Simulation Research On The Process Of Metal Hydride Absorption/desorption And The Performance Of Hydrogen Storage Container

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.