Thermal performance improvements for ribbed channels are attempted by installing auxiliary fillets on ribbed endwalls. Detailed heat transfer distributions over two opposite endwalls enhanced by 45° ribs and a row of tilted three-dimensional fillets of 1/2 rib heights with streamlined shape are measured at five flow configurations using steady-state infrared thermography method. Local, area-averaged and channel-averaged Nusselt numbers (Nu, N¯u and Nu), Fanning friction factors (f) and thermal performance factors (TPF) for each test channel are examined with Reynolds number (Re) in the range of 5000-15,000. The HTE properties and associated f augmentations for the compound HTE measures are assessed by comparing the N¯u and f data detected from present test channels with the Nusselt numbers (Nu∞) and f factors (f∞) of smooth plain tube. Empirical correlations evaluating N¯u and f factors for present ribbed channels with/without in-lined/staggered fillets are generated. With present in-lined (staggered) fillets on two opposite ribbed endwalls, the HTE ratios in terms of Nu/Nu∞ are raised to 4.43-4.21 (3.85-4.05) with forward flows and 4.31-4.02 (4.14-4.06) with backward flows at 5000 ≤ Re ≤ 15,000; whereas the corresponding f/f∞ ratios and TPF values fall in the respective ranges of 6.5-3.35 and 7.3-3.6 (7.5-5.6 and 9.06-7.39) with forward flows and 2.37-2.81 and 2.22-2.62 (1.97-2.29 and 1.99-2.09) with backward flows. As the Nu/Nu∞, f/f∞ and TPF values for present ribbed channels with in-lined/staggered fillets are generally raised from the ribbed channel counterparts of 3.93-3.61 (Nu/Nu∞), 1.63-1.53 (f/f∞) and 2.41-2.35 (TPF), the improved thermal performances by fitting the tilted fillets to enhance the rib-induced vortical flows are demonstrated.
|Number of pages||17|
|Journal||International Journal of Heat and Mass Transfer|
|Publication status||Published - 2016 May|
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes