Evaluation of Air Recirculation for Falling Particle Receivers

This paper presents simulations and designs of a prototype falling particle solar receiver with air recirculation as a means of mitigating heat loss and impacts of external wind on particle flow. The flow and dispersion of different sizes of ceramic proppant (CARBO HSP) particles (1 mm, 100 μm, and 10 μm) were simulated in recirculating air flows without heating effects. Particles on the order of 0.1–1 mm yielded desirable simulated flow patterns when falling through the cavity receiver with an air-injection velocity of 3 m/s. Simulations of smaller particles on the order of 10 microns yielded unstable flow patterns that may lead to large losses of particles through the aperture. A prototype cavity receiver with air recirculation was designed and fabricated to validate the unheated simulations. The blower nozzles and suction plenum were engineered to yield the most uniform flow pattern along the entire width of the aperture. Observed and simulated air velocity distributions around the aperture and particle flow patterns using CARBO HSP particles with an average diameter of ∼0.7 mm were found to be qualitatively similar.