This experimental study examines the detailed Nusselt number (Nu) distributions, pressure drop coefficients (f) and thermal performance factors (TPF) for a square spiral channel with two opposite endwalls roughened by in-line 45° ribs. Detailed Nu distributions over the rib floor with forward and backward flows are measured using the steady-state infrared thermo-graphic method at Reynolds numbers (Re) of 900-30,000. With the increased f from the smooth-walled straight tube references (f∞), the rib-induced sectional vortical flows interact with the centrifugal-force driven Dean vortices along the entire spiral passage to generate the considerable heat transfer enhancement (HTE) impacts that raise the area-averaged turbulent Nusselt numbers (Nu) to 8.41-3.66 and 5.05-2.78 times of the Dittus-Boelter Nusselt numbers (Nu∞) for forward and backward flows at 2700 ≤ Re ≤ 30,000, respectively. Comparisons of Nu/Nu∞,f/ f∞ and TPF obtained from the ribbed spiral channel with other types of HTE devices reveal the thermal performances of the present HTE measure. Two sets of Nu and f correlations for the square spiral ribbed duct with forward and backward flows are generated to assist the design applications using this HTE measure.
|Number of pages||12|
|Journal||International Journal of Heat and Mass Transfer|
|Publication status||Published - 2011 Jul 1|
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes