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● Fig. 3.1 shows the dimensions of what is called a “standard” stirred tank bioreactor vessel with Baffles.FIG. 3.1. Standard Stirred Tank Bioreactor Geometry [Adopted fromS. Aiba, A.E. Humphrey and N.F. Millis. “Bubble Aeration andMechanical Agitation”. In Biochemical Engineering, 2 nd Ed., Academic
Geometric Ratios for a Standard BioreactorImpeller D /D H /D Vessel /D H /D W /D No. Baffles L /D W i t L t i i i i b i b tTypeFlat-Blade 0.33 1.0 0.25 0.2 1.0 0.1 4TurbinePaddle 0. 3 3 1.0 - 0.25 1.0 0.1 4impellerMarine 0.33 1.0 pitch = Di 1.0 0.1 4PropellerWhere: Dt = tank diameter, HL = liquid height Di = impeller diameter Hb = impeller distance from bottom of vessel
FIG. 3.2 B. Mixing Patterns for Flat-Blade Turbine Impeller. Effect ofBaffles. Liquid agitation in presence of a gas-liquid interface, withand without wail baffles: (a) Marine impeller and (b) Disk flat-bladeturbines; (c) in full vessels without a gas-liquid interface (continuousflow) and without baffles.
3.1 Mixing and Power Requirements for Newtonian Fluids in a Stirred TankFIG. 3.3 NP vs. NRe; the power characteristics are shown by the powernumber, NP, and the modified Reynolds number, N Re, of singleimpellers on a shaft. [Adopted from S. Aiba, A.E. Humphrey and N.F.Millis. “Bubble Aeration and Mechanical Agitation”. In BiochemicalEngineering, 2nd Ed., Academic Press, Inc., New York (1973) 174].
Fig. 3.3 shows relationship between NP andNRe at three different flow regimes:● Laminar● Transient● Fully Turbulentfor three different impeller types:● Six-bladed flat blade turbine● Paddle impeller● Marine Propeller
The power number is given by Equ. 3.1 NP = Pgc/n3Di5ρ……………………… (3.1)The impeller Reynolds number is given by Equ. 3.2 NRe = nDi2ρ/µ…………….................. (3.2)Where:N = dimensionless Reynolds