Expanded graphite as heat transfer matrix in metal hydride beds

Metal hydrides can be used for a variety of applications. The thermal conductivity of metal hydride powders and the heat transfer coefficient between metal hydride powder beds and the walls of reaction beds are usually low. Heat transfer enhancement techniques have to be applied, when metal hydride powders are used. Here, expanded natural graphite/metal hydride compacts are described, possessing a high effective thermal conductivity (lambda(eff) approximate to 19 W m(-1) K-1). Reaction kinetics of these compacts have been measured and compared to those of metal hydride beds employing Al-foams as heat transfer matrices. It was found that hydrogen absorption rates were only slightly decreased by the expanded natural graphite/metal hydride compacts, thus providing an efficient, cost-effective and simple solution. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.