Direct measurement of through-plane thermal conductivity of partially saturated fuel cell diffusion media

An experimental study to investigate the through-plane thermal conductivity of three different diffusion media (DM) used in polymer electrolyte fuel cells (PEFCs) as a function of compression (from 0.1 MPa to 2 MPa) and saturation (from 0 to 25%) was performed. Additionally, measurements to determine the stress-strain relationship for the materials were made using an optical microscope. Both compression and water content had a significant impact on the through-plane thermal conductivity, which should be accounted for in multiphase modeling efforts. An analytical expression for the theoretical maximum of the through-plane thermal conductivity, as a function of both compression and saturation, was developed to help understand the nature of liquid connectivity in saturated pores. Additionally, a relationship was developed to predict actual thermal conductivity of the tested materials as a function of both compression and saturation based on experimentally measured data.