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External Stefan and Internal Marangoni Thermo-Fluid Dynamics for Evaporating Capillary Bridges
Arnov Paul1, Apurba Roy1, Purbarun Dhar1
1Hydrodynamics and Thermal Multiphysics Lab (HTML), Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 27, 2024
Summary
Evaporation of confined liquid bridges is mainly controlled by confinement, not wettability. Higher confinement reduces evaporation by increasing vapor concentration, while wetting influences internal hydrodynamics and external advection.
Area of Science:
- Fluid Dynamics
- Heat and Mass Transfer
- Surface Science
Background:
- Capillary bridges are crucial in various applications, but their evaporation dynamics under confinement are not fully understood.
- Internal Marangoni hydrodynamics and external Stefan advection during evaporation are complex phenomena requiring detailed investigation.
Purpose of the Study:
- To investigate evaporation mechanisms in wettability-moderated, confined capillary bridges and bulges.
- To explore internal Marangoni hydrodynamics and external Stefan advection dynamics.
- To analyze the effects of confinement, wetting state, and contact line dynamics on evaporation.
Main Methods:
- Transient simulation using the level set (LS) method and Arbitrary Lagrangian-Eulerian (ALE) framework.
- Fully coupled simulation of liquid and gas domains with appropriate boundary conditions.
- Modeling of generic contact line dynamics (CCR and CCA modes).
Main Results:
- Evaporation rate is primarily dictated by the degree of confinement, with higher confinement reducing evaporation.
- Wettability plays a marginal role in the overall evaporation rate but significantly affects internal Marangoni and external Stefan advection dynamics.
- Superhydrophobic confinements lead to augmented vapor concentration and enhanced thermal Marangoni flow compared to hydrophilic confinements.
Conclusions:
- Confinement is the dominant factor controlling evaporation rates in capillary bridges.
- Wetting state influences the internal flow and external vapor transport, impacting thermofluidic processes.
- Findings offer insights for designing efficient thermofluidic systems involving liquid bridges for thermal transport and material deposition.
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