Numerical investigation of several twisted tubes with non-conventional tube cross sections on heat transfer and pressure drop
Résumé
Numerical simulations were performed with the open-source CFD software OpenFOAM to investigate the ability of several configurations of short length twisted tube geometries with non-circular cross-section connected to tubes with circular cross-section to induce a swirling flow. The heat transfer and the pressure drop linked to the generated swirling flow are also calculated. The swirling flow is modeled using a k-ω SST turbulence model with a Low-Reynolds approach. It is shown that a short length twisted tube with an elliptical cross-section (STE) is able to generate a swirling flow but its intensity greatly depends on its twist pitch and its aspect ratio. The lower the aspect ratio, the higher the swirl intensity. For a Reynolds number ranging from 10 000 to 100 000, the results reveal that compared to a plain tube, the STE with the lowest aspect ratio achieves to enhance the heat transfer from 22 to 90 % at the cost of an increased pressure drop of respectively 63 and 129 %. The second part of the study is focused on a short length twisted tube with a three-lobed cross-section (ST3L) and the results reveal that the generated swirling flow is even more intense than with the STE and that the heat transfer enhancement goes from 30 to 105 % at the cost of an increased pressure drop from 137 to 180 %.
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