The technology is a heat transfer device. The key properties are a unidirectional heat flow, thin, sandwich structure, and a T-dependent thermal resistance. The technology functions via the heat pipe effect. The purpose of the technology is to provide a one-way heat flow in a compact form (in a thin layer) with T-dependent thermal resistance.
This is invention is a new type of heat transfer material, which can be fabricated on a micro scale. Its unique design allows for unidirectional transfer of heat across the material. The invention comprises a liquid-attracting element and a liquid-repelling element that are both enclosed within a sealed housing along with a liquid. When the elements are provided on opposite sides of the interior space of the housing, heat can flow from the liquid-attracting side to the liquid-repelling side of the device. The space between the middle and outer layers is filled with a working fluid and sealed by the outer layers.
Through the heat pipe effect, heat transfers only from the liquid-attracting to the liquid-repelling sides. The reverse heat flow by the heat pipe effect is prohibited because it is physically unfavorable for liquid working fluid to flow from the liquid-attracting to the liquid-repellingsides. By choosing a low-thermal-conductivity material as the liquid-repelling structure, the overall heat flow is dominated by the heat pipe effect, yielding thermal diodicity. The thermal diodicity can theoretically reach over 20, and over 100 diodicity is also achievable through intensive R&D. Additional benefit is the temperature-sensitive thermal resistance arising from the heat pipe effect. In some embodiments, the devices’ thermal conductivity has the potential of increasing by over 20% for every increase of ambient temperature of approximately 4°F. Such thermal devices can be incorporated into various other objects, such as clothing, helmets, gloves, electrical devices, thermal energy harvester/storage units, vehicles, buildings, and the like.One application is to design protecting clothes for firefighters: the high temperature of flames cannot be transferred through the clothes, while body heat produced by firefighters can be released to cooler local environments.
In a typical heat pipe, heat is transferred via a working fluid that is sealed into the pipe. The working fluid starts in contact with a “hot” thermally conductive surface and evaporates, absorbing heat and cooling the “hot” surface. The working fluid, now in a vapor phase, travels along the pipe to a “cold” surface where it condenses back into a liquid, transferring heat to the “cold” surface in the process. The newly condensed fluid then travels back to the “hot” surface to restart the process.
|United States Of America||Published Application||20150226497||08/13/2015||2012-130|
Department of Mechanical and Aerospace Engineering
Henry Samueli School of Engineering
University of California, Irvine