Heat transfer characteristics of the innovative spray-type packed bed thermal energy storage: An experimental study

The shift to clean energy and the promotion of renewable energy sources are the dominant trends in the sustainable development of global energy employment. Thermal energy storage (TES) technology can help reduce the mismatch between thermal energy supply and demand by smoothing out peak demand periods. The spray type packed bed thermal energy storage is an innovative heat storage technology that reduces the use of liquid heat transfer fluid (HTF) by introducing a spray device. However, the mechanism of flow and heat transfer inside the spray-type packed bed thermal energy storage is not yet clear. Therefore, in this study, a 10 kW/10 kWh spray-type packed bed TES test rig was established using aluminum spheres as storage media and thermal oil as HTF, and the heat transfer performance was studied experimentally. The results indicate that higher charging temperatures and flow rates lead to a higher liquid-to-particle heat transfer coefficient. An empirical correlation for heat transfer in spray-type packed bed TES was developed. With substantial reduction in HTF usage, the heat transfer Nusselt number of spray-type packed bed can basically approach that of a fully-filled packed bed.