Abstract
In a series of experiments, we study natural convection bubbly flows along a vertical heated plate with mixed wettability surfaces. The plate is hydrophilic, and its surfaces have several hydrophobic strips with a strip width, LH, of 0, 1, 2, or 4 mm. We carry out velocity and temperature measurements as well as visualization under a constant wall heat flux. For all values of LH, over the heated section, the heat transfer coefficient is much higher with bubble injection than without such injection. In addition, the heat transfer coefficient with bubble injection is highest for LH = 2 mm and is approximately 9% larger than that for LH = 0 mm. This result is caused by the promotion of wall-normal mixing of warm and cold liquid. Such mixing is considered to be induced by the activation of both wobbling motion of coalesced rising bubbles and vortex shedding from these bubbles.
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Acknowledgements
The authors gratefully acknowledge the support of Grant-in-Aid for Scientific Research (C) (Grant no. 19K04217).
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Kitagawa, A., Kobayashi, R. & Munezane, Y. Experimental investigation of natural convection bubbly flows along a vertical heated plate with mixed wettability surfaces. J Vis 25, 807–817 (2022). https://doi.org/10.1007/s12650-021-00819-2
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DOI: https://doi.org/10.1007/s12650-021-00819-2