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Numerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections

Modekurti, Arvind

Abstract Details

2017, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
The periodically fully-developed laminar flow and heat transfer for shear-thinning non-Newtonian fluids flowing through helically twisted ducts of elliptical cross-section have been numerically simulated using a finite-volume CFD solver. The geometry of the twisted duct is defined using the parameters aspect ratio, α and twist ratio, y. The present study considers duct geometries with the twist ratio, y = 3, 4.5, 6, ∞ and aspect ratio, α = 0.5,0.7,1. The shear-thinning non-Newtonian fluids chosen for the analysis comprise of three grades of aqueous solutions of Carboxymethylcellulose (CMC) which are CMC 7H3SF (High Grade), CMC 7M8SF (Medium Grade) and CMC 7LFPH (Low Grade). The properties of the non-Newtonian fluids are assumed to be temperature independent and their constant property values at 60°C are considered in the present study. A constant wall temperature boundary condition is assumed to perform the heat transfer simulations. The asymptotic modified power-law model has been used to describe the shear-thinning behavior of non-Newtonian fluids under consideration. The zero shear rate viscosity, μ0 which is known a priori for each shear-thinning fluid is used as a reference viscosity to define the flow Reynolds number, Re. The range of Reynolds number, Re within which the thermal and hydraulic performance parameters for various CMC polymers are evaluated is 2.20 = Re = 340 for CMC 7LFPH, 2.20 = Re = 74.2 for CMC 7M8SF and 2.20 = Re = 31.1 for CMC 7H3SF. The numerical analysis shows the influence of geometric parameters as well as the properties of non-Newtonian fluids on Fanning friction factor, f and Nusselt number, Nu. The enhancement in Nusselt number, Nu and decrease in friction factor, f with increasing shear-thinning nature of non-Newtonian fluids is observed in straight ducts with y = ∞. The enhancement in Nusselt number, Nu and the corresponding pressure drop penalty in a twisted duct with respect to a straight duct flow due to the additional presence of secondary swirl flows are expressed as Nu / Nuy=∞ and f / fy=∞ . The value of Nu / Nuy=∞ in the high Reynolds number range increases with a decrease in aspect ratio, α and decrease in twist ratio, y. The enhancement in Nu for a twisted duct is negligible in the low Reynolds number range and begins to rapidly increase at higher Reynolds number due to the onset of strong secondary swirl flows which improve the fluid mixing within the duct cross-section. In the present study, the enhancement in Nusselt number, Nu / Nuy=∞ and the corresponding increase in friction factor, f / fy=∞ was observed to be the highest in the case of a severely twisted duct with twist ratio, y = 3 and a low ellipse aspect ratio, α = 0.5 where the intensity of the secondary swirl flows induced by the curved walls of the twisted duct is the highest.
Milind Jog, Ph.D. (Committee Chair)
Je-Hyeong Bahk, Ph.D. (Committee Member)
Raj Manglik, Ph.D. (Committee Member)
130 p.

Recommended Citations

Citations

  • Modekurti, A. (2017). Numerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504782280273333

    APA Style (7th edition)

  • Modekurti, Arvind. Numerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections. 2017. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504782280273333.

    MLA Style (8th edition)

  • Modekurti, Arvind. "Numerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections." Master's thesis, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504782280273333

    Chicago Manual of Style (17th edition)