Increasing fuel consumption and rising greenhouse gas emissions are forcing industries to improve the energy efficiency of their processes. One way to achieve this goal is to use waste heat recovery systems. Latent heat energy storage using PCM is one of the promising solutions that gained the attention of researchers due to its worthwhile characteristics, including a high storage density, and the capability to restore energy at a constant temperature. However, PCMs, especially organic PCM, still suffer from a low thermal conductivity that reduces their thermal performance. The aim of this study is two folds. First, it provides a good understanding of heat transfer during the charging cycle (melting of the PCM). Then investigates the role of adding fins in enhancing the energetic performance of the regenerator. For this reason, a horizontal heat exchanger filled with PCM (Paraffin wax with melting temperature of 325 K) is numerically investigated using the commercial software Ansys Fluent. The numerical results demonstrate that the longitudinally finned case provides better thermal performance compared to the finless case. Thus, the addition of fins allows a reduction in the melting time by 46.3%.