Power measurement, stirred vessels

In the MBR, the applicator of plate steel was an important safety feature in the possible event of vessel rupture or explosion. Temperature and pressure measurements, stirring, infinitely variable control of microwave power input, the cold-finger, as well as a pressure relief valve, have all contributed significantly to the safety and reliability of the system. 

Ascanio, G., Castro, B., and Galindo, E. (2004), Measurement of power consumption in stirred vessels—a review, Chemical Engineering Research and Design Transactions of the Institution of Chemical Engineers Part A, 82(A9) 1282-1290. 

Power input per unit volume and impeller tip speeds are often used measures of the intensity of stirring, assuming correct proportions of the vessel and proper baffling. Appropriate ranges... 

Measurements were carried out in a 6-liter brass vessel stirred by means of a flat blade stirrer and equipped with 4 wall baffles. The influence of dispersed phase fraction and of stirring rate was investigated. The dispersed phase fraction was varied from 0.06 to 0.15 while the power input by the stirring was varied from 0.1 to 3 hp./m.8. The interaction rate found was invariably 0.035 sec.-1. Another experiment was carried out by Kramers and de Korver using a short rotary contactor (height = 10 cm., diameter = 9.3 cm., diameter of rotor = 8.0 cm.) which was made entirely of Teflon to prevent wetting of the wall by the aqueous dispersed phase. This reactor... 

The power density Py is the characteristic quantity of turbulent flow. It determines the size of the smallest eddies and the intensity of microturbulence. In addition, it is a measure of the shear intensity in laminar flows or the intensity of cavitation in ultrasonic fields (see above). The power input P in the dispersion zone can be derived from the pressure drop (e.g. in pipes and nozzles) or can be measured caloricafly (e.g. for rotor-stator systems and ultrasonication Pohl 2005 Kuntzsch 2004). Additionally, P can be roughly approximated by the electric power consumption of the dispersion machine (e.g. for ultrasonication Mandzy et al. 2005 Sauter et al. 2008), even though the real values may be lower by a factor of 2 to 5. A further source of uncertainty is the volume of the dispersion zone (Vdisp). since the stress intensities are not uniformly distributed in dispersion apparatuses. In particular, this applies to agitated vessels, where the highest dissipation rates are obtained in the vicinity of the stirring instmment (Henzler and Biedermann 1996),... 

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