Impeller helical ribbon

With a diameter ratio of 0.9-0.98, the helical ribbon belongs to the dose-clearance category of impellers. 

Low viscosity mixing applications can usually be handled efficiently with impeller systems consisting of one or more turbines. To obtain adequate mixing under the laminar flow conditions encountered in high viscosity applications, on the other hand, close-clearance impellers such as anchors and helical ribbons are required. These impellers sweep the whole wall surface of the vessel and agitate most of the fluid batch through physical contact. Helical ribbon impellers are typically used for industrial applications where the viscosity is in the range 20 000 to 25 000 Pa s. Wall scrapers can be mounted on the impeller blades to improve heat transfer. 

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P = pitch of a helical ribbon impeller, m W = blade width, m... 

Bourne, J. R. and Butler. H. Trans. Inst. Chem. Eng. 47 (1969) Til. On analysis of the flow produced by helical ribbon impellers. 

Helical complexes, chirality in, 26 803-804 Helical polypeptide, 24 58 Helical ribbon impeller, 16 690, 691 Helicobacter pylori, 15 303 antibiotic resistant, 3 36 Helio-photocatalysis, 19 78, 95 Heliotridine, 2 80... 

Research on the impeller method using the helical ribbon impeller is well documented (7,8). The impeller method is often employed to measure the rheology of suspensions. Previous researchers assumed that the effective shear rate of such a device is related to the impeller speed by a fluid-independent constant, but this assumption may not be accurate for all impellers (8,9). It has been suggested that a properly designed helical ribbon impeller might be more appropriate for this technique. 

The parameter c was found to be a linear function of Reynolds number with regression coefficients between 0.98 and 1.00. The shear rate constant, k, was within 10% of the values found by Donnelly (15) and Rieth (16) for a double-helical ribbon impeller. Furthermore, the Power Law could be used to describe corn stover suspension viscosity with correlation coefficients above 0.99 for all four concentrations tested. Finally, the yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of com stover. 

Two Brookfield viscometers were used to collect the data necessary for rheologic property studies of wet grains a Brookfield RVDV III viscometer with a cone-and-plate spindle and a Brookfield HBDV III viscometer with a double helical ribbon impeller attachment. The Brookfield RVDV III had a full-scale torque of 7187 dyn-cm, and the HBDV III had a full-scale torque of 57,496 dyn-cm. Each viscometer had a maximum rotational speed of 250 rpm. Both viscometers had accuracy limits of 5% full-scale torque. 

A helical ribbon impeller, 45 in (1.14 m) diameter, is operated in a 47-in (1.19-m) diameter reactor estimate the fluid viscosity from torque readings. The impeller is a single-turn helix with a 1 1 pitch, so the height of the impeller is the same as the diameter, 45 in (1.14 m). It is a double-flight helix, each blade of which is 4.5 in (0.114 m) wide. 

Estimate viscous power number for the helix impeller. A helical-ribbon impeller, also called a helix impeller, is used primarily when high-viscosity fluids are being processed. Most of the power data on such impellers have been obtained in the laminar and transitional flow ranges. The effect on power of common geometry factors, i.e., impeller diameter D, tank diameter T, helix pitch P, impeller height H, and helix (blade) width W, can be incorporated into a correlation for a (dimensionless) viscous power number ... 

This is still a low power level of 6.2/1.74 = 3.55 HP/1,000 gal. With this agitator, a reasonable upper hmit for agitator speed would be 100 rpm, for which the impeller power would be 22 HP with a specific power input of 13HP/l,000gal and Npe = 9. This change would move up into the Reynolds number near the lower limit recommended by Hemrajani and Tatterson (in Paul (2004), 345). This example illustrates the great impact of fluid viscosity on (1) the power requirement of a 6BD and (2) the choice of an impeller style between a turbine and a helical ribbon impeller. 

Most of the correlations were taken from Penney (1983) and from tables 5 and 6 in Fasano et al., (1994) for the HE-3 impeller and the bottom head. The correlation for heat transfer coefficients for helical ribbon impellers was taken from Ishibashi et al. (1979). The correlations given by Penney (1983) (p. 879) use the same sources. 

Impeller power requirement, ft Ibf/s or HP Pitch of a propeller or a helical ribbon impeller (forward motion of the impeller in one rotation when moving in an internal screw thread)... 

FIGURE 10.1 Types of stirred tank reactor, (a) Multiphase stirred reactor. I impeller, 2 baffles, 3 cooling coils, 4 gas sparger, (b) Stirred reactor with gas-inducing impeller (dead-end type), (c) Stirred reactor with helical ribbon impeller (used with or without a draft tube). 

FIG. 18-45 Power numbers for helical-ribbon impeller typical double-flight helixes 95 percent of tank diameter T and 90 percent of T single-flight helix 90 percent of T single-flight 95 percent of T similar to double-flight 90 percent of T. 

Espinosa-Solares T., Brito-De La Fuente E., Tecante A., Tanguy P.A., Power consumption of a dual turbine-helical ribbon impeller mixer in ungassed conditions, Chem. Engng. J. 67 (1997), p. 215-219... 

Kuriyama M., Ohta M., Yanagawa K., Arai K., Saito S., Heat Tranter and Temperature Distribution in an Agitated Tank equipped with Helical Ribbon Impeller, J. Chem. Eng. Japan 14 (1981) 4, p. 321-330... 

Savinsky )., Havas G., Deak A., Power requirement of anchor and helical ribbon impellers for the case of agitating Newtonian and pseudo-elastic liquids, Chem. Eng. Sci. 31 (1976), p. 507-509... 

Takahashi K., Yokota T, Konno H., Mixing of pseudoplastic liquid in a vessel equipped with a variety of helical ribbon impellers, J. Chem. Engng. Japan 21 (1988) 1, p. 63-68... 

Delaplace G., Leuliet J.C., Relandeau V., Circulation and mixing times for helical ribbon impellers. Review and Experiments, Exp. in Fluids 28 (2000), p. 170-182... 

Helical Ribbon Impeller Showing Geometric Variables (Helical Ribbon Pumping Down at Wall)... 

In addition to the primary flow pattern referred to above, secondary flow cells develop with increasing impeller speed and these are similar to those observed by Peters and Smith [1967] for class 11 agitators as can be seen in Figure 8.13. Carreau et al. [1976] have also recorded flow patterns for a helical ribbon impeller. sco-elasticity seems to cause a considerable reduction in the... 

Figure 8.15 Flow pattern produced by a helical ribbon impeller. [Nagata et al. 1956]...

Figure 8.16 Variation of axial fluid velocity in the core region of helical ribbon impellers pumping downwards in 27 and 730 litre tanks. The curves indicate the upper and lower bounds of data [Bourne and Butler, 1969]...

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