Dynamics Analysis Of Bubble In DMFC Anode Flow Channel Based On FLUENT

With the progress of science and technology,electronic products?mobile phones,laptops,etc.?have become an indispensable part of our life.With the increasing demand on portable power sources,direct methanol fuel cell?DMFC?attracts more and more researchers attention.DMFC has not been commercialized yet because it still has some important problems to be solved,one of which is how to accelerate the discharge of CO₂ gas in the channel.By considering this problem,this article established mathematic model based on FLUENT software to simulate direct methanol fuel cell.Simulation focus on the bubble discharge from micro pore,bubble coalescence phenomenon and coalescence section of the generated bubble,which under different work conditions.Transient capture of the dynamic movement of bubbles has been carried out,thus the bubble shape of certain moment obtained,and the dynamic analysis as well.The main research results are as follows:?1?A three-dimensional two-phase isothermal model of direct methanol fuel cell with horizontal straight channel has been established to study single bubble.Studies show that the diffusion layer with hydrophilic surface is helpful to the flow of air bubbles in the flow channel.Increase flow rate of liquid-phase decreases the volume of exit bubble rates the movement of bubble in the flow channel.Increase the flow rate of gas-phase increases the volume of exit bubble and shortens the discharge time of bubble.If the gas is generated too quickly,the inlet speed of liquid phase can be improved appropriately to prevent bubbles from blocking the flow path.?2?A two-dimensional two-phase isothermal model of direct methanol fuel cell with horizontal straight channel has been established to study the phenomenon of bubble coalescence by considering the oscillation of bubbles the right direction.The effects of bubble size,bubble spacing,liquid inlet velocity and other factors on CO2 bubble coalescence in the flow channel were studied.The height and position of the bubbles during the whole process of bubble coalescence were measured.Simulation analysis shows that the height of bubbles and the velocity of liquid phase inlet will affect the shear force on the bubbles,thus affecting the velocity of the bubbles.?3?A three-dimensional isothermal model of the serpentine flow channel has been established to study the bubble segments caused by bubble coalescence,the theoretical calculation method of the pressure loss between inlet and outlet of the serpentine flow channel,and the structural change of serpentine flow channel is analyzed.Simulation analysis shows that the bubbles with the curved structure are easier to flow and less likely to be blocked at the bend,which is beneficial for the rapid discharge of bubbles in the serpentine flow channel;As the depth of channel decreases,the velocity of the bubble section increases and the pressure loss between the inlet and outlet increases.When the width of shoulder is similar to the width of flow channel,the pressure loss is large,and the bubble section takes longer time to discharge form the flow channel.Therefore,the flow channel should be designed with curve at the corner,and the shoulder width is 0.75¹ times of the channel width as far as possible,as well as a appropriately reduced channel depth,beneficial to the removal of bubbles from channel.