2. m e
Based on References
.na
t t e
Fundamentals of Classical Thermodynamics, G.J.Van Wylen
a
and R.E.Sontag, John Wiley and Sons, 1994
sk
Thermodynamics - an engineering approach, Yunus A.
s
/
Cengel and Michael Boles, TATA McGraw Hill, 2003
: /
Thermodynamics, Holman J.P., 4th edition, McGraw Hill,
p
t
1998
ht
3. A strong dose for motivation …
“A theory is more impressive the greater is the
simplicity of its premises, the more different are the things it
relates, and the more extended its range of applicability.
Therefore, the deep impression which Classical
Thermodynamics made on me. It is the only physical theory
of universal content which I am convinced, that within the
framework of applicability of its basic concepts will never be
overthrown.”
- Albert Einstein
(as quoted in Fundamentals of Engineering Thermodynamics
by Howells, J. P., and Buckius, R. O.)
4. Introduction
Thermodynamics
m e
a
- study of energy transfer and transformation of energy
e .n
- its effect on physical properties of substances
t t
Generalisation of extensive empirical evidence
a
(however, most principles can be derived from kinetic
theory)
ss k
/ /
Energy propels society
:
t p
Thermodynamic laws govern principles of energy conversion
t
h
Provides scientific basis for analysis of energy conversion
schemes
6. Approaches
Microscopic or Statistical Thermodynamics
me
. na
Detailed molecular and atomic nature of matter considered
Behaviour described by summing up that of each molecule
t t e
Eg.: Pressure is average rate of change of momentum due to
a
all molecular collisions on a unit area
k
/ s s
Macroscopic or Classical Thermodynamics
: /
Only bulk nature and properties of matter considered
p
t t
Continuum assumed
h
Concerned with perceivable effects of many molecules
7. Dimensions and Units
Mass m kg
me
Force F = ma
W = mg
. na kg m/s2 or N
t e
g = 9.80665 m/s2 at MSL
t
a
max at 4500 m below MSL
k
at centre of earth?
/ s s
up to 30 km, variation < 1%
Volume
p : / V m3
t
Density ρ kg/m3
ht
Specific Volume v
(v = 1/ρ)
m3/kg
8. Pressure p = F/A
e
N/m2 or Pa
m
a
1 bar = 105 Pa
n
Atm pressure: 1.01325 bar
Temperature T
t e . K
a t K = oC+273.15
Molar specific volume
s sk
v=V n m3/kmol
Energy, Work
: / / F.s Nm or J
p
Power J/s or W
ht t
9. Basic Concepts
System
me
a
quantity of matter or region in space upon which attention
is focused in the analysis
e . n
Surroundings
a t t
matter and everything outside the system
Boundary
s sk
/ /
separation between system and surroundings
:
- fixed or moving
t p
- real or imaginary
t
h
Universe
comprised of system and its surroundings
10. Types of Systems
Isolated System
Open System No interaction with
(Control Volume) surroundings
Both energy and Mass and energy
mass cross boundary fixed
Not influenced by
surroundings
Eg.: Perfect flask,
Universe (?)
Closed System
(Control Mass)
Only energy
crosses boundary
11. Properties
physical condition may be described
me
Properties are characteristics of system by which its
. na
Intensive Properties are independent of quantity of matter
t e
in the system, Eg.: p, T, v, ρ, u, h, s
t
a
Extensive properties are dependent of quantity of matter in
k
s
the system, Eg.: m, V, U, H, S
/ / s
All specific properties (extensive properties per unit mass)
:
p
are intensive properties
ht t
Uppercase letters are used for extensive properties
Lowercase letters are used for intensive properties
12. me
a
p, V, T, m, v, ρ
e . n
t t
System divided into two equal parts
a
s sk
/
p, V/2, T, m/2, p, V/2, T, m/2,
: /
v, ρ v, ρ
t t p
h
Each part will have
- the same value of intensive properties
- half the value of extensive properties
13. exist at a definite State
me
When all properties have definite values, system is said to
a
Or
. n
State of a system is described by specifying its
e
thermodynamic co-ordinates, called properties
a t t
Whenever one or more properties of system change, we say
k
that Change of State has occurred
/ s s
For isolated system, the state never changes- no interaction
: /
Succession of states passed through during a change of state
p
t
is called Path
ht
When path is completely specified, change of state is called a
Process
14. e
For a series of changes of state, if the final state is identical
m
a
with the initial, a Thermodynamic Cycle is completed
Thermodynamic Equilibrium
e . n
t t
System is said to be in thermodynamic equilibrium when no
a
k
change in any property is observed if the system is isolated
s
Or
/ s
When the pressure, temperature and density are uniform
: /
t t p
h
15. Thermodynamic Equilibrium has to satisfy three conditions:
e
1. Mechanical equilibrium- no unbalanced forces within
m
a
the system and also between the system and
n
surroundings
t e .
2. Chemical equilibrium- no chemical reaction or diffusion
or solution (mass transfer)
a t
s sk
3. Thermal equilibrium- when a system in mechanical and
chemical equilibrium is separated from surroundings by
/ /
a diathermic* wall, there is no spontaneous change in
:
p
any properties, i.e., equality of temperature
ht t
* Diathermic wall allows heat transfer
Adiabatic wall does not allow heat transfer
16. An isolated system always reaches thermodynamic
equilibrium in a course of time
17. Quasi-static Process
e
Properties are defined only when the system is in
m
a
thermodynamic equilibrium
. n
Otherwise, different parts of system are at different states at
e
t
same time, it is not possible to define one “state” of system
a t
Since the process takes place only because of inequilibrium,
s sk
how to explain the states of the system during a process?
: / /
t t p
h
18. Ideal / Reversible / Quasi-static Process
me
equilibrium is infinitesimal
. na
A process in which deviation from thermodynamic
Or
t t e
All the states the system passes through may be considered
equilibrium states
k a
/ s s
p : /
ht t
19. State Principle
chemical composition through out its mass
me
Pure Substance is one that has homogeneous and invariable
. na
Pure substance may exist in more than one phase, a phase is
e
a quantity of matter that is homogeneous throughout
a t t
Homogeneous System- one in which the components and
k
phases are uniformly distributed though out the volume
/ s s
State Principle or Two-property Rule
: /
Certain properties are functionally related
p
h t
For a pure substance, only two properties are required to
t
define the state
This is an experimental fact!
20. State Diagram
The state thus can be represented as a point on property
diagram called State Diagram
Eg.: p-v, p-T, T-v, T-s, h-s diagrams
22. Answer to the Question …
(3)
me
. na
One would expect the pressure to increase and the volume to
e
decrease through the compressor. 2 and 3 meet this test
a t t
One would expect the exhaust of the engine to be hotter than
sk
the inlet flow, (at the same pressure, the volume is less at the
s
inlet- meaning it must be colder)
: / /
t t p
h
23. Ideal Gas
e
A mole is a quantity of a substance having a mass
m
a
numerically equal to its molecular weight
M = m/n
e . n
M
m
molecular weight, kg/kmol
mass, kg
a t t
n number of kmol
s sk
: / /
t t p
h
24. Equation of State
Regardless of the gas, all isotherms converge to a single
point for the limit of zero pressure
Isotherms
pv
pv/T Lim =R
p→0 T
Universal Gas Constant
R = 8314.4 J / kmolK
p
25. e
pv
Lim =R
p→0 T
a m
To a good approximation many gases, at pressures up to
. n
tens of atmospheres, behave according to (low temperatures)
e
p v = RT
a t t
since v = V n
s sk
V
p = RT
: / /
p
n
ht tpV = n RT
26. e
since v = V/m or V = mv
pmv = n RT
a m
or pv =
nR
T
e . n
m
a t t
k
since m = nM
pv = / T
nR
/ s s
/
nM
p : / R
t
by denoting Gas Constant R =
ht pv = RT
M
27. since v = V/m
me
a
V
p = RT
n
m
t e .
pV = mRT
a t
V
p = RT
s sk
/
m
or
p
p = ρRT
: /
ht t
28. for two different states
p1V1 = mRT1
me
p2 V2 = mRT2
. na
t t e
a
by dividing
/ /
p1V1 mRT1
=
s sk
/ /
p2 V2 mRT2
: / /
t t T1
=
p
p1V1 p2 V2
T2
h
