The nomenclature "entropy balance" is misleading and often deemed inappropriate because entropy is not a conserved quantity. In other words, the term S ˙ ˙ g e n is never a known quantity but always a derived one based on the expression above. Therefore, the open system version of the second law is more appropriately described as the "entropy generation equation" since it specifies that: S ˙ ˙ g e n ≥ ≥ 0 with zero for reversible process and positive values for irreversible one.