UNIT-V FMM.HYDRAULIC TURBINE - Construction and working
Thermo+rev+it.pdf
1.
2. The state variables (P, V, T, n) describe the condition of a system.
On changing any one or more of these variables the state of the
system changes.
Extensive Properties: Total Energy, volume, mass, etc.
Intensive Properties: Pressure, Density, Refractive Index, etc.
3.
4.
5.
6.
7.
8. Internal Energy (U)
It is the sum total of the components of energy of the system due
to the internal factors.
U = KE + PE
ΔU = q + W
Enthalpy (H)
It is the nnet heat content of the system. Mathematically:
H = U + PV
Remember:
ΔH = qp
ΔU = qv
10. Reversible Process:
A process whose direction can be changed by an infinitesimal
change to the system or surroundings and which can be reversed
by retracing the original path and both the system and surroundings
are restored to theinitial state.
Quasi Static State
System is always in equilibrium with the surroundings
11. Heat Capacity
Heat needed to raise the temperature of the system by 1K
C = q/ΔT
Molar Heat Capacity
Heat needed to raise the temperature of one mole gas by 1K
CM
= q/nΔT
Molar heat capacity constant pressure (CP
):
CP
= qP
/nΔT
Molar heat capacity constant volume (CV
):
CV
= qV
/nΔT
ΔH = qp
= nCP
ΔT
ΔU = qv
= nCV
ΔT
14. Entropy (S):
The degree of “randomness” of a system
2nd Law of Thermodynamics(2LoT):
The entropy of an isolated system/Universe always tends to increase
In a spontaneous process the entropy of the Universe increases
Remember:
In a reversible process the entropy of the Universe remains constant
i.e. ΔSTotal
= 0
15. ΔSsys
= nCV
ln(T2
/T1
) + nR ln(V2
/V1
)
This expression can be simplified for the four processes:
Isothermal process:
ΔS = nR ln(V2
/V1
)
Isochoric process:
ΔS = nCV
ln(T2
/T1
)
For isobaric process:
ΔS = nCP
ln(T2
/T1
)
Adiabatic process:
ΔS = 0 (qrev
= 0)
16. Gibbs Free Energy:
Gibbs Free energy function gives us a very convenient parameter to
judge the spontaneity of a process from the system’s perspective.
At constant temperature and pressure
ΔG = –TΔSTOTAL
For a process to be spontaneous
ΔG < 0
at a constant temperature
ΔGSYS
= ΔH – TΔSSYS
17. Types of Enthalpies:
Enthalpy of Formation ΔHf
0
Heat absorbed or released when one mole of a compound
is formed from its constituent elements under their standard
elemental forms. The enthalpy for formation of the following
substances is taken to be zero under 1 bar pressure and 298 K
H2
(g) + ½ O2
(g) H2
0(l) ΔHf
o
= -286 kJ/mol
18. Enthalpy of Combustion
Heat released or absorbed when one mole of a substance
undergoes combustion in presence of oxygen
Enthalpy of Solution
Heat released or absorbed when 1 mole of a compound is
dissolved in excess of a solvent (water)
19. Enthalpy of Hydration
Heat released or absorbed when 1 mole of anhydrous
or partially hydrated salt undergoes hydration by the addition of
water of crystallisation.
Enthalpy of Neutralization
Heat released or absorbed when one equivalent of an acid
undergoes neutralisation with one equivalent of a base.
20. Bond Dissociation Enthalpy
The energy needed to break the bonds of one mole molecules is
called the Bond Dissociation Enthalpy of the substance
H2
H + H BDE = 436kJ/mol
Resonance Energy
Many compounds exhibit resonance. Due to resonance they exist
in a structure which is different from the expected one and more
Stable. It is a negative value.
22. Free Expansion:
Expansion of gas in an isolated system in Vaccum
Pext
=0 w=0
q=0 ΔT = 0
ΔU= 0 ΔH= 0
ΔS > 0
Polytropic Process
Generalized form of any thermodynamic process where
PV
n
= constant, (n is a real number)
For an isothermal process n = 1
For an adiabatic process n = γ
