A recent article on Phys.org took a look at the Two-Phase Flow investigation by the Japan Aerospace Exploration Agency (JAXA) and by NASA, which is exploring two-phase boiling as a potential cooling solution for long-term space exploration.
The experiment hardware, which installs in the Multi-purpose Small Payload Rack in the KIBO module
of the space station. (JAXA)
The study is examining the thermal characteristics of boiling in microgravity to see if flowing boiling liquid over heated surfaces will provide the heat transfer and heat dissipation to make it a viable solution in space. The two-phase, according to the article, refers to vapor and liquid flowing together in a single channel.
“Boiling removes heat by turning liquid into vapor at the heated surface,” the article explained. “Cooling systems use condensers that cool the vapor and produce condensation on the surface of the unit, thus turning that vapor back into a liquid, in a continuous cycle. In a two-phase flow system, heat is removed when the liquid vaporizes during boiling, resulting in high-performance heat removal and transportation.”
As the author noted, this cooling solution has proven effective on Earth for high-powered computing and electronics, but the study currently taking place on the International Space Station (ISS) will demonstrate its capabilities in space.
An engineer from JAXA added that space travel has difficult requirements for the thermal management of its electronic systems. These requirements include large amounts of thermal energy that needs to be dissipated, cooling high levels of heat from components, and also transferring heat over long distances to radiators that can remove it.
The article continued, “On Earth, bubbles generated by boiling leave the surface of the liquid because of buoyant force - the bubbles are about 1,000 times less dense than the liquid. That buoyant force disappears in microgravity, so bubbles do not easily detach from the surface. They essentially form an insulating layer at the surface and could significantly decrease heat transfer.”
Learn more at https://phys.org/news/2017-02-cool-space.html.