Direct Numerical Simulation of Turbulent Heat Transfer Modulation in Micro-Dispersed Channel Flow

TL;DR

This study uses direct numerical simulation to analyze how micro- and nano-particles affect turbulent heat transfer in channel flows, revealing size-dependent effects on heat fluxes and providing insights for designing advanced heat transfer fluids.

Contribution

The paper introduces a DNS-based methodology to evaluate the impact of micro- and nano-particles on turbulent heat transfer, highlighting size-dependent effects on heat fluxes in channel flow.

Findings

Smaller particles increase heat transfer fluxes by about 2%.

Larger particles cause a slight decrease in heat transfer fluxes.

Results align with previous experimental observations.

Abstract

The object of this paper is to study the influence of dispersed micrometer size particles on turbulent heat transfer mechanisms in wall-bounded flows. The strategic target of the current research is to set up a methodology to size and design new-concept heat transfer fluids with properties given by those of the base fluid modulated by the presence of dynamically-interacting, suitably-chosen, discrete micro- and nano- particles. We run Direct Numerical Simulation (DNS) for hydrodynamically fully-developed, thermally-developing turbulent channel flow at shear Reynolds number Re=150 and Prandtl number Pr=3, and we tracked two large swarms of particles, characterized by different inertia and thermal inertia. Preliminary results on velocity and temperature statistics for both phases show that, with respect to single-phase flow, heat transfer fluxes at the walls increase by roughly 2% when the flow is laden with the smaller particles, which exhibit a rather persistent stability against non-homogeneous distribution and near-wall concentration. An opposite trend (slight heat transfer flux decrease) is observed when the larger particles are dispersed into the flow. These results are consistent with previous experimental findings and are discussed in the frame of the current research activities in the field. Future developments are also outlined.