Experimental investigation on bubbling behavior in anode channel of passive DMFC

The behavior of bubbling from anode diffusion layer into anode channel in passive DMFC was simplified as the formation and detachment of CO₂ bubbles at orifices immersed in a stagnant liquid，and was experimentally investigated by using a visual system. The effects of as flux，orifice submergence，gas nozzle size，liquid concentration were investigated. The results showed that in the process of bubble growth，the contact angle decreased sharply at first and then increased rapidly，then was maintained at a constant value until detachment. With the increase of gas flux，bubble departure diameter changed little and the detaching time tended to be constant after the first rapid decline. Bubble departure diameter decreased and bubble frequency increased with the increase of submergence，and there was a fall in detaching time at first and then became constant in the process. The impact of gas flux on detaching time was weakened with the increase of submergence. As aperture increased，bubble departure diameter increased，resulting in decreasing bubble frequency，and bubble detachment time decreased. When the concentration of methanol was increased，the bubbles produced became smaller and the fluctuation of bubble size became significant，and bubble frequency grew faster. In addition，detaching time decreased first and then became constant especially at a low concentration.