Woodruff School of Mechanical Engineering
Thermal Science Seminar - Two Presentations
H. Evan Bush and Andrew Schrader
Georgia Institute of Technology
Thursday, June 15, 2017 at 2:00:00 PM
MRDC Building, Room 3515
Abstract H. Evan Bush Design and characterization of a novel upward flow reactor for determining high-temperature thermal reduction kinetics for solar-driven processes The design and characterization of an upward flow reactor coupled to a high flux solar simulator under vacuum is presented for rapid heating of solid samples with concentrated irradiation to temperatures above 1000 °C, at heating rates over 50 K/s. The reactor allows kinetic modeling of rapidly-reacting mixed ionic and electronic conductors, for which slow heating rates and gas changeovers impossible the extraction of meaningful kinetics. These results are a foundation for studying rapidly reacting, redox-active materials in solar thermochemical cycles to produce fuels and chemically store heat—an integral component in the development and optimization of solar thermochemical reactors.
Abstract Andrew Schrader Design and Modeling of the Solar Thermochemical Inclined Granular Flow Reactor for Concentrated Solar Power Applications Major challenges to concentrated solar power systems include the effective storage of intermittent sunlight, an innovation which may improve cost competitiveness with traditional fossil fuel power generation systems. Thermochemical heat storage can be achieved with a two-step solar thermochemical cycle based on Co3O4/CoO redox reactions integrated into an Air Brayton cycle. The two-step cycle encompasses (1) the endothermic reduction of Co3O4 to CoO and O2 driven by concentrated solar irradiation and (2) the exothermic re-oxidation of CoO with O2 to Co3O4, delivering sensible heat to a power cycle. The laboratory-scale 5 kWth Solar Thermochemical INclined Granular-flow Reactor (STINGR) was designed to achieve direct irradiation and continuous flow of the reacting material, matching incident radiation with the combined material sensible and chemical energy storage rate. STINGR is designed to operate at reduced pressures to promote Co3O4 reduction and is sealed with a quartz window to introduce concentrated irradiation. A detailed mass and heat transfer analysis was performed coupling Monte Carlo ray tracing for radiative heat exchange to energy balances for the flow and the reactor cavity. Thermal reduction kinetics of Co3O4 were captured using an Avrami-Erofeyev nucleation model. Individual particle residence times were predicted from a velocity profile for dense, granular flows along inclined slopes which captured the combination of frictional and collisional effects between particle layers. The reactor model was analyzed using a parametric study with varying reactor cavity depth, particle inlet temperature, and incident solar concentration ratio. Optimal reactor performance was defined as achieving the highest outlet flow temperature and reduction extent while maintaining a maximum flow temperature below 1573 K to avoid particle sintering. The optimal STINGR design achieved a Co3O4-to-CoO reduction extent of 0.91, particle outlet temperature of 1385 K, maximum flow temperature of 1572 K, and absorption efficiency of 0.76.
H. Evan Bush is a third-year Mechanical Engineering PhD candidate, currently performing research in Georgia Tech’s Solar Fuels and Technologies Lab (SFTL). He received his undergraduate degree in 2014 in Mechanical Engineering from the University of Louisville and previously worked as an undergraduate student intern at Sandia National Labs’ National Solar Thermal Test Facility (NSTTF). Evan’s research focuses on identifying novel reduction-oxidation (redox) active materials for the storage of concentrated solar energy.
Andrew Schrader is a Mechanical Engineering PhD candidate in the Solar Fuels and Technologies Laboratory at Georgia Tech. He earned his BSME with a minor in Humanitarian Engineering from Valparaiso University in 2014. He identifies sustainable energy systems as tools to develop reliable, electrical infrastructures within developing countries.
Refreshments will be served.