Beating the Heat in Space
Jamal Yagoobi, left, floats beside a prototype of the EHD
pump during a test on the Vomit Comet.
In space, it’s hard to keep your cool—especially if you’re a high-powered electronic device. Much of the electronic hardware found in modern satellites and space vehicles generates considerable heat. If not adequately removed, that heat can impair the performance of these devices or even cause them to fail.
For many years, NASA has been in search of a new way to deal with that heat to improve the performance and reliability of electronics in its satellites, planetary robots, and manned platforms, including the International Space Station. As with all space hardware, the solution should use little electric power, be lightweight, and have few moving parts, which could create noise and vibrations.
A promising answer has emerged from work conducted over the past decade by a research team led by Jamal Yagoobi, professor and head of WPI’s Department of Mechanical Engineering. (Yagoobi is also director of the new National Science Foundation-funded Center for Advanced Research in Drying.)
With continuous support from NASA over that period, and working in collaboration with researchers at the agency’s Goddard Space Flight Center in Greenbelt, Md., and its Glenn Research Center outside Cleveland, Yagoobi and the team in his Multi-Scale Heat Transfer Laboratory have developed a novel cooling technology that appears to meet all of NASA’s requirements. After extensive testing on the ground and in the air, the innovation will fly aboard the International Space Station later this decade.
The cooling solution is based on electrohydrodynamics (EHD), which involves the use of electrically charged fluids. EHD devices convert electrical energy directly into kinetic energy, or motion. In the devices developed in the Multi-Scale Heat Transfer Lab, a nonsymmetrical electric field is used to move a charged liquid through tubes as thin as a human hair. The fluid picks up heat from a hot surface (such as an operating electronic device) and begins to boil.
The EHD pump moves the vapor away from the surface, where it is cooled back into liquid form so it can be circulated through the EHD pump again. Prototypes of the cooling technology have been tested by Yagoobi and his team on NASA’s reduced gravity aircraft, a modified Boeing 727 popularly known as the Vomit Comet, which follows a steep parabolic trajectory in order to generate 20-second periods of microgravity—up to 40 per flight.
To date, team members have made 10 research flights, which have allowed them to test variations in the design of a single-phase EHD system (one where the liquid does not boil) and an EHD-driven liquid film-flow boiling system. After additional ground tests of an improved two-phase (liquid/vapor) system, preparations are under way for a new test flight on the Vomit Comet in 2017.
The mission patch for the planned test of the
pump aboard the International Space Station.
Yagoobi’s team is also preparing for an even loftier milestone: developing an experiment for the International Space Station (ISS). NASA will spend about $7.5 million over the next several years on research into heat transfer using Yagoobi’s technology. Their mission is to develop an experiment to prove the ability of their two-phase EHD system to keep high-performance electronics cool on orbit. The experiment is expected to fly in 2020.
“We have successfully passed NASA’s science review of our project,” Yagoobi says, “and we are scheduled to pass the engineering review in late 2017 to conform to strict ISS requirements.”
Once the experiment is in orbit, Yagoobi and his team will have to be available around the clock to monitor and troubleshoot it. Duplicate experiments will be run on the ground at WPI and at either the NASA Goddard or NASA Glenn facility.
While work begins on the final design and fabrication of the experiment, other efforts are under way to demonstrate the usefulness of the EHD heat transfer pump in terrestrial applications. For example, Yagoobi says, he is working with three universities in France to enhance the energy efficiencies of thermal devices used in industry and in HVAC&R (heating, ventilating, air conditioning, and refrigeration) systems.
Keeping things cool, it seems, has become a hot field.
— Laurie Schlatter