Degradation of membranes in fuel cells 10 due to dehydration by
relatively dry incoming reactant gases is avoided through the use of a humidifier
56,58 in the incoming reactant streams, 12,14. At least one of the
humidifiers 56,58 is formed in a stack 66 having alternating flow
passages 68,70 with the former receiving reactant gases and including fins
102 therein and the latter receiving hot coolant from the fuel cell 10.
The fins 102 in the flow spaces 68 are provided with a hydrophilic
coating to foster filmwise evaporation of water introduced through a nozzle 82.
The humidifier causes the reactant gas to attain a desired dewpoint before
it is provided to the membranes of the fuel cell 10.
