The Effects of Anode Serpentine Flow Field Structure and Humidity on Performance of PEMFCs

Abstract

Hydrogen is one of the promising energy sources as its clean and effective properties. Proton exchange membrane fuel cell (PEMFC) utilizes hydrogen and oxygen to produce electrical energy through electrochemical reactions [1]. PEMFC shows many advantages as high conversion efficiency [2] and no poisonous emission [3], low working temperature [4], high power density [5], so that it can be applied in widely field. However, the water management is a critical issue which has great impact on the performance of PEMFC. The power density will greatly drop when the PEMFC suffer flooding problem [6]. The water transportation can be concluded as three ways, which is including proton drag, concentration diffusion, permeation by pressure deviation. Thus, flooding phenomenon can be found both in cathode side and anode side. Many researches have reported the flooding which occur in cathode side while the case located in anode side have less analysis.The bipolar plates play an important role in transporting gas and water. In addition, the flow field of the bipolar plates can greatly affect the distribution of two-phases flow, and it will further change the performance of the PEMFC [7]. The serpentine flow field is one of the typical flow fields as it can Facilitate the reactant convection and the mass transfer within the cell [8]. The serpentine flow field has a unique structure with the U-turn corner and the corner can cause local current density increases at the channel corner due to the blocking effect on the reaction fluid. At present, there are many researches on the optimal size of single serpentine flow field, while few researches investigate the impact of serpentine corners location. But this point undoubtedly needs to be further studied as it is an effective way to optimize the flow field design. In this paper, we explored the anode metal plate flow field characteristics with single serpentine and double serpentine influence toward the PEMFC performance under various humidification conditions. The drawing which presented the performance with two types serpentine flow field under different relative humidity (RH) was exhibited as Fig.1. It can be concluded that the highest power density achieved with the double serpentine flow field under the RH as 30%. What’s more, both these cells with two flow field structures show a trend as performance improve when the RH raise to 30% and then decrease as the gas humidity increase further. Moreover, the performance of single serpentine case drops greatly when RH raise to 70% while double serpentine flow field shows better performance under the high RH (RH70%), and get the lower pressure drop (Fig.2). The double serpentine flow field which located in anode side possess higher water removal capability than the single serpentine flow field so that it can prevent a sharp performance fall under the high gas humidity condition.[1] P. Ribeirinha, M. Abdollahzadeh, A. Pereira, F. Relvas, M. Boaventura, A. Mendes. Applied Energy, 2018, 215:659-669.[2] Y. Li, Y. Feng, X.D. Sun. ACS sustainable chemistry & engineering, 2018;6:12827-34.[3] S. Caux, W. Hankache, M. Fadel, D. Hissel. Energy Conversion and Management, 2010;51:320–8.[4] A. Raj, T. Shamim. Energy Conversion and Management, 2014;86:443–52.[5] H. Park. Energy Conversion and Management, 2015, 103:623-638.[6] Z. Shi, W. Xia. Journal of Power Sources, 2008, 185(2):985-992.[7] H. Kahraman, M.F. Orhan. Energy Conversion and Management, 2017;133:363–84[8] F.B Weng, A. Su, G.B. Jung. Journal of Power Sources, 2005, 145(2):546-554. Figure 1