Thermodynamic (energy and exergy) analysis provides new perspectives on the relative performance of different process chains. For example, the thermodynamic attribute known as ‘exergy' shows the ability to perform ‘useful work,' yet it does not adequately explain heating processes. Engineers use thermodynamic analysis to determine how energy impacts the performance of mechanical systems. It uses mathematical models to calculate the effects of various energy inputs as well as some of the energy outputs produced by a machine's operation.