Fundamental Studies of Jumping-Drop Thermal Diodes
Abstract
AFRL TPOC: Andrew Williams Manager, Integrated Structural Systems Program Space Vehicles Directorate Fundamental Studies of Jumping-Drop Thermal Diodes Research Objective The objective of this proposal is to study the performance of jumping-drop thermal diodes after repeated freeze-thaw cycles and at different orientations, both important in the context of space platforms that require reliable performance following frozen startups and orientation independence with respect to gravity. Technical Approaches The proposed thermal diode consists of two parallel plates. In the forward mode, the self-propelled jumping of condensate drops on the superhydrophobic plate is used to return the working fluid to the hotter superhydrophilic plate, resulting in effective phase-change heat transfer. In the reverse mode, the jumping return mechanism ceases to function when the working fluid condenses on the colder superhydrophilic plate, leading to ineffective heat transport by vapor conduction. This design enables thermal rectification over a large cross sectional area and is potentially suitable for thermal control in space vehicles. The proposed thermal diodes will be constructed with transparent sidewalls to enable direct imaging of the jumping return mechanism with and against gravity as well as the transient behavior during the frozen startup. Anticipated Outcome and Impact In addition to thermal characterizations of both the forward and reverse modes, the inner working of the jumping-drop vapor chamber will be directly visualized for the first time. The fundamental studies characterizing the thermal diode performance after frozen startup and at different orientations will provide guidelines for future applications of the jumping-drop diode toward space platforms. Public Purpose The proposed thermal diode has potential applications ranging from energy harvesting to electronics cooling. The effective thermal rectification and scalability to large areas are well suited for solar energy harvesting and the associated heat storage. The planar form factor and orientation independence are useful for the thermal management of mobile electronics including laptops and smartphones.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 18, 2016
- Source ID
- FA94531510312
Entities
People
- Chuan-Hua Chen
Organizations
- Air Force Research Laboratory
- Duke University
- United States Air Force