Bioprocess viscosity

Thermal Mass Flowmeters The trend in the chemical process industries is toward increased usage of mass flowmeters that are independent of changes in pressure, temperature, viscosity, and density. Thermal mass meters are widely used in semiconductor manufacturing and in bioprocessing for control of low flow rates (called mass flow controllers, or MFCs). MFCs measure the heat loss from a heated element, which varies with flow rate, with an accuracy of 1 percent. Capacitance probes measure the dielectric constant of the fluid and are useful for flow measurements of slurries and other two-phase flows. 

The viscosity of a bioprocess liquid is an important factor, affecting mass transfer, heat transfer, and power consumption. It is affected by the concentrations and types of microorganisms, substrates, products, and solids present in the liquid, and can vary during a fermentation or separation process. Unfortunately, on-line viscosity measurements are difficult, especially when significant amounts of air bubbles and suspended solids are present, and thus viscosity probes are not in widespread use. Sensors that have been applied for viscosity determination (usually in laboratory studies) are often various types of rotational viscosimeters [42]. 

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