Prediction of Mixing Pattern by Using Power Number Diagram in Baffled and Unbaffled Mixing Vessels

  • Kato Yoshihito
    Department of Life and Materials Engineering, Nagoya Institute of Technology
  • Tada Yutaka
    Department of Life and Materials Engineering, Nagoya Institute of Technology
  • Takeda Yasuhiro
    Department of Life and Materials Engineering, Nagoya Institute of Technology
  • Atsumi Naoka
    Department of Life and Materials Engineering, Nagoya Institute of Technology
  • Nagatsu Yuichiro
    Department of Life and Materials Engineering, Nagoya Institute of Technology

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Abstract

Mixing patterns generated in stirred vessels for a wide range of Reynolds numbers were observed using a decolorization method based on the reaction between sodium thiosulfate and iodine. A relationship was established between the power number diagram (NPRe diagram) and the shape of the isolated zone was observed. At low Reynolds numbers (laminar regime), the isolated zone resembled a doughnut ring, while a cylindrically rotating zone isolated at high Reynolds numbers (turbulent regime). Even with a small change in Reynolds number, the doughnut-ring-shaped isolated zone suddenly changed to a cylindrically rotating zone in an unbaffled vessel. The cylindrically rotating zone was not observed in baffled vessels at high Reynolds numbers. The clearance between the propeller impeller and the vessel bottom brought about a change in the mixing patterns, although the power consumption the remained constant.

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