Multi-physical Field Simulations And Parameter Sensitivity Analysis Of Hydrogen Storage Performance Of ZrCo-based Multilayer Thin-walled Tubular Reactor

With rapid economical-society growth,global natural resources are being consumed at an increasing speed.New energy development and utilization have received considerable attention.Hydrogen energy,as a green energy,is attracting more interests from countries around the world.However,hydrogen safe and effective storage have always been a problem that restricts its applications.Metal hydride is a very reliable solid hydrogen storage medium.Besides,it can be used for purifying hydrogen,heat engine component,preparing fuel cells,and even for ITER fuel cycle applications.Therefore,an investigation on metal hydride hydrogen storage technology is of great significance for hydrogen energy utilization.For metal hydride hydrogen storage,a hydrogen storage alloy is employed to generate a chemical reaction with hydrogen.Due to tiny molecular volume,generous hydrogens are stored in crystal voids,and in turn the hydrogen storage volume reaches more than a thousand times than its own volume.Because the chemical reaction between hydrogen and hydrogenated metal is reversible,it is possible for hydrogen storage alloys to absorb hydrogen like a "sponge" at an appropriate temperature and pressure,and release hydrogen in heating and pressuring states.As a carrier of hydrogen storage technology,such a reactor plays an important role in the process of hydrogen energy industrialization.Current work shows that the process of hydrogen absorption and release is characterized by intense heat transfer.How to effectively reduce negative thermal effects is key to improve hydrogen storage capacity and efficiency.At the same time,an effective transport of hydrogen during the process of hydrogen transmission is also an important factor affecting the hydrogen storage performance.Therefore,a comprehensive study is conducted to investigate heat and mass transfer and mechanical response of hydrogen storage reactors,and proposes a solution to optimize metal hydride hydrogen storage container.Heat transfer efficiency is a key factor that affects metal hydride bed perforamce,which deserves a priority.In this work,a three-dimensional model of a multilayer annular hydrogen storage reactor is established,and its thermal performance is evaluated through numerical simulations.Finite element simulation method is used to systematically study the influence of structure geometry,cooling method and material thermophysical properties on thermal diffusion behavior under the framework of convective heat transfer.The results show that the model can effectively characterize the temperature evolution during hydrogen absorption process.In addition,through statistical analysis,the total thermal performance of the sensitivity sequence of these factors is examined.The order of the influence of each factor on heat dissipation effect is: coolant > hydride layer thickness > cooling tube type > aluminum doping > flow velocity > wall surface thermal conductivity > fin arrangement.Similarly,mass transfer behavior is also important for reactor performance,because high-efficiency mass transfer can guarantee hydrogen absorption and release as quick as possible.Thus,a novel model is established to describe the coupling relationship between heat and mass transfer and reaction rate during hydrogen absorption and desorption in the reactor.This model is based on perfect mathematical and physical equations,and considers complex coupling effect between multiscale and multiphysics.Importantly,a mesoporous structure is introduced firstly to study the mass transfer.Meanwhile,hydrogen concentration profiles of packed bed and pores in the particle at two levels of pores.The heat and mass transfer are found to be dependent upon the chemical reaction.Thus,the effects of particle pore parameters and packed bed design parameters on the hydrogen absorption process were analyzed by three-dimensional numerical simulation.The calculation results demonstrate that the particle size,porosity,and packing method of hydride particles have a significant effect on entire transportation process,which means that an appropriate particle size,particle porosity,and packed bed compactness should be considered in reactor design.In addition,reactor aspect ratio is also one of key factors affecting the reactor performance.Afterwards,the reactor stability is evaluated through reactor temperature field.The thermal stress distribution and stress concentration area in the reactor are calculated.The results show that there are severe stress concentrations on the wall surface of cooling tubes,and the stress level inside the reactor is significantly higher than that of the outside.At the same time,the influence of bed characteristic parameters on hydrogen pressure in the reactor is investigated.Under the condition that supplied hydrogen concentration is constant,reducing the particle size or increasing the packed bed compactness obviously increases the hydrogen pressure level in the hydride bed.Reducing the bed aspect ratio has a significant effect on reducing the hydrogen pressure.In addition,the pressure generated by fluid flowing in cooling tubes is studied.Because the cooling tube circuit is connected by several elbows,the tube wall pressure takes a change.This work studies the influence of fluid flow velocity,fluid temperature and tube radius on wall pressure.The results show that when the fluid velocity exceeds 1 m/s,the tube wall pressure value increases rapidly.The fluid temperature increase can slightly reduce the wall pressure.The pressure level of the tube wall at the input increases for minor tube radius,and at this time,a large negative pressure and a positive pressure are formed at the elbow inside and outside,respectively.Finally,through the analysis of experimental results and the sensitivity evaluation of influencing factors,a scheme for optimizing the reactor is proposed.It mainly starts from improving the heat dissipation level,improving the hydrogen transmission capacity,reducing the reactor stress spikes,and improving weak links in actural structure.It also ensures that the structure is easily constructed to strive for a safe and efficient reactor solution suitable for practical applications.The purpose of this work is to study the thermal and mass transportation and structural safety of metal hydrogen storage reactors,by taking a multi-layer annular hydrogen storage reactor as one of typical representatives.It is expected to provide theoretical basis and technical support for design and development of industrial-grade metal solid hydrogen storage containers and performance optimization,and then promote a wide application of metal hydrogen storage technology.