Deciphering the fundamental limits of micro- and nano-scale phase change heat transfer
Abstract
Deciphering the fundamental limits of micro- and nano-scale phase change heat transfer PROJECT SUMMARY: The proposed research seeks to reveal the fundamental heat and mass transfer processes controlling phase-change heat transfer in micro-domains. To accomplish this challenging, > 50 year problem,[1] the proposed work focuses on heat transport within the liquid meniscus. The liquid meniscus is the most important region in particulate and multi-phase processes.[2] The liquid meniscus refers to the curved liquid/air interface formed above a solid surface in contact with a liquid. Within the fluid region of highest meniscus curvature, maximum (1) evaporation rates, (2) disjoining pressure gradients, and (3) hydrostatic pressure gradients are found, which can lead to many unique outcomes in particulate and multi-phase processes. For example, the physics and chemistry that ensues within the liquid meniscus has allowed both researchers and nature to “engineer” some very unique outcomes that include (but not limited to): insects that can walk on water, directed materials deposition and pattern formation. The research is motivated by the need to actively control heat and mass transport in a variety of different high heat-flux thermal management technologies. The project is built upon the PI’s recent findings in experimental and numerical studies of heat and mass transport at liquid interfaces and evaporating droplets. Fundamental studies of multi-physics flow phenomena are proposed for (1) two-phase flow and evaporation in the liquid meniscus and (2) nanoscale thermal transport at solid/liquid interfaces. The end goal is to understand and exploit unsteady behavior in multiphysics flow on surfaces exposed to large heat-fluxes and time-varying temperature gradients. Experimentally, a local, interfacial heat transfer coefficient will be measured using time-resolved laser pump-probe techniques in conjunction with high-speed photography and time-resolved optical spectroscopy, facilitating measurements of both the local surface temperature and fluid thin-film thickness. Numerically, an explicit volume-of-fluid (VOF) model – adapted to the Graphics Processing Unit (GPU) on a low cost high performance parallel computing platform – will track the time-dependent temperature distributions and volume fractions of fluid and gas. The numerical models will be developed to predict two-phase fluid flow, evaporation, and phase separations within multi-component fluids. This multidisciplinary work is expected to validate that the transitional fluid region between the intrinsic meniscus and adsorbed liquid thin-film is the most important region in unsteady solid-liquid-vapor systems. Moreover, the proposed work will aid the development of new thermal management methodologies – through identification and characterization of potentially new stability diagrams at high heat fluxes – which can actively-control a phase-change thermal management system, avoiding unwanted flow-field instabilities and, in result, enhancing the overall heat transfer performance during unsteady thermal transport.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512481
Entities
People
- Shawn Putnam
Organizations
- Office of Naval Research
- United States Navy
- University of Central Florida