ne of the discussed techniques in improving the performance of latent thermal energy storage applications is to use different phase change materials (PCMs) encapsulated in spherical nodules. However, the large number of spheres used in the storage applications pushes the researchers to neglecting the natural convection effect inside spheres. Consequently, they cannot observe the real thermal interaction effect between spheres. The objective of this work is to carry out a computational study on the thermal behavior of two adjacent different PCMs inside aluminum spherical capsules and taking into account the natural convection effect inside the spheres. Water is used as heat transfer fluid (HTF) at constant inlet temperature. The study shows that for the HTF inlet velocity lower than 10 −5 −5m/s, the thermal interaction between two adjacent different PCMs cannot be neglected. However, the thermal interaction appears more clearly in the discharging mode. The thermal interaction can accelerate the discharging of one of the PCMs by reducing the discharging of the other one.