A three dimensional computational fluid dynamics (CFD) model of a polymer electrolyte
membrane fuel cell (PEMFC) stack has been developed in order to study heat transfer
in single-cell and two-cell stacks. In order to simplify the computational model, the electrochemical
and water transport aspects of fuel cell operation were decoupled from those
of heat transfer; the PEMFC fuel cell membrane electrode assembly (MEA), which comprises
the electrode and electrolyte functional layers, was substituted with an electrically
heated-plate to simulate the heat generated by an MEA.
A fuel cell stack was manufactured and instrumented with calibrated thermocouples to
measure the temperature distribution. The effect of reactant gas flow rate and cell thermal
power density on the temperature distribution within the stack was studied with a view
to validating the CFD model over a broad range of operating conditions. Also, in order
to study the effects of natural and forced convection on the temperature distribution in
the stack, an infra-red imaging camera was used. The predicted temperature distribution
showed good agreement with the experiment over a wide range of gas flow rates, both in
terms of local temperature distribution and overall energy balance.
Results show that increasing the number of cells in a stack from one to two causes in
a larger temperature variation, and therefore heat management in the stack becomes increasingly
critical. The validated computational model was used as a modelling framework
to design and test different cooling plates for stacks in order to overcome this issue. As a
result, the bipolar plate in the two-cell stack was replaced with an air-cooled cooling plate
in order to minimise temperature variation and to improve overall stack performance.