Water recovery and air humidification by condensing the moisture in the outlet gas of a proton exchange membrane fuel cell stack

Humidification is one of the most important factors for the operation of proton exchange membrane fuel cell (PEMFC). To maintain the membrane at hydrated state, plenty of water is needed for the state-of-the-art of PEMFC technology, especially in large power applications or long time operation. A condenser is introduced to separate liquid water from the air outlet for air self-sufficient in water of the stack in this study. The condensed temperature at the outlet of the condenser and water recovered amount for air self-sufficient in water are investigated theoretically and experimentally. It is shown that the condensed temperature for air self-sufficient in water is irrelevant with the working current of the stack. When the condenser outlet temperature was above the theoretical line, recovery water was not sufficient for the air humidification. On the contrary, it is sufficient while the temperature was below the theoretical line. It is also shown that when the moisture is sufficiently cooled, large amount water can be separated from the outlet gas, and it increased almost linearly with the time. With the introduction of the condenser, the recovered amount of water can easily satisfy the air self-sufficient in water by condensing the outlet gas to a proper temperature.

► We introduce a condenser to separate liquid water from the air outlet in the stack.
► The mechanism of air self-sufficient in water by condensing gas is presented.
► The condensed temperature and water recovered amount are investigated.
► An experiment is present to validate simplicity and feasibility of the criterion.
► The criterion for air humidification is used for choosing the condenser.