Electrochimica Acta 147 (2014) 294–309 Contents lists available at ScienceDirect Electrochimica Acta j our na l ho me pa g e: www.elsevier.com/locate/electacta Analysis of non-isothermal effects on polymer electrolyte fuel cell electrode assemblies M. Bhaiya a , A. Putz b , M. Secanell a,∗ a Energy Systems Design Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada b Automotive Fuel Cell Cooperation, Burnaby, British Columbia V5J 5J8, Canada a r t i c l e i n f o Article history: Received 30 June 2014 Received in revised form 8 September 2014 Accepted 14 September 2014 Available online 19 September 2014 Keywords: Polymer electrolyte fuel cell Membrane electrode assembly Non-isothermal Open-source Macro-homogeneous model Sorption heat Reversible heat Thermal osmosis Finite elements a b s t r a c t A non-isothermal, single phase membrane electrode assembly (MEA) mathematical model accounting for most applicable heat sources, viz., reversible, irreversible, ohmic heating, phase change, heat of sorp- tion/desorption, is presented. The mathematical model fully couples a thermal transport equation with an MEA model and allows the study of non-isothermal effects, such as thermal osmosis through the membrane, local relative humidity variations in the catalyst layers and water sorption into the mem- brane. A detailed breakdown of various heat sources in the MEA at different current densities is provided and the impact of various thermal effects previously neglected in the literature such as thermal-osmosis, reversible heat distribution, and heat of sorption are studied. Results show that sorption heat cannot be neglected as it contributes up to 10% of the total heat under normal operating conditions. Reversible heat distribution can significantly affect the temperature distribution shifting the hottest location of the cell from anode and cathode. Analyzing the water transport across the membrane, results show that thermal-osmosis contributes up to 25% of the water flux inside the membrane at moderate and high current densities. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Thermal management can significantly influence polymer elec- trolyte fuel cell (PEFC) operation [1,2]. At high current density, the temperature inside the fuel cell can be significantly higher than at the end plates. In automotive applications, where high power densities are achieved, the temperature variations in the cell might be of the order of several degrees. Temperature influences mass, charge and reaction rates. Reaction rates and species transport rates improve at high temperatures. However, high temperatures also result in: i) a reduction of the open cell potential; ii) a reduction in local relative humidity (RH), due to the increased saturation pressure of water, resulting in a significant decrease in membrane hydration levels and thereby proton conduction; and iii) increased fuel crossover through the membrane. Local hot spots might also cause pin holes and degeneration of the membrane significantly reducing fuel cell performance and durability. ∗ Corresponding author. University of Alberta Mechanical Engineering University of Alberta 4-9 Mechanical Engineering Building Edmonton, Canada T6G2G8, Tel.: +0017804926961; fax: +001780 49202200 E-mail address: secanell@ualberta.ca (M. Secanell). Experimental results have recently shown that the tempera- tures are not constant inside the membrane electrode assembly (MEA) of a PEMFC [3,4]. A temperature difference of 5 ◦ C or more between the membrane-catalyst layer interface and the gas chan- nel was observed by Vie and Kjelstrup [3], thereby showing the limitations of the isothermal modeling assumption commonly used in the literature [2]. Nguyen and White [5] and Fuller and Newmann [6] first analyzed heat transfer in fuel cell MEAs. Assuming local thermal equilibrium between the different phases in the electrode, a single heat transfer equation was proposed. Then, an overall heat transfer coefficient for each layer was assumed in order to predict the heat transport inside the PEFC. In these preliminary studies, several heat sources, such as reversible and irreversible losses asso- ciated with the electrochemical reactions, were neglected. There are numerous heat generation mechanisms inside the PEMFC, viz., reversible and irreversible heat generation due to the electrochem- ical reactions, ohmic heating due to electron and ion transport, and heat released/absorbed due to phase change of water. In recent years, non-isothermal models have therefore been extended to account for each one of these mechanisms as shown in Table 1. Table 1 shows that, even though non-isothermal fuel cell model in the literature account for many of the heat sources, the heat released due to water sorption has been neglected in the major- ity of models. Furthermore, a complete MEA model that couples http://dx.doi.org/10.1016/j.electacta.2014.09.051 0013-4686/© 2014 Elsevier Ltd. All rights reserved.