Numerical Analysis of Mini-Channel Metal Hydride Reactor for Hydrogen Storage

Abstract

Fossil fuels are reducing day by day. This fossil fuel causes pollution, acid rain and global warming problems. To overcome these problems alternative fuel is needed. Hydrogen energy appears to be the best alternative fuel. Hydrogen possesses highest energy per unit weight of any chemical fuel. It is most abundant element available in the universe. Main problem in using hydrogen as alternative fuel is its low volumetric density. Hydrogen can be stored in vehicle by using metal hydride based hydrogen storage reactor. Process of refueling of metal hydride based hydrogen storage systems is a highly exothermic. Because of the need for fast refueling rates, thermal management of the storage system is very important. In this dissertation work numerical analysis of two dimensional heat and mass transfer during absorption of hydrogen in a metal hydride reactor is presented by using ANSYS FLUENT software. Initially numerical analysis of two dimensional heat and mass transfer during absorption of hydrogen in a circular mini-channel metal hydride reactor containing LaNi5 is developed and compared with published results. Average bed temperature profiles at 3 bar supply pressures showed good agreement with the experimental data reported in the literature. The metal hydride reactor is modified by using rectangular and triangular mini-channels in order to increase surface area by keeping mass of LaNi5 constant. Result shows that for rectangular mini-channels time required for hydrogen absorption is reduced by 19%. Instead of inline arrangement of the mini-channels, staggered arrangement is used in order to increase heat transfer. Result shows that for staggered arrangement time required for hydrogen absorption is reduced by 6%. Result shows that time required for hydrogen absorption is reduced by 12% with increasing pressure from 3 bar to 10 bar. As heat transfer coefficient increases from 1000 to 2500, hydrogen absorption time decreases.