| Energy issues have always been taken seriously,and energy is the material basis for human life and social development.And the insufficient per capita possession of energy in China has become an important factor limiting the sustainable development of our economy and society.In the process of vigorous energy development,the development of renewable and clean energy is an important part of it,and the use of liquid flow batteries provides a feasible way for the storage and transportation of electric power resources.Renewable energy sources have unevenness,intermittency and other uncertainties,so energy storage under the same system can provide a more advanced solution for stable storage,stable transmission and stable utilization of energy.The structural design and optimization research of liquid flow battery is one of the important ways to improve the electrolyte flow performance inside the battery and increase the power density and reliability of the stack.In this paper,we explain the influence of flow field structure and other effects on the performance of liquid flow battery,and propose the flow field structure form to further improve the battery performance and suitable for popular application.First,the proposed five flow channel structures are modeled using UG software in order to obtain uniform velocity and pressure distribution and enhance mass transfer.The five types of flow channel structures include the passage structure,two parallel flow channel structures and two truncated parallel flow channel structures formed by adding a blocking structure in the electrochemical reaction region on the basis of the passage structure.Secondly,a three-dimensional mathematical model was established for the five flow channel structures,and the ANSYS-Fluent numerical simulation software was applied to simulate the flow state of the five flow channel structures under different flow rates,and the influences of the inlet flow rate and the number and width of the blocking structures on the fluid pressure and velocity fields in the flow channel were analyzed.The simulation results show that: when the fluid enters the small diameter channel from the large diameter channel,vortices are generated,causing energy loss;with the increase of the number of blocking structures,the internal pressure increases;the increase of blocking structures and the formation of truncated structures also increase the velocity and pressure.Finally,the charging and discharging model of Zn Br liquid flow battery was established by COMSOL software,and the charging and discharging performance of five flow path structures were studied under three inlet flow rates,three cycle tank volumes and four charging current densities.The results show that: the increase of inlet flow rate prolongs the discharge time of all five flow structures and reduces the remaining bromine concentration in the tank;the increase of tank volume decreases the discharge time of all five flow structures;the increase of positive charging current density increases the charging voltage,decreases the initial voltage of discharge and increases the bromine concentration in the tank,and the slope of bromine concentration is proportional to the positive charging current density.The increase of the number of blocking structures and the setting of truncated structure can get more amount of bromine substance,shorter discharge time,less remaining bromine concentration and more recoverable charge of the battery under the same charging and discharging conditions.The results of this paper can be used to adjust the discharge performance of single cells or cell stacks,and provide a reference and basis for the design of the flow channel structure of zinc-bromine liquid flow batteries. |
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