A great improvement in mixing performance by the additional up-and-down motion of rotating impellers was confirmed from measurements of mixing time tM and power requirement P in a 5 / vessel. Of five impellers tested, the best mixing time was obtained with a cross-paddle consisting of two pairs of inner and outer blades pitched at opposite angles to each other. In a typical case, the mixing time was reduced to 1/3 of that for the conventional helical ribbon while the power remained unchanged, i.e. the energy for mixing completion was reduced to less than 10%. The double-stage arrangement of two impellers with spacing equal to stroke distance is preferable to the single stage, providing much improvement in mixing time in spite of the doubling of power required. The results are compared with those for conventional agitators in terms of the characteristic parameters of ntM9 tMVPJJt and V~Pv/pn2. The mechanics of simultaneous rotary and vertical motion of the impeller by a single-drive motor is also mentioned. Intro duction Conventional mixers for high-viscosity liquids are usually equipped with relatively bulky blades, e.g.
The mass exchange type "micromixing" model in a flow system is extended to batch mixing rate process accompanying a second-order reaction between miscible reactive fluids A and B. The performance of batch mixing rate process accompanied by reaction and the dimensionless parameter q=krCbolkm are obtained from theoretical analysis of the model. When the value of q becomes less than about 0.1, the mixing effect is negligible on the course of reaction. Through analysis of the mixing characteristics of the model, the mass exchange coefficient km can be correlated with mixing time as follows. Theoretical studies mentioned above are confirmed through experimental studies of the alkaline hydrolysis of ethyl chloroacetate, for which the reaction rate is comparable to the rate of mixing and the infinitely rapid reaction of ammoniumhydroxide and acetic acid. The experimental values of km determined in each experiment show that macromixing due to circulation of the fluid element has a dominant effect on the course of reaction in the experimental condition of 300 < Re < 5000.
An active shielding module consisting of a self-tunable loop-current array is verified experimentally. Loop currents in the array are independently controlled by the magnetometer dedicated to each of them. Since magnetic field decays as 1∕z3 along the distance z from the loop, the magnetic noise should be overcompensated at the location of the loop-current array to provide a good cancellation in the shielded area. In order to enable overcompensation in a stable feedback system, a small additional loop is combined to the magnetometer that reduces the magnetic direct coupling from the main loop current to the magnetometer. A feedback electronic circuit with a proportional-integral (PI) controller is combined with each of the array element to establish a stable canceling operation. An orthogonal fluxgate magnetometer is used to monitor incident magnetic noise. Shielding performance of an array consisting of nine loop currents arranged in a 3×3 grid was evaluated numerically and confirmed by experiments. Evaluation and measurements are done over the 1.5×1.5m2 area 2m in front of the array. The magnetic dipole disturbance source is placed 2m further beyond the array. Attenuation of the magnetic field is calculated as 1∕15. Experimental data show 1∕10 attenuation.
Intro duction In the previous report2\ it was shownthat a novel mechanics of dual mode (rotational and vertical) movementof an impeller reduces greatly mixing time without much increase in power consumption relative to the conventional single-mode (rotational) agitator. Up-and-down as well as circumferential
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