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Abstract: There
is no problem for mixing inside the stirred tank when the flow is in
turbulent state. However, how to improve the mixing efficiency becomes a
practical problem while the flow inside stirred tank is in laminar
condition. For the purpose of enhancing the mixing efficiency inside
laminar stirred tank, chaotic mixing is applied with the impeller
rotating in periodic form. The particle image velocimetry technique is
used to measure the laminar flow field inside the stirred tank, the
particle images acquired are post-processed by special image processing
software, radial velocity distributions at six different angles are
displayed in the form of flood contours. The results velocity curves of
mixing with variable rotation speed are compared with that of mixing
with constant rotation speed. The experimental study shows that the area
disturbed by radial velocity with variable rotating speed is larger than
that with constant rotating speed, and proves that the mixing effect and
the mixing efficiency are better with the axis rotating with variable
speed. The research work is significant for analyzing the mechanism of
chaotic mixing and for designing of large scale stirred tank.
Key words:Variable
speed Stirred tank Chaotic mixing Particle image velocimetry
Flow field
CLC No: TH137
河北省自然科学基金资助项目(E2005000333).Received
20050823,received in revised form 20060410
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