Research On The Influence Of Flow Field Parameters In μDMFC

With the strengthening of people's consciousness to protect our environment and the deficiency of nature resources, people attach more and more importance to fuel cells which are considered as green energy resources with advantages of high energy, convenience and environmental friendliness. Direct methanol fuel cell (DMFC) is the best portable power supply to enginery, notebook PC and so on, which is developing rapidly.A three-dimensional model of direct methanol fuel cell anode is presented based on the computational fluid dynamics method. The control-equation of the model is a coupling of continuity equation, momentum equation and Butler-Volmer equation, which is the simulation of electrochemical reaction.. The model consists of collector plate, flow channel, diffusion layer and catalyst layer. The fuel in the DMFC is supposed to be uncompressible liquid whose flow is according with laminar flow. Navier-Stokes equation is the basic transmission equation in the four parts. The mass transportation of fuel in porous medium is considered, as well as the mixture of carbon dioxide and liquid. The performance of the DMFC is investigated by calculation of the three-dimensional model. The distribution of carbon dioxide and fuel-cell concentration are also obtained from the simulation model and results of this study will show an important reference value for the further researches.At the same time, self- breathing DMFC made by our research group has been successfully evaluated in this paper. According to the different breadth, height and distance of the anode channels, there are twelve different anode flow plates consistent with twelve fuel cells. The anode channels are distributing in an area of 50mm~2 and the total area of anode flow plates is 300mm~2. The whole DMFC is composed of anode layer, anode flow channel, MEA, cathode collector plate and cathode layer. The material of anode flow channel is stainless steel so that it can be used as anode collector plate. Between the flow channels and MEA, there are collector nets to collect electricity effectively. Anode and cathode layers are made of glass.The testing system for the self-breathing DMFC is composed of stereoscopic microscope, micro injecting pump, electronic load, DMFC and controlling computer. The fuel cells' capability is tested on different working conditions (fuel concentration, flux and temperature) and different flow conformations (breadth, height and distance of the anode channels). Results show that the DMFC current density increases with the increases of velocity and the temperature, but the open circuit potential almost keeps in a constant value when theoperating condition is changed. The best fuel concentration is 2mol/L, which arises from the pervasion of methanol. When the breadth, height and distance of the anode channels are 600um, 600um and 400um respectively, the limiting current density and power reach the maximums. The conclusions are consistent with previous simulation. The process of chemical reaction is observed through stereoscopic microscope and useful images are obtained.