Effects evaluation of Fin layouts and configurations on discharging performance of double-pipe thermochemical energy storage reactor

Thermochemical energy storage (TCES) based on hydrated salts is gaining popularity because it can provide high storage capacity at low costs. It is critical to improving heat storage efficiency and capacity due to technical challenges such as low thermal conductivity of thermochemical materials (TCMs) and poor mass transfer. The reversible reaction of strontium bromide monohydrate (SrBr2·H2O) and water vapor forming strontium bromide hexahydrate (SrBr2·6H2O) for TCES is used in numerical simulation, aiming to investigate the discharging performance of a double-pipe closed TCES reactor considering the influences of fin layouts (radial and longitudinal fins) by evaluating several indicators such as the reaction time and outlet temperature. The results show that the use of fins can improve the exothermic process. The discharging time of the reactor with upward L-shaped fins is reduced by 8.6% for radial fins and by 8.9% for the reactor with four longitudinal fins. The addition of fins expands the heat transfer area and makes the hydration rate of TCM around fins significantly higher than other parts. The Taguchi method is adopted to optimize the structure parameters of case 7 as it has the highest heat transfer amount of heat transfer fluid (HTF), and the optimal combination (A (fin number) = 4, B (fin extension length) = 20 mm, C (fin thickness) = 2 mm) increases the peak value of average outlet temperature by 1.47% and the heat exchange efficiency by 4.7% compared with case 7.