Numerical Analysis of Hydrogen Bubble Behavior in a Zero-Gap Alkaline Water Electrolyzer Flow Channel

Bubble resistance remains a significant issue in alkaline water electrolyzers including emerging zero-gap alkaline water electrolyzers, and the understanding of bubble behavior and its influences in the flow channel of these electrolyzers is still limited. In this paper, bubble behavior in a milliscale flow channel is analyzed using a three-dimensional transient computational fluid dynamics model. The model is validated in terms of bubble shape and velocity against experimental data. The simulation results illustrate the flow regimes and slug formation process in the flow channel. The probability distribution histograms of the bubble volume of each flow regime are shown. The mean bubble volume increased from 0.027 mm3 at bubbly flow to 0.341 mm3 at slug flow. The bubble influences are analyzed in terms of flow velocity, pressure drop, and mass flux of the electrolyte. It is found that bubble slugs can decrease the mass flux of the electrolyte from 400 kg/m2·s to less than 50 kg/m2·s in the channel under the simulation conditions. The flow around squared and rounded bends of single serpentine flow channels has been studied and compared in terms of velocity and pressure drop. A rounded bend has a less low-velocity region and has 13% higher pressure stability than the squared bend under the simulation conditions. This model offers a cost-effective tool to understand and optimize the bubble resistance in electrolyzers.