The heat rate Q0 that is released during a phase transformation is characterized by the enthalpy per unit volume

(see
Ref. 5). The heat rate that is associated with the transformation of a source phase into a destination phase can be expressed as
where
is the sum of the contributions Q0 from each phase transformation (
Equation 3-38), and
T is the temperature degree of freedom used in the Heat Transfer in Solids interface.