3.1.4. Energetical efficiency
Some insights in the mixers energy efficiency can be provided
by the ratio of the apparent shear rate _ capp to the specific energy
E (per unit mass) required for the foaming. This specific energy is
are plotted for two fluids of different properties, one is a monophasic
oil (glycerol solution 25 wt%), and the other is a typical foam of
0.8 void fraction, by considering the density, qf, as (1 a) ql and
the velocity, Us, is the sum of liquid Ul and gas Ug velocities. The viscosity
used in the Reynolds number is of the order of magnitude
taken from our experiments, about 0.1 Pa s nearly constant for
the whole flow rates range. This diagram shows that even with
the highest flow-rates (gas and liquid) encountered in this study,
the flow is laminar, which justifies the use of the process viscosity
calculation.