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Experimental Investigation of Convective Heat Transfer and Pressure Loss in a Circular Tube With Suspeded Ball Turbulators

Aghli ChanCheh, Alireza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54262 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. Flow turbulators have crucial importance in heat transfer and energy harvesting applications. Therefore, in this study, the thermo-hydraulic and vibrational behavior of the floe inside a circular tube with vibrational ball turbulators (VBTs) on an axial elastic wire is experimentally studied for the first time. In this novel design, the elastic wire facilitates turbulence by allowing VBTs to move transversally and rotationally and agitate the flow substantially. The effects of diameter and longitudinal distance (pitch) ratios of VBTs, the Reynolds number, and the axial tension of the wire, on the flow friction factor (f), the Nusselt number (Nu), the thermal performance factor (η), in addition to the frequency (F) and amplitude (A) of the balls, are studied. To this end, different ball diameter (Db =8,10,12 mm) and ball pitches (λ =40,60,80 mm) in a tube with a constant inner diameter of Dp=26 mm are utilized at Reynolds numbers between 10000 and 15000. Our result reveal that the balls vibrate with higher amplitudes when the diameter is maximum and, counterintuitively, when their pitch is larger. Meanwhile, the friction factor and Nusselt number with VBTs are 17 and 2.87 times that of the plain tube. However, the thermal performance factor was greater than one for all arrangements. The correlations are also proposed to predict the flow friction factor, Nusselt number and thermal performance factor as a function of the ball distance ratio (X= λ/Dp), diameter ratio (Db/Dp) and the Reynolds number. This novel design benefits from straightforward implementation and the results of this study can be readily used to design more efficient heat exchangers, where a precise picture of the device's hydrodynamic and vibrational response is vital
  9. Keywords:
  10. Friction Coefficient ; Heat Transfer Enhancement ; Thermal Performance ; Energy Storage ; Ball Vibrational Turbulators ; Pressure Drop

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