ISENTROPIC AND ADIABATIC PROCESSES CLASS NOTES

ISENTROPIC AND ADIABATIC

PROCESSES CLASS NOTES

Isentropic process has constant entropy.

There is no loss. It is a theoretical process.

There is an adiabatic process which is

irreversible. There is heat addition. There is

internal and external losses.

ISEN-TROPIC PROCESS

Heat exchange is zero.
dq=0, Tds=0
s = entropy =  constant
There is no internal friction or ir-reversibility
There is no heat interaction between the system and the surroundings
dq =0
It is just a theoretical process which is not achievable in actual practical application.  This process does not exist.
Mathematically isentropic process is     pVγ=C
γ=1.4 for a diatomic gas
γ =1.65 for a mono-atomic gas

ADIABATIC PROCESS

No heat transfer
No heat gain or no heat loss
This process is very fast because of no heat transfer.
dq =o
dq =du + dw=0
dw=pdv
dq=Tds
But Tds is due to internal irreversibility.
Therefore Tds >o, there is increase in entropy in the process
Hence the process is irreversible due to internal and external irreversibility.
Mathematically adiabatic process is pVn =C
Examples of adiabatic process
(i) Compression process
(ii) Expansion process
(iii)  Firstly Flow in an insulated pipe
(iv) Secondly Flow in an insulated channel
(v) Thirdly Flow in an insulated nozzle
AN ISEN-TROPIC PROCESS IS ALWAYS ADIABATIC AND NOT VICE VERCA
AN ADIABATIC PROCESS IS NOT ISEN-TROPIC BECAUSE OF INTERNAL AND EXTERNAL IR-REVERSIBILITIES

Difference between an adiabatic process and an isentropic processes

Sr. No.

Adiabatic process

Isentropic process

1.
It is an actual process.
  It is a theoretical process.
2.
There is a heat generation due to friction within the process.
 There is no heat generation due to friction with in the process. Practically this process is not possible.
3.
It is an irreversible process.
 It is a reversible process.
4.
There is increase of entropy in this process.
 There is no change of entropy in this process.
5.
Useful work obtained in expansion process will be less.
 Useful work obtained in expansion process will be of fixed value.
6.
Work supplied in a compression process will be more than required.
 Work supplied in a compression process will be of fixed value.
7.
Efficiency of the process will be less than 100 %.
Process will be 100 % efficient.
8.
Mathematically pvn = C
 Mathematically pvγ= C
9.
Heat addition or rejection during the process
No heat addition or rejection during the process
10.
 There is more decrease of internal energy during expansion.  Work given out during expansion is less.
There is a decrease of internal energy during expansion.
11.
There is more increase of internal energy during compression.  More work input is there.
There is a certain increase of internal energy.

https://www.mesubjects.net/wp-admin/post.php?post=6231&action=edit                   MCQ thermodynamic processes