Читать книгу Agitator Design for Gas-Liquid Fermenters and Bioreactors - Gregory T. Benz - Страница 70

When an agitator is operated under gassed conditions (whether the gas is added or evolving from the process), it behaves differently from operating in liquid only. The presence of gas, in addition to possibly influencing mass transfer when the gas and liquid are not in equilibrium, can create several important effects. Among those are flooding of the impeller versus dispersing the gas, power draw effects, entrained gas, or holdup in the liquid and mechanical effects. We will go through each of these in turn, as well as the issue of what happens when there is a variable gas flowrate.

The above behaviors are mainly correlated by three dimensionless number groups: Reynolds number, Froude number, and Gassing factor. A fourth group, known as the dimensionless hydraulic force, is used for mechanical design and will be used in examples in Chapter 16.