Fuel cell humidifiers play a crucial role in maintaining the optimal performance of proton exchange membrane (PEM) fuel cells by regulating the humidity levels of the incoming air stream.
‍
Dry air enters the humidifier through the dry air inlet while water enters the humidifier through the water inlet. Inside the humidifier, the dry air passes through a series of channels or a porous membrane. The membrane is selectively permeable, allowing water molecules to pass through and mix with the dry air. This process can occur through diffusion, where water vapor naturally moves from a region of higher concentration to a region of lower concentration, or through pressure-driven flow, where pressure differences drive the movement of water vapor. The now humidified air, containing the optimal level of moisture, exits the humidifier through the moist air outlet. This moist air is then directed towards the fuel cell stack.

Fuel cell humidifiers help maintain the proton conductivity of the PEM, thereby enhancing the efficiency and longevity of the fuel cell. Proper humidification prevents the membrane from drying out, which can lead to decreased performance and potential damage, and also helps in managing the thermal balance within the fuel cell system.