Characteristics of Axial and Radial Development of Solids Holdup in a Countercurrent Fluidized Bed Particle Solar Receiver

A novel particle solar receiver (PSR) with gas-solids countercurrent fluidized bed (CCFB) was proposed. The cold-mold prototype was set up to investigate the gas-solids flow structure by using optical fiber probes. The local solids holdup distribution, its evolution with various operating conditions and the fluctuations of the local flow structures were investigated experimentally. The results show that the novel CCFB can achieve much higher solids holdup (similar to 9%) compared to the traditional downer ones (similar to 1%). The solid particles are mainly distributed in the near-wall region and the particles are more difficult to get a fully developed state in the near-wall region. The excellent gas-solids mixing and contacting demonstrated by the standard deviation and intermittency index means a better wall-to-bed heat transfer process. The distribution of the solid particles in the CCFB transport tube is revealed, which can provide a significant reference for the structure design of the hot-mold PSR. Moreover, the research can fill in the research gap in the gas-solids counterflow field.