|Title:||Diffusioosmotic effects on water transport in a PEM fuel cell||Authors:||Ma H.C.
|Keywords:||Diffusioosmosis;Electroosmosis;Fuel cell;Proton exchange membrane;Water transport||Issue Date:||2018||Journal Volume:||5||Journal Issue:||1||Start page/Pages:||35-48||Source:||American Journal of Heat and Mass Transfer||Abstract:||
The steady electrokinetic flow of the water in the ionic phase of the membrane of a polymer electrolyte fuel cell is theoretically investigated. The effect of diffusioosmosis induced by the concentration gradient of the protons on the fluid flow is considered. The membrane is modeled as a fibrous medium constructed by a homogeneous array of parallel, negatively-charged, circular cylinders. The electric double layer surrounding each cylinder may have an arbitrary thickness relative to the radius of the cylinders. A unit cell model which allows for the overlap of the double layers of the adjacent cylinders is employed to account for the effect of cylinders on each other. The electrostatic potential distribution in the fluid phase of a unit cell is determined as analytical and numerical solutions of the Poisson-Boltzmann equation. Solving a modified Navier-Stokes equation numerically, the electroosmotic and diffusioosmotic velocity distributions of the fluid caused by the macroscopic electric field and protonic concentration gradient are obtained as functions of the porosity of the array of cylinders. The results of the local and averaged electrokinetic velocities in a unit cell show that the effect of diffusioosmosis on the water transport in the proton exchange membrane can be significant in comparison with that of electroosmosis under practical operations. The electrokinetic velocities of the fluid increase with an increase in the electrokinetic radius or zeta potential of the cylinders and in the porosity of the membrane. ? The author(s) 2018.
|Appears in Collections:||化學工程學系|
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