金属氢化物储氢反应器放氢特性的数值模拟

为了研究金属氢化物储氢反应器放氢过程的热质传递特性，本文建立了金属氢化物反应器的二维轴对称数学模型。此反应器内装填了Ti0.95Zr0.05Mn1.55V0.45Fe0.09储氢合金和膨胀石墨组成的复合压块。通过与文献中实验数据的对比验证了所建立模型的有效性。论文考察了换热流体温度、流体平均流速和氢气排出压力变化对金属氢化物反应器放氢过程的影响，比较了优化操作参数和基准操作参数下的放氢性能。并对优化操作参数下放氢反应过程特征进行了分析。模拟结果表明：换热管附近床层区域的换热效果更好，放氢反应进行得更快。当换热流体温度从313.15K升高到353.15K时，放氢时间从17100s降低到了6700s。虽然提高换热流体平均流速可以缩短反应器的放氢反应时间，但其强化效果是很有限的。当换热流体流速超过3m/s时，氢化物床与换热管壁之间的接触热阻成为整个传热过程的主要热阻，增加流速的强化效果已不明显。优化后的操作参数为：氢气排出压力为0.3MPa、换热流体温度为353.15K、换热流体平均流速为3m/s。与基准操作参数相比，放氢反应时间缩短了约56%，对操作参数的优化能够显著地提高反应器的放氢速率。Ti0.95Zr0.05Mn1.55V0.45Fe0.09合金的放氢反应过程仅仅在前4s内主要受氢气压力的控制，而随后的反应过程主要是受传热过程控制。

Numerical Simulation of Hydrogen Desorption Characteristics in Metal Hydride Reactor for Hydrogen Storage

To study the heat and mass transfer characteristics of hydrogen desorption process in metal hydride hydrogen storage reactor, a two-dimensional axisymmetric mathematical model for metal hydride reactor was established. The reactor was filled with composite compacts made of Ti0.95Zr0.05Mn1.55V0.45Fe0.09 alloy and expanded natural graphite. The validity of the model was verified by the experimental data in literature. The effects of heat transfer fluid temperature, mean fluid velocity and hydrogen delivery pressure on the hydrogen desorption process were investigated, and the hydrogen desorption characteristics were compared at the optimal and baseline sets of the operating parameters. The kinetics characteristics of the hydrogen desorption reaction were analyzed at the optimal sets of the operating parameters. The simulated results show that the heat transfer performance is better near the heat exchanger tube wall, where the hydrogen desorption reaction proceeds more quickly. When the temperature increases from 313.15 K to 353.15 K, the hydrogen desorption time decreases from 17100 s to 6700 s. Increasing the mean velocity can accelerate the hydrogen desorption process, but its strengthening effect is limited. When the flow rate of heat transfer fluid exceeds 3m/s, the enhancement effect of increasing the mean fluid velocity is not obvious due to the contact thermal resistance between the metal hydride bed and the wall of the heat transfer tube becomes the main thermal resistance in the overall heat transfer process. The optimal operating parameters are as follows: the hydrogen delivery pressure is 0.3 MPa, the temperature of heat transfer fluid is 353.15 K, and the mean velocity of heat transfer fluid is 3 m/s. Compared with the baseline set of the operating parameters, the hydrogen desorption reaction time is shorten by about 56%, and hence the optimization of the operating parameters can significantly improve the dehydrogenation rate of the reactor. The hydrogen desorption process of the Ti0.95Zr0.05Mn1.55V0.45Fe0.09 alloy is mainly controlled by hydrogen pressure only in the first 4 s, while the whole reaction process is mainly controlled by the heat transfer process.