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Non‐Isothermal mixing of rheologically complex fluids with close‐clearance impellers: Effect of natural convection
Author(s) -
Fuente Edmundo BritoDe La,
Nuñez M. C.,
Tanguy P. A.
Publication year - 1997
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.270200308
Subject(s) - impeller , natural convection , grashof number , thermodynamics , buoyancy , isothermal process , mechanics , combined forced and natural convection , agitator , newtonian fluid , non newtonian fluid , mixing (physics) , heat transfer , shear thinning , chemistry , rheology , nusselt number , physics , reynolds number , turbulence , quantum mechanics
Transient heat transfer in a mechanically agitated vessel is studied in the case of an anchor and an helical ribbon impeller using Newtonian and shear thinning fluids. Temperature stratification is found more pronounced with the anchor, making this impeller clearly inadequate for heat transfer. The impact of natural convection is evaluated first using the classical Gr/Re 2 ratio. It is shown that the use of this criterion in viscous mixing is somewhat misleading. A new Grashof number is then proposed to assess the significance of the viscous and buoyancy effects in non‐isothermal, non‐Newtonian mixing applications. It is shown that the interpretation of this new number is strongly related to the concept of process viscosity.