Numerical optimization of a plate reactor for a metal hydride open cooling system

Abstract

Open cooling systems based on metal hydrides (MH) are promising as they are purely driven by the on-board available compression work of the compressed hydrogen in a fuel cell vehicle. In this study, the plate reactor is numerically optimized for fast reaction dynamics leading to an increased power density. Experimental results for the thermodynamic characterization of the applied Hydralloy C2 (Ti_0.98 Zr_0.02 V_0.41 Fe_0.09 Cr_0.05 Mn_1.46) in the temperature range of 0 to 50°C and a mathematical expression for the pressure–concentration isotherms are presented. The model is validated with data from the experimental literature for different cooling temperatures (15–25°C) and electrical fuel cell powers (4–6 kW). As the reactor alternately passes through two temperature levels in its continuous operation, the effects of thermal losses are evaluated in detail. The optimum thickness for the MH bed is close to the channel thickness of a commercially available reactor. A further increase of the cooling power can be obtained by reducing the distance of the hydrogen gas transport, porosity of the MH bed, and fuel cell backpressure.