Irreversible process Entropie-Change/cylinder

  • Thread starter Abigale
  • Start date
  • #1
56
0
Hi,

I have read that for an irreversible process the equation for the entropy is: $$ds>\frac{dQ}{T}$$
But if I regard a cylinder connected to a heatreservoir and want to callculate the entropychange of this cylinder, why can I use the equation: $$ds=\frac{dQ}{T}$$???

THX
 

Answers and Replies

  • #2
21,158
4,672
Your inequality applies to the closed system that you are applying the process to. Your second equation is not the entropy change for the material in the cylinder unless the process is reversible, irrespective of the heat reservoir. If you regard the heat reservoir as a system, then the second equation describes its change of entropy, since its temperature is constant and (virtually) uniform, and the heat addition takes place reversibly. The key to inequality vs equality is if the system under consideration is undergoing a reversible change.
 

Related Threads on Irreversible process Entropie-Change/cylinder

Replies
2
Views
5K
Replies
8
Views
2K
  • Last Post
Replies
11
Views
19K
Replies
1
Views
964
Replies
6
Views
3K
Replies
1
Views
1K
  • Last Post
Replies
2
Views
16K
  • Last Post
Replies
20
Views
4K
  • Last Post
Replies
1
Views
5K
  • Last Post
Replies
18
Views
4K
Top