Transport phenomena of convergent and divergent serpentine flow fields for PEMFC Mohammad Ziauddin Chowdhury a, b , Bora Timurkutluk a, b, * a Nigde Omer Halisdemir University, Mechanical Engineering Department, 51240, Nigde, Turkey b Nigde Omer Halisdemir University, Prof. Dr. T. Nejat Veziroglu Clean Energy Research Center, 51245, Nigde, Turkey article info Article history: Received 11 November 2017 Received in revised form 20 July 2018 Accepted 21 July 2018 Available online 24 July 2018 Keywords: Proton exchange membrane fuel cells Current distribution Flow field design Oxygen mass transport Water concentration Pressure distribution abstract Reactive species and water transport are crucial for the proton exchange membrane fuel cell operation and performance, and for this, effective flow field design can facilitate the desired transport character- istics of species. From this motivation, the conventional single serpentine flow field pattern is modified by convergent and divergent design concepts and the complex transport phenomena of the newly developed flow field designs are investigated by a numerical approach. For the numerical analyses, an experimentally validated mathematical model is developed to predict the current density, oxygen mass transport, water concentration and pressure distribution. The different configurations of modified convergent and divergent serpentine flow fields are then numerically solved and the results are compared with the conventional serpentine flow field pattern. The transport of reactive species and water concentration are analyzed from the different perspectives including cathode domains and sur- faces with a quantitative formulation of the transport species. The numerical results reveals that the modified convergent serpentine flow fields yield to a uniform current density due to the lower mass fraction of water concentration over the reaction zone facilitating better oxygen mass transport and also higher channel pressure distribution along the flow field comparing the conventional and divergent type serpentine flow fields. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction PEM fuel cell is being considered as a major sustainable energy system for the automotive sectors and portable power systems [1e4]. Among the different system components of PEMFCs, flow field design plays an important role on the PEM fuel cell efficiency and performance [5,6] as indicated by Ozden et al. [7], who numerically investigated that cell degradation is more prone to the bipolar plate than other system components. The deviations of the efficiency and performance from the ideal case in the PEMFCs are due to the activation loss, ohmic loss and concentration loss. The later one is responsible for the mal- distribution phenomena of reactants mass transport in the reac- tive zone. Therefore, a better mass transport in the PEMFCs is highly desirable to achieve a uniform current density distribution which can improve the cell performance. For this reason, a suitable flow field design is utmost necessary to distribute the reactants homo- genously [8e13] along the designed flow field in the reaction zone. There are several flow field patterns developed till date and each of them has its own flow characteristics with pros and cons. Among the flow field patterns, the serpentine type is one of the most recommended and studied flow field pattern due to its better mass transport and water removal characteristics compare to the others [14e18]. Still serpentine flow field pattern has some demerits like lower reactant concentration resulting from the long channel path which causes a continuous reduction in the reactant species con- centration [19,20]. Therefore, there can be found several attempts to modify serpentine flow field pattern in the literature. One of the common modifications is the introduction of parallel serpentine to reduce the long channel path [21 ,22]. Taccani et al. [23], for instance, numerically investigated 5-serpentine, 4-serpentine and parallel flow fields. The increase in the number of parallel serpen- tine for the same active area resulted in an increase in the cell performance. Shimpalee et al. [24] investigated single, double, cy- clic and symmetric serpentine flow field patterns and * Corresponding author. Nigde Omer Halisdemir University, Mechanical Engi- neering Department, 51240, Nigde, Turkey. E-mail addresses: zia72822@gmail.com (M.Z. Chowdhury), bora.timurkutluk@ ohu.edu.tr (B. Timurkutluk). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy https://doi.org/10.1016/j.energy.2018.07.143 0360-5442/© 2018 Elsevier Ltd. All rights reserved. Energy 161 (2018) 104e117