(404e) Thermo-Photo-Phoretic Phenomena Under High Solar Irradiance Levels for Chemical Processing of Aerosol Flows

Powder and particles serve as the key raw form for numerous industrial applications, such as the flame and spray pyrolysis, aerosol synthesis, latent and chemical energy storage. In a few of these established and modern applications, particles are exposed to intense temperature gradients and irradiance levels. On illumination, the particles heat up and move in response to the forces exerted by the temperature and/or photon pressure gradients, referred to as thermophoresis and photophoresis respectively. While the thermophoretic movement of particles were considered when designing heat and mass exchangers, since these can facilitate the formation of undesirable deposits on the reactor walls, the photophoretic were typically ignored as negligible. However, this is not quite true for particles under the irradiance of concentrated solar technologies.

Therefore, this study presents an investigation on the thermo-photo-phoretic phenomena encountered in solar aerosol synthesis and chemical processing of materials. Previous studies support the impact of thermo-photo-phoretic phenomena on the transport and deposition of aerosol particles during aerosol synthesis. It has been shown that thermophoresis can lead to the accumulation of particles near the reactor hot walls, while instead photophoresis could reduce particle deposition on the walls. A mathematical model was developed which accounts for the thermo-photo-phoretic phenomena under high solar irradiance levels, specifically for the synthesis of CaC₂.The model considers spherical particles passing vertically through a transparent tube exposed to concentrated light. The effect of different properties of the particles such as size and composition, sunlight (simulated via Xe-Arc light sources) radiation, temperature gradient, and different flow regimes and fluid's rheological properties were examined. In addition, the model was employed to analyze the reactor design, extract the reaction kinetics and process parameters, and quantify energy consumption. Understanding the effects of thermo-photo-phoretic on aerosol synthesis can lead to the development of an optimized reactor design that can be used to improve the efficiency and sustainability of the process. Finally, in this work the first design of an experimental configuration will be discussed in order to evaluate the mathematical model and investigate further the employed phenomena.