Simulationand Optimization Design On Flow Channelof Alkaline Solid Polymer Electrolyte Cell

Water electrolysis is one of the preparation methods of high purity Hydrogen, which is completely clean and comparatively simple. It also is one of the most widely used methods to covert Renewable Resources into hydrogen. Alkaline Solid Polymer Electrolyte, ASPE for short, is an emerging technology for hydrogen generation, the working principle of which can be regarded as the inverse process of Proton Exchange Membrane Fuel Cell. ASPE combines the high efficiency of Solid Polymer Electrolyte Cell and the low cost of alkaline water electrolysis. There are few researches on ASPE at present, so based on the researches on PEMFC and SPE, ASPE flow-fields is simulated and optimized by commercial CFD software FLUENT in this paper. Main research works are as follows:1) The effects of channel sizes and boundary conditions of different flow-field types on two-phase flow in parallel straight channel and serpentine channel flow-field are simulated. The results show that the best channel depth and width ratio of channel and ridge are 0.8 and 3:1 respectively for parallel straight channel. The multi serpentine has better performance than single serpentine channel flow-field. The performance of flow-field is relatively superior with 0.8~1.0 channel depth, 3:1 width ratio of channel and ridge. In condition of channel depth at 0.8 and width ratio of channel and ridge at 3:1, the pressure difference increases as the decrease of channel numbers, the increase of inlet water velocity, and the increase of hydrogen mass flow. The velocity of flow field depends on inlet water velocity, and the velocity and the flow distribution uniformity increases with the increase of influent water velocity. As the concentration of hydrogen is so little compared to the concentration of water inflow, so that the temperature field is well distributed and the boundary conditions has little effect on temperature field. The pressure difference increases at first, then decreases with the increase of wall temperature. Along the flow direction, the temperature of two-phase flow changes from the temperature of water inflow to the wall temperature. The larger difference of water temperature and wall causes the less stable of the temperature field.2) The effects of section shape in simplified model of parallel straight channel are simulated. The results show that the cross-section area of obround is smaller and the velocity is faster under the same condition. The arc-design on bottom of channel decreases the viscous resistance of bottom surface, which is not only good for drainage, but also prevents obstruction, and then improves electrolyzer performances, under the same condition of structure size and boundary conditions.3) Wall hydrophilic-to-hydrophobic on bubble and gas film flow transport in simplified parallel straight channel are investigated. The results show that hydrophobic surface of diffusion layer and non-hydrophobic-to-non-hydrophobic surface of channel wall are favorable to drainage and mass transfer.In this paper, the simulation and optimization of ASPE flow-field is realized by computer simulation, and relatively ideal structure size, flow-field type, cross-section, and boundary conditions, hydrophilic-to-hydrophobic are found, which has certain guiding significance for the design and manufacture of flow-fields.