What is the chemical equation, along with the change in heat of the crystallization process of Sodium Acetate
There is no chemical reaction.

The heat is released as the latent heat of crystallisation of a supercooled solution of sodium acetate trihydrate; you can obtain similar effects with sodium sulfate decahydrate or sodium thiosulfate pentahydrate.

When heated up, the hydrate dissolves in its own crystal water, which absorbs thermal energy similar to melting; when cooled down, the solution becomes supercooled.

Their state is called the metastable state: this means that it is not thermodynamically stable, but conditionally stable for kinetic reasons, as the crystallization requires a trigger.

The triggering can be done by, for example: insertion of a small crystal of the same salt, bending a steel chess (used in pocket heaters) or vigorous shaking.