Agitator

About: Agitator is a research topic. Over the lifetime, 8758 publications have been published within this topic receiving 35418 citations.

Stirring by chaotic advection

Abstract: In the Lagrangian representation, the problem of advection of a passive marker particle by a prescribed flow defines a dynamical system. For two-dimensional incompressible flow this system is Hamiltonian and has just one degree of freedom. For unsteady flow the system is non-autonomous and one must in general expect to observe chaotic particle motion. These ideas are developed and subsequently corroborated through the study of a very simple model which provides an idealization of a stirred tank. In the model the fluid is assumed incompressible and inviscid and its motion wholly two-dimensional. The agitator is modelled as a point vortex, which, together with its image(s) in the bounding contour, provides a source of unsteady potential flow. The motion of a particle in this model device is computed numerically. It is shown that the deciding factor for integrable or chaotic particle motion is the nature of the motion of the agitator. With the agitator held at a fixed position, integrable marker motion ensues, and the model device does not stir very efficiently. If, on the other hand, the agitator is moved in such a way that the potential flow is unsteady, chaotic marker motion can be produced. This leads to efficient stirring. A certain case of the general model, for which the differential equations can be integrated for a finite time to produce an explicitly given, invertible, area-preserving mapping, is used for the calculations. The paper contains discussion of several issues that put this regime of chaotic advection in perspective relative to both the subject of turbulent advection and to recent work on critical points in the advection patterns of steady laminar flows. Extensions of the model, and the notion of chaotic advection, to more realistic flow situations are commented upon.

Mixing efficiency determinations for continuous flow systems

Abstract: Models are defined for various mixing conditions, in continuous flow systems. Differential equations are derived which take into account an effective volume of mixing, possible short-circuiting, hold-up time of the system, partial displacement or piston flow. The values of the different factors contained in the integrated equations can he determined experimentally by the particular response of a given system to a sudden change in composition of the feed. A correlation of the effective volume of mixing and the agitator r.p.m. is presented. A design procedure is suggested for tank flow reactors when partial mixing occurs.

Imaging apparatus cartridge including an encoded device

Abstract: A cartridge for an electrophotographic machine having a sump for carrying an agitator rotatably mounted in the sump for engagement with a toner; an encoded device coupled to a first end of the agitator; and a torque sensitive coupling connected to a second end of the agitator which is connectable to a drive mechanism of the machine. The encoded device includes coding representing cartridge characteristic information.

Gas-liquid dispersion with dual Rushton turbine impellers.

Abstract: Aerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height-to-diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding-loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed-filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller-impeller flow pattern interactions occur.