Computational Investigation of High-Flux Heating of Supercritical Fluids in Microscale Geometries
Open Access
- Author:
- Nabil, Mahdi
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 25, 2019
- Committee Members:
- Alexander S Rattner, Dissertation Advisor/Co-Advisor
Alexander S Rattner, Committee Chair/Co-Chair
Karen Ann Thole, Committee Member
Stephen P Lynch, Committee Member
Xiaofeng Liu, Outside Member
Daniel Connell Haworth, Program Head/Chair - Keywords:
- Supercritical fluid
Carbon dioxide
Microchannels
Heat exchanger
Large eddy simulation
Mixed convection
Supercritical Fluid
Carbon Dioxide
Micro-pin-fins
Heat Exchanger
Large Eddy Simulation
Mixed Convection - Abstract:
- Near-critical-point supercritical fluid convection is a promising alternative for emerging high-flux thermal management needs because of the high fluid thermal conductivities and specific heats. However, limited information is available on transport processes to guide engineering of high-flux compact supercritical heat transfer equipment, which often have non-uniform heating distributions. To address this need, large eddy simulations (LES) are employed in this dissertation to study supercritical CO2 convection in microchannels and micro-pin-fin enhanced geometries. Following mesh independence studies, the simulation approach is validated with published experimental data as well as relevant empirical correlations. Numerical results are used to assess the applicability of published supercritical convection correlations for microchannel heat exchangers. Parametric studies are conduced to characterize the onset of mixed convection and non-uniform heating effects in microscale test sections. Furthermore, a representative case is evaluated to assess the impact of conjugate heat transfer at microchannel walls on microscale supercritical convection performance. In addition, a new 2D map was suggested to predict zones of heat transfer deterioration and/or considerable mixed convection effects in the microchannel. Finally, thermal-hydraulics performance of parallel-plates and aligned square micro-pin-fins enhanced heat exchangers is investigated and compared against available single-phase flow correlations.