11/14/2023
By Danielle Fretwell
Candidate Name: Ephraim Mutemwa Simasiku
Degree: Doctoral
Defense Date: November 27, 2023
Time (from/to): 10 a.m. to Noon
Location: Zoom meeting (contact juan_trelles@uml.edu for link)
Committee:
Advisor: Juan Pablo Trelles, Professor, Mechanical and Industrial Engineering, UMass Lowell
Committee Members*
Ofer Cohen, Assoc. Professor, Physics and Applied Physics, UMass Lowell
John Hunter Mack, Assoc. Professor, Mechanical and Industrial Engineering, UMass Lowell
Noah van Dam, Asst. Professor, Mechanical and Industrial Engineering, UMass Lowell
Brief Abstract:
The use of renewable energy to convert carbon dioxide (CO2) into higher-value products can help meet the demand for fuels and chemicals while reducing CO2 emissions. Solar-Enhanced Microwave Plasma (SEMP) CO2 conversion aims to combine the scalability and sustainability of solar thermochemical methods with the high efficiency and continuous operation of plasmachemical approaches. A computational study of a built SEMP reactor operating with up to 1250 W of microwave power together with up to 525 W of concentrated solar power at atmospheric pressure is presented. The study is based on a fully-coupled computational model comprising the description of fluid flow, heat transfer, Ar-CO2 chemical kinetics, energy conservation for electrons and heavy-species, electrostatics, and radiative transport in participating media through the reactor chamber, together with the description of the microwave electromagnetic field through the waveguide and the reactor chamber. Preliminary numerical simulations, using a 2D implementation of the model together with geometry-based scaling of input power, revealed that the plasma is concentrated near the location of incident microwave energy, which is aligned with the radiation focal point, and that CO2 decomposition is highest in that region. The incident solar radiation flux leads to more uniform distributions of heavy-species temperature with moderately greater values throughout most of the discharge tube. Modelling results showed that, at 700 W of electric power, conversion efficiency increases from 6.8% to 10.0% with increasing solar power from 0 to 525 W, in reasonable agreement with the experimental findings of 6.4% to 9.2%. The enhanced process performance can be a consequence of the greater power density of the microwave plasma due to the absorption of solar radiation. The proposed work encompasses a 3D implementation of the model to accurately describe the SEMP reactor geometry, avoiding the need for drastic a-priori modeling simplifications and hence enabling the accurate description of the interaction between incident microwave and solar power and the generated plasma.