The gas flows of the EL-FLOW Select or EL-FLOW Prestige devices are adapted for the specific use. High accuracy with the lowest possible pressure differential is required, and these thermal gas flow meters are suitable for this job. Regarding the water vapour supply, we can generate a very high level of control stability, which relies mainly on the mixing valve in the CEM.
More about Hydrogen applications
In this application, for single stack research, the typical water flow range is 100 to 1000 grams per hour supplied to the fuel cell, with matching amounts of oxygen and hydrogen carrier gas so that the relative humidity is in the 5 to 95% range. Besides that, controlling water flows up to 1 gram an hour is technically possible as well.
Some fuel cells will eventually be operated in practice at elevated pressures, and with a lowest possible pressure difference over the membrane, so with an equal pressure at both electrode sides. The current setup for single stack research is such that a measuring range up to 100 bar is possible - for specific types of membranes which will perform better at higher pressures. The absolute pressure and pressure difference are controlled by Bronkhorst IN-PRESS instruments. The Bronkhorst CEM system is typically used for accurate low water flows as used in single stacks, up to 1000 g/h water.
With respect to automation and communication, for mass flow controllers and vaporising systems there are several control bus systems available which are integrated in the measurement setup: analogue signal, Profibus, Flowbus as well as systems like Profinet or EtherCat. LabVIEW is often used in these research environments. This way all process parameters are available immediately, making these values controllable and allowing good monitoring and quality assurance.
Due to its working principle, the working point of the CEM based vaporisation system can be changed quickly. This is a big advantage compared to traditional bubblers, especially at higher gas flows.
We have more than 20 years of experience in the field of fuel cells. If you need advice on evaporation systems for humidification of fuel cells, ask our advice.