Probing fundamental contact line physics using high speed endoscopy for delayed dryout in high-quality refrigerant flow boiling
Abstract
The performer will develop and use high-magnification in-liquid endoscopy to study bubble and three-phase contact line dynamics of refrigerant flow boiling. Visualization will be performed at:1) Low heat fluxes near the onset of nucleate boiling. Bubble departure and coalescence with the corresponding three-phase contact line dynamics on both unmodified and structured surfaces will be observed in-situ using the endoscopic microscopy technique. The effects of surface properties, such as roughness, wettability, and wickability on bubble behavior and dry spot dynamics during flow boiling will be investigated on scalable surface structures.2) Intermediate heat fluxes, where the microlayer evaporates rapidly due to the high thermal conductance of the microlayer. He will measure the thickness of the liquid microlayer under the bubble in the bubbly flow regime and thickness of the thin liquid film in the annular flow region through interference measurements coupled to the endoscopy system to investigate the effects of micro/nanostructures and flow boiling conditions, such as mass flux and heat flux, on liquid microlayer behavior.3) High heat fluxes near critical heat flux, where optical and infrared microscopy will be used to visualize dry patches with corresponding three-phase contact line dynamics from the backside on transparent structured surfaces to identify the mechanisms of liquid film dryout during annular flow. The coalescence mechanism among dry patches, density of nucleation sites and the proportion of dry patch area prior to dryout occurring will also be used to gain an understanding of the mechanism for delay in dryout to higher vapor qualities with flow boiling of refrigerant and to use this knowledge to enable design of advanced scalable and durable surfaces to further increase flow boiling quality prior to reaching CHF.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 06, 2021
- Source ID
- N000142112089
Entities
People
- Nenad Miljkovic
Organizations
- Office of Naval Research
- United States Navy
- University of Illinois Urbana–Champaign