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Power and mean flow characteristics in mixing vessels agitated by hyperboloid stirrers
Author(s) -
Pinho F. T.,
Piqueiro F. M.,
Proençla M. F.,
Santos A. M.
Publication year - 1997
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450750503
Subject(s) - impeller , hyperboloid , reynolds number , mechanics , agitator , shroud , turbine , flow (mathematics) , physics , rushton turbine , mathematics , circulation (fluid dynamics) , engineering , geometry , mechanical engineering , thermodynamics , turbulence
The mean flow and energy consumption in vessels powered by hyperboloid stirrers was investigated. The Newton number followed an inverse linear law for Reynolds numbers below approximately 200, which had values more than twice higher the corresponding Newton number for a standard Rushton turbine. At high Reynolds number flows the Power number varied between 0.5 for a D/T = 0.78 impeller to 0.95 for a D/T = 0.24 impeller, as compared to a value of 5 for the standard Rushton stirrer, and to values of 0.31 and 1.58 for the Chemineer and Prochern hydrofoils. The power consumption did not change with the fluid height and was double for the double‐stack configuration. The shear ribs below the impeller were the main contributor to the increased energy loss relative to a non‐shear ribbed impeller and the small clearance had no major effect upon the power consumption. For the D/T = 1/3 hyperboloid stirrer the flow in the whole tank was rather gentle, defining a circulation number of 0.57, thus leading to a circulation efficiency more than 7 times lower than that of the hydrofoils.