【作者】 王兴国；

【导师】 刘学武；

【作者基本信息】 大连理工大学 ， 安全工程（专业学位）， 2021， 硕士

【摘要】 随着不可再生能源的枯竭,新能源的开发和利用已迫在眉睫。氢气完全燃烧的产物只有水,能降低温室气体排放,是最有发展前景的能源。金属氢化物储氢容器作为氢气储运的关键部件,其使用压力低,在合适的温度下自由吸/放氢,提高氢能应用安全性。现有的金属氢化物储氢容器换热性能差,极大影响容器吸/放氢效率,制约金属氢化物储氢技术的发展。因此,研究换热性能更优的金属氢化物储氢容器对发展固态储氢技术具有积极意义。论文取得的结果与结论如下:基于质量、动量、能量守恒方程和反应动力学方程,在COMSOL Multiphysics中建立了填充La Ni₅的金属氢化物储氢容器二维轴对称模型,并验证了模型正确性。传热传质模拟结果表明:吸/放氢时温度和平衡压力沿换热壁至容器中心方向逐渐降低/升高;吸/放氢区域从换热壁向容器中心移动。初始温度越低吸氢性能越好,初始温度越高放氢性能越好;入口压力0.8 MPa时吸氢性能较好,出口压力越低放氢性能越好;空隙率变化不能表示吸/放氢性能的优异;增加对流换热系数和合金导热系数提升吸/放氢性能。设计了不同结构的金属氢化物储氢容器,并进行了换热模拟研究。在内壁加翅片和内部加螺旋管换热器显著提升吸/放氢性能;容器内最大储氢量相等时,加螺旋管换热器的储氢容器吸/放氢性能更佳。加螺旋管换热器的金属氢化物储氢容器内最大储氢量相等时,螺旋管同心排列在吸/放氢过程前期更能提升吸/放氢性能;螺旋管环形排列在吸/放氢过程后期更能提升吸/放氢性能;增加螺旋管数量与提升吸/放氢性能没有必然联系;容器内加5个螺旋管环形排列时吸/放氢性能最好,与初始模型相比,达到最大吸/放氢量的90%所需时间分别减少52.63%和52.34%。为提高换热效率及合理利用反应热,建立了含相变换热器的金属氢化物储氢容器（MH-PCM）二维轴对称模型。明确MH-PCM吸/放氢过程中金属氢化物（MH）床和相变材料（PCM）中传热传质的耦合过程:吸/放氢时,MH床吸/放氢区域从换热壁向中心移动;PCM熔化/凝固部分从换热壁逐渐延伸至PCM罐外壁;储氢合金的吸/放氢量和PCM液相分数变化趋势相同。固相导热系数对吸/放氢性能影响效果不显著;增加液相导热系数和潜热提升吸/放氢性能;增加相变温度降低吸氢性能,但提升放氢性能;当PCM质量能吸收/提供合金完全吸/放氢放出/所需的热量时,增加PCM质量对吸/放氢性能影响效果不显著。PCM中加翅片能提升MH-PCM吸/放氢性能,与初始MH-PCM相比,达到最大吸/放氢量的90%所需时间分别减少27.82%和22.26%。更多还原

【Abstract】 With the depletion of non-renewable energy,the development and utilization of new energy is imminent.The product of complete combustion of hydrogen is only water,which can reduce greenhouse gas emissions and is the most promising energy source.As a key component of hydrogen storage and transportation,the metal hydride hydrogen storage container has a low operating pressure and can freely absorb/desorb hydrogen at a suitable temperature,which improves the safety of hydrogen energy application.The existing metal hydride hydrogen storage container has poor heat exchange performance,which greatly affects the hydrogen absorption/desorption efficiency of the container and restricts the development of metal hydride hydrogen storage technology.Therefore,research on metal hydride hydrogen storage containers with better heat exchange performance is of positive significance for the development of solid hydrogen storage technology.The results and conclusions of the paper are as follows:Based on mass,momentum,energy conservation equations and reaction kinetics equations,a two-dimensional axisymmetric model of a metal hydride hydrogen storage container filled with La Ni₅ was established in COMSOL Multiphysics,and the correctness of the model was verified.The heat and mass transfer simulation results show that the temperature and equilibrium pressure gradually decrease/increase from the heat exchange wall to the center of the container during hydrogen absorption/desorption,and the hydrogen absorption/desorption region moves from the heat exchange wall to the center of the container.The lower the initial temperature,the better the hydrogen absorption performance,and the higher the initial temperature,the better the hydrogen release performance;the hydrogen absorption performance is better when the inlet pressure is 0.8 MPa,the lower the outlet pressure is,the better the hydrogen release performance;the change in void ratio cannot indicate hydrogen absorption/desorption Excellent performance;increase convection heat transfer coefficient and alloy thermal conductivity to improve hydrogen absorption/desorption performance.Metal hydride hydrogen storage containers with different structures were designed,and heat exchange simulation studies were carried out.Adding fins on the inner wall and adding spiral tube heat exchangers significantly improves the hydrogen absorption/desorption performance;when the maximum hydrogen storage capacity in the container is equal,the hydrogen storage container with spiral tube heat exchanger has better hydrogen absorption/desorption performance;spiral tube heat exchanger has better hydrogen absorption/desorption performance;When the maximum hydrogen storage capacity in the metal hydride hydrogen storage container of the tube heat exchanger is equal,the spiral tube is arranged concentrically in the early stage of the hydrogen absorption/desorption process to improve the hydrogen absorption/desorption performance,and the spiral tube is arranged in a ring shape at the later stage of the hydrogen absorption/desorption process.It can further improve the hydrogen absorption/desorption performance,and increasing the number of spiral tubes is not necessarily related to the improvement of hydrogen absorption/desorption performance;the hydrogen absorption/desorption performance is the best when 5 spiral tubes are arranged in a circular arrangement in the container.Compared with the initial model,it reaches The time required for 90%of the maximum hydrogen absorption/desorption is reduced by 52.63%and 52.34%,respectively.In order to improve the heat exchange efficiency and rationally utilize the reaction heat,a two-dimensional axisymmetric model of a metal hydride hydrogen storage container（MH-PCM）with a phase change heat exchanger was established.Clarify the coupling process of heat and mass transfer between the metal hydride（MH）bed and the phase change material（PCM）in the MH-PCM hydrogen absorption/desorption process:when hydrogen is absorbed/desorbed,the hydrogen absorption/desorption area of the MH bed is separated from the heat exchange wall Move to the center;the PCM melting/solidification part gradually extends from the heat exchange wall to the outer wall of the PCM tank;the hydrogen absorption/desorption amount of the hydrogen storage alloy has the same change trend as the PCM liquid fraction.The solid-phase thermal conductivity has no significant effect on the hydrogen absorption/desorption performance;increasing the liquid thermal conductivity and latent heat improves the hydrogen absorption/desorption performance;increasing the phase transition temperature reduces the hydrogen absorption performance,but improves the hydrogen desorption performance;when the PCM quality can absorb/desorb hydrogen When providing the heat required for the alloy to completely absorb/desorb hydrogen and release/deliver,increasing the quality of PCM has no significant effect on the hydrogen absorption/desorption performance.Adding fins to the PCM can improve the hydrogen absorption/desorption performance of MH-PCM.Compared with the initial MH-PCM,the time required to reach 90%of the maximum hydrogen absorption/desorption is reduced by 27.82% and 22.26%,respectively.更多还原