Mass Transfer Simulation And Performance Experiments Of Direct Methanol Fuel Cells

The direct methanol fuel cell (DMFC) is a highly efficient and clean power generation apparatus, which could transfer the the chemical energy stored in methanol directly into electrical energy through electrochemical reactions.DMFC has been extensively studied and paalied because of its advantages such as simple structure, high specific power, the fuel is cheap and easy to get and without reforming. However, the high cost of the cell directly restricts the pace of the DMFC to achieve commercial production applications. Improve the performance of the DMFC is an important way to reduce the cost of the cell. The most important reason affect the performance of the direct methanol fuel cell is that the oxidation reaction proceeds at the anode slower and much complex than the hydrogen oxidation. And that made the power of DMFC is much lower than proton exchange membrane fuel cell using hydrogen as fuel in the same circumstances. Simulation of mass transfer distribution in the DMFC anode during reaction process and the research about distribution regularity changes with the opetating parameters are one of the important research directions to improve the anode reaction rate of DMFC.After read and sunmed up a lot of direct methanol fuel cell and analysised the results of precious studies, this paper introduces the history of the development of proton exchange membrane fuel cell, especially the direct methanol fuel cell and expounds the operating principles and purposes and characteristics of DMFC.The paper also focuses on the analysis of components, research status and the application of DMFC and try to explain the voltage reduce of DMFC and theoretical solutions from the point of view of thermodynamics and electrode kinetics.The paper built a the DMFC test the system using a fuel cell test equipment.The experiment designed serpentine flow fields contain different number of channels and analysis the influence on the performance and impedance of the DMFC with changing the operating parameters such as cell temperature, methanol concentration, methanol flow rate and cathode humidiflcation temperature. The experimental results show that:the performance of multichannel serpentine flow field methanol fuel cell is better than the single channel serpentine flow field methanol fuel cell; the ohmage and electrode reaction impedance of the multichannel serpentine flow field methanol fuel cell are smaller according to the analysis of the AC impedance with equivalent circuit; the electric double layer characteristic of multichannel serpentine flow field methanol fuel cell approach in resistance characteristics.Paper established a three-dimensional two-phase flow model on the basis of the previous studies to simulate the distribution of methanol, carbon dioxide and other substances on the anode side of DMFC and analyzed the impact on the distribution of the mass transfer on the anode of DMFC by changing the operate parameters-Analysis results indicate that the methanol concentration decreased while the CO2concentration elevated along the channel direction; the mass concentration of methanol and CO2under the channel is lower than that under the flow ridge; Increase the fuel cell temperature, the electrochemical reaction would be accelerated and methanol concentration would decreased while CO2concentration elevated; increase the methanol access velocity would elevated the mass concentration of CO2. Meanwhile, the comparison of the experimental and simulation results show that this model can be an effective simulation of DMFC anode side and mass distribution.