Thermal Behavior of Encapsulated Phase Change Material Energy Storage

The performance of thermal solar systems can be enhanced by extending its operational time by the aid of thermal energy storage. In the present work, the transient behavior of packed bed thermal energy storage was investigated experimentally and numerically. An experimental set up was designed and fabricated to simulate the charging and discharging operational modes of the system. 101 spherical capsules were filled with wax paraffin as PCM and packed in cylindrical container bed of 105 mm diameter and 2400 mm long. The processes of the experimented storage system were simulated mathematically and solved numerically by finite difference technique. The analyses were carried out at two different mass velocity of the working fluid. The numerical model described the transient behavior of the system and it was in acceptable agreement with the experimental results. The transient period in the charging mode of the tested storage was around 30 minutes, while the energy recovery period in the discharging mode was around 60 minutes. The achieved results demonstrated that the tested TES could be used to enhance the performance of the thermal solar systems. The proposed packed bed thermal energy storage is easy to implement with low cost.

Key words: Numerical modeling; Phase change energy storage; Phase change material; Thermal energy storage; Transient heat transfer; encapsulated packed bed.