Numerical study of vapor behavior in high temperature PEM fuel cell under key material and operating parameters

ABSTRACT

The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rarely studied in the previous work. However, the different water vapor behaviors might greatly influence both cell performance and stability. In order to gain a fundamental understanding of the vapor behaviors in HT-PEMFC, a 3D computational fluid dynamics model and a 2D transient model were developed to investigate the effects of materials properties and operating parameters on the vapor behavior. Temperature, membrane materials, and phosphoric acid doping degrees are examined. The results show that higher temperature and phosphoric acid doping degrees with PBI membrane would lead to a significant increase of water vapor generation at cathode. For the transient model, the dynamics of vapor accumulation were observed with the dead-end anode. It is revealed that vapor transport and distribution get adapted to a dynamic equilibrium after 18 sec. According to these results, a periodic purging at anode with optimized purging time is still needed to remove the accumulated water vapor. The findings of this paper can be further applied in the design of fuel cell controller.

KEYWORDS:

• HT-PEMFC
• membrane material
• vapor distribution
• doping level
• dynamic equilibrium

Acknowledgments

This work was supported in part by the national nature science foundation of China (51806024), the national key research and development program (No.: 2018YFB0105402 and No.: 2018YFB0105703), the Chongqing Research Program of Foundation and Advanced Technology (No.: cstc2017jcyjAX0276), the Venture & Innovation Support Program for Chongqing Overseas Returnees (cx2018051), and the Fundamental Research Funds for the Central Universities (No.: 2019CDXYQC0003, 244005202014, and No.: 2018CDXYTW0031). M. Ni thanks the grants (Project Number: PolyU 152214/17E and PolyU 152064/18E) from Research Grant Council, University Grants Committee, Hong Kong SAR.

Disclosure statement

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Nomenclature

$E$-Thermodynamic prediction voltage, V-${\eta }_{ohmic}$-Ohmic loss, V$E^0$-Open circuit voltage, V-${\eta }_{conc}$-Concentration loss, V$R$-Universal gas constant, J/mol/K-${\eta }_{act}$-Activation loss, V$T$-Operating temperature, ^oC-$R_{ohmic}$-Ohmic resistance, ohm$a_{products}^{v_i}$-Product pressure, Pa-$R_{elec}$-Electron resistance, ohm$a_{reac\mathrm{t}\mathrm{a}\mathrm{n}ts}^{v_i}$-Reactant pressure, Pa-$R_{ionic}$-Ionic resistance, ohm$\alpha$-Charge transfer coefficient-$E_{Ner\mathrm{n}st}^0$-Nernst voltage with $c_{\hspace{0.17em}}^0$, V$n$-Moles, mol-$E_{Ner\mathrm{n}st}^{\ast }$-Nernst voltage with $c_{\hspace{0.17em}}^{\ast }$, V$F$-Faraday constant, C/mol-$c_R^0$-Reactant concentration in gas diffusion layer$j_0$-Exchange current density, A/cm²-$c_R^{\ast }$-Reactant concentration in catalyst layer$j$-Current density, A/cm²-$\mathrm{a}$-Tafel curve constant$i$-Cell current, A-$\mathrm{b}$-Tafel slopeu-Gas mixture velocity vector, m/s-$\rho$-Gas mixture density, kg/m³Q-Source term, kg/m³s-$\mu$-Dynamic viscosity of the mixture, kg/m·s