Distribution of relaxation times: A method for measuring air flow distribution in high-temperature proton exchange membrane fuel cell stacks

• Published in: Journal of power sources 2022-03, Vol.523, p.231000, Article 231000
• Main Authors: Ruan, Kangfu, Yang, Linlin, Sun, Hai, Sun, Gongquan
• Format: Article
• Language: English
• Subjects: Air flow distribution; Channel impedance; Characteristic frequency (CF); Distribution of relaxation times (DRT); Electrochemical impedance spectroscopy (EIS); High-temperature proton exchange membrane fuel cell (HT-PEMFC)
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2022.231000

Measurement of flow distribution in the fuel cell stack is a challenging task. This study proposes a new method to measure air flow distribution in high-temperature proton exchange membrane fuel cell stacks. The characteristic frequency related to channel impedance is extracted using the distribution of relaxation times analysis. A simple correlation between the air stoichiometry and the characteristic frequency is developed. The influence of various factors on the correlation, including cell operation conditions, fluid physical properties and channel dimensions, are investigated. The experimental results show a good agreement with the correlation. Error estimation indicates that the temperature distribution of the stack, gas humidity and pressure distribution in the inlet manifold have no significant effect on the proposed method under normal conditions. The accuracy and practicability are verified using a three-cell stack with separate mass flow controller (MFC) systems. The results show less than 3.11% of relative error between the reference air stoichiometry given by the MFC and those measured from our proposed method for air stoichiometry below 3.0 at 0.1 A cm−1. The present method provides powerful support for designing high consistency stacks and the real-time monitoring cells state-of-health in stacks. [Display omitted] •Distribution of relaxation times analysis of the channel impedance in fuel cells.•Correlating the characteristic frequency of mass transport and air stoichiometry.•Measuring the air flow distribution in the fuel cell stack through the correlation.•Understanding the impact of the stack parameters' consistency on the measurement.