Modeling Sand Particulate Flows Through Angled Apertures and Surfaces in Concentrated Solar-Thermal Power Receivers

Abstract

Concentrated solar-thermal power towers are increasingly migrating toward sand-based particle receiver designs to improve thermal efficiency and reach temperatures above 1000 °C for air Brayton power cycles and supercritical CO2 power cycles. However, utilizing sand affords complexities in modeling particle flow characteristics due to variable geometric shape, size, and composition. Thus, the objective of this study is to model the particle flow characteristics of sand through variable angled chevron shapes and receiver hoppers to help formulate robust modeling for flow dynamics. Treating the chevrons as an array of apertures, a novel method of calculating sand particle mass flowrate across angled apertures and surfaces is developed. Employing high-speed photography and particle imaging velocimetry techniques, our results incorporate the impact of effective angles upon velocity, residence time, and breakage profiles of falling sand particles. This study determines that a Beverloo equation incorporating effective angles for velocity and aperture size effectively predicts mass flowrate through chevrons, which can serve as a reference for future particulate flow modeling in this field. Furthermore, increasing hopper and chevron tip angles resulted in a more significant decrease in particle diameter and curtain opacity after sand flow trials.