Fourier Pipeflow Manipulation for Thermal Energy Systems

• Author / Creator

  Salem, Nawaf Talal Mohammed

• This dissertation numerically evaluates the performance of targeted wall-shape pipe inserts on reducing heat convection and frictional drag of turbulent pipeflow at a range of Reynolds numbers, Re = 2.5 × 10^4 − 7.5 × 10^4. The wall modifications are constructed to closely follow three azazimuthal Fourier modes corresponding to m = 3 (Case I), 15 (Case II), and 3+15 (Case III). The implementation of these pipe-inserts generates flow features that can render significant improvements to the efficiency of subsurface thermal processes, including extraction and harvesting of geothermal energy. First, thermal response is investigated by characterizing mean flow and convective heat transfer features downstream of the pipe-inserts at Re = 7.5 × 104. Particularly, the results exhibit a maximum reduction of 9% in near-wall heat transfer for Case II and Case III, compared to a smooth pipe. The fully-developed thermal condition is recovered at an axial location of x/D = 40 from the perturbation, where D is the pipe diameter. Further, a significant attenuation in skin-frictional drag is observed, hinting at maximum decrease of 17.4% and 16.5% for
  Case II and Case III, respectively. At x = 2D−10D following the inserts, the maximum averaged contractions in near-wall heat transfer and frictional drag are depicted for Case II, corresponding to 3.4% and 5.0%, respectively. The wall modification of Case I results in a relatively minor impact on convective heat transfer and frictional drag, before returning to fully-recovered state. Reynolds number implications suggest increasing reductions of near-wall convective heat transfer and frictional drag with decreasing Re. The maximum reductions of 10.5% and 20.5% in near-wall convective heat transfer and frictional drag are achieved at the lowest Reynolds number of 2.5×10^4, indicating averaged reductions of 5.7% and 8.3% within x = 2D−10D, respectively. Increasing Reynolds number delays heat transfer recovery, which depicts an asymptotic trend for Re ≥ 5.0×10^4. This research found that targeted wall-shape pipe inserts contribute to mitigation
  of near-wall convective heat transfer with a decrease in frictional drag. These contributions hint at extensive enhancements to the efficiency of energy extraction and transportation in subsurface thermal applications.

• Subjects / Keywords

  • Turbulent pipe flow
  • Heat transfer
  • RANS
  • Wall shape modifications
  • Pipe insert
  • Fourier modes
  • Geothermal systems
  • Subsurface thermal systems

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-4411-af04

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.