All-angle removal of CO2 bubbles from the anode microchannels of a micro fuel cell by lattice-Boltzmann simulation

The removal of carbon dioxide (CO2) at the anode of a micro direct methanol fuel cell (mu DMFC) is critical. The bubbles are generated at the anode and may block part of the catalyst/diffusion layer, causing the mu DMFC to malfunction. This work discusses the CO2 bubble dynamics of microfluidics in a mu DMFC from a microscopic perspective. A two-dimensional, nine-velocity lattice-Boltzmann model was adopted in this work to simulate the two-component (CO2 bubble plus methanol solution) two-phase (gaseous and liquid) micro flow in a microchannel. The liquid-gas surface tension, the buoyancy force and the fluid-solid wall interaction force play the major roles in the bubble dynamics. They are treated as source terms in the lattice momentum equation. Simulation results indicate that the methanol stream flow rate, the pore size and the channel incline angle significantly affect the removal of CO2 bubbles. The effect of the incline angle is substantial at low stream flow rates. The critical pore size in the microchannel for removing bubbles at all angles under various flow conditions has been predicted quantitatively.