Numerical simulations of hydrogen production in alkaline water electrolysers

Alkaline water electrolysers are commonly used for the industrial-scale production of hydrogen, and the gas-liquid flow within the electrochemical cell has an influence on the electrolyser performance. Operating at higher current densities often leads to enhanced hydrogen production but lower efficiency, due to blockage of the electrode surface and reduced electrical conductivity of the electrolyte arising from an increase in void fraction. We use a multifluid Eulerian model to perform three-dimensional numerical simulations of the bubbly flow in a small electrochemical cell immersed in a sodium sulphate solution. Hydrogen and oxygen are modelled as dispersed phases, and flow through the cell is driven from buoyancy of the generated gas bubbles. We explore the impact of bubble size, distribution and inter-phase coupling terms on the gas-liquid flow in the cell, including the study of bubble induced turbulence and the unsteady behaviour of the bubble layer along the electrodes. Gas volume fractions, velocity profiles and turbulent intensity are compared with experimental work at current densities of 500, 1000 and 2000 Am^-2. Improved modelling of flow within electrolysers paves the way for optimisation of cell design and operation from a fluid mechanics perspective.