Performance analysis of a metal hydride reactor for hydrogen storage using ethylene glycol-based coolants as heat transfer fluids

This study numerically investigates the performance of a hydrogen storage metal hydride reactor using ethylene glycol (EG)-water mixtures as Heat Transfer Fluid (HTF). A comprehensive numerical model was developed and validated against published experimental data demonstrating satisfactory agreement between the numerical predictions and the published experimental data for the validated water-cooled absorption process. The primary outcome of the investigation is the evaluation of the hydrogen storage cycle time which is reflective of absorption/desorption kinetics in the metal hydride reactor. The performance of a metal hydride reactor employing ethylene glycol–water mixtures as heat transfer fluids was numerically investigated under realistic operating conditions. The validation yielded a coefficient of determination of R 2 = 0.987 a maximum deviation of 3.51%, an average deviation of 1.54%, and a root-mean-square error of 6.14 K. For the assumed values, pure EG had the shortest cycle times of 285 s absorption time, 880 s desorption time, and 1165 s total cycle time. This represents a 10.7% cycle time saving relative to water. However, the intermediate EG-water mixtures had rather low savings in cycle time, ranging from 3.1% to 3.6%. These results show that the selection of the coolant depends on cycle time, viscosity, pressure drop, pumping power and cost. The predicted cycle times for EG-water mixtures and the desorption process are based solely on numerical simulations and require future experimental validation.