Enhancing Heat Transport in Multiphase Rayleigh-Bénard Turbulence by Changing the Plate-Liquid Contact Angles

Abstract

This numerical study presents a simple but extremely effective way to considerably enhance heat transport in turbulent multiphase flows, namely by using oleophilic walls. As a model system, we pick the Rayleigh-Bénard setup, filled with an oil-water mixture. For oleophilic walls, e.g. using only $10\%$ volume fraction of oil in water, we observe a remarkable heat transport enhancement of more than $100\%$ as compared to the pure water case. In contrast, for oleophobic walls, the enhancement is then only about $20\%$ as compared to pure water. The physical explanation of the highly-efficient heat transport for oleophilic walls is that thermal plumes detach from the oil-rich boundary layer and are transported together with the oil phase. In the bulk, the oil-water interface prevents the plumes to mix with the turbulent water bulk. To confirm this physical picture, we show that the minimum amount of oil to achieve the maximum heat transport is set by the volume fraction of the thermal plumes. Our findings provide guidelines of how to optimize heat transport in thermal turbulence. Moreover, the physical insight of how coherent structures are coupled with one phase of a two-phase system has very general applicability for controlling transport properties in other turbulent multiphase flows.

11 pages, 4 figues

References in corpus (6)

• Comparison between two and three dimensional Rayleigh-Bénard convection
• Controlling heat transport and flow structures in thermal turbulence using ratchet surfaces
• Heat transport in boiling turbulent Rayleigh-Bénard convection
• Enhanced heat transport by turbulent two-phase Rayleigh-Bénard convection
• An efficient phase-field method for turbulent multiphase flows
• Global and local statistics in turbulent emulsions

Cited by in corpus (6)

• Heat transfer in turbulent Rayleigh-Bénard convection within two immiscible fluid layers
• Evaporating Rayleigh-Bénard convection: prediction of interface temperature and global heat transfer modulation
• Analysis of the heat transfer fluctuations in the Rayleigh-Bénard convection of concentrated emulsions with finite-size droplets
• Turbulent Rayleigh-Bénard convection with bubbles attached to the plate
• Role of interfacial stabilization in the Rayleigh-Bénard convection of liquid-liquid dispersions
• Dynamical regimes of thermally convective emulsions