Alkaline water electrolysis(AWE)is the most mature technology for hydrogen production by water electrolysis.Alkaline water electrolyzer consists of multiple electrolysis cells,and a single cell consists of a diaphragm...Alkaline water electrolysis(AWE)is the most mature technology for hydrogen production by water electrolysis.Alkaline water electrolyzer consists of multiple electrolysis cells,and a single cell consists of a diaphragm,electrodes,bipolar plates and end plates,etc.The existing industrial bipolar plate channel is concave-convex structure,which is manufactured by complicated and high-cost mold punching.This structure still results in uneven electrolyte flow and low current density in the electrolytic cell,further increasing in energy consumption and cost of AWE.Thereby,in this article,the electrochemical and flow model is firstly constructed,based on the existing industrial concave and convex flow channel structure of bipolar plate,to study the current density,electrolyte flow and bubble distribution in the electrolysis cell.The reliability of the model was verified by comparison with experimental data in literature.Among which,the electrochemical current density affects the bubble yield,on the other hand,the generated bubbles cover the electrode surface,affecting the active specific surface area and ohmic resistance,which in turn affects the electrochemical reaction.The result indicates that the flow velocity near the bottom of the concave ball approaches zero,while the flow velocity on the convex ball surface is significantly higher.Additionally,vortices are observed within the flow channel structure,leading to an uneven distribution of electrolyte.Next,modelling is used to optimize the bipolar plate structure of AWE by simulating the electrochemistry and fluid flow performances of four kinds of structures,namely,concave and convex,rhombus,wedge and expanded mesh,in the bipolar plate of alkaline water electrolyzer.The results show that the expanded mesh channel structure has the largest current density of 3330 A/m^(2)and electrolyte flow velocity of 0.507 m/s in the electrolytic cell.Under the same current density,the electrolytic cell with the expanded mesh runner structure has the smallest potential and energy consumption.This work provides a useful guide for the comprehensive understanding and optimization of channel structures,and a theoretical basis for the design of large-scale electrolyzer.展开更多
In order to evaluate the effects of mesh generation techniques and grid convergence on pump performance in centrifugal pump model, three widely used mesh styles including structured hexahedral, unstructured tetrahedra...In order to evaluate the effects of mesh generation techniques and grid convergence on pump performance in centrifugal pump model, three widely used mesh styles including structured hexahedral, unstructured tetrahedral and hybrid prismatic/tetrahedral meshes were generated for a centrifugal pump model. And quantitative grid convergence was assessed based on a grid convergence index(GCI), which accounts for the degree of grid refinement. The structured, unstructured or hybrid meshes are found to have certain difference for velocity distributions in impeller with the change of grid cell number. And the simulation results have errors to different degrees compared with experimental data. The GCI-value for structured meshes calculated is lower than that for the unstructured and hybrid meshes. Meanwhile, the structured meshes are observed to get more vortexes in impeller passage.Nevertheless, the hybrid meshes are found to have larger low-velocity area at outlet and more secondary vortexes at a specified location than structured meshes and unstructured meshes.展开更多
针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流...针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流域水平梯田为例,利用现有1∶1万格网DEM、梯田特征点线及其外围边界线,构建出能够充分顾及梯田地形的GT-DEM。研究表明,利用现有格网DEM和梯田地形特征点线构建顾及梯田地形GT-DEM的技术可行。GT-DEM不仅可对研究区全局地形进行粗略表达,而且可对其局部梯田地形进行精细表达。该研究是对如何提高DEM的梯田地形数字表达能力的有益探索,对进一步提高DEM对淤地坝、鱼鳞坑等其他人工地形的数字表达能力具有重要借鉴意义。展开更多
基金financially supported by the National Natural Science Foundation of China(No.52074130)the Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality,Ministry of Education。
文摘Alkaline water electrolysis(AWE)is the most mature technology for hydrogen production by water electrolysis.Alkaline water electrolyzer consists of multiple electrolysis cells,and a single cell consists of a diaphragm,electrodes,bipolar plates and end plates,etc.The existing industrial bipolar plate channel is concave-convex structure,which is manufactured by complicated and high-cost mold punching.This structure still results in uneven electrolyte flow and low current density in the electrolytic cell,further increasing in energy consumption and cost of AWE.Thereby,in this article,the electrochemical and flow model is firstly constructed,based on the existing industrial concave and convex flow channel structure of bipolar plate,to study the current density,electrolyte flow and bubble distribution in the electrolysis cell.The reliability of the model was verified by comparison with experimental data in literature.Among which,the electrochemical current density affects the bubble yield,on the other hand,the generated bubbles cover the electrode surface,affecting the active specific surface area and ohmic resistance,which in turn affects the electrochemical reaction.The result indicates that the flow velocity near the bottom of the concave ball approaches zero,while the flow velocity on the convex ball surface is significantly higher.Additionally,vortices are observed within the flow channel structure,leading to an uneven distribution of electrolyte.Next,modelling is used to optimize the bipolar plate structure of AWE by simulating the electrochemistry and fluid flow performances of four kinds of structures,namely,concave and convex,rhombus,wedge and expanded mesh,in the bipolar plate of alkaline water electrolyzer.The results show that the expanded mesh channel structure has the largest current density of 3330 A/m^(2)and electrolyte flow velocity of 0.507 m/s in the electrolytic cell.Under the same current density,the electrolytic cell with the expanded mesh runner structure has the smallest potential and energy consumption.This work provides a useful guide for the comprehensive understanding and optimization of channel structures,and a theoretical basis for the design of large-scale electrolyzer.
基金Projects(51109095,51179075,51309119)supported by the National Natural Science Foundation of ChinaProject(BE2012131)supported by Science and Technology Support Program of Jiangsu Province,China
文摘In order to evaluate the effects of mesh generation techniques and grid convergence on pump performance in centrifugal pump model, three widely used mesh styles including structured hexahedral, unstructured tetrahedral and hybrid prismatic/tetrahedral meshes were generated for a centrifugal pump model. And quantitative grid convergence was assessed based on a grid convergence index(GCI), which accounts for the degree of grid refinement. The structured, unstructured or hybrid meshes are found to have certain difference for velocity distributions in impeller with the change of grid cell number. And the simulation results have errors to different degrees compared with experimental data. The GCI-value for structured meshes calculated is lower than that for the unstructured and hybrid meshes. Meanwhile, the structured meshes are observed to get more vortexes in impeller passage.Nevertheless, the hybrid meshes are found to have larger low-velocity area at outlet and more secondary vortexes at a specified location than structured meshes and unstructured meshes.
文摘针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流域水平梯田为例,利用现有1∶1万格网DEM、梯田特征点线及其外围边界线,构建出能够充分顾及梯田地形的GT-DEM。研究表明,利用现有格网DEM和梯田地形特征点线构建顾及梯田地形GT-DEM的技术可行。GT-DEM不仅可对研究区全局地形进行粗略表达,而且可对其局部梯田地形进行精细表达。该研究是对如何提高DEM的梯田地形数字表达能力的有益探索,对进一步提高DEM对淤地坝、鱼鳞坑等其他人工地形的数字表达能力具有重要借鉴意义。
