Scott and Tabibi Fig. 16 High-speed disperser. (From Ref. 22.) ity. Hence, the high-speed disperser does its best job of deagglomerating particles when the viscosity is between 10,000 and 20,000 centipoise. If the shear rate is calculated in a fashion similar to the method used for a rotor/stator, it is found to be very low, since the "gap" between the disperser blade (rotor) and the vessel bottom (stator) is usually around 30 cm. For a disperser with a 30 cm blade running at 2000 rpm located 30 cm off the bottom of a vessel dv/dx = (7t) (30)(2000)/(30)(60) = 104 sec (6) where dv = velocity difference between the moving impeller and the stationary object (bottom of the vessel); and dx = distance between moving impeller and stationary object. Clearly, the maximum shear rates are higher than this in the vicinity of the blade tip, but there has not been much research into the velocity gradients set up by high-speed dispersers. Much of this lack of research is no doubt because the bulk of the commercial applications for the disperser deal with viscous liquids that are completely opaque, making the measurement of the various velocities difficult. However, there has

DOI link for Scott and Tabibi Fig. 16 High-speed disperser. (From Ref. 22.) ity. Hence, the high-speed disperser does its best job of deagglomerating particles when the viscosity is between 10,000 and 20,000 centipoise. If the shear rate is calculated in a fashion similar to the method used for a rotor/stator, it is found to be very low, since the "gap" between the disperser blade (rotor) and the vessel bottom (stator) is usually around 30 cm. For a disperser with a 30 cm blade running at 2000 rpm located 30 cm off the bottom of a vessel dv/dx = (7t) (30)(2000)/(30)(60) = 104 sec (6) where dv = velocity difference between the moving impeller and the stationary object (bottom of the vessel); and dx = distance between moving impeller and stationary object. Clearly, the maximum shear rates are higher than this in the vicinity of the blade tip, but there has not been much research into the velocity gradients set up by high-speed dispersers. Much of this lack of research is no doubt because the bulk of the commercial applications for the disperser deal with viscous liquids that are completely opaque, making the measurement of the various velocities difficult. However, there has

Scott and Tabibi Fig. 16 High-speed disperser. (From Ref. 22.) ity. Hence, the high-speed disperser does its best job of deagglomerating particles when the viscosity is between 10,000 and 20,000 centipoise. If the shear rate is calculated in a fashion similar to the method used for a rotor/stator, it is found to be very low, since the "gap" between the disperser blade (rotor) and the vessel bottom (stator) is usually around 30 cm. For a disperser with a 30 cm blade running at 2000 rpm located 30 cm off the bottom of a vessel dv/dx = (7t) (30)(2000)/(30)(60) = 104 sec (6) where dv = velocity difference between the moving impeller and the stationary object (bottom of the vessel); and dx = distance between moving impeller and stationary object. Clearly, the maximum shear rates are higher than this in the vicinity of the blade tip, but there has not been much research into the velocity gradients set up by high-speed dispersers. Much of this lack of research is no doubt because the bulk of the commercial applications for the disperser deal with viscous liquids that are completely opaque, making the measurement of the various velocities difficult. However, there has