Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.
Impinging jets are widely used in applications where high rates
of heat and mass transfer are required. Similarly, an efficient
operation of the Proton Exchange Membrane Fuel Cell
(PEMFC) relies on high heat and mass transfer rates to and
from the catalyst layers on the anode and cathode side, which
raises the question of whether jet impingement could be
employed for a PEMFC as well. To answer this question, a
laminar non-isothermal gas-phase model for a PEMFC
equipped with a porous flow field is solved numerically for five
different cases: (i) single jet (cathode); (ii) double jet (cathode);
(iii) triple jet (cathode); (iv) single jets (anode, cathode); (v)
ordinary flow without jets. It is found that the jets reduce the
size of the concentration boundary layers in the net at the flow
field/gas diffusion layer interface (GDL), but do not penetrate
significantly into the GDL for low permeabilies of around 10-12
m2. For macroporous layers with permeabilities of around 10-9
m2, the jets are able to penetrate deeply. For multiple jets, the
risk of entrainment with oxygen depletion between jets is
demonstrated, with a resulting loss in cell performance.
Overall, this initial study indicates that jets can enhance cell
performance, but care must be taken so as to avoid entrainment
effects when employing multiple jets in a PEMFC.