What Is Exergy And Anergy

Exergy / Anergy image

Exergy to determine the potential for useful work in a certain amount of energy; otherwise the exergy is the portion of energy that can be transformed into useful work. The remaining part is called anergy. Unlike energy, there is no conservation law for exergy.

ie Energy = Exergy + Anergy

Exergy is the quantitative measure of the maximum amount of work obtainable from an imbalance between a physical system and the surrounding environment. When the system becomes equilibrium with surrounding, then there is no exergy available. 

Exergy is consumed completely when the parameter that differentiates a system from its surroundings (pressure and temperature or other state variables such as potential energy, voltage, etc.) is equal to that of the environment. Once the system temperature is equalized with the ambient, and the pressure is equalized with the outside, no additional energy can be extracted.

Example: consider a vessel containing a gas at high pressure and high temperature. If we make a hole in the container and let the air out into the atmosphere, we lose all the energy available as quickly the pressure and temperature are equalized to ambient temperature and pressure. Then we have wasted all available energy or exergy.

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