Physics of High-Quality Phase Change Under Extreme Confinement
Abstract
Approved for Public ReleaseIn depth understanding of the physics of phase change under extreme confinement is both rare and essentia l to development of universal two-phase boiling models and high-performance cooling systems. A high degree of confinement could resu lt in formation of flow regimes that could generate extraordinarily high heat transfer coefficients. High density surface microstruc tures also provide extremely high surface areas that, if properly utilized, can result in unprecedented heat transfer coefficients a nd surface heat fluxes at a high vapor quality. To explore these opportunities, a comprehensive study is proposed to characterize th e phase change heat transfer process under extreme confinement, and to understand the process physics and its thermal performance li mits. This study is enabled by a unique micro heat flux sensor with unprecedented spatial and temporal resolutions developed to stud y different mechanisms of heat transfer in the boiling process, and recently advanced under an ongoing ONR project to study the phys ics of thin liquid films formation and evaporation in channel sizes of O(100) m with different aspect ratios. Under this study, new microfluidic experimental platforms and sensors layouts will be developed to enable mapping the wall temperature and heat flux and determine the heat transfer coefficient and mechanisms of heat transfer with temporal and spatial resolutions of 50 s and 10 m, re spectively, and flow regimes in microgaps with sizes ranging from ~10 to ~50 m and aspect ratios of up to ~20. The impact of surfac e nanostructures on formation (and evaporation) of thin liquid films on the microgap wall will be studied. These studies will be con ducted using FC-72 and water, as representatives of low and high surface tension fluids. Contributions of different mechanisms of he at transfer and distribution of heat transfer coefficient as a function of channel size, mass flux, and vapor quality will be determ ined, and a comprehensive understanding of the process physics will be presented. Conditions that could lead to the highest heat tra nsfer coefficient and heat flux at the maximum vapor quality will be presented.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 07, 2021
- Source ID
- N000142112787
Entities
People
- Saeed Moghaddam
Organizations
- Office of Naval Research
- United States Navy
- University of Florida