Characterization of electrochemical reaction and thermo-fluid flow in metal-supported solid oxide fuel cell stacks with various manifold designs

Abstract

The metal-supported solid oxide fuel cell (SOFC), in which a metal plate is bonded to a ceramic cell, was recently introduced as a new fuel cell design. Metal-supported SOFCs do not suffer from gas leakage, because the metal plates are welded to the metallic interconnects, which also provides high mechanical strength. However, the bonding layer existing between the interconnect and the ceramic cell increases mass transfer resistance, resulting in decreased performance. To better understand and control the mass transfer rate, the manifold structure of the fuel cell stack as well as the channel design in each single cell should be studied. Using a numerical approach, physical property models, governing equations and electrochemical reaction models were calculated simultaneously. The experimentally measured current density–voltage curves were compared with the simulation data to validate the code. Current densities, temperatures and pressure distributions resulting from various manifold designs were presented as numerical results. The parallel manifold design displayed an average current density of 2820.1A/m2 and a relatively uniform current density distribution. The serpentine design yielded the highest average current density among the studied manifold designs, but the maximum pressure was 32 times higher than with the parallel design. Moreover, the large temperature difference observed with the serpentine design may result in a thermal expansion problem. The expanding manifold design yielded an average current density of 2885.9A/m2 and a maximum pressure of 6350Pa. The pressure distribution with this manifold design was clearly related to the manifold structure. The tapering manifold design is the opposite of the expanding manifold; with this design, the average current density and maximum pressure were slightly lower than the expanding manifold. The dual-flow hybrid manifold design combines two different manifold structures: a serpentine hydrogen manifold and a parallel air manifold. The dual-flow hybrid design yielded an average current density of 2905.4A/m2 and a maximum pressure of 750Pa.