Influence of the particle trajectory patterns on the heat transfer efficiency in the finite-size particle-laden thermal convection

Particle-laden thermal convection exists in a variety of natural phenomena and engineering applications. Compared to the single-phase thermal convection flows, particle-laden thermal convection flow involves more governing parameters, and the alteration of thermal transport by the presence of solid particles is still not well understood. In this work, three-dimensional Rayleigh-Bénard convection in a half cubic cell laden with finite-size solid particles is simulated. Two-way momentum and thermal couplings between the particulate phase and the carrier fluid are considered in the simulations. The flow Rayleigh number is fixed at 10⁷, and the particle volume fraction is varied from 1% to 9%. For small to moderate particle volume fraction, the increase of particle volume fraction is found to augment the heat transfer efficiency of the system, due to the enhanced heat transport carried by the solid particles. The simulation results reveal four typical particle transport modes: the large-scale circulation, vertical/horizontal spiral motion, small-scale circulation, and the trapped motion. The enhanced heat transport by solid particles is found to be mainly associated with the larger-scale circulation and vertical spiral motion of the particles.