Abstract
Axial Nusselt number (Nu) distributions and tube averaged Fanning friction factors (f) for the tubular flows enhanced by twin or four twist-fin inserts with five twist ratios (y) of 2, 2.5, 3, 3.5 and ∞ (straight fins) were measured at Reynolds numbers (Re) of 750-70,000. For each enhanced tube with a twist-fin insert, the Nu and f augmentations from the plain-tube developed flow Nu∞ and f∞ references were compared with thermal performance factors (TPF) evaluated. Acting by the respective single- or twin-cellar axial swirls along the helical passages formulated by present twin or four twisted fins in the test tubes, the Nu/Nu∞ ratios at laminar and turbulent reference conditions are respectively raised to 1.87-4.98 and 1.3-1.95; or 3.93-9.03 and 1.37-2.83. Relative to the Nu and f results measured from the test tubes enhanced by the two co-twisted tape inserts, present four twist-fin inserts considerably amplify both laminar and turbulent HTE ratios at the expenses of f augmentations with the laminar and turbulent TPF values in the respective ranges of 1.45-2.84 and 0.56-0.98. For assisting the relevant applications using present sets of Nu and f data generated by this study, the heat transfer and pressure drop correlations for the tubes with twin or four twist-fin inserts are devised.
Original language | English |
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Pages (from-to) | 220-234 |
Number of pages | 15 |
Journal | Experimental Thermal and Fluid Science |
Volume | 74 |
DOIs | |
Publication status | Published - 2016 Jun 1 |
All Science Journal Classification (ASJC) codes
- General Chemical Engineering
- Nuclear Energy and Engineering
- Aerospace Engineering
- Mechanical Engineering
- Fluid Flow and Transfer Processes