Transport Process Study in Sodium Alanate Hydrogen Storage System During Desorption

Transport processes in a sodium alanate hydrogen storage system during desorption are presented. The mathematical model, which considers heat conduction and convection, hydrogen flow governed by Blake-Kozeny law and the chemical kinetics, is solved using the COMSOL Multiphysics^® finite element software. The numerical simulation is used to present the time-space evolutions of the temperature, pressure and hydride concentration. The results are discussed for two cases: a finned storage system and a finless one. It is shown that the whole process occurring in the bed is governed and controlled by heat transfer from the heating fluid to the storage media and strengthened by axial heat transfer through the fins. The importance of the hydride bed thermal conductivity has also been evaluated. It was observed that the hydrogen discharge rate in a finless system can be improved if we find ways of increasing the thermal conductivity of the storage media. On the other hand, for a reservoir with fins, heat transfer is good enough that the discharge rate is limited by the kinetics.