Diffuser shaped fuel channel design study in solid oxide fuel cell stacks.

Abstract

Solid oxide fuel cell (SOFC) stacks were operating with metallic interconnects that separate each cells. Metallic interconnects play an important role in gas flow system and heat transfer mechanism, because its geometry makes gas flow channel and it has a high thermal conductivity. Many researcher design the flow channel for optimizing the cell performance like a ratio of height and width, channel to channel distance, or new type channels. For high conversion efficiency, most solid oxide fuel cell in power generation application operate at high fuel utilization and low current condition. However, high fuel utilization condition makes a large gradient of chemical potential by fuel depletion and it induces a low cell performance and a large chemical stress in flow direction. This phenomena can be observed at high performance cell or high operating temperature condition, because almost fuel is consumed at upstream of fuel channel by high electrochemical reaction kinetics and most cell area has a low chemical potential environment. Therefore, even distribution of electrochemical reaction rate is important. In this study we reduce the gradient of chemical potential by using diffuser-shape fuel channel, and optimize the diffuser-shape by design study. In chemical species conservation law, higher flow velocity at upstream makes higher convective flux in flow direction compared to diffusive flux in cell-thickness direction, and it can reduce the electrochemical reaction rate at reacting electrode. Optimized diffuser-shape fuel flow channel from this study may enhance the performance and the durability of solid oxide fuel cell stacks.