A new approach is introduced to model the discharge behavior of a metal hydride hydrogen
storage bed. The reversible reaction kinetics and the empirical van't Hoff relationship used in
a typical reactor model are replaced by a solid-phase diffusion equation and a semiempirical
equilibrium P−C−T relationship. Two new semiempirical P−C−T models are also introduced
based on modified virial and composite Langmuir expressions. By varying the heat- and mass-transfer coefficients, the model was calibrated to experimental pressure and temperature histories
obtained from a commercially viable metal hydride bed containing Lm1.06Ni4.96Al0.04. Overall,
the results of this study showed that a fairly simple numerical model can do a reasonable job in
predicting the discharge behavior of a fairly complicated metal hydride hydrogen storage bed
over a wide range of hydrogen flow-rate demands. The extreme theoretical limits of isothermal
equilibrium (analytical model), adiabatic equilibrium, nonadiabatic equilibrium, isothermal
nonequilibrium, and adiabatic nonequilibrium conditions were also studied and compared to
the actual behavior under nonadiabatic nonequilibrium conditions. These limiting cases revealed
that the metal hydride hydrogen storage vessel was definitely heat-transfer-limited and only
minimally mass-transfer-limited over a wide range of hydrogen discharge flow rates.