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Plastic granulator is completely filled with technology
In order to study the residence time distribution in a twin-screw plastic granulator, experiments have been carried out with liquid at room temperature using the same model of the fully filled zone described in the chapter. At time t=0, when a transparent fluid is added to the stable working plastic granulator, a step change is applied thereto, so that the plastic granulator is completely filled with the blue fluid, and the fluid component at the outlet The change gives a direct measure of the cumulative export time-dependent distribution, since the color measured at time t corresponds to a material that has a residence time t or longer than t in a plastic granulator. The change in color is achieved by two valves mounted directly on the two screws. The time required to change the added material from blue to transparent fluid is less than 0.18 because of the average residence of the material in the plastic granulator. The time is about a few minutes, so no serious errors are formed when adding materials. The material flowing from the plastic granulator is passed through two holes very close to each screw instead of using a valve. The material coming out of these two holes is free to fall into the test tube. In this way, it is avoided that the outlet residence time distribution is superimposed on the residence time of the plastic granulator. The fluid used was an aqueous polyethylene-pyrrolidone solution which was actually a Newtonian fluid which was dyed with methylene blue. The concentration of methylene blue in the obtained fluid sample was measured by a photographic spectrometer. It is possible to accurately measure a concentration as low as 1% of the initial value. In these measurements, the distance between the two screws (control calendering gap) and the die pressure were varied.
It is also non-linear when some of the experiments to be done are converted into the coordinate system used here. The non-linearity at least reflects the partial separation of the fluid through the plastic granulator and reflects the mixing of the limited scene in the chamber. The non-linearity is not obvious only with the small helix angle of the experimental case with a wide calendering gap, which implies that these geometries will be most suitable when good homogenization is required, as in the case of chemical reactions. In combination with the interactions between the chambers discussed in the previous section, there is an indirect argument that the calendering gap controls the degree of homogenization in the plastic granulator. When there is no calendering gap at all, the leakage flow mixes poorly with the rest of the fluid in the chamber. This allows certain materials to stay in the plastic granulator for a long period of time. Therefore, the residence time distribution has a particularly long tail. When a reasonable calendering gap is used, all or most of the tetrahedral leaks are sheared and mixed as they are towed there, and no bends are visible in the log yield concentration curve.
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