This design project will design, provide various options, and prototype an
acceptable instrumentation system to properly measure humidity at the inlet to the fuel
cell stack and verify and validate our assumptions and analysis.
Note, the reactant gasses themselves are somewhat reactive, so an acceptable and safe
instrumentation systems are not easy to find.
- JSC is currently developing a breadboard integrated Proton Exchange Membrane (PEM) fuel
cell spacecraft power system
- One of the concerns with the design currently being pursued is the level of
humidification of inlet reactant (both hydrogen and oxygen) streams to the fuel cell stack.
These reactant streams are passively humidified by mixing incoming dry consumption reactants with
recycled humid reactant exit streams from the outlet ports of the fuel cell stack. We
have analysis capability that can predict the level of humidification based on assumptions associated
with the recycle ratio (quantity of recycled, high-humidity reactants ratioed to the quantity of
incoming dry consumption reactants), temperatures in the flow streams, and recycled reactant humidity level.
- This Design project will provide added test capability and is relevant to the Development of second generation fuel cells
Requirements: Design, and develop a prototype of a humidity sensor instrumentation system that can be
configured so that the sensor is:
- Inline with the inlet reactant stream (i.e., no tap-offs or bypass lines will be required which can
complicate the measurement at hand)
- Requires a minimum of low voltage electrical power to operate
- The design must operate at acceptable safety so that it can be approved for installation in
pressurized (up to 75 psia) hydrogen and oxygen streams at temperatures up to 170F
- JSC EP5 personnel can provide hardware like some variable capacitance sensors and
suggested circuits, electrical feedthrough components, and some equipment that could be used ultimately to test the device