Title page for ETD etd-06042005-145209


Type of Document Master's Thesis
Author Patrick, Wilfred Vinod
Author's Email Address wipatric@vt.edu
URN etd-06042005-145209
Title Computations of Flow Structures and Heat Transfer in a Dimpled Channel at Low to Moderate Reynolds Number
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Tafti, Danesh K. Committee Chair
Ragab, Saad A. Committee Member
Vick, Brian L. Committee Member
Keywords
  • Flow structure
  • Transition
  • DNS
  • Concavities
  • Dimples
Date of Defense 2005-04-25
Availability unrestricted
Abstract
Time-accurate calculations are used to investigate the three-dimensional flow structure and understand its influence on the heat transfer in a channel with concave indentations on one wall. A dimple depth to channel height ratio of 0.4 and dimple depth to imprint diameter ratio of 0.2 is used in the calculations. The Reynolds number (based on channel height) varies from Re = 25 in the laminar regime to Re = 2000 in the early turbulent regime. Fully developed flow and heat transfer conditions were assumed and a constant heat flux boundary condition was applied to the walls of the channel. In the laminar regime, the flow and heat transfer characteristics are dominated by the recirculation zones in the dimple with resulting augmentation ratios below unity. Flow transition is found to occur between Re = 1020 and 1130 after which both heat transfer and friction augmentation increase to values of 3.22 and 2.75, respectively, at Re = 2000. The presence of large scale vortical structures ejected from the dimple cavity dominate all aspects of the flow and heat transfer, not only on the dimpled surface but also on the smooth wall. In all cases the thermal efficiency using dimples was found to be significantly larger than other heat transfer augmentation techniques currently employed.
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