochoric → constant volume
(e.g. heating of gas in a sealed metal container)
Reversible process → the system is close to equilibrium at all times (and infinitesimal
alteration of the conditions can restore the universe (system + surrounding) to the original
Irreversible Process: The reversal of the process leaves some trace on the system and its
Cyclic process → the final and initial state are the same. However, q and w need not be zero.
Adiabatic process → dq is zero during the process (no heat is added/removed to/from the
37. Thermodynamics processes
of Perfect Gas
1) Const. Volume/ isochoric process:
-Temperature and Pressure will increase
-No change in volume and No work done by gas
-Governed by Gay-Lussac law
2) Const. Pressure/ isobaric process:
- Temperature and volume will increase
- Increase in internal energy
- Governed by Charles law
3) Constant temperature/ isothermal process:
- No change in internal energy
- No change in Temperature
- Governed by Boyles law (p.v = constant)
4) Adiabatic/ isentropic process:
- No heat leaves or enters the gas Q = 0,
- Temperature of the gas changes
- Change in internal energy is equal to the work done
5) isentropic process:
- Entropy remains constant dS = 0,
- Temperature of the gas changes
- Change in internal energy is equal to the work done
5) Polytropic process:
- It is general law of expansion and compression of the gases.
p.v^n = Constant
6) Free expansion:
- When a fluid Is allowed to expand suddenly into a vacuum chamber
through on orifice of large dimensions.
Q = 0, W = 0, and dU = 0.