Design and analyses of an AB5 - metal hydride based canister for hydrogen compressor application

Abstract

The reversible hydrogen storage nature of metal hydride (MH) is widely accepted for the development of MH based energy devices like energy storage, hydrogen compressors, etc. For efficient working of such devices, the appropriate thermal management of canister is very important i.e. extraction and supply of heat during hydrogenation and dehydrogenation, respectively. The accumulation of heat reduces the hydrogen storage capacity as well as detoriarates the reaction rates because of increase in MH temperature. Therefore, to optimise the MH heat transfer, in the present work, a helical coil is introduced within the MH Canister (MHC) to circulate the heat transfer fluid in addition to an external cooling jacket. The purpose of using helical coil is to get more surface contact with MH because of the poor thermal conductivity of MH. The performance analyses have been carried out through a 3-D Finite Volume Approach employed with La0.9Ce0.1Ni5. The analyses include the influence of coefficient of heat transfer, pressure, and temperature on the designed canister as well as the compressor performance. Initially, the numerical model is validated with experimental results available in the literature and observed in good match. Later, the performance of MHC is predicted for different operating conditions which results in the estimated storage capacity of hydrogen is about 1.48wt% at 25bar and 298K. In addition, it is observed that at an elevated supply pressure, the reaction rates increased as well as the rise in MHC temperature increased due to exothermic heat. Later, the MHC is tested for the application as hydrogen compressor which results in the compression ratio of 10.8 with a discharge pressure of 270bar at 140°C providing ~20% efficiency.