Phase Change — Melting, Solidification & Latent Heat
Stefan condition, enthalpy method, mushy zone modeling, casting solidification simulation, PCM thermal storage, and freezing problems.
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Quick Explainer
What is the Stefan condition and why do moving boundaries make phase change hard?
The Stefan condition balances energy at the moving solid-liquid interface: interface velocity equals net heat flux discontinuity divided by latent heat. The boundary location is part of the solution — a free boundary problem requiring either adaptive meshing or a fixed-mesh method like the enthalpy approach.
How does the enthalpy method handle phase change without tracking the interface?
The enthalpy method defines enthalpy as a function of temperature that includes the latent heat jump at the phase change temperature. You solve a single energy equation in terms of enthalpy throughout the domain. Phase change appears as a temperature plateau (mushy zone) where enthalpy changes without temperature change — no mesh remeshing needed.