The present study aims at investigating numerically the thermal performance of a shell-and-tube phase change material (PCM) storage system for district heating network (DHN). A transient thermal model, which is based on energy balances, is developed and validated with experimental data from a full-scale 180 kWh PCM storage installed in the DHN of Flaubert substation (France). The effect of several design and operation parameters such as the target thermal power by the DHN during the discharging process, the PCM type, the number of tubes in the storage unit and the water return temperature on the storage performance is presented and analyzed. The results show that the studied system, under specific conditions, can supply hot water to the DHN at a temperature equal to or higher than 70°C for a certain period. The thermal power released by the storage system can be kept constant during this period by regulating the flow rate of the water. This period is reduced by decreasing the number of tubes in the storage unit or increasing the value of the water return temperature. Finally, the choice of the melting temperature of the PCM is crucial to maximize the performance of the storage system.