Experimental and numerical study of a membrane humidifier equipped with bypass for PEM-FC: analysis and controllability under low loads and hard transients

Optimal water management of the PEMFC membrane is essential to ensure their performance and durability, particularly in operating long-duration highly dynamics operations. This study presents an experimental and numerical investigation of a hollow-fiber membrane humidifier, equipped with a bypass branch, used for water management of a 100 kWe PEMFC system. A 2100s-long load profile with frequent and wide (up to 40 % change) variations is used to emulate a driving cycle. A zero-dimensional model has been developed in AMESim environment. For validation purpose, pressure, temperature and dew point have been compared. The model replicates the dynamic response of the real system accurately: relative error less than 1 % on pressure, absolute error less than 3 °C on temperature and dew point. Modeling the thermal inertia of components, has led to 8 °C maximum absolute error reduction on temperature. The role of the bypass valve in regulating humidity at the stack inlet has been investigated. The proper regulation of the bypass valve position is effective for transients and steady phases comprised between 30 % and 80 % of the maximum load. Loads over 90 % and under 30 % lead to slight overshooting and undershooting, respectively. Loads below 20 % require heating up the air stream. • Zero-dimensional model of air passive membrane humidification system for PEMFC. • Experiments and simulations under hard transients and low load. • Model's high accuracy and reliability mainly thanks to thermal inertia modeling. • Optimum humidification with loads 20 %–95 % with proper bypass valve controlling. • Loads <20 % can't be controlled with bypass. Heating-up with external device needed.