Visualisation of water accumulation in the flow channels of PEMFC under various operating conditions

Abstract

This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThe accumulation of water in the cathode/anode serpentine flow-channels of a transparent PEMFC has been investigated by direct visualisation where water droplets and slugs formed in these channels were quantified over a range of operating conditions. Four operating parameters concerning air stoichiometry, hydrogen stoichiometry, cell temperature, and electric load were examined to evaluate their effects on the formation and extraction of water from the flow channels. The results showed that hydrogen and air stoichiometry contribute almost equally to the water formation process in the cathode channels. However, their effects on the water extraction from the channels were quite different. Air stoichiometry proved capable of extracting all the water from the cathode channels, without causing membrane dehydration, contrary to hydrogen. Increasing the operating temperature of the cell was found to be very effective for the water extraction process; a temperature of 60C° was sufficient to evaporate all the water in the channels as well as enhancing the fuel cell current. The electric load was strongly associated to the water formation in the channels but had no influence on water extraction. Finally, no water was present in the anode flow channels under all examined operating conditions.

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

“…Ous and Arcoumanis [107] found that flooding in the cathode channels can be overcome by raising the temperature from 30˚C to 60˚C under the testing conditions shown in Figure 2. The benefit of using heat as a mechanism for water extraction from the cell can be extended to the polarisation performance of the cell.…”

“…Based on these design considerations, it is clear that unless the stoichiometric air flow is high water slugs will develop leading to flooding in the cathode channels [107]. It was shown by Ous and…”

“…Generally, flooding can be prevented by running the cell with high stoichiometric flow rates [105] or elevated temperatures [106,107,108]. Ous and Arcoumanis [107] found that flooding in the cathode channels can be overcome by raising the temperature from 30˚C to 60˚C under the testing conditions shown in Figure 2.…”

“…To be noted is the improvement with temperature in the exchange current density and Tafel slope for both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). Figure 2 Images of water accumulation in the cathode flow channels for different fuel cell operating temperatures [107] Currently, major research activities are focusing on the development of next generation membranes that can operate efficiently at high operating temperatures (≥100˚C) [112][113][114][115][116][117][118][119][120]. If successful, issues related to water management, cooling, CO tolerance of the cell etc will be much simplified [109,121].…”

“…Arcoumanis [107] ( Figure 6) that water disappeared completely from the channels only when air stoichiometry (λ air ) reached the value of 36. Below that stoichiometric point, water films start to evolve from the channel walls and gradually grow in size until they merge and block the access of the air flow in the channels.…”