The thermal-hydraulic performance of five oval tubes is experimentally investigated and compared with that for a circular tube in a cross-flow of air. The range of Reynolds numbers ReD is approximately between 1,000 and 11,000. The nominal axis ratios R (major axis/minor axis) for three of the investigated oval tubes are 2, 3, and 4. Two other configurations of oval tubes are also tested, an oval tube R=3 with two wires soldered on its upper and lower top positions, and a cut-oval tube. The performance of the tubes is corrected for the effects of area blockage and turbulence intensity. The measurement results show that the mean Nusselt numbers NuD for the oval tubes are close to that for the circular tube for ReD<4,000. For a higher ReD, the NuD for the oval tubes is lower than that for the circular tube and it decreases with the increase in the axis ratio R. The drag coefficients C d for the tubes are measured and the combined thermal-hydraulic performance is indicated by the ratio Nu D/C d, which shows a better combined performance for the oval tubes.
|Number of pages||10|
|Journal||Heat and Mass Transfer/Waerme- und Stoffuebertragung|
|Publication status||Published - Jun 2005|
|MoE publication type||A1 Journal article-refereed|
- Drag coefficient
- Heat transfer