Enhanced heat transport in thermal convection with suspensions of rod-like expandable particles

Thermal convection of fluid is a more efficient way than diffusion to carry heat from hot sources to cold places. Here, we experimentally study the Rayleigh-Benard convection of aqueous glycerol solution in a cubic cell with suspensions of rod-like particles made of polydimethylsiloxane. The particles are inertial due to their large thermal expansion coefficient and finite sizes. The thermal expansion coefficient of the particles is three times larger than that of the background fluid. This contrast makes the suspended particles lighter than the local fluid in hot regions and heavier in cold regions. The heat transport is enhanced at relatively large Rayleigh number (Ra) but reduced at small Ra. We demonstrate that the increase of Nusselt number arises from the particle-boundary layer interactions: the particles act as 'active' mixers of the flow and temperature fields across the boundary layers.

Automated summary

Thermal convection of fluid is a more efficient way than diffusion in heat transportation. The experiment studied Rayleigh-Benard convection of aqueous glycerol solution with inertial rod-like particles, demonstrating an increase in heat transport due to particle-boundary layer interactions.