The flow pattern around a 180 degree turn in a square section 2mm gas channel of an optically accessible operating PEM fuel cell has been investigated using the non-invasive laser Doppler anemometry technique.The results reveal the symmetrical Ekman vortex pair expected to be present while operating at Reynolds and Dean numbers of 80 and 54,but also that additional complexity due to the combination of the operating MEA (membrane electrode assembly) and the abrupt change in wall direction.Measured velocities normal to and near the gas diffusion layer (GDL) surface were compared to expected velocities assuming pure diffusion,and found to exceed these diffusion velocities by several orders of magnitude implying that flow into the GDL is not inconsequential,contrary to the assumption made in many models.
展开▼
