The document discusses entropy, which is a thermodynamic property that serves as a tool for analyzing engineering devices according to the second law of thermodynamics. Entropy can be viewed as a measure of disorder in a system, with more disorganized systems having higher entropy. The Clausius inequality and definition of entropy using heat transfer and temperature are provided. The principles of entropy change for open and closed systems, as well as the increase of entropy principle and third law of thermodynamics, are summarized.

1. -:Entropy:-
Submitted to:- Mr. Mitesh Gohil
By:-Harsh Parmar(PG-18)
Akash Parikh(PG-02)
Devarsh Jadavanee(PG-22)
Moyun Sherasiya(PG-43)
Smith Parekh (PG-34)
Vivekkumar Boda (FOE-23
Yug TripathiI (FOE-21)
Harsh Dalsania(PG-11)

2. Entropy:- The Entropy is a thermodynamic property of a working
substance and serves as a valuable tool in the second law
analysis of engineering devices.
• Entropy is afunction of a quantity of heat which shows the
possibility of conversoin of that into work.
• Entropy is a thermodynamic property; it can be viewed as a
measure of disorder i.e. More disorganized a system the higher
its entropy.

5. Clausius Theorem

6. • Entropy is a thermodynamic property; it can be viewed as a
measure of disorder. i.e. More disorganized a system the
higher its entropy. Defined using Clausius inequality
• where Q is the differential heat transfer & T is the absolute
• temperature at the boundary where the heat transfer occurs
0 





revT
Q

7. th, from Carnot efficiceny 1 1 ,
Q Q
Therefore, 0 for a reversible Carnot cycle 0
T T
H L L L L L
H L H H H H
rev
Q Q Q Q T Q T
T T T Q T Q T


 
      
 
  
 

 
Ñ
Ñ Ñ
• Clausius inequality is valid for all cycles,
reversible and irreversible.
• Consider a reversible Carnot cycle:

8. • Since entropy is a thermodynamic property, it has
fixed values at a fixed thermodynamic states.
Hence, the change, S, is determined by the initial
and final state. BUT..
• The change is = only for a Reversible Process 





T
Q

10. Consider a cycle, where Process 2-1 is reversible and 1-2 may
or may not be reversible
2 1
1 2
2 2 2
2 1
1 1 1
2 1
2 1
1 2
0
From entropy definition
Q Q
dS= , 0
Therefore,
rev
rev rev revrev
rev
Q Q Q
T T T
Q Q
dS
T T T T
Q Q
dS S S S
T T
Q
S S S
T
  
   
 

   
     
   
       
          
       
   
        
   
 
     
 
  
   
  
Ñ
Ñ Ñ
2
1
, This is valid for all processes
Q Q
, since = ,
T Trev irrev
Q
dS dS dS
T
     
    
   

1
2
reversible
process
any
process
T
S

12. Entropy change for Open System

13. Processes can be discussed profitably using the entropy concept.
For a reversible process:

B
A
AB
T
Q
SSS

• If the reversible process is isothermal:
STQ
T
Q
Q
T
SSS
B
A
AB  
1
S increases if the system absorbs heat, otherwise S decreases
00   S
T
Q
SSS
B
A
AB

Reversible isothermal processes are isentropic
But in irreversible ones the entropy may change
• If the reversible process is adiabatic:

14. Increase of Entropy Principle
2
2 1 gen
1
2 2
2 1
1 1
, define entropy generation S
where 0. If the system is isolated and "no" heat transfer
The entropy will still increase or stay
system gen
gen
Q
S S S
T
Q Q
S S S S
T T
S

 
 
     
 
   
        
   


 
the same but never decrease
0, entropy increase principlesystem genS S  
Entropy change
Entropy Transfer
(due to heat transfer)
Entropy Generation
The principle states that for an isolated Or a closed adiabatic Or
System + Surroundings.A process can only take place such that Sgen 0
where Sge = 0 for a reversible process only
And Sge can never be les than zero.
Increase of Entropy Principle

15. • Entropy, unlike energy, is non-conservative since it is always
increasing.
• The entropy of the universe is continuously increasing, in
other words, it is becoming disorganized and is
approaching chaotic.
• The entropy generation is due to the presence of
irreversibilities. Therefore, the higher the entropy generation
the higher the irreversibilities and, accordingly, the lower the
efficiency of a device since a reversible system is the most
efficient system.
• The above is another statement of the second law

16. Third law of Thermodynamics
• The Third Law of Thermodynamics was first
formulated by German chemist and physicist
Walther Nernst.
• The Third Law states, “The entropy of a
perfect crystal is zero when the temperature of
the crystal is equal to absolute zero (0 K).”

17. Applications of Third law of
Thermodynamics
• Provides an absolute reference point for the
determination of entropy.
• Explaining the behavior of solids at very low
temprature.
• Measurement of action of chemical forces of the
reacting substances.
• Analysing the chemical and Phase Equilibrium.