Simulation Study On Flow Characteristics In The Unit Of Filter-Press Water Electrolyzer

The filter-press electrolyzer for hydrogen production is a common alkaline water electrolyzer,which is composed of several electrolysis cells stacked according to the rules.It has the advantages of high electrolysis efficiency,small volume,high gas purity and simple structure of alkaline liquid circulation system.It is widely used in power,chemical,electronic,building materials and other industries for hydrogen or oxygen supply.The channel structure of the filter-press water electrolyzer has a direct impact on the distribution of reaction liquid and heat in the electrolysis process.The uniformity of reactant electrolyte distribution will affect the bubble generation rate and the distribution of gas-liquid two-phase,as well as the temperature distribution in the channel.Conversely,the temperature will also affect the reaction rate in the electrochemical hydrogen production or fuel cell chemical process.By studying the electrolyte distribution in the flow channel of the electrolyzer,it can provide reference for the improvement of the equipment structure and guide to improve the efficiency of water electrolysis hydrogen production in the actual process,so it has a certain engineering practical significance.In this paper,firstly,by means of numerical simulation,the flow field in the unit of the filter-press water electrolyzer has been researched.The flow field characteristics such as velocity,temperature and vortex flow have been analyzed,and then the velocity distribution uniformity index is used to characterize the flow field uniformity and a comparison has been made.Secondly,the channel structure is improved from the number of the inlet structure,including the corresponding arrangement position and the form of the inlet structure.The advantages and disadvantages of each inlet structure have been compared.Finally,the improved design of the concave-convex structure in the channel is proposed,and the influence of the shape and arrangement of the concave-convex structure on the flow uniformity in the channel are analyzed.It is shown that:(1)The simulation results of RNG k-ε model are in good agreement with the experimental data.The vortex flow caused by the concave-convex structure on the main plate in the channel determines the location of the vortex distribution.Its disturbing effect affects the velocity distribution and improves the uniformity of the flow field distribution in the channel.With the increase of inlet flow,the intensity of vortex increases,as well as the disturbance degree.The relationship between temperature and velocity distribution follows as high velocity,low temperature.(2)The velocity and temperature fields of the 3-inlet structure are more uniform than that of the 1-inlet and 2-inlet structure,and the circulation flow area is the smallest.The diverging inlet structure improves the distribution uniformity in the flow passage,when the angle exceeds 30°,the velocity distribution uniformity index does not increase and a new reflux area appears,so it is appropriate to choose the 30° diverging inlet structure.(3)The shape of the concave-convex structure affects the local flow details in the channel,which can improve the flow field distribution in the local area.The teardrop structure with the smallest windward area has the best distribution uniformity.The results show that the distribution uniformity of the channel with square staggered arrangement and rhombus sequential arrangement II is similar,and better than that with square sequential arrangement and rhombus sequential arrangement I.