چكيده به لاتين
Mixing is one of the important processes that is effective in many industries. One of the most common uses of mixing, the use in the pharmaceutical industry is a stirred reactor. Considering the wide applications, design of such tanks has been investigated, characteristics such as velocity profiles, turbulence parameters, air distribution, etc. can be used in optimal acting of stirred reactors (CSTRs). The purpose of this study is CFD simulation of these reactors. A rotating frame and mesh motion models have been used to simulate the tank. A single impeller reactor in the reported research was studied and the most suitable turbulence model for this agitators was selected based on CPU time and accuracy of the model. Height and diameter of the selected rotating frame model were chosen to be 1.6 of the diameter of the blade. Then, the agitator power and flow pattern based on RNG k-ε model were examined. In the next part of the study, a double-bladed reactor with gas sparger was studied. The power and mixing time were measured experimentally by tracer method. In non-aeration mode, the total reactor power was increased by increasing the impeller rotation, but the mixing time was decreasing. In aeration mode, with increasing sparger flow the total power of the reactor decreased and the mixing time increase to a fixed value. The CFD results were validated by experimental works. The approximate power number was obtained seven, then the sparger was started and the parameters of gas consumption and mixing time were investigated again. The reactor power number decreased from 5.5 to 4.5 with increasing the sparger gas flow (200-1500 milli-liter per minute). As the mentioned sparger flow range, the mixing time raises to a constant value at a constant rotational speed of 200 rpm. Three patterns of impeller placement in the reactor (parallel, divided and merging patterns) were investigated. The merging pattern has the lowest power consumption, then the divided pattern and, ultimately, the parallel pattern had more power consumption from the others. In addition, the lowest mixing time was related to the merging pattern and after that was parallel pattern, and finally the divided pattern had the longest mixing time.
Keywords: Sttired tank, Multiple Refrance Frame, Turbulence model, mixing
