Mechanism Of Water Transport In Proton Exchange Membrane Fuel Cell

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...