The present work examines leaching of lipoxygenase-1 from soybean flour employing STIRRED TANK vessel. The effect of operating parameters, impellers speed, operational period, temperature, pH and scale-up were considered. The acetic acid pH: 5.2 increased the leaching of lipoxygenase- 1. The sensitivity of agitator speed and geometrical-scale-up on the enzyme leaching has been conducted. The effect of agitator speed on the geometrically-scaled- up reactor has shown that similar amount of enzyme is leached at lower speed. The result is in para with the conventional system. The importance of operational period from 5 to 50 min on the enzyme leaching was evaluated and higher enzyme leaching obtained within 10 min. of operation. The Sigmaplot-6 for statistical verification and developing a correlation for the enzyme leaching was used.

In the present study, commonly used weakly compressible lattice Boltzmann method and Guo incompressible lattice Boltzmann method have been used to simulate fluid flow in a STIRRED TANK. For this purpose a 3D Parallel code has been developed in the framework of the lattice Boltzmann method. This program has been used for simulation of flow at different geometries such as 2D channel flow and 3D STIRRED TANK flow. It has been shown that in addition to elimination of compressibility error, the Guo incompressible method eliminates mass leakage error from the fluid flow simulations although its implementation is as easy as the weakly compressible Lattice Boltzmann method. For example in presented STIRRED TANK problem mass leakage in Guo method is about 0% while for LBGK method is about 1.4%. By the way, comparison between results of the two methods shows that differences in local flow quantities are negligible in both methods; however, for overall flow quantities, the results of Guo incompressible method are more accurate than those of weakly compressible method.

Multiphase impeller STIRRED TANK reactors enhance mixing of reacting species used in a variety of chemical industries. These reactors have been studied based on Computational Fluid Dynamics (CFD) that can be used in the analysis, design and scale up of these reactors. Most of the researches done in this area are limited to single phase reactors, and a few remaining two phase flow investigations have been done based on MRF (Multi Reference Frame) and Snapshot approach. However, the MRF and snapshot approaches cannot be used in rigorous simulation of unsteady state problems. In order to simulate the unsteady state behavior of the multiphase STIRRED TANK reactors we have used sliding mesh technique to solve the problem rigorously. In this work a 3D CFD model is used to investigate hydrodynamics of a fully baffled cylindrical STIRRED TANK containing air-water in which air is sparged. The TANK is equipped with a standard Rushton turbine impeller. This work has been done based on two fluid (Eulerian-Eulerian) model and finite volume method, along with standard k-e model to address turbulent behavior of both phases. The results obtained for velocity field show a good agreement with the corresponding data published by researchers in this field for the same case. The effect of gas inlet velocity on the gas holds up distribution has been studied. According to the obtained results, there should be an optimum value for gas inlet velocity in order to achieve appropriate gas distribution in the liquid. The most important parameter affecting the optimum value is impeller rotational speed.

Knowledge of mixing time is of fundamental importance for investigation of mixing efficiency in agitation systems. The mixing time obtained by using the correlation and formula in large scale mixing systems was incorrect. Again, the number of available correlations in this scale of mixing systems is limited. To predict the mixing time of STIRRED TANKs with dual impellers commonly used in industry, a third-compartment mixing model was used. The time of homogenization of the charge (mixing time) was calculated from the time dependency of the local concentration of tracer measured at various locations. Experimental data on mixing time were obtained with a conductivity technique. In the present study distribution of tracer in the bulk of the liquid was described by compartment model (CM) as well as for STIRRED vessel with dual Rushton impellers. As for the model, a good agreement between the experimental data and the calculated values was apparent.

Computational fluid dynamics (CFD) is a powerful numerical tool that is becoming widely used to simulate many processes in the industry. In this work, a study of the STIRRED TANK with 7 types of concave blade with CFD was presented. In the modeling of the impeller rotation, sliding mesh (SM) technique was used, and RNG-k-ε model was selected for turbulence. Power consumption at various speeds in the single phase, mean tangential, radial and axial velocities in various points, effects of disc diameter and thickness, and mixing time were investigated. The optimum concave impeller was selected, and the effect of tracer feed position and probe location was investigated on it. Results suggested that power consumption was exactly dependent on impellers’ scale and geometry; results are in good agreement with the experimental data, and turbulent flow is relatively independent of Reynolds number. Power number increases by increasing disc diameter for both concave and Rushton, and concave´ s power is relatively independent of disc thickness; however, increasing it decreases Rushton´ s power. The data revealed that the power number was 2. 3± 0. 3 for a blade angle of 40° , whereas, for blade angles 25° , 50° , and 55° , it was 43 % lower and 57 % and 43 % higher, respectively.

Blakeslea trispora, a filamentous fungus, was cultured both in a 15lit STIRRED TANK and 75lit airlift bioreactor. Different rates of aeration and agitation were investigated in related bioreactors in order to find the more appropriate culture conditions for better production of ß-carotene. The results showed that the ß-carotene production by Blakeslea trispora is highly dependent on the degree of aeration of culture medium. ß-carotene yield was enhanced up to 120mg/L when the aeration and agitation rate was increased in STIRRED bioreactor, up to 2vvm and 400rpm, respectively. However, under similar aeration condition, the production of the desired product was about 0.7 times more in airlift than the STIRRED bioreactor.

This work compares the accuracy and calculation efficiency of various tetrahedral and polyhedral meshes in a Computational Fluid Dynamic (CFD) simulation of a STIRRED TANK. The polyhedral mesh was found leading to much fewer mesh cells than the tetrahedral one without missing the calculation accuracy. The CFD numerical simulation results of the polyhedral mesh better agree to the experimental data comparing to the tetrahedral one at the same mesh cell number. In addition, the results of polyhedral mesh were also found to be more accurate than the tetrahedral one which was refined by adaptive meshing based on the velocity gradient.

Three dimensional turbulent flow in a STIRRED TANK with moving blades has been numerically studied. For the numerical simulation, a 3D parallel flow solver has been developed based on the lattice Boltzmann method. The large eddy simulation method has been used for the turbulence modeling. To improve the accuracy of the flow simulation in STIRRED TANKs, a commonly used boundary condition for moving walls as well as a proposed alternative boundary condition have been investigated in great details. The present investigations show that the proposed improved bounce-back method generates accurate results compared with those obtained using commonly used force field method. However, the implementation of the proposed boundary condition is more difficult for cases with complex moving walls.

The turbulent flow field generated in a baffled STIRRED TANK was computed by large eddy simulation (LED) and the flow field was developed using the Sliding Mesh (SM) approach. In this CFD study, mixing times and power number have been determined for a vessel agitated by a 6-blade Rushton turbine. The predicted results were compared with the published experimental data. The satisfactory results of comparisons indicate the potential usefulness of this approach as. a computational tool for designing STIRRED reactors.