Modeling and Analysis of Membrane Humidifiers for Fuel Cell Applications

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