Uniform flow distribution to stacked parallel disk channels in a disk shape small-capacity SOFC stack model

Abstract

The design of a flow distribution to multiple branch channels is one of the key factors to realize the flow uniformity in a fuel cell stack. Especially for a disk-shape solid oxide fuel cell (SOFC) stack, it is necessary to clarify the optimum structure of the multiple branch channel composed of a multitude of disks. In this study, velocity fields in the parallel-stacked disk channels connected to a circular supply tube are measured by using a particle image velocimetry (PIV). The PIV experiments are performed in the SOFC stack model consisting of five-layers of disk channels. Each channel has a curvature at the inlet corner of the bottom wall, and a cylinder is installed coaxially inside the circular supply tube to control an inflow condition. Mean velocity vector fields in the disk channel indicate that a small scale vortex appears near the inlet of a lower disk channel and develops into a separation bubble with an increase in the cylinder diameter. The length and height of the separation bubble are found to increase with channel inlet Reynolds number, even at very low Reynolds numbers. Distributions of the flow rate through each disk channel are also examined. The curvature of the channel inlet corner has little influence on the flow rate profile, but the cylinder diameter significantly affects the flow distribution in each channel. A standard deviation of the flow rate distribution suggests that the method of installing a cylinder with optimum diameter is effective for realizing a uniform flow distribution.

Keywords

• solid oxide fuel cell
• disk shape channel
• flow distribution
• recirculation region
• separation bubble
• piv