Table of Contents
What is an Irreversible process?
Before understanding an irreversible process let us first understand a reversible process.
A reversible process is a process in which both system and surrounding can be restored to original state after the conclusion of the process, by any means.
Now it is obvious that a process which is not reversible is an irreversible process.
Practically all the processes are irreversible processes.
Causes of irreversibility in a process
- Lack of thermodynamic equilibrium
That includes
- Mechanical equilibrium
- Chemical equilibrium
- Thermal equilibrium
- Dissipative effects
Examples of dissipative effects are Mechanical friction, Fluid viscosity, Magnetic hysteresis, Inelasticity, Electrical resistance etc.
As mentioned earlier that a process can never be reversible but it can be in the limit.
Below is a comparison between a complete reversible process and a process reversible in the limit.
| Process | Perfectly reversible process | Process reversible in the limit |
| Mechanical work transfer | ΔP = 0 | ΔP → 0 |
| Heat transfer | ΔT = 0 | ΔT → 0 |
| Mass transfer | ΔC = 0 | ΔC → 0 |
| Chemical reaction | Δµc = 0 | Δµc → 0 |
Where:
P = Pressure
T = Temperature
C = Concentration
µc = Chemical potential
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