In this study, eight configurations of oval and flat tubes in annular finned-tube thermal devices are examined and compared with the conventional circular tube. The objective is to assess the effect of tube flatness and axis ratio of the oval tube on thermal-flow characteristics of a three-row staggered bank for Re (2600 ≤ Re ≤ 10,200). It has been observed that the thermal exchange rate and Colburn factor increase according to the axis ratio and the flatness, where O1 and F1 provide the highest values. O1 produces the lowest friction factor values of all the oval tubes at all Re, and F4 gives 13.2–18.5% less friction than the other tube forms. In terms of performance evaluation criterion, all of the tested tubes outperformed the conventional circular tube (O5), with O1 and F1 obtaining the highest values. The global performance criterion of O1 has been found to be 9.6–45.9% higher as compared to the other oval tube geometries at lower values of Re, and the global performance criterion increases with the increase in flatness. The F1 tube shape outperforms all the examined tube designs; thus, this tube geometry suggests that it be used in energy systems.
In this study, numerical studies to clarify the influence of wave number and
amplitude on thermal-flow behavior of wavy annular finned-and-tube heat
exchangers are described. For a range of Reynolds number from 4400 to
14300, the influence of wave amplitude, 1.5 ? A ? 4.5 mm, and wave numbers,
2 ? Nw ? 6, on forced convection heat transfer was examined. It was revealed
that the wave amplitude and number have an impact on the heat flux, Colburn
factor, and friction factor. The wavy annular-fins with a 3 mm amplitude and
Nw = 4 waves obtained the highest values at all Reynolds numbers in terms of
the overall performance criterion (j/f1/3).
This paper aims to investigate the influence of tube shapes on thermal-flow characteristics of sinusoidal wavy finned-tube heat exchangers. Two row staggered bundle with six geometries of tubes (four flat tube geometries, one oval tube and a circular tube) are analyzed for a range of (1600 Re 4800). The inspection revealed that the heat flux and the pressure drop decrease with the tube flatness for all Reynolds values. However, the oval tube O1 reaches, for all Reynolds values, the lowest values of heat flux and pressure drop. Regarding the global performance criterion, the sinusoidal wavy fins with O1 shaped tubes reached the highest global performance values, being 14.8–24.4% and 31.6–36.3% higher than the fin with F1 and O2 tube geometry, respectively.
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