Online ISSN : 1881-1299
Print ISSN : 0021-9592
Volume 55, Issue 5
Displaying 1-3 of 3 articles from this issue
Editorial Note
Transport Phenomena and Fluid Engineering
  • Stoyan Nedeltchev, Jakub Katerla, Ewelina Basiak
    Article type: Research Paper
    2022 Volume 55 Issue 5 Pages 201-216
    Published: May 20, 2022
    Released on J-STAGE: May 21, 2022

    New, reliable, and innovative methods (the new hybrid index (NHI) and the information index (II)) for flow regime (FR) identification in bubble columns (BCs) operated with air–deionized water or nitrogen–tap water systems (at ambient conditions), as well as nitrogen–ethanol systems (at pressures of 0.1 and 0.3 MPa) systems have been successfully developed. New parameters extract useful hidden information from time series measurements by division of various signals (gas holdup, differential pressure (DP) and gauge pressure fluctuations) into different equal parts. Salient advantage of the new parameters is that their definitions are not based on any assumption.

    Based on the local minima in the NHI profile extracted from gas holdup time series, two transition gas velocities Utrans at 0.032 and 0.046 m/s have been identified in an air–deionized water BC (0.1 m in ID). The NHI profile based on DP fluctuations in a nitrogen–tap water BC (0.102 m in ID) distinguishes similar Utrans values at 0.029 m/s and 0.047 m/s. In a nitrogen–ethanol system at ambient pressure, the NHI identifies only the first Utrans value at Ug=0.028 m/s. At elevated pressure (0.3 MPa), it has been found that this first Utrans value shifts to a higher Ug value (0.045 m/s). In the annularly aerated BC (operated with an air-deionized water system), the main transition velocities have been identified at Ug=0.026 m/s and 0.073–0.079 m/s (depending on the clear liquid height), respectively, based on the newly defined II profile.

    In summary, this work presents novel and reliable methods for FR identification in several BCs and reports new, useful experimental results about the FR boundaries based on them.

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Materials Engineering and Interfacial Phenomena
  • Sukhbaatar Batchuluun, Kentaro Yasui, Hideki Matsune, Koichiro Shiomor ...
    Article type: Research Paper
    2022 Volume 55 Issue 5 Pages 217-224
    Published: May 20, 2022
    Released on J-STAGE: May 21, 2022

    Polystyrene microcapsules were prepared by using the solvent evaporation method from S/O/W emulsion which contains fine particles of CaCl2 in the organic phase. The microcapsules were fractionated by their size and permeability of the wall using settling difference in methanol. Further, phase change materials that have two different wet-ability characters were successfully impregnated. The hydrophobic compound was easily impregnated to microcapsules which have hydrophobic wall material. Meanwhile, the hydrophilic compound, which is salt hydrate, was not impregnated to the same microcapsules via direct impregnation but the salt hydrate was successfully impregnated by the volatile exchange impregnation method. Simple thermal properties of the prepared phase change material microcapsules were examined by TGA and DSC methods.

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