Session: 01-14 Thermal Management and Aero-engine Oil Systems II

Paper Number: 128907

128907 - Liquid Cooling of Fuel Cell Powered Aircraft: The Effect of Coolants on Thermal Management 

The aerospace industry is developing new propulsion technologies to enable net zero aviation. One such technology is the Polymer Exchange Membrane Fuel Cell (PEMFCs); often these are cooled by liquid coolants. To increase the system specific power and therefore improve the performance of fuel cell powered aircraft, there is a need for higher temperature PEMs. However, many of the liquid coolants that were suitable for Low Temperature PEMFCs (LT-PEMFCs) will now boil due to the increase in temperature. This warrants the selection of alternative coolants that can meet the requirements of these “High” Temperature PEMs (HT-PEM) and of the overall Thermal Management System (TMS).

The methodology for selecting favourable liquid coolants for different PEMFC operating temperatures is threefold. 1) Initial screening: down-selection of liquid coolants using a fluid property Figure of Merit (FoM). 2) Model screening: employ a coolant loop model to assess component sizing and parasitic power, facilitating a performance comparison among different coolants. 3) Final selection: evaluate the remaining coolants against system requirements to identify the most suitable coolant for the specific application. This approach is applied in the context of a hybrid-electric aircraft, using a Proton Exchange Membrane Fuel Cell (PEMFC) Auxiliary Power Unit (APU) as a representative case study.

A liquid coolant selection methodology is developed. The study indicates that heat exchanger mass decreases exponentially with increasing operating temperature. Aqueous-based coolants exhibit better performance than hydrocarbon-based coolants, but the latter are needed at higher temperatures to prevent boiling. The choice of coolant depends on specific criteria, such as reducing mass, parasitic power and pressure drop, or fuel consumption. As the operating temperature rises, the rate of change in fuel consumption approaches zero. Beyond 120°C, various liquid coolants exhibit similar performance. Indeed, further improvements in system-level performance must come from other developments in the thermal management system beyond coolant selection.

Presenting Author: Adam Frey University of Bath

Presenting Author Biography: Adam is a research student at the University of Bath studying for a PhD in thermal management systems for hydrogen fuel cell powered aircraft. He did a Master's degree in Mechanical Engineering, also at Bath, where he won the Chancellor's Prize for best undergraduate student.

Authors:

Adam Frey University of Bath
David Bosak GKN Aerospace
Joseph Stonham GKN Aerospace
Carl Sangan University of Bath
Oliver Pountney University of Bath