Heat and mass transfer of hydrogen storage in metal-hydrogen Reactors

Abstract

Hydrogen energy is the best alternative to fossil fuels due to its high calorific value and being environmentally friendly. Hydrogen also produces more energy per unit weight than any other fuel. However, storage problem of hydrogen prevents its wide usage and commercialization. Hydrogen absorption in two LaNi5-H2 reactors is experimentally and theoretically investigated. In the experimental program, two tanks are filled with LaNi5 alloy and hydrogen is charged with a constant pressure. The temperature changes in the tanks are measured at several locations and recorded in a computer. Hydriding process is identified from measured temperature histories. An experimental set up is designed to study main characteristics of hydriding process and effect of bed geometry and heat transfer on the hydriding process. Hydriding process is characterized by exothermic reaction between LaNi5 and H2 and rapid temperature increase due the heat release. Hydriding time mainly depend on the successful heat removal from the bed. A bed geometry which provides more heat transfer area significantly reduces hydriding time In the theoretical program, a two dimensional mathematical model, which considers complex heat and mass transfer and fluid flow is developed and numerically solved. The governing equations are numerically solved and calculated results are compared with experimental data. It is found that mathematical model adequately captures the main physics of the hydriding process and can be employed for a better hydride bed design to reduce hydriding time. A reasonable agreement between the numerical results and experimental data is obtained. Copyright © (2006) by AFHYPAC.