Enthalpy in apparent heat capacity method

Feng

I am using Fluent to treat a solidification process. My method is apparent heat capacity method because it is easy to implement. So far, my solution agrees well with that obatined by solidification model in Fluent. Using apparent heat capacity method, if the domain is defined as liquid, the enthalpy profile is all right in that there is a jump at the phase chage interface. However, when I define the domain as solid, the enthalpy profile is difficult to understand, because the profile shows a peak at the interface, which looks pretty much like the shape of the artificial specific heat defined on the mushy zone. Anyone knows how does this thing happen? Thanks for any information!