Towards high throughput PEMFC testing: Dynamic and Precise Humidification of Reaction Gases

For the optimum operation of proton exchange membrane fuel cells (PEMFCs), controlled humidification of the reaction gases is essential and therefore also vital in PEMFC testing and test configurations. The ability to rapidly alter the humidity of the reaction gases is valuable not only for dynamic operation trials but also for cost-effective, high-throughput testing. In PEMFC tests, the time required to attain stable operating conditions is typically dominated by the humidification system. As recent studies show, conventional external humidification techniques like the bubble humidifier exhibit a lack of flexibility in adapting to changing conditions [1]. To address these limitations, this study experimentally investigates the controlled addition of liquid water into an evaporator, whereby the water is completely vaporized and then combined with a preheated gas flow in a mixing area. A comprehensive water mass balance can be derived from the quantity of water supplied by the mass flow controller and the amount collected by the condensate separator at the outlet of the fuel cell. The behavior of the evaporator during altered humidity is analyzed with respect to dynamic and stationary characteristics. Therefore, the water mass supplied to the evaporator is changed at a standard fuel cell operation point. The resulting water content measured with a humidity sensor is investigated regarding real-time behavior and reproducibility. The investigated humidification system represents an improvement on conventional humidification methods, as the amount of water in the system can be precisely controlled, thereby enhancing the dynamic and accuracy of the humidification process.