Technical Note Conjugate heat and mass transfer in metal hydride beds in the hydriding process

Metal hydride applications span a wide variety of tech! nologies\ e[g[\ energy conversion\ chemical compressors and hydrogen storage[ A knowledge of heat and mass transfer in a metal hydride reactor during the absorption and desorption of hydrogen is important for performance optimization of the reactor[ One of the key requirements in the design of metal hydride bed is the enhancement of the e}ective thermal conductivity of metal hydride powders ð0Ð2Ł[ A literature survey reveals that many attempts have been made to analyze the hydride dynamic character during the absorption:desorption process ð0Ð 5Ł[ The main factors governing the dynamics of the metal hydride bed are ð3Ł] heat transfer from:to hydration zone\ hydrogen _ltration through the metal hydride matrix and kinetics of the hydrogen sorption processes\ etc[ As to the heat transfer from:to the metal hydride bed\ a major concern is the limited reacting rate process\ because of its fast kinetics and low hydride thermal con! ductivity ð0\ 1Ł[ To increase the lower thermal con! ductivity of the bed\ several methods have been proposed\ e[g[\ addition of a wire\ employment of metal powder of high thermal di}usivity\ and use of an aluminum foam matrix to contain the hydride particles[ The installation of internal plates\ among others\ is considered in the present study to enhance the lower thermal conductivity and to improve the reaction dynamics[ One of the central ingredients in the present modeling is the treatment of the conjugate nature of heat and mass transfer\ which is