Influence of Thermal Conductivity and 2-D Temperature Distribution of Liquid Water Saturation

For use in automotive power, polymer electrolyte fuel cells are being pushed to ever higher levels of performance and efficiency. At these high performance levels, large thermal gradients can exist across the diffusion media. These large gradients can have a strong influence on water transport in the cell via phase-change-induced flow and thermally driven diffusion. The focus of this work is to elucidate the effects of diffusion media thermal conductivity on through-plane 2-D temperature and saturation distributions. Neutron imaging was conducted at the NIST Center for Neutron Research BT-2 neutron imaging facility and used to measure how saturation levels were influenced by the internal heat generation and temperature distributions. A custom 4.8 cm² fuel cell with precision liquid coolant temperature control was used for the high resolution through-plane radiography. The precision liquid coolant ensures stable, high accuracy thermal boundary conditions for the analysis. Temperature distributions were computed in COMSOL using experimentally measured dry and wet thermal conductivity values for commercial diffusion media. These temperature distributions were then coupled to the measured saturation distributions from neutron imaging to determine the relationships between level of saturation and temperature gradient as shown in Figure 1. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EERE supported program (Award Number DE-EE0000470). Additional funding provided by Department of Energy interagency agreement No. DEAI01-01EE50660.