If there is no difference in the final and initial state of entropy then entropy will be zero. Devices with a steady state of flow of energy like nozzles, and turbines have zero entropy. Reversible processes also have zero entropy. The amount of thermal energy per unit temperature in a system that is not available for useful work is referred to as entropy. Explanation: Entropy is constantly increasing because every particle and atomic structure accelerates through time and space. If there is no difference in the final and initial state of entropy then entropy will be zero. Devices with a steady state of flow of energy like nozzles, and turbines have zero entropy. Reversible processes also have zero entropy.