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Parametric Study via Numerical Simulations of Natural Convection in Laterally Heated Cylindrical Enclosures: Investigating Characteristic Length

Hirt, David M
http://rave.ohiolink.edu/etdc/view?acc_num=akron15227528176693

Abstract Details

2018, Master of Science, University of Akron, Mechanical Engineering.
This study numerically investigates the laterally heated vertical cylinder and the length scale associated with this reactor. For natural convection the important dimensionless characteristic is the Rayleigh number, which predicts the flow regime as laminar, transitional, or turbulent. The Rayleigh number is useful as a design tool for scaling a reactor. Up to this point the associated length scale has been assumed as various definitions of length and diameter and has not yet been thoroughly investigated. The current assumed definitions for the length scale: height, diameter, and volume to lateral surface area, are directly studied in a multi-dimensional (2D and 3D) numerical parametric study involving these length scales and aspect ratio (height/diameter). Other important characteristics such as the ratio of heating to cooling and thickness of the divider (insulator) between heating and cooling are also studied. The study begins with turbulent transient 2D axisymmetric simulations and proceeds to turbulent transient 3D simulations then compares the 3D and 2D simulations. Finally, 2D and 3D laminar simulations are investigated. Presented are the results of the fluid flow speeds, thermal environments, flow patterns, boundary layer thickness, boundary layer velocity, and normal probability density functions which provide a unique way of studying how the Rayleigh number is influenced by variables. The numerical simulations are examined for spatial step, time step, and relative convergence by a mesh study, time step study, and thermal analysis, respectively. The turbulence model used (k-ω SST) is based on recent published studies. All simulations were conducted with the commercially available software ANSYS FLUENT. Findings are discussed when they prove significant, and aid in developing a fundamental understanding of the physics occurring inside this reactor setup. The results indicate that the current the length scales assumed for this reactor are incorrect, and a new definition needs to be considered. A new length scale is proposed but needs continued investigation. A significant finding is that two-dimensional (axisymmetric) simulations do not properly capture the flow physics, and result in large modeling errors. These errors dramatically affect the design of a reactor and need to be addressed with three-dimensional simulations.
Braun Minel, J (Advisor)
Nicholas Garafolo, G (Committee Member)
Scott Sawyer (Committee Member)
Abhilash Chandy, J (Other)
186 p.
Mechanical Engineering
natural convection; gallium nitride crystals; lateral heating; cylindrical reactor; turbulent; laminar; boundary layer; characteristic length; simulations; transient; steady state; crystal growth; aspect ratio

Recommended Citations

Citations

  • Hirt, D. M. (2018). Parametric Study via Numerical Simulations of Natural Convection in Laterally Heated Cylindrical Enclosures: Investigating Characteristic Length [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron15227528176693

    APA Style (7th edition)

  • Hirt, David. Parametric Study via Numerical Simulations of Natural Convection in Laterally Heated Cylindrical Enclosures: Investigating Characteristic Length. 2018. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron15227528176693.

    MLA Style (8th edition)

  • Hirt, David. "Parametric Study via Numerical Simulations of Natural Convection in Laterally Heated Cylindrical Enclosures: Investigating Characteristic Length." Master's thesis, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron15227528176693

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.