Inter-phase enthalpy calculation
 

Hello !

I am now having diffiulty in understanding the concept of "inter-phase enthalpy" while referring to the Ansys Fluent Theory Guide document. The detail is shown in attach file.

The text in the attach file confuses me. Take the process of ice melting into liquid water as an example, how to calculate interphase enthalpy (hpq, p-ice, q-water) ? Is hpq a difference between the enthalpy under the phase state of p and q or the enthalpy under either of the two phase states ?