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A Computational Study of Enhanced Heat Transfer in Low Reynolds Number Flows through Axially Twisted Ducts of Rectangular Cross Section

Patel, Prashant
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380620409

Abstract Details

2013, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Low Reynolds number fully developed swirl flows through rectangular ducts that are helically twisted along their axis are computationally modeled. The twist ratio ζ(= 180° twist pitch / hydraulic diameter) and rectangular flow cross-section aspect ratio α(= height / width) characterize the duct's geometrical attributes. A parametric study delineates the influence of flow rate (10 ≤Re ≤1000), type of fluid (Pr = 5, 45 and 100) and duct geometry (ζ= 3.0, 6.0, and 12.0; α= 1.0, 0.75, and 0.5) on swirl-flow generation, convection and wall friction behavior. The twisted duct-surface curvature is found to induce lateral fluid circulation, which results in the formation of axially helical swirl in the core of the duct. With increasing severity of duct twist (ζ= 12.0 →3.0) and flow Reynolds number, or decreasing cross-section aspect ratio (α= 1.0 or square →0.5 or slender rectangle), the swirl structure breaks up into multiple peripheral vortices but with increased magnitude of the primary core secondary-flow cell. Consequently, in fixed pressure-gradient driven flows, the resultant lateral mixing of flow increases convection heat transfer significantly for twisted ducts relative to that in straight ducts of same cross section. ). Increasing swirl-induced mixing as α →0.5, ζ → 3.0, and Re > O[100], characterized by pronounced core circulation accompanied with multiple peripheral vortices, is found to enhance the heat transfer coefficient by 2.6 to 14 times that in an equivalent straight duct. The larger benefits accrue in higher Pr liquids, and 2.4 to 13 times higher heat transfer rate can be accommodated on a fixed pumping power basis; alternatively, 50% to 90% reduction in heat exchanger surface area can be achieved on a fixed pressure drop and heat load basis
Raj Manglik, Ph.D. (Committee Chair)
Shaaban Abdallah, Ph.D. (Committee Member)
Milind Jog, Ph.D. (Committee Member)
79 p.
Mechanical Engineering
Heat Transfer; Twisted ducts

Recommended Citations

Citations

  • Patel, P. (2013). A Computational Study of Enhanced Heat Transfer in Low Reynolds Number Flows through Axially Twisted Ducts of Rectangular Cross Section [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380620409

    APA Style (7th edition)

  • Patel, Prashant. A Computational Study of Enhanced Heat Transfer in Low Reynolds Number Flows through Axially Twisted Ducts of Rectangular Cross Section. 2013. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380620409.

    MLA Style (8th edition)

  • Patel, Prashant. "A Computational Study of Enhanced Heat Transfer in Low Reynolds Number Flows through Axially Twisted Ducts of Rectangular Cross Section." Master's thesis, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380620409

    Chicago Manual of Style (17th edition)

ucin1380620409
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This open access ETD is published by University of Cincinnati and OhioLINK.