Novel technology will enable the smart thermal management of electronics, aircraft, and spacecraft.
Jonathan Boreyko, an associate professor in mechanical engineering and his team, developed the planar bridging-droplet thermal diodes as a novel approach to thermal management. Their research is published in Advanced Functional Materials.
Boreyko, an associate professor in mechanical engineering, was the recipient of a Young Investigator Research Program award in 2016, given by the Air Force Office of Scientific Research. This award funded the development of the new thermal diode technology, which was primarily developed for aircraft thermal management.
In general, a diode is an electrical component that conducts electric current in one direction and resists the flow in the opposite direction. A thermal diode enables the dumping of heat entering one side while resisting heat on the opposite side.
The team created a thermal diode using two copper plates in a sealed environment, separated by a microscopic gap. One of the plates is engineered with a wick structure to hold water, while the other plate is coated with a water-repelling layer. The copper plate with the wicking surface acts as the thermal conducting side and receives heat. The water evaporates into steam, and as it moves across the narrow gap, cools and condenses into fine droplets on the water-repelling layer on the opposite plate. These droplets continue to grow large enough to bridge the gap between the plates, get absorbed back into the wick structure, and restart the whole process again. If heat is applied to the water-repelling side, no steam is produced as the water is trapped in the wick.
The research has shown the approach to be highly efficient and extremely versatile. According to Boreyko, present-day diodes are either not very effective in terms of conduction or require gravity. The new diode provided a 100-fold increase in heat conduction on the water-wicked side compared to the water-repelling side, which is a significant improvement to existing thermal diodes. It can also be used in any direction and would even work in the microgravity of space.
The practical use of this technology would be to absorb heat from an overheated aircraft, a CPU chip, and any object producing heat that has to be absorbed and, at the same insulate it from the outside environment.
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