Abstract
An application of latent-type thermal energy storage (TES) system and its issues associated with the safe operation for TES composite materials (i.e., solar salts (KNO3/NaNO3) and expanded graphite) are investigated. This work is aimed to present the compatibility of various compositions of TES materials with a heat transfer fluid (HTF) to provide a guideline for safe and reliable system usage. The thermochemical characteristics and chemical kinetic mechanism for HTF-diluted TES samples were measured using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) with additional numerical analysis for validation of the constructed reaction kinetics. Amongst the range of percent HTF dilutions, 20 wt% HTF dilution in comparison to no HTF dilution showed the strongest exothermic runaway reaction. For instance, with a decrease in the onset temperature, the time to runaway was shortened, while the change in the heat of reaction was not significant. The numerical simulations with chemical kinetics obtained using thermochemical analysis revealed that the reaction runway characteristics of HTF-diluted TES materials show a similar detonative behavior as of gunpowder. Moreover, the function of HTF in TES system appeared to be identical to that of sulfur in gunpower as its specific percent composition was responsible for accelerating an exothermic chemical reaction.
NSTL
Elsevier