Modeling of heat and mass transfer in metal hydride matrix during hydrogen absorption-desorption cycle

摘要

Packed bed reactors using metal hydride are attracting a lot of attention as potential hydrogen storage systems. Some operational and design variables are major constraints to obtain proper inflow/outflow of hydrogen in a metal hydride reactor. These variables include packed bed thermal conductivity, porosity, pressure and temperature distributions in reactor during absorption/desorption cycle and also induced by temperature gradient mechanical stress. In this paper, two dimensional model is implemented in COMSOL multiphysics to simulate the hydrogen flow, pressure and temperature distributions in the packed bed reactor during absorption/desorption cycle. Also, stresses in porous metal hydride induced by temperature variation in the heating/cooling cycle were evaluated. Possible effect of stress induced porosity changes on diffusion and heating of hydrogen in both radial and axial direction in packed bed is discussed. The model consists of a system of partial differential equations (PDE) describing structural mechanics of stress, heat and mass transfer of hydrogen in porous matrix of packed bed reactor.