来源：塑料托盘 发布时间：2010年7月23日
塑料托盘首先分析质子交换膜燃料电池催化层三相通道微观结构及其间发生的电化学反应，研究水在催化层、扩散亚层、扩散层等多孔介质结构部件的生成、输运、相变塑料托盘条件，考虑了材料疏水性、亲水性及微孔尺寸对水蒸汽饱和压力的影响。认为电化学反应生成的水开始应该是气态，在传输中可能成为液态。材料亲、疏水性和孔径对饱和蒸汽压力有巨大的影响，据此提出了相变模型。 随后根据多孔介质的UFT(Unsaturated Flow Theory)模型，导出了一维的梯度扩散塑料托盘层液态水相饱和度分布方程、液态水流量方程、液态水残留量方程、气体扩散因子方程。以此为基础，计算了不同孔隙结构的扩散层的相饱和度分布、液态水残留量、液态水排量和有效气体扩散因子，得到了一些有意义的结论。随后基于Fluent(Proton Exchange Membrane)PEM模块，考虑反应气体加湿、电化学反应、相变等因素的影响，计算了燃料电池扩散层中水的传输和分布状态。最后对梯度扩散层的爆破压力塑料托盘和凝结相饱和度进行了测试，定性的印证了理论计算的正确性。 对于气体流道中液态水的传输，本文首次考虑构成流道壁面的扩散层和石墨板的疏水性和亲水性作用，利用VOF(Volume Of Flow)模型，模拟了不同风速下直流道和蛇型流道中液态水的运动特征。先比较详细研究了微流动中表面张力、壁面粘性力、气体惯性力等对液态运动状态影响的判断准则数；根据计算条件，认为表面张力对液态水运动有重要影响，进而确定以We数(同时也考虑塑料托盘风速)的变化来考察液态水的运动状态。之后分析了液态水滴和水膜在直流道和蛇型流道中在4种We数下的运动状态计算结果。结果表明，GDL(Gas Diffusion Layer)的疏水性、石墨板流道的亲水性对液态水在流道中的运动起着重要作用；在所计算的条件下，We数大于4.4(或气流速度低于4m／s)时，表面张力和壁面粘性力的影响对液态水的运动起主要作用，石墨板的亲水性具有重要作用；We数小于4.4(或气流速度塑料托盘高于4m／s)时，惯性力的影响对液态水的运动起主要作用；石墨板流道的亲水性可以将扩散层表面的液态水“吸附”到石墨板壁面上，有利于氧气经扩散层向催化层扩散，因而对电池的性能产生影响；考虑到壁面改性应该有利于液态水的排出和氧气的扩散，碳纸应该尽可【Abstract】 First in this paper, the microstructure of the three-phase-channel in the catalyst layer (CL) and the electrochemical reaction over there is analyzed, the produce, transport and phase change of the water in the CL and/or gas diffusion layer (GDL) is studied, while the hydrophilic nature, the hydrophobic nature and the pore size of the porous material are taken into account. The conclusions think the water is of vapor state when produced first; the hydrophilic nature, the hydrophobic nature and the pore size have large influence on the saturation pressure, therefore a phase change judge criteria is put forward.Thereafter, according to the unsaturated flow theory (UFT) model, the equations are derived of one dimensional liquid saturation, liquid flux, liquid remaining in GDL, gas diffusion coefficient for gradient GDL. Based on these the liquid saturation, liquid flux, liquid remaining in GDL, gas diffusion coefficient are calculated for GDL with different porosity structures, some useful conclusions are gotten. Then based on the PEM model in Fluent, the water transport and distribution in GDL in a one-channel fuel cell is calculated, the humidification of react gases, the electrochemical action and the phase change, etc. are taken into account. At last the breakthrough pressure and the critical saturation of the gradient GDL are measured, the theoretical calculation is validated qualitatively.For the water transport in the gas channel, considering for the first time the hydrophilic nature of graphite plate and the hydrophobic nature of the GDL, which form the walls of the gas channel, using the VOF (Volume Of Flow) model of FLUENT software, the movement of liquid water under different gas velocity has been simulated in a straight channel and a serpentine channel. The results show that the hydrophilic nature of graphite plate and the hydrophobic nature of GDL play an important role to the liquid water movement. When Weber number is larger than4.4 (gas velocity is lower than 4m/s), effects of surface tension and wall surface adhesion on the motion of liquid water in the gas channel are very obvious; when Weber