Characterization of Critical Two-Phase Flow Regimes for Design and Reliable Operation of Compact Naval Energy Systems
Abstract
Task 1: Microfabrication, Packaging and Calibration of Test DevicesTo conduct measurements over a wide parametric range, necessary for development of mechanistic models promised in this proposal, new test devices will be fabricated. Under this project, devices with channel sizes up to ~1 mm and different aspect ratios and sensor patterns will be fabricated for additional tests on FC-72. New devices will also be developed for testing water. DrasticallyTask 2: Determine Thin Film Thickness as a Function of Channel Cross-section Geometry and Fluid PropertiesA comprehensive study will be conducted to determine the impact of channel cross-section geometry and size on the initial thickness of the liquid film formed on the channel wall. Eighteen test devices (9 for FC- 72 and 9 for water tests) will be fabricated with different channel aspect ratios and sizes and measurements will be conducted on FC-72 and water over a wide range of heat and mass flux. The data will be used to develop a new model for calculating thickness of the liquid film around elongated bubbles as a function of channel geometry and fluid and flow properties. This model will then be utilized to develop correlations for heat transfer coefficient and pressure drop.Task 3: Determine Transition Criteria for Elongated/Coalescing Bubbles Regime to Semiannular RegimeCapture of a unique surface thermal signature associated with the change from the coalescing bubbles regime to semi-annular regime will aid in the development of a theoretical framework for transition to semi-annular flow regime. Under this project, this transition process will be characterized over a wide range of channel geometries, flow properties and wall thermal boundary conditions.Task 4: Develop Flow and Heat Transfer Models for Annular RegimeThe new test devices will be utilized to produce the annular flow regime at a wide range of conditions. The liquid film thickness and velocity will be determined and used to develop a mechanistic-based model for the annular flow regime. Task 5: Characterize the Entrainment Process and its Impacts on Heat Transfer and Pressure dropThe new sensing platform will be utilized to accurately characterize this phenomenon through measurement of the films mass loss/gain. An interface instability analysis will be conducted to determine a criterion for onset of this process and quantify its contribution to the axial flow of the liquid mass within the vapor core. The knowledge gained through the proposed experimental and analytical studies will be utilized to develop a holistic model for quantitative assessment of the flow boiling heat transfer and pressure drop. These models are key to the design and performance evaluation of heat exchangers for compact and efficient energy systems.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 09, 2018
- Source ID
- N000141912007
Entities
People
- Saeed Moghaddam
Organizations
- Office of Naval Research
- United States Navy
- University of Florida