Chris Liebold
The efficiency of sensible heat thermal energy storage systems highly depends on preventing mixing between the hot and cold fluid regions. In our recent paper in PRX (https://journals.aps.org/prxenergy/abstract/10.1103/PRXEnergy.2.043001#), which was featured in the Physics magazine (https://physics.aps.org/articles/v16/s141), it is shown that an unsteady inherent flow develops and promotes mixing. For a better understanding, the velocity fields were investigated by laser-based measurements in a model system. A frequency analysis has shown that wall-jets in the near-wall region start to fluctuate periodically. This phenomenon was assigned to the transition from laminar to turbulent flow. Moreover, the wall-jets trigger additional fluctuations in the tank that further mix the fluid. The comparison to the large-scale TES at DLR using molten salt as storage fluid has shown similar fluctuations proving the phenomena observed are very relevant in real-world TES. These findings have to be considered to increase the efficiency of future systems for a significant contribution to a higher share of renewables in our energy supply.
https://journals.aps.org/prxenergy/abstract/10.1103/PRXEnergy.2.043001#
