Mixers correction factor

Correlating factor for viscous flow power, Table 5-1 Mixing factors, turbulent flow power. Table 5-1 Viscosity correction factor for turbulent How (static mixer)... 

The flow patterns in static mixers are very complex and only finite element methods can be used to analyze the details of these flows. The shear rates generated in these devices are rather low (on the order of 10 s ), and hence, the pressure drop across the static mixer can be estimated from the expression for flow of a Newtonian fluid through a tube with a correction factor for the given geometry as... 

These estimated doses are believed to be correct within a factor of two. They are not very large compared with the doses for other applications of HDEHP reported in the literature (9) and comparable with the doses for TBP reported for reprocessing of high burnup fuel using mixer-settlers — 1.02 Wh/L at 43 000 MWd/te and 50 days cooling (10). 

For an inline mixer, a value for the specific power (P/pV) can easily be estimated from the manufacturer s (or measured) friction factor, adjusted for the gas-liquid ratio using the correction of Lockhart and Martinelli (1944). Although this may not be rigorously applicable, some success has been achieved by applying the approach to static mixers using the laminar gas-turbulent liquid regime factors. 

Noting that power = volumetric flow rate x pressure drop, the overall power per unit mass of liquid is straightforward to calculate for single-phase systems given the friction factors and voidage fraction in the mixer as supplied by mixer manufacturers or measured in the laboratory. For gas-liquid systems the volume of fluid in the mixer must be multiplied by (1 — c )) to obtain the liquid volume, so the gas fraction 4) must be known (see Section 11-5). It has been found that the Lockhart-Martinelli (1944) correction for the effect of the gas phase on pressure drop in pipe flow can be applied to static mixers with reasonable accuracy ( 20%). 

The correct mixing of the adhesive is a precondition to achieve a good homogeneity of the mixture and to obtain the best mechanical performance of the hond. There are many different kinds of mixers and stirring elements available on the market. Which kind of mixer is adequate depends on chemical nature of the adhesive, the viscosity of the adhesive, and its sensitivity to external factors like humidity or oxygen. It is proposed to investigate together with the equipment supplier, which equipment suits best for the intended application. 

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