Performance investigation of various cold thermal energy storages .

摘要

This study deals with the process of solidification and melting of some typical encapsulated ice thermal energy storage geometries. Using ANSYS GAMBIT and FLUENT 6.0 software, fluid motion past cylindrical, slab and spherical capsules containing phase change materials are examined and the resulting energy and exergy efficiencies are analyzed. The main source of irreversibility was from entropy generation due to heat transfer accompanying phase change, although viscous dissipation was included.;The most influential variable affecting exergy efficiency was the inlet HTF temperature, with very small differences in efficiency occurring when varying geometries. Though the most efficient geometries varied according to inlet HTF temperature; the spherical capsules provided competitive values, and due to ease of manufacturing and usage should not be discarded when designing systems such as these.;Keywords: Thermal, energy, storage, heat, transfer, energy, exergy, efficiency, encapsulated, ice, charging, numerical, sphere, cylinder, slab, CFD, dissipation, viscous, charging, discharging, flow rate, temperature, geometry, capsule, HTF, TES, PCM.;All energy efficiencies were well over 99% for all cases; which was found to be quite unreasonable. However, during exergy analysis the efficiencies ranged from around 70% to 92%. It was found that all efficiencies increased with decreased HTF flow rate, while exergetically all processes were most efficient with inlet HTF temperatures closer to the solidification temperature of ice.