METAL HYDRIDE ENERGY-SYSTEMS PERFORMANCE EVALUATION .A. DYNAMIC ANALYSIS MODEL OF HEAT AND MASS-TRANSFER

This paper presents a numerical model to evaluate the dynamic behaviour of heat and mass transfer in metal hydride energy systems. At first, with reference to each metal hydride reactor (i.e. heat exchanger filled with metal hydride), both the equations which describe the hydrogen absorption-desorption and the heat transfer are derived. Then, the ''core'' of metal hydride energy systems, i.e. coupled metal hydride reactors, has been considered and, by the use of the previous correlations and by further equations taking into account the transient phenomena in the gaseous hydrogen line linking the reactors, the complete numerical modelling has been carried out. This model, founded on a typical thermodynamic approach, is a lumped-parameters model. and thus its numerical resolution is rather easy and fast. The numerical model is able to take into account the fundamental determinants of coupled metal hydride operations: the dynamic of hydrogen transfer between paired metal hydride containers and the dynamic of the heat transfer process in the containers. Thus the model allows us to know and to foresee the effects of operational and design parameters on the mass and heat transfer performance of the metal hydride energy systems. The validation of the model has been carried out by comparison with experimental results obtained by other authors and the results of this validation procedure, which are in good agreement with the experimental ones, are presented and discussed.