Enhanced Coolant for Low Temperature



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50th International Conference on Environmental Systems


In many applications, e.g. aerospace thermal conditioning, there is a need for liquid heat carriers or coolants, which are used at low temperatures. Perfluorocarbons often apply in such applications due to their low freezing points and low viscosities. However, thermal properties of perfluorocarbons such as heat capacity and thermal conductivity are unfavourable compared to other heat carriers. Fraunhofer UMSICHT developed phase change slurry designed as coolants for aerospace applications. Phase change slurries are dispersions of water as inner phase and perfluorocarbons as continuous phase. The water is dispersed into the perfluorocarbon and serves as phase change material, meaning that it absorbs and releases latent heat during the phase transition, while the perfluorocarbon remains in the liquid state. The latent heat of the phase transition increases the heat storage and heat transportation capability of the fluid. The phase transition of the water droplets changes the dispersion from an emulsion into a suspension and vice versa, but the dispersion remains viscous due to the continuous liquid phase of the perfluorocarbon. This paper describes the dispersion and provides measurements to determine the fluid properties. These are a Differential Scanning Calorimetry, measurements of thermal conductivity, viscosity, and density as well as microscopy pictures. The phase transition of the phase change material takes place in the temperature range between -25 �C and 0 �C. The expected operating temperature of the dispersion is in the range from -80 �C to 40 �C. In view of the potential use of the coolant for human spaceflight, toxicity and flammability have been two of the criteria in selecting the perfluorocarbon for the continuous phase.


Clemens Pollerberg, Fraunhofer UMSICHT
Mathias Gralher, Airbus Defence & Space
Jan Persson, European Space Research and Technology Center, European Space Agency
Andreas Sengespeick, Fraunhofer UMSICHT
ICES104: Advances in Thermal Control Technology
The 50th International Conference on Environmental Systems was held virtually on 12 July 2021 through 14 July 2021.


Coolant, Phase Change Slurry, Thermal control, Phase Change Material, Thermal properties