Stirrer optimization
Stirrer are used in many different industries. To procedurally optimize your stirrer, you need detailed knowledge about the processes in your stirring tanks. By means of high-resolution 3D CFD flow simulations, the mixing processes can be calculated in a short period of time and with little effort. The simulation graphics are clearly illustrated and enable to analyse the data.
Therefore, CFD simulations are a reliable Tool for all thinkable configurations.
Advantages of CFD simulations:
- reproducible results
- no time-consuming measurements
- direct identification of the problem areas
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With our simulations, you can optimize various stirring systems,
for example:
- tank
- vessel head
- rotor / stator
- micromixers
- pipeline mixer
The achievement of optimum stirring results depends on various factors. Optimum results are achieved by stirrers which mix all molecules in the plant in the required manner and ensure that all molecules remain in certain places in the plant only as long as it is necessary for optimum reaction. This means, for example, that no particles settle at the bottom of the stirrer or accumulate at certain points in the plant.
The following two methods are particularly suitable for analyzing this:
The combination of these two methods is ideal for improving reaction control in a reactor and identifying problem areas.
A look into practice: Identification of a short-circuit flow
In the following example, the mixing of fluids in a stirred tank is simulated and optimized. The initial situation in the stirring tank corresponds to a short-circuit flow. Due to an unsuitable design of the stirring tank, some molecules are transported directly from the inlet (top right) to the outlet (top left) without reacting with each other.
To investigate the described problem above, the flow field was firstly calculated (picture on the right). This provides the basis for analysing particle spread in the stirrer tank.
In a next step, massless particles that follow the flow, so-called tracers, were used to illustrate the flow process. The image below shows the flow lines of the mixing process created by the tracers. Here it is particularly easy to see that the stirrer does not mix the molecules uniformly throughout the stirrer tank. Instead, the whole movement is concentrated in the area at the top left.
A mean-age analysis was carried out here. The mean-age field indicates that the fluid elements in the stirred part have a mean age of about 400 seconds. This can be recognised by the yellowish to reddish colouring of the corresponding area. (colour scale on the left) This is comparatively much higher than the target value of about 270 seconds, which is also found at the outlet. Optimally, the stirring tank should be as uniformly greenish in colour as possible.
After the mean-age analysis, we optimized the mixing by changing the stirrer tank design. To do this, we placed the outlet below the stirrer to avoid the dead zone. Thus, the stirred tank is uniformly green and corresponds to the target value of the mixing, only the inlet region is blue.
