Abstract:

A three-dimensional mathematical model of a magnesium-based solid-state hydrogen storage reactor was developed to explore factors influencing hydrogen storage reaction rates. The model was validated by comparison with experimental data in the literature. Numerical techniques were used to study how the hydrogen storage reaction rate was affected by inlet temperature, hydrogen supply pressure, and oil layer thickness of annular heat conduction oil. Simulation results show that the reactor has an optimal reaction temperature, and that the hydrogen storage reaction speed is reduced if the heat conduction oil inlet temperature is too high or too low. When the oil inlet temperature rises from 548 K to 573 K, the hydrogen storage rate increases from 3.38 g/min to 8.75 g/min. When the oil inlet temperature rises from 573 K to 648 K, the hydrogen storage rate decreases from 8.75 g/min to 3.91 g/min. The higher the hydrogen supply pressure, the faster the reaction rate, but at the expense of increasing bed temperature. A pressure rise from 0.5 MPa to 3 MPa leads to an 81.8% reduction in hydrogen storage time and a temperature rises of 65 K. For the condition of constant hydrogen storage mass, thickening the annular heat conduction oil layer on the outer wall of the reaction bed significantly improves hydrogen storage reaction speed. When that oil layer thickness is increased from 0 mm to 18 mm, hydrogen storage time decreases from 550 s to 380 s (about 30.9%). Increasing the thickness of the annular heat conduction oil layer can shorten the hydrogen storage time significantly but the volumetric hydrogen storage density is reduced. When the reservoir thickness increases from 9 mm to 18 mm, hydrogen storage time is shortened only 5 s, while the volumetric hydrogen storage density decreases from 59.68 g/L to 41.16 g/L.

Key words: magnesium hydride, reaction rate, reservoir thickness, numerical analysis