Motion Distribution Characteristics of Regular Tetrahedral Particle Population in Vertical Uppipe

Liquid-solid two-phase flow technology is widely applied to the heat transfer enhancement in heat exchanger design, the key lies in guiding low-volume-fraction particles to the wall region to disrupt the thermal boundary layer and thereby improve the heat transfer efficiency. The movement behavior of particles is a key factor for deep analysis of heat transfer enhancement mechanism. Non-spherical particles have better disturbance effects and more complex movement behaviors due to the anisotropy of their shapes. This paper takes regular tetrahedral particle groups as the research subject to analyze their motion and distribution law in liquid-solid two-phase flow in vertical uppipe. In the investigation, the effects of particle inlet volume fraction (1%, 2%, 3%, 4% and 5%) and liquid inlet velocity (1.0, 1.2, 1.5, 1.8 and 2.0 m/s) on the average velocity and relative volume fraction distribution of particle groups in tubes are simulated based on CFD-DEM (Computational Fluid Dynamics-Discrete Element Model) coupling method, and the accuracy of the numerical simulation is verified by PIV (Particle Image Velocimetry) experiments. The results show that, within the studied parameter range, the average velocity of particle groups exhibits axial fluctuations, with a fluctuation amplitude intensifying as the liquid inlet velocity increases, and decreases radially from the pipe center to the wall. Furthermore, the velocity distribution becomes increasingly centralized as the fluid flow develops axially. Along the radial direction, the relative volume fraction of particles follows the double peak law, that is, being higher in the central area and near the wall of the tube, while being lower in the transition area. When the particle inlet volume fraction is 1% and the liquid inlet velocity is 2.0 m/s, the particle volume fraction near the pipe wall is the highest.