"24.22 Researchers are proposing the development of a ‘‘nano- channel reactor'' for steam reforming of methane (CH4) to fuel- cell hydrogen gas to power microscale devices. Gas phase diffusion in nanochannel A = CH4, B= H2O A+B 20 mol% CH 4 -----------------------------> Nanochannel ( NA/NB) = 0.25 300 degrees C, 0.5 atm, 200Nm diameter As each channel diameter is so small, the gas flow is likely to be very small within a given channel. Hence, gas diffusion pro- cesses may play a role in the operation of this device, particularly during the mixing and heating steps. We are specifically inter- ested in evaluating the effective diffusion coefficient of methane gas (species A, MA 1?4 16g/g: mol) in water vapor (species B, MB 1?4 18 g/g: mol) at 3008C and 0.5 atm total system pressure. The diameter of the channel is 200nm (1x 10^9 nm = 10m) A feed gas containing 20 mol % CH4 in water vapor is fed to the nanochannel with a flux ratio NA/NB = 0:25. What is effective diffusion coefficient of CH4 in the nanochannel at the feed gas conditions? Is Knudsen diffusion important?