Heat transfer in iron titanium hydride Beds

New data on the thermal conductivity of FeTi hydride at pressure of hydrogen were obtained. They were found to be inverse related to absolute temperature. Comparing with the previous results, their dependence on hydrogen pressure is considered more reliable and should be used in modeling study to predict the behavior of the hydride beds.

The experimental results show that before a practical reaction is obtained, activation (conditioning) of the FeTi hydride is necessary. Since even at the pressure of 5C0 psig hydrogen, there is no indication of reaction between hydrogen and FeTi hydride not previously activated.

According to the mathematical model study, the addition of aluminum in the form of reticulated open—cell does benefit the reaction in the hydride bed. The heat transfer improvement is a strong function of the form of the aluminum. The smaller the cell size, the faster the hydrogen charging/discharging rate.

The aluminum content and the cell size in the Al—enhanced hydride bed are determined by at least two factors: (1) the expected rate, and (2) the amount of hydrogen to be charged/ discharged. For more detailed design purpose, the model developed in the report can be used to assess the bed performance.

For the Al-enhanced FeTi hydride bed with very small cells, the heat transfer resistance may not be the controlling step. In these case, an accurate knowledge of kinetics is needed for predictions.