The phase change material (PCM) considered is a commercial paraffin wax. The main enclosure that contains the wax has a rectangular geometry and is placed in a vertical position. One of the walls is heated at constant rate during the charge process and the-other wall is cooled by an airflow stream during the discharge. To describe the performance of the store a one-dimensional model based on the enthalpy method is developed. An apparent specific heat of the PCM is determined using a differential scanning calorimeter (DSC). This parameter permits the enthalpy of the PCM to be determined, and linearized for the numerical model. The results show that the simplified numerical model can be used to predict, with reasonable accuracy the dynamic performance of this kind of heat exchange unit.