In this paper, entropy is presented as an important variable in effectively describing and predicting various phase change processes. An interfacial entropy constraint, downward concavity condition and Second Law formulation are obtained. Modelling of interfacial momentum interactions and thermal recalescence are based on heat-entropy analogies. It is shown that deeper insight into phase change processes with fluid flow can be realized through consideration of the analogy variable (entropy). Also, an entropy-based approach provides effective guidelines for interface tracking and numerical stability in phase change computations involving a control volume-based finite element method (CVFEM) formulation.