Optimal Design Of Hydrogen Storage Reactor Based On Structural Bionics

Hydrogen is a clean energy with high energy density,while the technical bottleneck of H₂ storage has seriously hindered the promotion and application of H₂ energy.Metal hydride（MH）has been demonstrated to be one of the most efficient H₂ storage methods due to its safety and high H₂ storage capacity.For practical applications,the hydrogenation/dehydrogenation of MH is usually performed inside MH reactor accompaning with strong thermal effect,and thus the structural design of MH reactor based on heat transfer enhancement tends to be an important issue in current research.In this work,several novel MH reactors are proposed to tackle the complicated heat transfer difficulties based on the bionic optimization concept in heat transfer field,and the optimal design parameters of MH reactors are obtained by comparison.Meanwhile,the simulation models for various applications are established and the calculation results present the outstanding performance of the proposed reactors.Moreover,the excellent H₂absorption/desorption rate of MH reactors are confirmed through experiments.The major results are as follows:（1）Inspired by the DNA structure,a novel duplex helical elliptical-tube reactor（DHER）was proposed.The comparison results indicated that DHER can save 14%hydrogenation time and 15%dehydrogenation time compared with that of the single helical elliptical-tube reactor,and the radial projected area of the heat exchange tube was proved to be the dominant factor for the reaction performance of DHER.Meanwhile,the regression model between the projected area and the reaction time was obtained,and the minimal cycle time was 1227 s.（2）In view of the radiation structure of tree trunks in nature,a novel radiation mini-channel reactor（RMCR）was proposed,and the comparison results indicated RMCR can reduce hydriding time by 54%and dehydriding time by 20%compared with the straight tube reactor,which verified the feasibility of the bionic optimization design in H₂storage reactor.The optimal structure parameters and operating conditions of RMCR were achieved,and the sensitivity orders affecting the reaction performance were obtained.（3）Based on the bifurcation structure of venation in nature,a novel branch mini-channel reactor（BMCR）was proposed,and the results illustrated that the sensitivity order of the operating conditions was consistent with that of RMCR,indicating that the order was universal in a certain range.In addition,the quadratic polynomial regression models of reaction time and the optimal values of operating conditions were obtained by response surface analyses,and the models were proved to own good prediction performance.（4）A novel disc mini-channel reactor（DMCR）was developed based on limit thought,and the results indicated that DMCR can complete the reaction process within about 200 s,and the change of the reactor shape had little influence on its excellent heat transfer performance.Meanwhile,the optimal height of heat transfer layer and MH layer were 0.9mm and 5 mm,respectively.The optimal layer height ratio was 0.176,and the optimal MH filling fraction was 0.7.（5）The reaction performance of various H₂ storage reactors were extensively compared,and the results showed DMCR could shorten absorption time of 89%and desorption time of 93%compared with the straight tube reactor,indicating that the uniform arrangement of heat exchange tubes owned outstanding heat transfer performance and reaction characteristics,which was in accordance with the uniform distribution theory in the heat transfer,providing guidance for the subsequent optimization design of the reactor.Meanwhile,a three-dimensional model of the reactor filled with Mg was established,and the performance comparison results indicated that DMCR still behaved excellent reaction characteristics when the internal materials were replaced,and the stable operating range of DMCR was analyzed and obtained.Moreover,a three-dimensional calculation model of the reactor combined with phase change material was established,and the results illustrated that DMCR behaved the best heat storage characteristic when the initial temperature was at phase change temperature.In addition,the reaction performance of the smallest unit of DMCR was experimentally studied,illustrating the favorable application characteristics of DMCR,and the optimal heat transfer fluid temperatures were 20℃（absorption）and 80℃（desorption）.