The Removal Of CO₂ In Anode Flow Field And Water-Heat Management Of Direct Methanol Fuel Cell

Direct Methanol Fuel Cell (DMFC) is considered as a promising power sources with great potential for electric vehicle in 21st century. The two-phase flow of methanol-water solution and CO₂ in the anode flow field of DMFC, the heat management of DMFC stack were fully investigated in this thesis. Moreover, a test system for single DMFC was designed and assembled in-house.Analogizing the two-phase flow in anode flow field that was caused by liquid-gas transfer on the interface of flow field and diffusion layer with the flow boiling behavior in traditional heated tubes, introducing the concept of quasi-boiling, a model of the two-phase flow in DFMC anode flow field was developed. The business CFD software"FLUENT"was used creatively to simulate the model and reasonable, convinced results were obtained. The simulation method presented in this thesis can be applied to varying patterns of flow field in different working conditions to specify the distribution of CO₂ in the flow field and predict the spots where the phenomena of CO₂ blocking-up was most possible to take place, which will have positive effects in improving flow patterns and optimizing the management of CO₂ (especially in evaluating the advantages and disadvantages of a new flow pattern).A new fractal tree-like flow pattern was investigated systematically, whose characteristics of heat transfer and pressure drop were fully analyzed. The feasibility and advantage of its application in DMFC stack as a cooling system were discussed. This new flow pattern can induce a strong heat conduction effect in the cooled plane, and develop a uniform temperature distribution. The CFD software"FLUENT"was used to simulate this effect, fully considering the coupling of the convection in flow field and conduction in solid region. The results show the great advantage of this new fractal tree-like flow pattern in temperature control and the great potential of its application in the heat management of DMFC stack.After several days of stably operating of the test system, a part of the polarizing curve in the Ohmic polarizing region was completed. A substantial ground for the future experiment work was set up.