Patent ID: 7052791

Claim:
An apparatus for humidifying a process gas stream, in combination with a fuel cell stack, the combination comprising: a first humidification unit having an inlet for the process gas stream, for adding humidity to the process gas stream at a first temperature, to a humidity in excess of a required humidity level; a first heat exchanger connected to the first humidification unit, for cooling the process gas stream to a second, lower temperature, whereby excess moisture in the process gas stream condenses, and for removing the condensed moisture, whereby the process gas stream leaving the first heat exchanger has a known temperature and a known absolute humidity level; a fuel cell stack having a first process gas inlet connected to the first heat exchanger, and a first outlet for exhausted process gas; a second heat exchanger connected between the first heat exchanger and the fuel cell stack, for heating the process gas stream to a third temperature, greater than the second temperature, whereby the process gas stream has a known relative humidity level; a common coolant supply; a first temperature control circuit including the first heat exchanger and a third heat exchanger connected to the common coolant supply; and a second temperature control circuit including the second heat exchanger and a fourth heat exchanger connected to the common coolant supply.