Agitator with flow sensor to operate the agitator

Abstract

Agitator (10) for mixing a fluid, comprising a drive device (12), in particular a drive motor, a stirring propeller (14) that can be driven at least indirectly by the drive device (12), and a connecting pipe (16) that connects the drive device (12) to the stirring propeller (14) and has a longitudinal center axis (L), characterized in that at least one first flow sensor (18) is arranged on an outer side of the connecting pipe (16) that can be assigned to the fluid, around which the fluid flows at least partially, and said first flow sensor (18) has at least one measuring point (M) for detecting fluid parameters of the fluid, wherein the first flow sensor (18) is arranged in a rotationally fixed manner relative to the stirring propeller (14).

Description

[0001] The invention relates to an agitator for mixing a fluid, comprising a drive device, in particular a drive motor, a stirring propeller which can be driven at least indirectly by the drive device and a connecting pipe which connects the drive device to the stirring propeller and has a longitudinal central axis. STATE OF THE ART

[0002] A variety of different agitators of the type mentioned above are known from the state of the art.

[0003] Such agitators typically have at least one propeller, which is usually coupled to a drive device, usually an electric motor, via a shaft. The drive device drives the propeller.

[0004] The agitator is generally used in a wide variety of industrial applications that require the mixing of a fluid. Examples of such applications include the wastewater industry, the food industry, and construction.

[0005] In these applications, the agitator is immersed in the fluid at least partially, but always with its propeller, during normal operation. The force generated by the drive device causes the propeller to rotate, thereby thoroughly mixing the fluid throughout the period of normal operation.

[0006] In this regard, EP 2 193 837 B1 discloses an agitator, in particular a slurry agitator, comprising a drive motor and an agitator screw arranged at the end of a drive shaft. The agitator is mounted on a wall of a fluid-filled container. The agitator screw is mounted longitudinally displaceably on a connecting pipe, and the drive shaft is provided with a fixed bearing and a longitudinally displaceable bearing arranged inside the connecting pipe.

[0007] Furthermore, EP 2 361 673 A2 discloses an agitator with a stirring propeller connected to a drive device by means of a connecting rod. The agitator can be arranged on a fluid container such that the stirring propeller and at least portions of the connecting rod are arranged within the fluid container, while at least the drive device is located outside the fluid container.

[0008] Furthermore, DE 20 2016 100 518 U1 discloses an agitator mounted on a guide rail for longitudinal movement. When used as intended, the guide rail is arranged on an inner side wall of a fluid container in such a way that the agitator can be immersed in the fluid and removed again as needed by sliding it along the guide rail.

[0009] Other agitators of this type are known from DE 10 2020 127 757 A1 and DE 10 2016 103 456 A1.

[0010] In addition, DE 10 2015 117 441 A1 discloses a method for determining the viscosity and / or homogeneity and / or density or density change in a particle-containing liquid substrate of a biogas plant, which enables energy-saving operation of a corresponding agitator of the biogas plant.

[0011] Typically, a mixing process using conventional agitators is fully automated. This frequently presents the problem that a statement about the mixing state of the fluid, particularly regarding whether the fluid is now sufficiently mixed, can only be made through a visual assessment or inspection. Understandably, however, such a visual inspection is relatively unreliable and subject to a relatively high error rate due to the subjectivity of the inspector, the lighting conditions on site, and other factors. This leads to a reduced efficiency of the mixing process, particularly with regard to energy efficiency and achieving an optimal mixing state or degree of mixing.

[0012] It is therefore desirable, particularly by means of the agitator, to create a possibility to make a statement about the mixing state of the fluid based on reliable and objectively assessable data in order to improve the efficiency of the mixing process and, above all, the energy efficiency of the agitator.

[0013] The object of the invention is therefore to provide an improved agitator which provides a possibility for collecting data regarding the mixing state of the fluid and thus enables a reliable statement regarding the degree of mixing of the fluid to be mixed.

[0014] This object is achieved by an agitator according to the independent claim. Advantageous embodiments of the invention are the subject of the dependent claims. DISCLOSURE OF THE INVENTION

[0015] The invention is based on an agitator for mixing a fluid, wherein the agitator has a drive device, in particular a drive motor, a stirring propeller that can be driven at least indirectly by the drive device and a connecting pipe that connects the drive device to the stirring propeller and has a longitudinal center axis.

[0016] According to the invention, at least one first flow sensor, around which the fluid can flow at least partially, is arranged on an outer side of the connecting pipe that can be assigned to the fluid, and has at least one measuring point for detecting fluid parameters of the fluid.

[0017] In this respect, when used as intended, the agitator is arranged at least partially or in sections within the fluid, with the agitator propeller and at least those areas of the connecting pipe where the flow sensor is arranged being immersed in the fluid, so that the fluid flows around the flow sensor. By allowing the fluid to flow around the flow sensor, the flow sensor is able to detect the fluid parameters of the fluid.

[0018] The invention is based on the consideration that at least some fluid parameters do not remain constant with increasing mixing or stirring time, with the viscosity of the fluid, in particular, not decreasing linearly and the shear rate increasing. Thus, the flow behavior of the fluid at the agitator propeller changes over time depending on the viscosity. For example, with a horizontally acting agitator propeller, the flow is almost horizontal in a low-viscosity state and acquires more vertical components as the fluid viscosity increases.

[0019] The solution according to the invention now makes it possible to reliably determine when the fluid is sufficiently stirred or mixed by measuring the relevant fluid parameters using the flow sensor. In other words, the flow sensor collects reliable data regarding the fluid's mixing state, which allows a reliable assessment of the fluid's current degree of mixing. Advantageously, this allows for a statement regarding maintenance and changes in the fluid, based on which the mixing process can be optimized, thereby advantageously increasing its efficiency.

[0020] The solution according to the invention is therefore particularly well-suited for industrial agitators in wastewater management, tunnel construction, the cement industry, the food industry, the chemical and petrochemical industries, the paper and pulp industry, aquaculture and fish farming, as well as many other industrial sectors where a corresponding mixing process is regularly required. Further possible applications include biogas agitators for use in fermenters, secondary digesters, final storage facilities, and manure mixers for the agricultural sector.

[0021] In particular, a shaft is rotatably mounted inside the generally non-rotatable connecting tube, by means of which the drive force generated by the drive device is transferred to the agitator propeller. The connecting tube preferably serves as a shell for the shaft to protect it from damage caused by the surrounding fluid, such as corrosion or mechanical blockages, and also to mechanically connect the agitator propeller and the drive device. However, the power transmission between the drive device and the agitator propeller takes place via the shaft.

[0022] According to a preferred development, the fluid parameters include flow parameters and / or viscosity parameters of the fluid. In this respect, changes in flow / viscosity resulting from stirring or mixing, or viscosity-related flow changes, are preferably detected by the flow sensor. This advantageously allows a reliable statement to be made regarding the current mixing state of the fluid, in particular regarding whether the fluid is sufficiently mixed.

[0023] According to a preferred embodiment, the first flow sensor is arranged to extend radially away from the connecting pipe, allowing the fluid to flow completely around it. This results in the advantage that particularly meaningful data regarding the fluid parameters can be recorded.

[0024] Preferably, an axial position, a radial position, and / or an angular position of the first flow sensor relative to the longitudinal center axis of the connecting pipe can be predetermined and / or adjusted. This advantageously provides the possibility of adjusting the position of the flow sensor as needed depending on the prevailing operating situation. Furthermore, the position of the first flow sensor can be reliably determined using a cylindrical coordinate system.

[0025] According to a preferred development, the first flow sensor is designed as a measuring finger with a strain gauge, in particular an internal one. This is a particularly well-suited embodiment of the flow sensor for the application described above, since the flow of the fluid and thus the fluid parameters can be easily detected based on a bending of the flow sensor resulting from the flow forces. Advantageously, the measuring finger also represents an easy-to-manufacture and thus cost-effective embodiment of the flow sensor.

[0026] Alternatively, the first flow sensor is preferably designed as a load cell or flow sensor. In principle, other flow sensor designs are also conceivable, provided they are suitable for the application described above. Depending on the design of the flow sensor, further advantages in terms of efficiency and cost arise.

[0027] According to the invention, the first flow sensor is arranged in a rotationally fixed manner relative to the agitator propeller. The first flow sensor therefore does not rotate with the agitator propeller, but remains static relative to it. Thus, the connecting pipe is also arranged or mounted in a rotationally fixed manner relative to the agitator propeller. Advantageously, the detection of the fluid parameters is thus decoupled from the rotational speed or rotational force of the agitator propeller, which would otherwise affect the flow sensor, thus providing a particularly reliable and easily evaluated method for detecting the fluid parameters.

[0028] According to a preferred development, at least one further flow sensor is provided, in particular a plurality of further flow sensors are provided, wherein the further flow sensor or the further flow sensors are arranged along the longitudinal center axis of the connecting pipe at the same axial height as the first flow sensor and / or axially spaced from it. Preferably, at least one further flow sensor is arranged radially and / or angularly spaced from the first flow sensor. spaced from one another, and at least a third, possibly even further flow sensors, are arranged axially spaced from at least the first flow sensor.

[0029] In this context, "at the same axial height" means that the at least two flow sensors are distributed radially and / or angularly around the circumference of the connecting pipe and are therefore arranged in a common radial plane. "Axially spaced" in this context means that the additional flow sensor is arranged (axially) below or above the first flow sensor, i.e., not in the same radial plane.

[0030] This advantageously significantly improves the measurement of fluid parameters, as they can be recorded independently by multiple flow sensors. Furthermore, it is possible to average the fluid parameters recorded by the respective flow sensors, so that the overall statement regarding the fluid mixing state can be made particularly reliably based on statistics. Furthermore, a fail-safe mechanism is advantageously provided, since even if the first flow sensor is unable to record the fluid parameters, for example, due to damage, these can be recorded alternatively and / or additionally by at least one additional flow sensor.

[0031] According to a preferred development, the flow sensors, or at least three flow sensors, are evenly spaced from one another, at least at the beginning of the agitator's intended operation. The flow sensors are thus all at the same distance from neighboring flow sensors in the radial and / or axial direction of the connecting pipe. In this context, the beginning of the intended operation is, so to speak, the initial state of the agitator. This provides the advantage that, at least in the initial state of the agitator, reliable detection of the fluid parameters and an objective assessment of the existing mixing state are possible.

[0032] According to a preferred development, the flow sensors are mounted radially and / or axially (relative to the longitudinal center axis) displaceably on the connecting pipe, so that the distance between the flow sensors can be changed as needed. This results in the advantage that the distance between the flow sensors can be individually adjusted depending on the respective requirements of the intended operation, so that the overall arrangement of the flow sensors can always be adapted to the specific case at hand, and thus the detection of the fluid parameters and the associated possibility of assessing the existing mixing state can be optimally tuned or optimized.

[0033] Preferably, the distance between the flow sensors can be adjusted remotely. Alternatively, the distance can also be adjusted manually.

[0034] According to a preferred development, the first flow sensor and at least one further flow sensor have different radial distances from the longitudinal center axis of the connecting pipe with respect to their respective measuring points, at least in one degree of freedom. In other words, one flow sensor measures closer or farther from the connecting pipe than the other. This advantageously enables comprehensive detection of the fluid parameters and advantageously minimizes the potential error component during detection.

[0035] According to a preferred development, the first flow sensor and at least one further flow sensor are designed differently. In this respect, different types or types of flow sensors can be used. For example, the first flow sensor is designed as the aforementioned measuring finger with internal strain gauges, while the further flow sensor is designed as a load cell. The design or type of flow sensors can also be the same, for example, all flow sensors can be designed as measuring fingers, but the specific embodiment of the respective flow sensors can be different. For example, in this case, the flow sensors can differ in terms of their geometric design (dimensions, in particular length and / or shape) and / or their sensitivity. The detection of the fluid parameters is thereby advantageously further improved or optimized.

[0036] According to a preferred development, the agitator, in particular the agitator propeller, is designed to mix a non-Newtonian fluid. The agitator therefore has mechanical configurations or properties of the individual components suitable for this purpose, for example, a fluid-tight connecting pipe, a comparatively powerful drive device, or a correspondingly designed agitator propeller. In this context, the agitator propeller can be designed in particular as a normal rotor blade, i.e., with at least two, in particular curved, rotor blades, or as a spiral blade. Advantageously, the agitator is thus optimized for the intended application.

[0037] Furthermore, a method for operating the agitator described above is presented. It is provided that a) Fluid parameters of the fluid are recorded by measured values ​​of the first flow sensor, in particular flow parameters and / or viscosity parameters, and b) a mixing state of the fluid is determined on the basis of the recorded fluid parameters, the mixing state providing information as to whether the fluid has been sufficiently mixed, and c) based on the determined mixing condition, the operating parameters of the agitator, in particular stirring speed and / or stirring force, are adapted, in particular optimized.

[0038] Adjusting in step C means that the agitator continues to operate unchanged, stirring parameters such as stirring speed, intensity, etc. are changed, or the agitator is shut down. Optimized means that the parameters regarding energy consumption, mixing condition improvement, etc. are adjusted based on a characteristic map, an AI, or at least a change gradient.

[0039] When applying the method described above, the advantages already mentioned with regard to the corresponding agitator arise.

[0040] According to a preferred development, it is provided that the fluid parameters are detected by a functional relationship, preferably by an averaging, of measured values ​​of the first flow sensor and at least one further flow sensor, and / or the mixed state is determined by a functional relationship, preferably an averaging, of fluid parameters of the fluid, which are detected by the first flow sensor by at least one further flow sensor.

[0041] If multiple flow sensors are present, either the fluid parameters can be determined from the measured values ​​of the flow sensors (averaged or via a function / characteristic map, etc.), and / or the mixing state can be determined from the fluid parameters of the individual flow sensors or from groups of flow sensors. This has the advantage of enabling particularly precise statements regarding the existing mixing state. Furthermore, redundancy is advantageous because if one of the flow sensors fails, it can be disregarded due to the averaging of the values ​​recorded by the other flow sensors. Furthermore, flow sensors with different measuring ranges can be used advantageously, and depending on the signal values, those flow sensors that operate most accurately in the various measuring ranges can be taken into account.Overall, the process is thus advantageously further optimized.

[0042] According to a preferred further training, it is planned that - when the determined mixing state indicates that the fluid has been sufficiently mixed, the agitator is switched off, and - if the determined mixing state indicates that the fluid has not yet been sufficiently mixed, the agitator continues to operate but the operating parameters are changed, or the agitator continues to operate unchanged with regard to the operating parameters:

[0043] This advantageously further optimises the process, particularly with regard to energy efficiency.

[0044] According to a preferred embodiment, the method is carried out over the entire period of intended operation of the agitator, with process steps A to C being repeated continuously or at specified intervals. The mixing process of the fluid is thereby advantageously further optimized while still being efficient. DRAWINGS

[0045] Further advantages will become apparent from the accompanying drawing description. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0046] They show: Fig. 1 a simplified representation of an advantageous agitator according to a first embodiment, Fig. 2 a second embodiment of the agitator, and Fig. 3 a third embodiment of the agitator.

[0047] In the figures, similar elements are numbered with the same reference numerals. The figures are merely examples and are not to be construed as limiting.

[0048] Fig. 1 shows a simplified representation of an advantageous early mechanism 10 which is suitable or designed for mixing a fluid, in particular a non-Newtonian fluid.

[0049] In the Fig. In the first embodiment of the agitator 10 shown in Figure 1, it is designed as a rod agitator. The agitator 10 has a drive device 12, a stirring propeller 14 driven by the drive device 12, and a connecting pipe 16 that at least mechanically connects the drive device 12 and the stirring propeller 14.

[0050] The drive device 12 is a drive motor of a known type, which is why, for the sake of clarity, its construction and operation will not be discussed further here. The stirring propeller 14 is Fig. The first embodiment shown in Figure 1 is designed as a conventional agitator propeller, which in this respect has at least one rotor blade, which in this case is curved at least in some areas. Alternatively, the agitator propeller 14 can also be designed, for example, as a spiral propeller or spiral-shaped. The structure and function of the agitator propeller 14 are also generally known and will therefore not be discussed in detail here.

[0051] As already mentioned above, the connecting tube 16 serves at least for the mechanical connection of the stirring propeller 14 to the drive device 12. In this respect, the stirring propeller 14 is arranged at a first end of the connecting tube 16, and the drive device 12 is arranged at a second end of the connecting tube 16 opposite the first end. The connecting tube 16 has a longitudinal central axis L, along which the connecting tube 16 extends from the drive device 12 to the stirring propeller 14. According to the present exemplary embodiment, a shaft (not shown here for reasons of clarity) is arranged inside the connecting tube 16, by means of which shaft the drive force generated by the drive device 12 can be transmitted to the stirring propeller 14 in order to set the stirring propeller 14 in rotation to stir or mix the fluid.In this respect, the drive device 12 and the stirring propeller 14 are coupled by the shaft in terms of power transmission.

[0052] When used as intended, the agitator 10 is arranged at least partially within the fluid. Fig. In the first embodiment shown in Figure 1, at least the agitator propeller 14 is arranged inside the fluid. In the conventionally known application forms of the rod agitator 10, at least sections of the connecting pipe 16 are also arranged inside the fluid. Specifically, in the embodiment shown in Fig. 1, the drive device 12 is outside, but the connecting pipe 16 and the agitator propeller 14 are inside a container containing the fluid, so that the agitator propeller 14 and the connecting pipe 16 are essentially completely immersed in the fluid. The boundary of the container, i.e. its wall, is shown in Fig. 1 is shown in outline.

[0053] With conventional agitators, the problem regularly arises that a statement about the mixing state of the fluid, namely whether it is sufficiently stirred or mixed, can only be made through a visual assessment or inspection. As already discussed above, the assessment of the degree of mixing is therefore essentially based on the subjective assessment of the inspector and not on objectively assessable and reproducible data.

[0054] In order to enable objective data collection regarding the degree of mixing of the fluid, the present agitator 10 advantageously provides that at least one flow sensor 18 with at least one measuring point M is arranged on an outer side of the connecting pipe 16 that can be assigned to the fluid or, when the agitator 10 is used as intended, is assigned to the fluid. The flow sensor can be or is flowed around at least in some areas by the fluid and is designed to detect fluid parameters of the fluid.

[0055] The fluid parameters detected by the flow sensor 18, which include, among other things, flow parameters and / or viscosity parameters of the fluid, can advantageously be used as the basis for an objectively feasible data evaluation after detection in order to determine the degree of mixing of the fluid. At least some fluid parameters do not remain constant with increasing mixing or stirring time, but change over time. In particular, the viscosity of the fluid decreases more non-linearly, whereas the shear rate increases with increasing mixing time. Thus, the flow behavior of the fluid changes over time, which can be reliably detected by the flow sensor 18 immersed in the fluid. Based on the correspondingly detected fluid parameters, conclusions can be drawn about the current degree of mixing of the fluid, so that, based on reliable data, a reliable statement can be made as to whether the fluid is now sufficiently mixed.

[0056] According to the present embodiment, the flow sensor 18 is designed as a measuring finger with a strain gauge. Fig. In the first embodiment shown in Figure 1, several flow sensors 18 are present, which are preferably of the same type, i.e. also designed as measuring fingers, but can differ with regard to the positioning of their respective measuring point M, as shown in Fig. 1 is illustrated by way of example. In this respect, the measuring point M of one of the flow sensors 18 can have a different radial distance from the longitudinal center axis L than that of another flow sensor 18. In other words, one of the flow sensors 18 measures closer to the connecting pipe 16 than the other flow sensor 18.

[0057] Advantageously, the fluid parameters are thereby measured at different positions or at different distances relative to the connecting pipe 16. Based on a statistical evaluation or averaging of the measured fluid parameters, the degree of mixing of the fluid can be assessed in a particularly reliable manner.

[0058] As in Fig. As shown in Figure 1, the flow sensors 18 extend radially away from the connecting tube 16, allowing the fluid to flow completely around them. Furthermore, the flow sensors 18 are axially spaced from each other relative to the longitudinal center axis L in order to cover a larger area of ​​the fluid for detecting the fluid parameters, thus further improving data collection.

[0059] In addition, it is provided that the flow sensors 18 are each displaceable radially and axially along or around the longitudinal center axis L, as indicated by two double arrows in Fig. 1 is shown as an example. Therefore, the distance between the flow sensors 18 can be radially and axially changed or adjusted as needed. This further optimizes data collection.

[0060] Based on the fluid parameters detected by the flow sensors 18 and, in particular, statistically evaluated or averaged, the current degree of mixing of the fluid is evaluated using a corresponding evaluation method, on which basis the further operation of the agitator 10 can be adjusted. If the fluid is not yet sufficiently mixed, the agitator 10 is preferably continued to operate unchanged, particularly with regard to stirring speed and force, or its operation is adjusted to ensure even better mixing of the fluid. However, if the evaluation shows that the fluid is already sufficiently mixed, the operation of the agitator 10 is preferably discontinued for energy efficiency reasons.

[0061] In summary, the provision of the advantageous flow sensors 18 on the agitator 10 enables a reliable determination of the current degree of mixing of the fluid in order to be able to advantageously adapt or optimize the mixing process with regard to efficiency, in particular energy efficiency, based thereon.

[0062] Fig. Figure 2 shows the agitator 10 according to a second embodiment. Identical elements are provided with the same reference numerals, and only the differences will be discussed below.

[0063] The Fig. The agitator 10 shown in Figure 2 differs from the one shown in Fig. 1 in that the flow sensors 18 are designed differently. In the present case, all flow sensors 18 are still designed as measuring fingers, i.e., of the same type, but differ in their specific embodiment. Specifically, the flow sensors 18 differ, as shown in Fig. 2, in terms of their length and, in particular, their (length-dependent) sensitivity. Additionally or alternatively, the flow sensors 18 can also differ in their type, so that, for example, one of the flow sensors 18 is not designed as a measuring finger, but rather as a load cell.

[0064] Furthermore, the Fig. In the second embodiment shown in Figure 2, at least some of the flow sensors 18 are located at the same axial height (relative to the longitudinal center axis L) and are therefore only radially spaced from one another. In other words, several flow sensors 18 are located at certain points on the connecting pipe 16, distributed over its circumference.

[0065] Due to the different design of the flow sensors 18 and the provision of additional flow sensors 18 at the same axial height, the collection of the fluid parameters is statistically further improved, since even more measuring positions are covered.

[0066] Fig. 3 shows a third embodiment of the agitator 10 described above. Identical elements are provided with the same reference numerals, and only the differences will be discussed below.

[0067] The Fig. The third embodiment shown in Figure 3 differs from the previous two embodiments in that the agitator 10 is no longer designed as a rod agitator 10, but as a submersible agitator 10.

[0068] As in Fig.3, the connecting pipe 16 of the submersible agitator 10 is comparatively short. In addition, the entire submersible agitator 10 is mounted on a guide rail 22 for longitudinal displacement by means of a carriage 20. This allows the submersible agitator 10 to be displaced along the guide rail 22. In typical applications, the guide rail 22 is arranged along an inner wall of a fluid-filled container (usually vertically), so that the submersible agitator 10 can be completely immersed in the fluid by means of the carriage 20 along the guide rail 22, as required, and can be arranged, in particular locked, at a predetermined position within the fluid. Furthermore, the submersible agitator 10 can be completely withdrawn from the fluid again, for example after the mixing process has been completed. Accordingly, the submersible agitator 10 is preferably designed to be fluid-tight.

[0069] In the third exemplary embodiment, the advantageous provision of at least one flow sensor 18 also enables reliable data collection regarding the degree of mixing of the fluid on the basis of fluid parameters, on the basis of which, after a corresponding evaluation, a data-supported and thus reliable statement can be made regarding the existing degree of mixing and thus the operation of the agitator 10 and thus also the entire mixing process can be advantageously optimized, in particular with regard to energy efficiency. List of reference symbols 10 agitator 12 Drive device 14 agitator propellers 16 Connecting pipe 18 Flow sensor 20 sleds 22 Guide rail L Longitudinal center axis M measuring point

Claims

[1] Agitator (10) for mixing a fluid, comprising a drive device (12), in particular a drive motor, a stirring propeller (14) which can be driven at least indirectly by the drive device (12) and a connecting pipe (16) connecting the drive device (12) to the stirring propeller (14) and having a longitudinal central axis (L), characterized by that at least one first flow sensor (18) is arranged on an outer side of the connecting pipe (16) which can be assigned to the fluid and around which the fluid can flow at least partially, and which has at least one measuring point (M) for detecting fluid parameters of the fluid, wherein the first flow sensor (18) is arranged in a rotationally fixed manner relative to the stirring propeller (14). [2] Agitator according to claim 1, characterized by that the fluid parameters include flow parameters and / or viscosity parameters of the fluid. [3] Agitator according to one of the preceding claims, characterized bythat the first flow sensor (18) is arranged to extend radially away from the connecting pipe (16) so that the fluid can flow around it completely, wherein preferably an axial position, and / or a radial position and / or an angular position of the first flow sensor (18) with respect to the longitudinal center axis (L) is predeterminable and / or adaptable. [4] Agitator according to one of the preceding claims, characterized by that the first flow sensor (18) is designed as a measuring finger with a strain gauge, in particular an internal one, as a load cell or flow sensor. [5] Agitator according to one of the preceding claims, characterized bythat at least one further flow sensor (18) is provided, in particular a plurality of further flow sensors (18) are provided, wherein the further flow sensor (18) or the further flow sensors (18) are arranged along the longitudinal center axis (L) of the connecting pipe (16) at the same axial height as the first flow sensor (18) and / or axially spaced from it, wherein preferably at least one further flow sensor (18) is arranged radially and / or angularly spaced from the first flow sensor (18). [6] Agitator according to claim 5, characterized by that at least three flow sensors (18) are evenly spaced from one another at least at the beginning of the intended operation of the agitator (10). [7] Agitator according to claim 4 or 5, characterized bythat the flow sensors (18) are mounted radially and / or axially displaceably on the connecting pipe (16) so that the distance between the flow sensors (18) can be changed if necessary. [8] Agitator according to one of claims 5 to 7, characterized by that the first flow sensor (18) and at least one further flow sensor (18) have different radial distances from the longitudinal center axis (L) of the connecting pipe (16) with respect to their respective measuring point (M), at least in one degree of freedom. [9] Agitator according to one of claims 5 to 8, characterized by that the first flow sensor (18) and at least one further flow sensor (18) are designed differently.

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