The aim of this paper is to comprehensively study the mathematical modeling applied for phase change taking into consideration the convection in liquid state during melting. Different methods used to model the phase change with convective motion of liquid phase are discussed. First, models based on CFD (computational fluid dynamics) are presented; the solution of Navier-Stokes equations determines the effect of convection in a Newtonian fluid. Secondly, simplified methods are presented, where the convection in the liquid phase change material (PCM) is modeled without the need of the full solution of Navier-Stokes equations. It is clear that the methods based on CFD models are more accurate and express the realistic behavior of the convection effect; however their computational time is very long compared to simplified one.