The enthalpy of the material is computed as the sum of the sensible
enthalpy, 
, and the latent heat, 
:
 | (15–1) |
where
 | (15–2) |
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and | |
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The liquid fraction, 
, can be defined as
 | (15–3) |
The latent heat content can now be written in terms of the latent
heat of the material, 
:
 | (15–4) |
The latent heat content can vary between zero (for a solid)
and 
(for a liquid).
For solidification/melting problems, the energy equation is written as
 | (15–5) |
|
where | |
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The solution for temperature is essentially an iteration between
the energy equation (Equation 15–5) and
the liquid fraction equation (Equation 15–3). Directly using Equation 15–3 [680] to update the liquid fraction usually results
in poor convergence of the energy equation. In Ansys Fluent, the method
suggested by Voller and Swaminathan is used to update the liquid fraction.
For pure metals, where 
and 
are equal, a method based on specific heat,
given by Voller and Prakash [679], is
used instead.