A thermodynamic model of membrane humidifiers for PEM fuel cell humidification control

Maintaining proper membrane humidity is crucial to ensure optimal operation of a polymer electrolyte membrane fuel cell system. A membrane humidifier using the fuel cell exhaust gas to humidify the dry air is studied in this paper. We first develop a thermodynamic model, which captures the crucial dynamic variables of the humidifier including the pressure, flow rate, temperature, and relative humidity of the air flow. Steady-state simulations are then conducted to optimize the humidifier design. Subsequently, dynamic simulations are performed to predict the behavior of the humidifier during transient operations typical for automotive applications. A simple proportional controller was designed to control the humidifier operation.