Variable property fluids for dynamic environments

Often in developing a thermal control system for environment control and life support systems a heat transfer fluid is selected on the basis of compromises between its heat transfer characteristics, operating range, and safety, among other parameters. The resulting choice is often a mediocre fluid with less than ideal performance or a complicated multi-fluid system. This study seeks to establish the merit of a fluid system having dynamic fluid properties, and whether better performance can be had from a dynamic fluid. Specifically, this study considers a representative water-based solution as the working fluid in a system where fluid properties are adjusted in response to the thermal environment and identifies whether turn-down ratio for heat rejection can be improved. Spacecraft designed to meet current safety standards use a two-loop thermal control architecture. This project explores the merit of dynamic fluids as a technology to enable single loop architecture. A dynamic fluid is a solution or suspension where the composition is adjusted to tailor fluid properties throughout a mission to a spacecraft's environment. Often in developing a thermal control system for environment control and life support systems a heat transfer fluid is selected on the basis of compromises between its heat transfer characteristics, operating range, and safety, among other parameters. The resulting choice is often a mediocre fluid with less than ideal performance or a complicated multi-fluid system. This study seeks to establish the merit of a fluid system having dynamic fluid properties, and whether better performance can be had from a dynamic fluid. Specifically, this study considers a representative water-based solution as the working fluid in a system where fluid properties are adjusted in response to the thermal environment and identifies whether turn-down ratio for heat rejection can be improved. This study modeled a conventional single loop vehicle thermal control system with a dynamic fluid in one case and a static fluid in another. The dynamic fluid was modeled over a range of compositions where the static fluid contained a representative constant composition. The results of this model show up to a 17% improvement in turn-down with the selected fluid. This enhancement becomes single-loop enabling when employed in conjunction with variable heat rejection technology. Thermal desktop modeling of a simple vehicle thermal control system with freezable (also known as stagnating) radiator technology indicates that system turn-down can be improved significantly, approaching a 6:1 system turndown through to the lower freezing point of the dynamic fluid.

This promises mass and volume savings by enabling a single loop thermal control architecture.#The advanced thermal group within EC6 has been investigating single loop enabling technologies. The merit of this technology may be further investigated and developed for spacecraft applications.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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