In this study, experimental and numerical investigation for melting of paraffin wax is carried out for a portable thermal energy accumulation system in a rectangular enclosure of size 200 mm × 160 mm × 20 mm. The studied paraffin wax is typically used for a wide variety of applications including thermal management of buildings and solar energy storage. The melting behaviour was also investigated numerically with the help of FVM (Finite Volume Method) approach based commercial code Ansys Fluent. The melting behavior is observed for 1500, 1930, 2500 and 3100 W/m2 of heat flux values that suits for thermal accumulation and thermal regulation of the buildings. The images of the PCM domain have been captured at regular intervals of 30 min and the temperature readings at fifteen different locations in the PCM domain have been recorded simultaneously. The differences between experimental and numerical results were observed to be in acceptable range. The investigation reveals the facts about the transient behaviour of melting interface, melted proportion and the stored energy for melting cycle of 5–5.5 .