Patent ID: 7754364

Claim:
A method for designing a hydrophobic porous plug ( 28 ) for passing air from a PEM fuel cell water coolant flow field ( 12 ), said water coolant flow field having a coolant inlet ( 54 ) and a coolant outlet ( 56 ) and which contains a pressurized non-circulating water coolant which has a known coolant outlet pressure, said method comprising the steps of calculating an average pore size and a thickness for said hydrophobic porous plug which calculated average pore size and thickness will enable air to pass through said plug but prevent water from passing through said plug at said coolant flow field outlet; said step of calculating the plug pore size comprising the step of solving the equation: d = 4 ⁢ ∂ cos ⁢ ⁢ ∅ P b ; wherein: d is the average pore diameter for the plug: ∂ is the surface tension of water; ∅ is the contact angle between the water coolant and the surface of the plug; and P b is a bubble pressure for the plug which is greater than the coolant water pressure at the coolant flow field outlet minus the gas pressure downstream of the plug.