金属氢化物放氢过程数值分析

MATHEMATICAL MODEL AND NUMERICAL ANALYSIS FOR DESORPTION IN METAL HYDRIDE BED

通过分析外壁处有恒温热源条件下贮氢合金放氢过程的传热现象,建立多孔介质的传热模型,研究分析了真空烧结的多孔贮氢复合材料放氢过程中温度场和速度场变化规律．计算结果表明,当反应焓变小于外界传入的热量时,温度逐渐上升．由于从内壁到外壁热阻很大,导致靠近内壁处温度难以上升,氢气也就难以释放,故为提高合金利用率,须减小传热间隔,并适当提高初始温度。氢气流速刚开始时大,很快趋于平稳．孔隙率对温度分布和流速影响很大,孔隙率越大,则气流速度更平缓易于控制,但使合金含氢量减小．选取合适的贮氢合金孔隙率对金属氢化物放氢过程较为关键．

A diathermanous phenomena in metal hydride bed circled by constant high temperature was described in a mathematical and physical model. The FTCS format and first order upwind difference were employed to solve the conservation equations. The results show that it is necessary to increase the heat conduction coefficient and shorten the length of heat transfer path. The primary velocity of hydrogen is very large, but it would be calm soon. At the same time, the volume fraction of fibrous preform in porous materials strongly affects the distribution of hydride temperature and hydrogen velocity. So it is most important to select an appropriate porosity.