This study used latent heat thermal energy storage (LHTES) within a commercial plate-type heat exchanger (PHE) to numerically investigate the solidification process of phase change material (PCM). PCM fills the space between corrugated steel plates, and water at a certain temperature passes from top to bottom between two neighboring plates as heat transfer fluid (HTF). To determine the optimum geometry and operating conditions for the solidification process, the phase change process was investigated with three different plate geometries, different heat transfer fluid input temperatures (12 degrees C, 17 degrees C, and 22 degrees C), different steel plate thicknesses (0.4 mm, 0.6 mm, and 0.8 mm) and different Phase Change Materials (RT-35 and n-octadecane). Numerical analyses were simplified to two dimensions based on the finite volume method. The study results show that using the same phase change material, boundary conditions, and geometric features, the time for full solidification of phase change material decreased by a maximum of 63% in the plate heat exchanger-latent heat thermal energy storage system designed with geometry-A as phase change material layer compared to a cylindrical latent heat thermal energy storage system with the same volume of phase change material.