Tech Briefs Magazine - October 2023 - Comsol-11A

RESEARCH SPOTLIGHT
simulation can accelerate
innovation. " We think that
the inverse approach can
revolutionize current design
practice, " says Yuqing Zhou, a
research scientist at TRINA.
FIGURE 2 A generic fuel cell design.
» GENERATIVE DESIGN ENABLED BY SIMULATION
Toyota Research Institute of North America (TRINA) has
developed a simulation-driven generative design method and
applied it to the design of flow field microchannel plates,
which direct the movement of fluid reactants in microreactors
like hydrogen-oxygen fuel cells. While much of Toyota's fuel
cell R&D is confidential, the TRINA team has published an
article in Chemical Engineering Journal about their simulationenabled
" inverse design " process. Applying this process to flow
field plates resulted in four distinctive microchannel designs
(Figure 1).
Each of the four designs has particular merits; all of them
outperform existing benchmark designs in terms of key
metrics. Just as important, they exemplify the power of
process. TRINA has shown how generative design enabled by
» CLEANER
POWERTRAIN OPTIONS
While a hydrogen-oxygen
fuel cell may seem like an
exotic way to supply power
to a car, the technology
itself is not new, and its
operation is appealingly
straightforward. Figure 2
presents the fundamentals of
a generic fuel cell in action.
As hydrogen gas flows across
the anode, it encounters a
catalyst, which separates
it into hydrogen ions and
electrons. Whereas the
hydrogen ions move through
the electrolyte to reach the
cathode, the electrons move
through a conductor outside
the fuel cell. It is this electric
current that can be harnessed
to perform useful work.
As oxygen gas from the
air flows across the cathode,
it encounters the hydrogen
ions and returning electrons
at the surface of the cathode.
Here, the oxygen molecules
split and combine with the
hydrogen ions and electrons
to form water.
» A REACTANT'S
PATH THROUGH A
FLOW FIELD PLATE
For as long as hydrogen and
oxygen keep flowing, a fuel
cell will keep generating
electric current. Managing
the distribution of these
essential gases is the job of
the cell's flow field plates.
Each plate includes both a
microchannel structure and a
porous sublayer. As hydrogen
moves through the channels
of the anode-side plate, it is
also being forced through the
sublayer toward the anode.
Meanwhile, air is channeled
through the flow field plate
on the cathode side of the
fuel cell. Air and water are
exchanged through the
cathode-side porous material
layer, and the plate then
channels excess air and water
away from the cell stack.
Figure 3 offers a simplified
close-up of this essential
process for the cathode side.
In their journal article, the
TRINA team explains that
" uniformity of fluid residence
time or fluid flow distribution,
and the relationship to
optimal heat transfer, is
directly related to the design
of the flow structure, which
is of primary importance for
proper control of chemical
reactions. " Accordingly, the
two main objectives for fuel
cell flow field plate design are
to maximize fluid flow across
the plate's microchannel flow
field and through the porous
material layer, in order to
supply sufficient reactant to
the electrode.
» A SIMPLER PROCESS
FOR CREATING
COMPLEX FORMAL
SOLUTIONS
FIGURE 3 A microchannel structure (shown in dark gray) defines a path through which
reactant fluid moves. Some of the fluid is diverted away from the flow field through a
porous material layer, toward the cathode surface.
The physical arrangement
of microchannels helps
determine how well a
flow field plate meets its
performance objectives.
Historically, microchannel
COMSOL NEWS 11a
Tech Briefs Magazine - October 2023

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