Planar Bridging-Droplet Thermal Diodes
Abstract
We invented and characterized a one-way heat transfer device that we call a bridging-droplet thermal diode. While several types of thermal diodes already exist, they are all hampered by severe constraints that limit practical application. Solid-state thermal diodes are highly ineffective, while phase-change thermal diodes are effective but constrained by either a gravitational dependence, a one-dimensional configuration, or poor durability. Our bridging-droplet thermal diode was demonstrated to bypass all these shortcomings of existing thermal diodes. Two opposing copper plates were separated by an insulating gasket to form a vapor chamber; one plate contained a super hydrophilic wick structure while the other contained a smooth hydrophobic coating. The interior of the chamber was charged with water and the noncondensable gases were evacuated. In the forward mode of operation, water evaporates from the heated wicked plate and condenses on the hydrophobic plate. When dew drops grow large enough to touch the opposing wicked evaporator, they bridge across the gap to return to the wick, resulting in sustained phase-change heat transfer. Conversely, in the reverse mode of operation, the heat source is on the side featuring the hydrophobic plate. This results in all water getting trapped in the opposing wick structure, causing dry out at the heat source to enable excellent insulation across the vapor space. An orientation-independent heat transfer ratio (i.e. diodicity) ranging from roughly 10-100 was demonstrated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 10, 2021
- Accession Number
- AD1153194
Entities
People
- Jonathan B Boreyko
Organizations
- Virginia Tech