Impact of surface and physical property on multiphase flow in sealed vessel: Liquid dropdown performance

This study explores multi-phase (i.e., liquid-gas) and multi-fluid (i.e., air-water, and water-silicone oil) flow-pattern and flow-blockage physics phenomena for wall wettability conditions ranging from superhydrophilic to superhydrophobic cases in sealed vessels utilizing computational fluid dynamics (CFD) simulation tools and volume-of-fluid (VOF) method with sharp interface modeling. Detailed modeling and simulation (M&S) of such physics phenomena—in which liquid (e.g., water) stands over top of gas (e.g., air or steam) in a closed channel and exhibited flow blockage, flow reversal related challenges—are pivotal for design, analysis, and qualification of component-level (e.g., heat pipes, heat exchangers) to system-level (e.g., emergency core cooling systems in nuclear reactors) heating and cooling industrial applications. Results show that, these physics phenomena are dependent on factors like contact angle (CA), channel diameter, gravity, and viscosity which impact the flow behavior in an adiabatic, and closed environment. Key observations include the role of CA (for 10-, 50-, 90-, 130-, and 170-degree) in dropdown time: (a) a quicker dropdown for higher wettability surfaces (CA < 90 degrees); and (b) a slower dropdown for normal (CA = 90 degrees) and lower wettability surfaces (CA > 90 degrees). Other important observations are: (a) channel diameter (for 3, 10, and 100 mm) emerges as a crucial factor, a completely blocking flow case; (b) gravity variations introduce further complexities, leading to more unpredictable and unsteady flows under reduced gravity conditions. These findings, observations, and insights, including quantitative, qualitative, and nondimensional analysis supports design optimization, enhanced components-to-system level heat-transfer performance f or relevant engineering applications.