What is an Irreversible Adiabatic Process?

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Discussion Overview

The discussion revolves around the concept of an irreversible adiabatic process, exploring its definition, characteristics, and examples. Participants also compare it to free expansion and ordinary expansion, examining the implications of these processes in thermodynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether an irreversible adiabatic process is characterized by a net heat transfer within the system while maintaining constant net heat exchange with the surroundings.
  • Another participant describes an irreversible adiabatic process as one where no heat enters or leaves the system, and the process is rapid enough to be considered non-quasi-static, leading to a change in the surroundings if reverted.
  • A further contribution suggests that an irreversible adiabatic expansion can be viewed as a dynamic process where one part of the system does work on another, resulting in a temporary state of non-equilibrium.
  • Examples such as free adiabatic expansion into a vacuum are provided to illustrate the concept, highlighting that the gas does work on itself without external pressure.
  • Participants inquire about the differences between free expansion and ordinary expansion, with one noting that free expansion occurs into a vacuum.
  • Questions arise regarding the feasibility of expansion in a vacuum and its implications for power output and work done.

Areas of Agreement / Disagreement

Participants express various interpretations of irreversible adiabatic processes and their characteristics, with no consensus reached on the definitions or implications of the processes discussed. Multiple competing views remain regarding the nature of free expansion versus ordinary expansion.

Contextual Notes

Some participants' definitions and examples rely on specific assumptions about system boundaries and thermodynamic principles, which may not be universally accepted or applicable in all contexts.

Who May Find This Useful

This discussion may be of interest to students and professionals in thermodynamics, physics, and engineering who are exploring the nuances of adiabatic processes and their implications in various scenarios.

iScience
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*edited*

Just realized that's not what i wanted to ask, sorry.

New Question: What is an irreversible adiabatic process? is it when the net q(sys) remains the same but there is heat transferred within the system?
 
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iScience said:
*edited*

Just realized that's not what i wanted to ask, sorry.

New Question: What is an irreversible adiabatic process? is it when the net q(sys) remains the same but there is heat transferred within the system?
No heat enters or leaves he system at any time during the process, and the deformation is rapid enough that the process cannot be considered quasi-static. Once the final state is attained, there is no way of getting the system back to the initial state without also causing a change in the surroundings.

Chet
 
iScience said:
*edited*

Just realized that's not what i wanted to ask, sorry.

New Question: What is an irreversible adiabatic process? is it when the net q(sys) remains the same but there is heat transferred within the system?
Just to add to what Chet has said, you could think of an irreversible adiabatic expansion as a dynamic process in which one part of the system does work on another part, which takes the system out of equilibrium. Since it is adiabatic, the work done has to be at the expense of the system's internal energy. When the system returns to equilibrium the energy gained by the part on which work was done is distributed back to the system as a whole. This could be viewed heat transfer within the system.

A free adiabatic expansion of a gas into an empty chamber is an example of such a process. When the throttle valve to the empty chamber is opened, the gas expands rapidly. Gas molecules escaping through the throttle valve experience an increase in kinetic and, possibly, potential energy (where there are intermolecular forces). The gas, effectively, does work on itself. It occupies more volume but has not had to push anything out of the way to make room. So it does no work on its surroundings. When everything reaches equilibrium, the gas must have the same internal energy as it had before expansion (first law).

AM
 
What is differece between free expansion and ordinary expansion ??
 
Sanky123 said:
What is differece between free expansion and ordinary expansion ??

Free expansion means there's no external pressure or membrane inhibiting the expansion. In other words, a free expansion would be an expansion into a vacuum.
 
Matterwave said:
Free expansion means there's no external pressure or membrane inhibiting the expansion. In other words, a free expansion would be an expansion into a vacuum.
But how is this possible?

expansion in vaccume?
 
Sanky123 said:
But how is this possible?

expansion in vaccume?

For example, if you have a container which is at first separated. One side of the container has a gas, and the other side is a vacuum. When you remove the separating membrane, you have "free expansion".
 
Ok..,
if we have to take into consideration power output,

then which will be effective one?
 
Or if we have to consider work-done?
 

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