Thermal conductivity and temperature profiles of the micro porous layers used for the polymer electrolyte membrane fuel cell

Abstract

The thermal conductivity and the thickness change with pressure of several different micro porous layers (MPL) used for the polymer electrolyte membrane fuel cell (PEMFC) were measured. The MPL were made with different compositions of carbon and polytetrafluoroethylene (PTFE). A one-dimensional thermal PEMFC model was used to estimate the impact that the MPL has on the temperature profiles though the PEMFC. The thermal conductivity was found to vary from as low as 0.05 up to as high as 0.12 W K 1 m 1 while the compaction pressure was varied from 4 bar and up to around 16 bar resulting in a decrease in thickness of approximately 40%. The PTFE content, which varied between 10 and 25%, did not result in any significant change in the compression or thermal conductivity. Both the thickness and the thermal conductivity changed irreversibly with compaction pressure. Considering a MPL thermal conductivity of 0.1 W K 1 m 1, a MPL thickness of 45 mm, a current density of 10 kAm 2 (1.0 A cm 2), liquid water (production and sorption), and a 30 mm membrane it was found that the MPL is responsible for a temperature increase of up to 2 C. This contribution can be lowered by integrating the MPL into the porous transport layer.