Irreversible Process: Heat Transfer Dynamics

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    Irreversible Process
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Discussion Overview

The discussion revolves around the nature of irreversible processes in thermodynamics, particularly focusing on heat transfer and entropy. Participants explore the relationship between energy transfer, entropy changes, and the conditions under which a process is deemed irreversible.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that any process involving heat transfer to or from a system is irreversible, questioning if energy must always leave or enter the system through heat in such processes.
  • Others argue that conservation of energy is not the only relevant law, emphasizing the importance of entropy in defining irreversible processes.
  • A participant suggests that a system can have conserved energy while experiencing an increase in entropy, thus being in an irreversible process, and questions the terminology for such a process.
  • There is contention over the definition of irreversible processes, with one participant asserting that the entropy of a system can decrease during an irreversible process, which is challenged by others who maintain that entropy in irreversible processes always increases.
  • One participant provides an example of removing heat from a hot body in contact with a colder reservoir, prompting further discussion about the isolation of systems and entropy changes.
  • Clarifications are made regarding the identification of systems as isolated, with some participants acknowledging the need for clearer definitions in their earlier posts.

Areas of Agreement / Disagreement

Participants express disagreement on the definitions and characteristics of irreversible processes, particularly regarding entropy changes. There is no consensus on whether the entropy of a system in an irreversible process can decrease, and the discussion remains unresolved on this point.

Contextual Notes

Limitations in the discussion include assumptions about system isolation and the definitions of irreversible processes that are not universally agreed upon. The relationship between energy conservation and entropy changes is also not fully resolved.

Pushoam
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Does this mean that any process in which energy goes away\comes into from the system to the surrounding as heat is irreversible and in any irreversible process, energy must go away
\come into from the system to the surrounding through heat?
 
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Conservation of energy is not the only law relevant. Think of entropy as well as energy.
 
anorlunda said:
Conservation of energy is not the only law relevant. Think of entropy as well as energy.
This reminds me the following:
Irreversible process is that process in which entropy of the system increases.
So, if I get a system whose energy remains conserved ( that is it doesn't get lost through heat) ,but entropy increases, then the system will be in irreversible process. For example, isolated ideal gas as ideal gas has only elastic collision, their energy remains conserved but the entropy increases, hence the ideal gas are in irreversible process. But, what is the name of this irreversible process?

So, in irreversible process, loss of energy through heat is not necessary. Right?
 
Pushoam said:
This reminds me the following:
Irreversible process is that process in which entropy of the system increases.
So, if I get a system whose energy remains conserved ( that is it doesn't get lost through heat) ,but entropy increases, then the system will be in irreversible process. For example, isolated ideal gas as ideal gas has only elastic collision, their energy remains conserved but the entropy increases, hence the ideal gas are in irreversible process. But, what is the name of this irreversible process?

So, in irreversible process, loss of energy through heat is not necessary. Right?
Your definition of an irreversible process in terms of an entropy increase is incorrect. The entropy of a system in an irreversible process can also decrease.
 
Chestermiller said:
The entropy of a system in an irreversible process can also decrease.
Entropy of an irreversible process always increases.
Entropy of a reversible process remains constant.
I have never heard that the entropy of a system in an irreversible process can also decrease.
Will you please give me an example?
 
Pushoam said:
Entropy of an irreversible process always increases.
Entropy of a reversible process remains constant.
I have never heard that the entropy of a system in an irreversible process can also decrease.
Will you please give me an example?
I remove heat from a hot body (my system) by contacting it with a colder reservoir.
 
Chestermiller said:
I remove heat from a hot body (my system) by contacting it with a colder reservoir.
But then the hotter body is not an isolated system.
The hotter body with the cold reservoir is the isolated system. And the entropy of this isolated system increases.
 
Pushoam said:
But then the hotter body is not an isolated system.
The hotter body with the cold reservoir is the isolated system. And the entropy of this isolated system increases.
This is correct. But, in you previous posts, you did not identify the system under consideration as being isolated. You just identified it as a "system."
 
Chestermiller said:
This is correct. But, in you previous posts, you did not identify the system under consideration as being isolated. You just identified it as a "system."
I am sorry for not being clear in the earlier post.
I assumed that by system it is meant an isolated system.

Thanks for pointing it out.
From next time I would be clear.
 

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