Exergy or Availability

Exergy of a system is defined as the theoretical maximum amount of work that can be obtained from the system at a prescribed state (P, T, h, s, u, v) when operating with a reservoir at the constant pressure and temperature P0 and T0. The specific exergy of a non-flow system is:

and for a steady flow system:

where, 
u= Specific internal energy, 
h= Specific enthalpy, 
v= Specific volume, 
s= Specific entropy, 
C= Velocity, 
Z= Height of the system measured from a fixed datum, 
g= Gravity constant.
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