Mechanics & Industry c  AFM, EDP Sciences 2012 DOI: 10.1051/meca/2012021 www.mechanics-industry.org Mechanics & Industry Heat fluxes and electrodes temperature in a proton exchange membrane fuel cell Anthony Thomas a , Gael Maranzana, Sophie Didierjean, J´ erˆ ome Dillet and Olivier Lottin Universit´ e de Lorraine, LEMTA, UMR 7563, 54504 Vandoeuvre-l` es-Nancy, France Received 6 July 2012, Accepted 29 August 2012 Abstract – Measurement of heat fluxes and electrodes temperature in a proton exchange membrane fuel cell were performed using platinum wires and heat flux sensors. A temperature difference of 6 ◦ C to 9 ◦ C between the electrodes and the bipolar plates was observed for a cell operating at a current density of 1.5 A.cm -2 . These measurements show a strong non-uniformity of the temperature profile through the membrane electrode assembly that future models should take into account. Simultaneous heat fluxes measurements have allowed to evaluate in situ the effective thermal conductivity of the porous layers. Values of the order of 0.3 W.m -1 .K -1 were found. Key words: Electrodes temperature / platinum wires / heat fluxes / fuel cell / PEMFC 1 Introduction Proton Exchange Membrane Fuel Cells (PEMFC) make it possible to convert efficiently chemical energy into electrical energy. Using hydrogen as fuel, they can pro- duce electricity over a wide range of power without on-site emission of greenhouse gases, the only reaction product being water. PEMFC are currently used for powering elec- tric vehicles, portable electronic devices and cogeneration systems of small and medium power. Despite recent technological advances, their large- scale commercialization is still hampered by issues of cost (platinum catalyst and polymer membrane prices) and durability that can be related to water management within the cell (through electrode corrosion, dissolution of platinum, oxygen transport). The study of water trans- port in a proton exchange membrane fuel cell is therefore fundamental. 50% to 70% of the energy exiting the cell as heat, the impact of the temperature field on water transport in the Membrane Electrodes Assembly (MEA) was there- fore considered in recent works [1–10]. In 2002, Djilali and Lu [1] focused on the modeling of non-isothermal and non- isobaric effects (including Knudsen diffusion and Soret ef- fects). They found a typical mean temperature difference of 1 to 5 ◦ C, between the bipolar plate and the cath- ode, function of the current density and thermo-physical properties of materials. Weber and Newman [2] and a Corresponding author: anthony.thomas@univ-lorraine.fr Wang and Wang [3] showed, by considering the non-isothermal operation of fuel cells, that evapora- tion/condensation (i.e., heat pipe effect) through the porous layers may have a significant impact at high cur- rent densities. Eikerling [4] also showed that at a current density of 1 A.cm -2 , the evaporation rate at the electrode is sufficient to remove all water produced at the cathode in vapor phase. Hickner et al. [5, 6], Kim and Mench [7, 8] and Fu et al. [9] used neutron radiography to visualize this phe- nomenon and they put forward the importance of evap- oration at high current densities. The temperature is a significant parameter, in terms of water condensa- tion/evaporation and considering the fluxes in vapour phase. Indeed, the works of Kim and Mench, Fu et al. or Hatzell et al. [10] showed that water goes preferen- tially towards the colder side of the fuel cell. Because of this phenomenon, it is important to realize accurate mea- surements of temperature in all parts of the cell. Temperature measurements within an operating fuel cell have been already performed. In 2004, Vie and Kjelstrup [11] were the first to measure the local temper- ature near the electrodes using thermocouples (120 μm in diameter). By measuring the temperature at the mem- brane/electrode interface and channel/gas diffusion layer (GDL) interface, they estimated the thermal conductiv- ity of the membrane and of the electrode+GDL. Zhang et al. [12, 13] used thermocouples with a diameter of 100 μm that they placed at the GDL/electrode interface to measure the temperature difference between the air Article published by EDP Sciences