Solidification Heat Transfer

The theoretical background on transient heat transfer of a phase change is directly related to melting and solidification processes used in casting practices. For a pure metal, the melting or solidification process occurs at a single temperature \(\mathrm {T}_{\mathrm {f}}\) , while an alloy undergoes either process at a temperature range \(\mathrm {T}_{\mathrm {s}} < {\mathrm {T}_{\mathrm {f}}}^{\ast } < \mathrm {T}_{\mathrm {l}}\) , where \(\mathrm {T}_{\mathrm {s}}\) and \(\mathrm {T}_{\mathrm {l}}\) are the solid and liquid temperatures, respectively. Actually, phase transformation occurs when an amount of energy is either absorbed (melting) or released (solidification) at specific temperatures. Melting is a heating process where solid-to-liquid transformation ( \(\mathrm {S} \rightarrow \mathrm {L}\) ) is induced when the supplied thermal energy reaches the latent heat of fusion \(\mathrm {DH}_{\mathrm {f}}\) at the fusion temperature \(\mathrm {T}_{\mathrm {f}}\) . Conversely, solidification is a cooling or freezing process for converting a liquid into a solid ( \(\mathrm {L} \rightarrow \mathrm {S}\) ) when the latent heat of solidification \(\mathrm {DH}_{\mathrm {s}}\) is released at the freezing temperature \(\mathrm {T}_{\mathrm {f}}\) or below. The use of \(\mathrm {DH}_{\mathrm {s}}\) compensates for the superheating effect \(\mathrm {DT}_{\mathrm {s}} > 0\) ) on solidification; otherwise, \(\mathrm {DH}_{\mathrm {s}} = \mathrm {DH}_{\mathrm {f}}\) at \(\mathrm {DT}_{\mathrm {s}} = 0\) . By definition, melting and solidification are energy absorption and release processes, respectively.