Outer space is a place of temperature extremes, so astronauts and scientists rely on sophisticated temperature control systems to create stable temperatures conducive to human activity, high-powered electronics and sensitive measurement systems.
Existing technologies rely on single phase convection, which requires large, heavy heat exchange equipment. More advanced heat exchange methods can potentially reduce the size, weight and energy needs of this equipment, if they can be designed to function reliably.
That task is the subject of a three-year NASA research grant at the University of Nevada, Reno. The project aims to develop new lightweight, energy-efficient heat-transfer technologies for use on near-earth satellites.
"NASA space systems must be lightweight and compact," said Miles Greiner, project lead scientist and mechanical engineering professor at the University. "In many applications this is achieved by using more powerful pumps or blowers to move the fluid faster. However, the challenge NASA faces is that the energy supply on a space system is extremely limited. Moreover, these systems can't be fixed after they are deployed."
The temperature of many NASA systems must be carefully controlled in order for them to function properly. One example is the proposed Surface Water Ocean Topography project, which aims to gather very precise measurements of water levels and ocean currents. The data generated would allow for detailed assessment of surface water resources and ocean mapping, ultimately supporting more exact climate modeling.
Near the earth, the amount of direct and cloud-reflected sunlight and shade change regularly with the position of the satellite. To achieve the accuracy needed for measurement, the instruments on board the satellite must be kept at an extremely accurate temperature - with a rate of temperature change 20 times smaller than that of a typical instrument on board a spacecraft.
The research team, which is led by Greiner at the University of Nevada, Reno and Kwang Kim at the University of Nevada, Las Vegas, will develop a system that uses fluids to cool heat-producing instruments and then circulates those heated fluids to cooler components that can use that energy or dissipate it into outer space.
In particular, the research team will investigate how changing the surface of the tubes through which the fluid flows can promote heat transfer and improve efficiency.
"The objective of this work is to develop heat exchanger surfaces that reliably enhance single-phase and phase-change heat transfer without requiring more pumping or blower power," Greiner said. "We will use surface treatments to trigger flow instabilities and mixing at low flow rates, where the flow would normally be laminar."
The enhanced heat exchange technology developed through the research could also help power plants operate more efficiently and consume less fresh water.
The grant, titled Advanced Transport Technologies for NASA Thermal Management/Control Systems, is a joint collaboration between the University of Nevada, Reno; the University of Nevada, Las Vegas; Desert Research Institute; and Truckee Meadows Community College. The project is funded under the Nevada EPSCoR program in the amount of $1.1 million, of which $445,000 will come to the University.