Journal of Power Sources 195 (2010) 4842–4852 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour A study of multi-phase flow through the cathode side of an interdigitated flow field using a multi-fluid model Torsten Berning ∗ , Madeleine Odgaard, Søren Knudsen Kær Department of Energy Technology, Aalborg University, Pontoppidanstraede 101, 9220 Aalborg, Denmark article info Article history: Received 31 October 2009 Received in revised form 14 January 2010 Accepted 8 February 2010 Available online 13 February 2010 Keywords: Polymer electrolyte membrane fuel cells Fuel cell modeling Multi-phase flow Multi-fluid model CFD modeling abstract This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte mem- brane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability. The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher. In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell in the form of latent heat which reduces the load on the coolant. Finally we see that the micro-porous layer might help keep the gas diffusion layer substrate dry due to a potentially higher evaporation rate caused by a combination of the Kelvin effect and a larger specific surface area compared to the diffusion layer substrate. © 2010 Elsevier B.V. All rights reserved. 1. Introduction One general major question of fuel cell design concerns the detailed geometry of the flow field plates. The different possible designs include straight, parallel channels which have a small pres- sure drop and gas velocities, serpentine channels which have a larger pressure drop and higher gas velocities, or the interdigitated design where straight inlet channels are dead-ended and a con- vective flow of the gas and liquid is enforced through the porous gas “diffusion” media (GDM) to the straight outlet channels at the cost of an increased pressure drop. This paper describes a numeri- cal study that compares the interdigitated cell design with straight channel cell design employing a newly developed computational model that is based on the formerly commercial software code CFX-4.4. The model employs the so-called multi-fluid approach, which solves one complete set of transport equations for each phase. The physics of phase change have now been implemented and the model also accounts for the Kelvin effect. Other details of the model have been described in a previous publication [1]. In brief, the model allows for the specification of material parameters ∗ Corresponding author. Tel.: +45 9940 9261; fax: +45 98151411. E-mail addresses: tbe@iet.aau.dk, torsten.berning@alumni.uvic.ca (T. Berning), skk@iet.aau.dk (S.K. Kær). such as the irreducible saturation, the in- and through-plane per- meability, porosity and average contact angle of the liquid phase in every porous layer, i.e. catalyst layer (CL), micro-porous layer (MPL) and gas diffusion layer (GDL). The structure of this paper is as follows: first a description of the model is given and the equations that account for phase change effects are listed in detail. Then a standard case of the interdigi- tated cell design is investigated, highlighting the different physical effects and showing detailed distributions of important properties such as predicted liquid saturation, relative humidity distribution, oxygen distribution and gas and liquid phase pressure distribu- tion. A detailed study then compares the interdigitated channel design with the parallel channel design under specified operating conditions with varying stoichiometric flow ratio. Advantages of the interdigitated design include a possibility to operate at lower stoichiometric flow ratio, a higher concentration of oxygen inside the catalyst layer, a lesser amount of product water leaving the cell in the liquid phase and a lower and more stable load on the coolant. Next a second case will be investigated in detail where more realistic material parameters are employed than in the first case (irreducible saturation, in- and through-plane permeability, porosity) and it is found that the micro-porous layer may help keep- ing the gas diffusion layer substrate dryer by enforcing a higher evaporation rate. Finally the Conclusions section will summarize the main findings of this study. 0378-7753/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2010.02.017