Irreversible Process and Causes of Irreversibility

By | February 12, 2019

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

  1. Lack of thermodynamic equilibrium

That includes

  • Mechanical equilibrium
  • Chemical equilibrium
  • Thermal equilibrium
  1. 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


P = Pressure

T = Temperature

C = Concentration

µc = Chemical potential

Also read:

What is a heat pump?

What is a heat engine?

What are laws of thermodynamics?

What is dead state of a thermodynamic system?

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