Abstract
Turbulence is known for its ability to vigorously mix fluid and transport heat. Despite over a century of research for enhancing heat transport, few have exceeded the inherent limits posed by turbulent-mixing. Here we have conceptualized a kind of “active particle” turbulence, which far exceeds the limits of classical thermal turbulence. By adding a minute concentration (ϕv ∼ 1%) of a heavy liquid (hydrofluoroether) to a water-based turbulent convection system, a remarkably efficient biphasic dynamics is born, which supersedes turbulent heat transport by up to 500%. The system operates on a self-sustained dynamically equilibrated cycle of a “catalyst-like” species, and exploits several heat-carrier agents including pseudo-turbulence, latent heat and bidirectional wake capture. We find that the heat transfer enhancement is dominated by the kinematics of the active elements and their induced-agitation. The present finding opens the door towards the establishment of tunable, ultra-high efficiency heat transfer/mixing systems.
Highlights
Turbulence is known for its ability to vigorously mix fluid and transport heat
The primary heat transporters of thermal turbulence are the “plumes”[6], and they form an essential component in ocean currents[9,10], atmospheric and mantle convection[11], volcanic eruptions[12], biochemical and combustion reactions[13], as well as in the sustenance of thermonuclear phenomena in the sun, the stars, and other galactic powerhouses[14,15]
Here we show that introducing a minute volume fraction of a hydrofluoroether liquid (HFE-7000) to a classical turbulent convection system based on water, the heat transport can enhance up to 500%
Summary
Turbulence is known for its ability to vigorously mix fluid and transport heat. Despite over a century of research for enhancing heat transport, few have exceeded the inherent limits posed by turbulent-mixing. A central question for any heating or cooling device is to establish a robust relationship between an applied temperature difference and the corresponding heat flux[6] For thermal turbulence, this can be expressed in dimensionless form as a relation between Nusselt number Nu (or the dimensionless heat flux) and Rayleigh number Ra (or the dlaiwm5e:nNsiuon∝leRssaβt.eHmepreer, aNtuure1⁄4dQif=feÀrλeΔnHTcÁe,),Rwa i=thgγaΔnTeHff3e/cνtκiv,ewshcearleinQg is the measured heat input through the bottom plate into the system per unit time, λ the thermal conductivity of the working fluid, ΔT the temperature difference, H the thickness of the working fluid layer, g the gravitational acceleration, γ the isobaric thermal expansion coefficient, ν the kinematic viscosity, κ the thermal diffusivity, and β the effective scaling exponent. We explain the underlying mechanism of heat transfer enhancement and find that it is dominated by the kinematics of the active elements and their induced-agitation
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