Bioreactor Impeller Power Draw Calculator
Biochemical engineering & hydrodynamics: Calculate impeller Reynolds number (Re), ungassed power (P₀), gassed power draw (P_g), and tip speed shear velocity.
Impeller & Agitation Parameters
Power Dissipation & Hydrodynamic Regime
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Frequently Asked Questions
Why does an agitator draw less power when gas is sparged into the bioreactor?
When air is sparged underneath an impeller, gas cavities form behind the rotating blades. The lower density of the two-phase gas-liquid mixture reduces frictional drag and hydrodynamic resistance, dropping power consumption (P_g / P₀) by 30% to 60% compared to ungassed liquid.
What is impeller "flooding" and why must it be avoided?
Flooding occurs when the upward buoyant gas flux exceeds the pumping capacity of the impeller. Instead of dispersing bubbles radially into the vessel, gas rushes directly up the drive shaft in an eruptive geyser, causing torque oscillations, foaming, and a catastrophic drop in oxygen transfer efficiency.
What is the recommended specific power input (P/V) for bioprocesses?
For shear-tolerant industrial microbial fermentations (E. coli, yeast), specific power input typically ranges from 1.5 to 5.0 kW/m³. For shear-sensitive mammalian cell cultures (CHO cells producing monoclonal antibodies), P/V is kept much lower, typically 0.05 to 0.3 kW/m³.