Direct measurement of through-plane thermal conductivity and contact resistance in fuel cell materials

摘要

An experimental study to determine the through-plane thermal conductivity of dry Nafion~R, various diffusion media, catalyst layer, and the thermal contact resistance between diffusion media and a metal plate as a function of temperature and pressure was performed. Dry Nafion~R thermal conductivity was determined to be 0.16 + - 0.03 Wm~(-1) K~(-1) at room temperature, which decreases to 0.13 + - 0.02Wm~(-1) K~(-1) at 65 deg C Diffusion media thermal conductivity was found to be function of PTFE content and manufacturer, and was 0.48 + - 0.09 W m~(-1) K~(-1) for untreatedand 0 22 + - 0.04 Wm~(-1)K~(-1) for 20 wt. percent PTFE treated SIGRACET~R diffusion media, respectively. Toray diffusion media thermal conductivity was measuredtobe l.80 + - 0.27Wm~(-1)K~(-1) at26 deg Candd decreases to l.24 + - 0.19Wm~(-1) K at 73 deg C. The thermal contact resistance between Toray carbon paper andaluminium bronze material was determined to vary from6.7x 10~(-4) to 2.0 x 10~(-4) m~2 KW~(-1) for an increase in compression pressure from 0.4 to 2.2 MPa. The equivalent thermal conductivity of a 0.5 mg cm~(-2) platinum loaded catalyst layer was estimated to be 0.27 + - 0.05 W m~(-1)K~(-1). A one-dimensional analytical model was also used to estimate the temperature drop in the fuel cell components. A maximum of 3-4 deg C temperature drop can be expected for a 200 jxm thick SIGRACET* diffusion media at 1 A cm~2. The thermal properties characterized should be useful to help modelers accurately predict the temperature distribution in a fuel cell.