Regimes of heat transfer in particle suspensions

TL;DR

This study uses interface-resolved simulations to analyze heat transfer mechanisms in particle suspensions across different flow regimes, revealing how particle motion influences thermal transport and identifying conditions where heat transfer is enhanced or suppressed.

Contribution

It provides a detailed characterization of heat transfer regimes in particle suspensions using advanced simulations, linking flow regimes to thermal transport behavior.

Findings

Heat transfer is mainly due to diffusion in viscous regime.

Maximum heat transfer enhancement occurs in turbulent-like regime.

Heat transfer decreases in particulate shear-thickening regime at high volume fractions.

Abstract

We present results of interface-resolved simulations of heat transfer in suspensions of finite-size neutrally-buoyant spherical particles for solid volume fractions up to 35% and bulk Reynolds numbers from 500 to 5600. An Immersed Boundary-Volume of Fluid method is used to solve the energy equation in the fluid and solid phase. We relate the heat transfer to the regimes of particle motion previously identified, i.e. a viscous regime at low volume fractions and low Reynolds number, particle-laden turbulence at high Reynolds and moderate volume fraction and particulate regime at high volume fractions. We show that in the viscous dominated regime, the heat transfer is mainly due to thermal diffusion with enhancement due to the particle-induced fluctuations. In the turbulent-like regime, we observe the largest enhancement of the global heat transfer, dominated by the turbulent heat flux. In the particulate shear-thickening regime, however, the heat transfer enhancement decreases as mixing is quenched by the particle migration towards the channel core. As a result, a compact loosely-packed core region forms and the contribution of thermal diffusion to the total heat transfer becomes significant once again. The global heat transfer becomes, in these flows at volume fractions larger than 25%, lower than in single-phase turbulence.