High-Temperature Activated AB2 Nanopowders for Metal Hydride Hydrogen Compression

A reliable process for compressing hydrogen and for removing all contaminants is that of the metal hydride thermal compression. The use of metal hydride technology in hydrogen compression applications though, requires thorough structural characterization of the alloys and investigation of their sorption properties. The samples have been synthesized by induction - levitation melting and characterized by Rietveld analysis of the X-Ray diffraction (XRD) patterns. Volumetric PCI (Pressure-Composition Isotherm) measurements have been conducted at 20, 60 and 90 oC, in order to investigate the maximum pressure that can be reached from the selected alloys using water of 90oC. Experimental evidence shows that the maximum hydrogen uptake is low since all the alloys are consisted of Laves phases, but it is of minor importance if they have fast kinetics, given a constant volumetric hydrogen flow. Hysteresis is almost absent while all the alloys release nearly all the absorbed hydrogen during desorption. Due to hardware restrictions, the maximum hydrogen pressure for the measurements was limited at 100 bars. Practically, the maximum pressure that can be reached from the last alloy is more than 150 bars.Comment: 9 figures. arXiv admin note: text overlap with arXiv:1207.354

Study on the Hydrogenation of a Mm-based AB5-Intermetallic for Sustainable Building Applications

In the present study, a numerical approach regarding the thermal management of a Mm-based AB5-intermetallic (MmNi4.6Al0.4) for the hydrogenation process is introduced and analysed. Several heat management scenarios are studied. The numerical model was supported and validated with experimental data in terms of hydrogenation capacity and temperature distribution. The numerical analysis is based on the introduction of the energy, mass and momentum conservation equations to numerically describe the hydrogenation reaction. The main aim of the present study is the numerical description of the heat management when 200 g of hydrogen are stored (13 kg of the hydride). The heat management cases consider the usage of cooling tubes in combination with high thermal conductivity fins. In general, various parameters affect the efficiency of the heat management. The parameters considered are the fin thickness, the fin number - which is directly connected to the metal hydride thickness convective heat transfer coefficient. A non-dimensional parameter (NDC) specially modified to describe the role of the fins in addition to the cooling tubes is introduced to evaluate the heat management. The target of the study was to reduce the hydrogenation time of almost 13 kg of MmNi4.6Al0.4 and from the parametric study it has been found that the more efficient conditions are fin thickness between 5-8 mm and the convective heat transfer coefficient of 2000 W/m2K