Ultrasonic measuring device for determining flow rate and method for determining temperature

Abstract

To provide means for more accurately determining a temperature of a fluid flowing in a measuring tube.SOLUTION: An ultrasonic measuring device determines a flow rate of a fluid flowing in a tube passage. The ultrasonic measuring device is proposed that has: a measuring tube 2 having a central axis M defining a flow direction A for the fluid; at least two ultrasonic transducers 11 and 22 arranged and aligned so as to exchange measurement signals 12 and 21 with each other; a control unit 20 for controlling the ultrasonic transducers 11 and 22 and for evaluating the measurement signals 12 and 21; and a first temperature sensor 61 for determining a first temperature T1, which is arranged so as not to be contactable by the fluid. A second temperature sensor 62 is provided for determining a second temperature T2 and is arranged so as not to be contactable by the fluid. Further, a method for determining a temperature of the fluid in such an ultrasonic measuring device is proposed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic measuring device for determining the flow rate of a fluid flowing in a pipeline according to the preamble of the independent claim. The invention further relates to a method for determining the temperature of the fluid in such an ultrasonic measuring device. [Background technology]

[0002] In process engineering, non-invasive methods are used to inspect fluids or measure fluids flowing through pipelines, for example, flexible plastic pipes. This is particularly true for highly pure or highly sensitive fluids, where contact between the fluid and the measuring device must be avoided as much as possible, for example, to prevent contamination of the fluid. Examples include the pharmaceutical, semiconductor, and biotechnology industries. In these industries, solutions and suspensions are frequently produced and transported, which place very high demands on the purity and / or integrity of the fluid. Often, such liquids even need to be processed under sterile conditions. Non-invasive methods are also used when the chemical resistance of the measuring device cannot be guaranteed.

[0003] Ultrasonic measurement techniques have proven their worth, particularly as a non-invasive method for measuring fluids flowing in pipelines. Ultrasonic measurement devices for measuring fluids flowing in pipelines are used, among other things, to determine the flow rate of the fluid flowing through the pipeline. Typically, ultrasonic measurement devices include a plurality of ultrasonic transducers capable of applying ultrasonic signals to the fluid and receiving the ultrasonic signals.

[0004] Inline ultrasonic measuring devices are known that are designated as measuring systems. In these measuring systems, for example, a separate measuring tube is provided and a part of the ultrasonic measuring device, such as a separate measuring tube, is inserted into a fluid-flowing pipe so that the fluid flows from the pipe into the measuring tube, through the measuring tube, and back into the pipe at its other end. In this case, ultrasonic measurements are performed in the area of the measuring tube. Also known are arrangements in which the measuring path, i.e., the path along which the ultrasonic transducers exchange signals, extends parallel to the direction of fluid flow in the measuring tube. In such arrangements, measuring signals propagating in the direction of fluid flow and measuring signals propagating counter to the direction of flow are typically transmitted and acquired. Consequently, the flow rate of the fluid can be determined from the transit time difference of such measuring signals. Such ultrasonic measuring devices with measuring tubes whose ends are connected to the pipe are described, for example, in EP 3 770 561 A1.

[0005] Furthermore, ultrasonic measuring devices designed as clamping devices are also known. Such devices are also called "clamp-on" devices. Such clamping devices are designed so that they can be clamped to a flexible pipe, so that the measuring tube of the ultrasonic measuring device surrounds the pipe so that the pipe is clamped within the measuring tube of the ultrasonic measuring device. The pipe, through which a fluid flows, is then subjected to an ultrasonic signal. After passing through the pipe and the fluid, the ultrasonic signal is received by an ultrasonic transducer, and the received signal is evaluated.

[0006] It is known that an ultrasonic measuring device for determining the flow rate includes at least two ultrasonic transducers, which are arranged laterally on opposite sides of a pipeline when in operation. The two ultrasonic transducers are arranged offset from each other with respect to the fluid flow direction and aligned so that the first ultrasonic transducer can receive the signal transmitted by the second ultrasonic transducer and the second ultrasonic transducer can receive the signal transmitted by the first ultrasonic transducer. Due to the offset from each other, the two ultrasonic transducers are aligned so that they transmit their ultrasonic signals obliquely in each case to the fluid flow direction, with one ultrasonic transducer transmitting a signal obliquely to the flow direction and the other ultrasonic transducer transmitting a signal obliquely opposite to the flow direction. Here, a measurement signal is transmitted by the first ultrasonic transducer, which is received by the second ultrasonic transducer, and then the measurement signal is transmitted by the second ultrasonic transducer, which is then transmitted by the first ultrasonic transducer.

[0007] The measurement signal transmitted obliquely to the flow direction is accelerated by the flow, and the measurement signal transmitted obliquely against the flow direction is decelerated by the flow. The transit time difference between the two measurement signals is proportional to the fluid flow velocity, and the flow rate through the flexible conduit can therefore be determined from this transit time difference.

[0008] Ultrasonic measuring devices designed as clamping devices in which a fluid-flowing line is clamped in a measuring tube of the ultrasonic measuring device are disclosed, for example, in EP 3 489 634 A1 or also in EP 3 816 590 A1.

[0009] In ultrasonic measuring devices designed as clamping devices, it is also possible to design the line not to be clamped in the measuring tube but to connect it to both ends of the measuring tube. This connection can be made, for example, by means of a barbed fitting. In this case, the fluid flows from the line to the measuring tube, through the measuring tube and back into the line at the other end.

[0010] Depending on the application, a design in which the lines are connected to both ends of the measuring tube may be advantageous. Particularly in the measurement of highly sensitive or highly invasive substances, cleaning or sterilizing an ultrasonic measuring device is very time-consuming, material-intensive, and expensive. For this reason, it is often necessary to design the components that come into contact with the substance, i.e., the measuring tube, for example, as single-use parts for single-use. In single-use designs, the components that come into contact with the fluid to be treated are preferably used exactly once and then replaced with a new, i.e., unused, single-use part at the next use. When manufacturing or constructing single-use parts, it is an important criterion that they can be assembled as simply as possible with other components of the measuring device. It is desirable that this assembly, and of course also the disassembly, can be performed quickly, preferably without tools, in a few steps, and with as little effort as possible.

[0011] Regardless of the specific design of the ultrasonic measurement device, it is essential in many applications that the temperature of the fluid in the measuring tube be known when measuring flow or determining other parameters. Temperature affects many variables, such as density, speed of sound, refractive index, sound path length, viscosity, friction, elastic modulus, or electrical resistance. Therefore, knowing the temperature of the fluid in the measuring tube is often important. The temperature of the fluid in the measuring tube can also be used, among other things, to modify the flow rate value determined by the measurement or to compensate for other temperature-dependent effects. Furthermore, it is advantageous if the temperature of the fluid in the measuring tube is available as a process parameter.

[0012] For the reasons already mentioned, it is also desirable that the temperature measurement be performed non-invasively, which means that direct physical contact between the temperature sensor and the fluid should be avoided.

[0013] For non-invasive temperature measurement of a fluid, EP 3770531 A1 proposes, for example, that a temperature sensor be provided on the outside of the wall of the measuring tube. The difference between the actual temperature of the fluid in the measuring tube and the temperature determined by the temperature sensor, caused by the wall, is determined, for example, by a calibration measurement, so that the temperature of the fluid in the measuring tube can then be determined from the temperature determined by the temperature sensor. Furthermore, the possibility of providing a recess on the outside of the wall of the measuring tube to reduce the wall thickness at that point is disclosed. In this case, a temperature sensor is placed in this recess, and the thinner wall at that point makes it possible to measure a temperature closer to the temperature of the fluid flowing in the measuring tube.

[0014] In such designs, where the conduit is clamped within the measuring tube, it is even more difficult to determine the temperature accurately, since the influence of the conduit wall on the temperature measurement also needs to be taken into account.

[0015] Even if this ultrasonic measuring device has proven itself useful, in many applications it is desirable to more accurately determine the temperature of the fluid flowing in the measuring tube. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] EP3770561A1 [Patent Document 2] EP3489634A1 [Patent Document 3] EP3816590A1 [Patent Document 4] EP3770531A1 Summary of the Invention [Problem to be solved by the invention]

[0017] Starting from this state of the art, it is therefore the object of the present invention to propose an ultrasonic measuring device for determining the flow rate of a fluid flowing in a pipeline, with which the temperature of the fluid can be determined non-invasively with the highest possible accuracy, and further to propose a method by which the temperature of the fluid in such an ultrasonic measuring device can be determined as accurately as possible. [Means for solving the problem]

[0018] The subject matter of the invention that meets this objective is characterized by the features of the respective types of independent patent claims.

[0019] Therefore, according to the invention, an ultrasonic measuring device for determining the flow rate of a fluid flowing in a pipeline is proposed, the ultrasonic measuring device having a measuring tube with a central axis defining the direction of flow of the fluid, at least two ultrasonic transducers arranged and aligned so as to be able to exchange measurement signals with each other, a control unit for controlling the ultrasonic transducers and for evaluating the measurement signals, a first temperature sensor for determining a first temperature that is arranged so as not to be accessible to the fluid, a second temperature sensor for determining a second temperature that is arranged so as not to be accessible to the fluid.

[0020] By arranging the two temperature sensors so that they cannot come into contact with the fluid, i.e., for example, next to the measuring tube, it is ensured that the two temperature sensors do not come into contact with the fluid flowing through the measuring path in the operating state, thus enabling non-invasive temperature measurement.

[0021] In an ultrasonic measuring device in which a fluid is flowing, if the temperatures at two fixed measuring points are known, the temperature of the fluid in the measuring tube can be determined with high accuracy from these two temperature values.

[0022] For this purpose, according to the invention, a method for determining the temperature of a fluid in an ultrasonic measuring device according to the invention is proposed, wherein a first temperature is determined by a first temperature sensor and a second temperature is determined by a second temperature sensor, and a correlation function with input variables and output variables is stored in the control device, the input variables including the first temperature and the second temperature, and the output variable is the temperature of the fluid in the measuring tube.

[0023] This correlation function, which is stored in the control unit, is determined experimentally on the basis of a number of measurements in which the first and second temperatures are measured in each case for different known ambient temperatures and for different known temperatures of the fluid in the measuring tube. A correlation function having the first and second temperatures as input variables and the temperature of the fluid in the measuring tube as output variable can then be created from such measurements.

[0024] It is understood that the correlation function can also have more than two input variables. For example, additional temperature values can be used as input variables determined by, for example, a third, fourth, etc. temperature sensor. Here, it is preferable to position the temperature sensors at positions where they are primarily affected by different heat sources or heat sinks. For example, this is possible by positioning different temperature sensors at different vertical distances from the central axis of the measuring tube so that the temperature sensors are at different distances from the fluid flowing in the measuring tube during operation.

[0025] It is also possible to take into account in this context other operating parameters, for example the power of the control unit, the flow rate of the fluid through the ultrasonic measuring device, or the power or rotational speed of the pump through which the fluid is conveyed through the measuring tube.

[0026] The correlation function between the first and second temperatures and the temperature of the fluid preferably takes into account both the individual system characteristics, i.e. in particular the characteristics of the ultrasonic measuring device and of the pipeline, and the ambient conditions, e.g. the ambient temperature, which means the temperature of the environment in which the ultrasonic measuring device is placed.

[0027] All heat transfer or transport occurring in the system made up of the ultrasonic measuring device, the pipeline, the environment, and the fluid can be taken into account in the correlation function. For example, the environment can supply heat to the system or remove heat from the system. The fluid can supply heat to the system or remove heat from the system. The amount of heat transferred depends on the temperature of the fluid and its flow rate. Electrical components, such as an electronic printing device that may be provided in the control unit, consume electricity, which is partially dissipated into the system as energy loss in the form of heat.

[0028] Particularly preferably, the first temperature sensor is positioned so that the first temperature is determined primarily by the temperature of the fluid in the measuring tube, for example by more than 50 percent, and the second temperature sensor is positioned in a position whose temperature is less dependent on the temperature of the fluid but is primarily dependent on another heat source or heat sink in the overall system.

[0029] Preferably, the second temperature sensor for determining the second temperature is positioned such that the second temperature represents the ambient temperature or the temperature of the control unit. Ambient temperature refers to the temperature of the environment in which the ultrasonic measuring device is located. Since the ambient temperature or the control unit may represent a heat source or a heat sink, it is advantageous to determine the second temperature at a point where the second temperature represents the ambient temperature and / or the temperature of the control unit.

[0030] Preferably, the first temperature sensor has a first distance perpendicular to the central axis, and the second temperature sensor has a second distance perpendicular to the central axis, the second distance being greater than or equal to the first distance. Particularly preferably, the second distance is simply greater than the first distance, such that the second temperature sensor is further away from the fluid than the first temperature sensor. As a result, the second temperature sensor is less affected by the temperature of the fluid than the first temperature sensor.

[0031] When the first distance is the same or approximately the same as the second distance, the second temperature sensor is positioned much closer to a different heat source or heat sink than the first temperature sensor, for example closer to the control unit or closer to the environment, in this way ensuring that the second temperature sensor is much more affected by this other heat source or heat sink and therefore that the effect of the fluid temperature on the second temperature sensor is smaller than the effect on the first temperature sensor, even if both temperature sensors are at the same vertical distance from the fluid.

[0032] Preferably, the first temperature sensor is arranged in the measuring tube, in this way the first temperature is measured at a point close to the fluid.

[0033] In a preferred embodiment, the control unit comprises an electronic printing device and the second temperature sensor is located on the electronic printing device, so that the second temperature is measured at a point where heat is typically generated.

[0034] In a preferred embodiment, in operation, the fluid flowing in the measuring tube is bounded perpendicular to the flow direction by a wall having a wall thickness, and the first temperature sensor has a vertical distance from the fluid in the measuring tube that is equal to or greater than the wall thickness and equal to or less than 20 times, preferably equal to or less than 10 times, the wall thickness, or the first temperature sensor is connected to the wall via a heat-conducting layer. If the ultrasonic measuring device is designed such that a conduit can be inserted into the measuring tube of the ultrasonic measuring device, the wall bounding the flowing fluid is the wall of the conduit. In embodiments in which a conduit is connected to the measuring tube but not inserted into it, the wall bounding the flowing fluid is the wall of the measuring tube.

[0035] Preferably, the ultrasonic measuring device includes a housing in which the measuring tube and the control unit are disposed, and the second temperature sensor is disposed in the housing or the control unit.

[0036] In this embodiment, the enclosure is preferably separated from the environment by an enclosure wall, the enclosure wall having an enclosure wall thickness, and the second temperature sensor is disposed at a vertical distance from the environment that is equal to or greater than the enclosure wall thickness and is 20 times, preferably less than 10 times, the enclosure wall thickness, or the second temperature sensor is connected to the enclosure wall via a thermally conductive layer. Since the ambient temperature prevails in the environment outside the enclosure and in this arrangement the second temperature is measured near the enclosure wall, the second temperature represents the temperature of the enclosure or the ambient temperature.

[0037] According to a preferred embodiment, the measuring tube is designed to receive the conduit so that the conduit is surrounded by the measuring tube.

[0038] Here, it is particularly preferred that the ultrasonic measuring device is designed as a clamping device for clamping connection to a pipe, so that the pipe can be clamped in the measuring pipe. The ultrasonic measuring device can in particular be designed as a clamp-on device.

[0039] According to a further preferred embodiment, the measuring tube extends in the flow direction from a first end to a second end, and the measuring tube has at its first end a first connector designed for connection to a pipeline and at its second end a second connector designed for connection to a pipeline. In this embodiment, the pipeline is therefore not inserted into the measuring tube, but is connected to both ends of the measuring tube. Such an embodiment is particularly advantageous when the measuring tube and possibly other components of the ultrasonic measuring device are designed as single-use parts for single use.

[0040] If the measuring tube is designed as a single-use part for a single use ("single-use part"), this has various advantages. These range from the production of the measuring tube as a single-use part to the use of the measuring tube in an ultrasonic measuring device. The measuring tube is produced under sterile conditions according to a precisely predetermined shape, template or pattern. The production process can be carried out, for example, by injection molding or 3D printing. Other production methods are also possible. One advantage of this production method is that each produced single-use part has exactly the same dimensions or measurements and material properties. This is advantageous for the use of single-use parts in ultrasonic measuring devices.

[0041] When each single-use portion is inserted into the ultrasonic measuring device, the same measurement conditions are provided for each single-use portion, which ensures, for example, a reliable and always consistent measurement of the temperature. Another advantage of the single-use measuring tube compared to conventional pipes is that, due to the always consistent dimensions of the measuring tube as a single-use portion, the central axis of the measuring tube always coincides with the central axis of the ultrasonic measuring device. This achieves a generally symmetrical structure of the ultrasonic measuring device. This also results in a always consistent enclosure of the measuring tube by the housing of the ultrasonic measuring device. For example, the cross section of the ultrasonic measuring device, i.e., the socket for the measuring tube, can be designed as a hexagon. However, other geometric cross sections, such as a circle, an ellipse, or a polygon, are also possible.

[0042] The hexagonal cross-section of the ultrasonic measuring device ensures increased accuracy and resolution in the measurement. The hexagonal design makes it possible to measure along multiple measurement paths in the measuring tube or in the fluid flowing in the measuring tube. As a result, for example, a higher tolerance to air bubbles is achieved in the fluid when measuring with the ultrasonic measuring device.

[0043] The always identical enclosure of the measuring tube by the housing of the ultrasonic measuring device ensures, among other things, that an optimal and reproducible thermal interaction between the ultrasonic measuring device and the fluid flowing through the measuring tube is possible. When using ultrasonic measuring devices in conventional pipelines such as hoses, problems can arise in terms of the enclosure due to the different dimensions of the various hoses. The optimal thermal interaction, as well as the always identical positioning and always identical material properties of the measuring tube as a single-use part, have the effect that the temperature measurement of the medium is significantly more accurate and at the same time the response time of the measurement is improved, for example when the temperature of the medium changes.

[0044] Another advantage of measuring tubes as single-use sections compared to conventional flexible hose lines clamped in ultrasonic measuring devices is that the measuring tubes are designed to be dimensionally stable as single-use sections. This means that while attaching an ultrasonic measuring device causes slight deformation of the measuring tube, using a hose clamp-on ultrasonic measuring device can cause the hose to be squeezed and contracted at the attachment point, which on the one hand means that the fluid experiences a higher resistance than usual and on the other hand means that, for example, temperature measurements are not constant or that calibration needs to be performed before each measurement for accurate temperature determination.

[0045] Needless to say, the advantages and properties of the measuring tubes mentioned within the framework of this application are also applicable to measuring tubes designed as single-use parts.

[0046] For the method according to the invention, it is preferred that the correlation function having the temperature of the fluid in the measuring tube as output variable is based on a plurality of isotherms, each of which is a linear equation with a slope and an axis intercept, which equation represents the first temperature as a function of the second temperature for a constant temperature of the fluid in the measuring tube.

[0047] Here, the temperature of the fluid in the measuring tube is determined by a determination function having exactly one variable, which variable is preferably the axis intercept of the isotherm.

[0048] Preferably, the decision function is a polynomial of at most second order, although in some applications it may be sufficient to use a straight line as the decision function, as a polynomial of first order.

[0049] In a preferred embodiment, specific offset values for the input variables are determined for the ultrasonic measuring device based on the isotherms. Component tolerances can be compensated for, for example, using these offset values. For example, temperature sensors, such as thermocouples or infrared sensors, are often subject to such tolerances, i.e., nominally identical components may actually have slight deviations from one another. Such component tolerances can be optionally taken into account or compensated for in the method according to the present invention.

[0050] Further advantageous measures and embodiments of the invention result from the dependent claims.

[0051] In the following, the invention is explained in more detail on the basis of embodiments and on the basis of drawings, both in terms of equipment and process technology. [Brief explanation of the drawings]

[0052] [Figure 1] 1 is a schematic diagram of a first embodiment of an ultrasonic measurement device according to the present invention. [Figure 2] 2 is a perspective view of a second embodiment of an ultrasonic measurement device according to the present invention; FIG. [Figure 3] FIG. 10 is a schematic cross-sectional view of a modified example of the second embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view of a further modified example of the second embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view of a third embodiment of an ultrasonic measurement device according to the present invention. [Figure 6] 1A and 1B are cross-sectional views of three variations of the embodiment of the wall that separates the fluid flowing in the measuring tube perpendicular to the flow direction. [Figure 7] 1 is a schematic cross-sectional view of an embodiment of a housing of an ultrasonic measurement device. [Figure 8] FIG. 2 is a schematic diagram of a measurement arrangement for determining a correlation function between the first and second temperatures and the temperature of the fluid. [Figure 9] 10A-10C are various diagrams for explaining the determination of a correlation function; [Figure 10] 10A-10C are various diagrams for explaining the determination of a correlation function; [Figure 11] 10A-10C are various diagrams for explaining the determination of a correlation function; [Figure 12] 10A-10C are various diagrams for explaining the determination of a correlation function; DETAILED DESCRIPTION OF THE INVENTION

[0053] 1 shows, in a schematic diagram, a first embodiment of an ultrasonic measuring device according to the invention, which is designated in its entirety by the reference number 1. The ultrasonic measuring device 1 is designed for measuring the flow rate of a fluid through a pipeline 100. The ultrasonic measuring device 1 comprises a measuring tube 2 having a central axis M which defines a flow direction A of the fluid. In the first embodiment, the ultrasonic measuring device 1 is designed such that the measuring tube 2 can receive the pipeline 100, i.e. such that the pipeline 100 can be inserted into the measuring tube 2, preferably such that the pipeline 100 is surrounded by the measuring tube 2.

[0054] In the following, reference will be made to the particularly important case in practice where the conduit 100 is a flexible conduit 100, i.e. a conduit 100 whose wall 101 can be deformed. The flexible conduit 100 is, for example, a plastic hose made from silicone rubber or PVC. Naturally, the conduit 100 can also be made from other materials, in particular from plastic or rubber. Naturally, the conduit 100 can also be designed as a rigid, i.e. non-flexible conduit. Preferably, the measuring tube 2 is made from plastic, is preferably significantly stiffer than the conduit 100, and is designed to be particularly dimensionally stable.

[0055] A fluid flows through a conduit 100 in a flow direction A. At least two ultrasonic transducers 11, 22, namely a first ultrasonic transducer 11 and a second ultrasonic transducer 22, are provided for transmitting and receiving ultrasonic measurement signals 12, 21. In operation, the first ultrasonic transducer 11 is disposed laterally on a first side 51 of the conduit 100, and the second ultrasonic transducer 22 is disposed laterally on a second side 52 of the conduit 100, the second side 52 being opposite the first side 51. The ultrasonic transducers 11, 22 are positioned and aligned such that they can exchange measurement signals 12, 21 with each other. In particular, the ultrasonic transducers 11, 22 are positioned such that the first ultrasonic transducer 11 can transmit a first measurement signal 12 to the second ultrasonic transducer 22 obliquely to the fluid flow direction A and can receive a second measurement signal 21 transmitted by the second ultrasonic transducer 22 obliquely to the flow direction A.

[0056] The measurement signals 12, 21 are symbolized in FIG. 1 by dashed straight lines each with an arrow. This should be understood so that the dashed lines indicate the main direction of propagation of the ultrasonic signal transmitted by the corresponding ultrasonic transducer 11, 22 in each case, and the arrows indicate the direction, i.e., whether the respective ultrasonic signal is traveling toward the respective ultrasonic transducer 11, 22, i.e., being received, or traveling away from it, i.e., being transmitted. The main direction of propagation is typically perpendicular to the surface of the CMUT (Capacitive Micromachined Ultrasonic Transducer) or the piezoelectric element of the corresponding ultrasonic transducer 11 or 22. The main direction of propagation includes an angle α with the flow direction A that is different from 0° and different from 90°.

[0057] In ultrasonic measuring devices 1 designed as in-line measuring devices (see for example FIG. 5), this angle α is often equal to 0° or 180°, i.e. the measuring signals are transmitted in such a way that their main direction of propagation is equal to or exactly opposite to the flow direction A. This can also be achieved, for example, with ultrasonic measuring devices designed in a U- or Z-shape.

[0058] 1, for example, the following procedure is used to determine the flow rate of a fluid flowing through a pipeline 100: a first ultrasonic transducer 11 transmits a first measurement signal 12, which is transmitted obliquely in the flow direction A at an angle α, meaning that the main direction of propagation of the first measurement signal 12 also has a component in the flow direction A. a second ultrasonic transducer 22 transmits a second measurement signal 21, which is transmitted obliquely in the flow direction A at an angle α, meaning that the main direction of propagation of the second measurement signal 21 also has a component opposite to the flow direction A.

[0059] After passing through the fluid, the first measurement signal 12 is received by the second ultrasonic transducer 22 and transmitted via signal line 22a to the control unit 20. After passing through the fluid, the second measurement signal 21 is received by the first ultrasonic transducer 11 and transmitted via signal line 11a to the control unit 20.

[0060] In the control unit 20, the transit time difference between the first measurement signal 12 accelerated by the flowing fluid and the second measurement signal 21 decelerated by the flowing fluid is determined. This transit time difference between the first measurement signal 12 and the second measurement signal 21 depends directly on the flow velocity of the fluid in the conduit 100. The flow velocity and therefore the flow rate of the fluid through the conduit 100 can therefore be determined from the transit time difference.

[0061] Furthermore, at least four ultrasonic transducers 11, 22 are often provided in the ultrasonic measuring device 1 for respectively transmitting and receiving ultrasonic signals, i.e., at least two of the first ultrasonic transducers 11 arranged laterally on the first side surface 51 and at least two of the second ultrasonic transducers 22 arranged laterally on the second side surface 52. In this case, the ultrasonic transducers 11, 22 are arranged and aligned so that in each case one of the first ultrasonic transducers 11 can transmit a first measurement signal 12 obliquely to and in the flow direction A to one of the second ultrasonic transducers 22 and can receive a second measurement signal 21 transmitted by this second ultrasonic transducer 22 obliquely to and opposite the flow direction A. In this case, the four ultrasonic transducers 11, 12 are arranged, for example, in the shape of an X. Such an arrangement of ultrasonic transducers 11, 22 is disclosed, for example, in EP 3 489 634 A1. In each case, in this arrangement with four ultrasonic transducers, it is advantageous that two measurements are made independently of one another both in the flow direction A and opposite to the flow direction A, thereby significantly increasing the accuracy and reliability of the determination of the flow rate. The ultrasonic measuring device 1 according to the invention can also be designed similarly to the ultrasonic transducer arrangement disclosed in EP 3 489 634 A1.

[0062] EP 3 816 590 A1 also discloses an ultrasonic measuring device with at least four ultrasonic transducers, and furthermore shows a design with six ultrasonic transducers. A particular feature of the ultrasonic measuring device disclosed in EP 3 816 590 A1 is that measurements are carried out in at least two different measuring planes, the intersection of which is the central axis of the measuring tube. Such a design is also possible for the ultrasonic measuring device 1 according to the invention.

[0063] The ultrasonic measuring device 1 further comprises at least two temperature sensors, namely a first temperature sensor 61 for determining a first temperature T1 (FIG. 9), which is arranged, for example, next to the measuring tube 2 so that it cannot be contacted by the fluid and at a first distance D1 perpendicular to the central axis M of the measuring tube 2, and a second temperature sensor 62 for determining a second temperature T2 (FIG. 9), which is arranged, for example, next to the measuring tube 2 so that it cannot be contacted by the fluid and at a second distance D2 perpendicular to the central axis M of the measuring tube 2.

[0064] In the embodiment described here, the second distance D2 is greater than the first distance D1, which will be described in more detail. However, embodiments in which the first distance D1 is the same or substantially the same as the second distance are also possible. The two temperature sensors 61, 62 are each signal-connected to the control device 20 so that the measured temperature values determined by the two temperature sensors 61, 62 can be evaluated by the control device 20.

[0065] Generally, all kinds of temperature sensors are suitable as temperature sensors 61, 62, for example thermocouples, thermometers, infrared (IR) sensors or other radiation sensors. In the case of non-contact temperature sensors 61, 62, for example IR sensors, the point at which the first or second temperature is determined is not the same point at which the temperature sensor 61, 62 is installed, but the measurement point at which the respective temperature sensor 61, 62 determines the temperature.

[0066] It is a substantial aspect of the present invention that the temperature of the fluid in the measuring tube 2 can be determined non-invasively. This means that the two temperature sensors 61, 62 are arranged so that they are not in direct, i.e. physical, contact with the fluid flowing through the measuring tube 2. For example, the two temperature sensors 61, 62 can be arranged "next to" the measuring tube 2. The temperature sensors 61, 62 can be, for example, located in the measuring tube 2, but they are not touched by the fluid flowing in the measuring tube 2.

[0067] The term "next to the measuring pipe" means that the temperature sensors 61, 62 are arranged, for example, above or below the measuring pipe 2 or to the right or left of the measuring pipe 2. In embodiments in which the conduit 100 is inserted into and surrounded by the measuring pipe 2 (see also, for example, FIG. 4), the temperature sensors 61, 62 can also be arranged in the measuring pipe 2, for example, so that they rest on the wall 101 of the conduit 100. Since the wall 100 separates the temperature sensors 61, 62 from the fluid in the conduit 100, the temperature sensors 61, 62 are not contacted by the fluid even when they are arranged inside the measuring pipe 2.

[0068] During operation of the ultrasonic measuring device 1, a first temperature T1 and a second temperature T2 are determined in each case by the temperature sensors 61, 62. The temperature TM of the fluid in the measuring tube 2 is then determined in the control unit 20 from the first temperature T1 and the second temperature T2, as will be explained in more detail hereinafter.

[0069] Preferably, the first distance D1 is different from the second distance D2. However, embodiments in which the first distance D1 is the same or substantially the same as the second distance D2 are also possible. Here, the first distance D1 is significantly smaller than the second distance D2. The first temperature T1 measured by the first temperature sensor 61 is therefore measured much closer to the fluid than the second temperature T2 measured by the second temperature sensor 62. For this reason, the first temperature T1 measured close to the fluid is significantly more dependent on or more representative of the temperature of the fluid in the measuring pipe 2 than the second temperature T2 measured further away from the fluid. Based on the second temperature T2, environmental influences, i.e., the influence of other heat sources or heat sinks that supply or remove heat from the entire system created by the ultrasonic measuring device 1, the pipe 100, and the fluid, can be determined. Such a heat source or heat sink may be, for example, the control device 20, which has electrical or electronic components that generate heat, or the environment of the ultrasonic measuring device 1, which supplies heat to the ultrasonic measuring device 1 when the ambient temperature is higher than the temperature of the ultrasonic measuring device 1, or which removes heat when the ambient temperature is lower than the temperature of the ultrasonic measuring device.

[0070] Before explaining in more detail how the method for determining the temperature of the fluid in the measuring tube 2 can be performed based on the first and second temperatures T1, T2, further equipment design options for the ultrasonic measuring device 1 will first be described.

[0071] FIG. 2 shows a perspective view of a second embodiment of an ultrasonic measuring device 1 according to the invention.

[0072] In the following, only the differences from the first embodiment will be described. Identical or functionally equivalent parts of the second embodiment are designated with the same reference signs as in the first embodiment. In particular, the reference signs have the same meaning as those already explained in connection with the first embodiment. It will be understood that all previous descriptions of the first embodiment also apply equally or similarly to the second embodiment.

[0073] The second embodiment of the ultrasonic measuring device 1 is designed as a clamping device, so that the pipeline 100 can be clamped in the ultrasonic measuring device 1 .

[0074] The ultrasonic measuring device 1 comprises a housing 40. The ultrasonic measuring device 1 is designed as a clamping device for clamp connection with a pipeline 100, i.e. the housing 40 of the ultrasonic measuring device 1 can be clamped to the pipeline 100 such that the pipeline 100 is fixed relative to the housing 40. The main design of an ultrasonic measuring device 1 with a housing 40 is known per se, for example from EP 3 489 634 A1. EP 3 816 590 A1 also discloses an ultrasonic measuring device 1 designed as a clamping device for detachable attachment to the pipeline 100.

[0075] The housing 40 is designed as a closable housing 40 and comprises a first housing part 41 and a second housing part 42, which are articulated to one another via a joint 43. Figure 2 shows the housing 40 in the open state. The housing 40 further has a continuous central recess which extends throughout the entire housing 40 in the flow direction A and which, in the closed state of the housing 40, forms a measuring tube 2 for receiving the conduit 100. The longitudinal extension of the central recess determines the flow direction A in which the fluid flows through the conduit 100 or the housing 40, respectively.

[0076] The housing 40 further comprises a closing mechanism 44 for closing the housing 40 and thus clamping the conduit 100 in the measuring pipe 2. The closing mechanism 44 is here arranged in the first housing part 41 and comprises a bracket 46 and a folding strap 45 for tensioning the bracket 46. The conduit 100 is inserted into the measuring pipe 2, after which the two housing parts 41, 42 are folded together, i.e. the first housing part 41 is folded over the conduit 100. The bracket 46 engages with a protrusion 47 on the second housing part 42, and the two housing parts 41, 42 are tensioned together by applying the strap 45. The housing 40 is then in the closed state, and the conduit 100 is clamped in the measuring pipe 2 and fixed relative to the housing 40.

[0077] In the closed state of the housing 1 , the conduit 100 is therefore fixed between a first side 51 and a second side 52 which are opposite each other relative to the measuring tube 2 .

[0078] Furthermore, marking elements (not shown), for example arrows defining the direction in which fluid will flow through the ultrasonic measuring device 1, may be provided on the housing 40.

[0079] The measuring tube 2 is preferably designed so that in the closed state of the housing 40 it has a substantially rectangular, in particular square, cross section perpendicular to the flow direction A. This has the advantage that the ultrasonic measuring signal applied to the conduit 100 strikes a flat surface, i.e. does not strike a curved surface, which considerably simplifies the detection and evaluation of the measuring signals 12, 21 and increases the accuracy of the measurement.

[0080] Also known are embodiments in which the measuring tube 2 is designed so that in the closed state of the housing it has a different polygonal cross section, for example a hexagonal cross section, perpendicular to the flow direction A. Furthermore, embodiments are known in which this cross section is circular or elliptical. In such embodiments, an acoustic lens in front of the ultrasonic transducers 11, 22 is often then used to transmit and / or receive the measurement signals 12, 21.

[0081] The ultrasonic transducers 11, 22 as well as the two temperature sensors 61, 62 are located inside the housing 40 and therefore not visible in Figure 2. The first ultrasonic transducer 11 is located on the first side 51 and the second ultrasonic transducer 22 is located on the second side 52.

[0082] In a second embodiment of the ultrasonic measuring device 1, an embodiment with exactly two ultrasonic transducers 11, 22 (similar to the one presented in Figure 1), an embodiment with exactly four ultrasonic transducers 11, 22 or an embodiment with six or more ultrasonic transducers 11, 22 is possible. Preferably, at least four ultrasonic transducers 11, 22 are provided.

[0083] Each ultrasonic transducer 11, 22 is in each case signal-connected to the control unit 20 via one of the signal lines 11 a, 22 a (similar to FIG. 1 ). The signal lines 11 a, 22 a as well as the control unit 20 are arranged in the housing 40 and are therefore not visible in FIG. 2 . Via the respective signal line 11 a, 22 a, the ultrasonic transducers 11, 22 are activated to emit ultrasonic signals and transmit the respective received measurement signals 12, 21 to the control unit 20. The received measurement signals 12 and 21 are analyzed in the storage and evaluation unit 20 and the flow rate of the fluid through the pipeline 100 is determined in each case with the aid of the measurement signals 12 and 21.

[0084] The ultrasonic transducers 11, 22 can be designed in any manner known per se, in particular as piezoelectric transducers. Typically, the frequency of the ultrasonic signals is in the megahertz range, for example in the range of 1 MHz to 30 MHz.

[0085] The first temperature sensor 61 and the second temperature sensor 62 are also located within the housing 40 and are therefore not visible in Figure 2. However, the temperature sensors 61, 62 may be located, for example, as shown in Figure 3 or Figure 4.

[0086] 3 shows, in a schematic cross section, a second embodiment variant of the ultrasonic measuring device 1 according to the invention. In this variant, the measuring tube 2 is a separate component that is designed for connection to the pipeline 100. In this variant, the pipeline 100 is therefore not surrounded by the measuring tube 2, but the measuring tube 2 is connected to the pipeline 100.

[0087] The measuring tube 2 extends from a first end 110 to a second end 120 in the flow direction A, the length of the measuring tube 2 being dimensioned here such that both the first end 110 and the second end 120 extend from the housing 40 of the ultrasonic measuring device 1. In other embodiments, the first end 110 and / or the second end 120 can also be arranged within the housing 40. All ultrasonic transducers 11, 22 (not shown in FIG. 3 ) of the ultrasonic measuring device 1 are arranged within the housing 40 in the flow direction A between the first end 110 and the second end 120 of the measuring tube 2. The measuring tube 2 has at its first end 110 a first connector 115 designed for connection to the pipeline 100 and at its second end 120 a second connector 125 also designed for connection to the pipeline 100. The first and second connectors 115, 125 may be designed in any configuration known per se that is suitable for connecting the measuring pipe 2 to the pipe 100, and they may in particular be designed to be flexible. In particular, the first and second connectors 115, 125 can be designed as barbed pipe joints, so that the pipe 100 can simply be pushed into the first connector 115 or the second connector 125, respectively, so that the pipe 100 is connected to the measuring pipe 2 in a sealed manner.

[0088] In barbed pipe couplings, each connector 115, 125 is usually provided in each case with a conical section, over which the line 100 or one end of the line 100 is pulled or pushed in. This conical section is usually provided with one or more ribs, which are not shown in the schematic representation of Figure 3 but which can of course be provided in a manner known per se.

[0089] The measuring tube 2 is inserted into the ultrasonic measuring device 1 in the same way as described above for the conduit 100 with reference to Fig. 2 when the housing 40 is in the open state. After the measuring tube 2 has been inserted into the ultrasonic measuring device 1, the housing 40 is closed and the measuring tube 2 is clamped and thus fixed relative to the housing 40. A holder 3 may be provided on the ultrasonic measuring device, which tightly surrounds the measuring tube 2 in the closed state of the housing 40, so that the measuring tube 2 is fixed to the housing 40.

[0090] In embodiments with a separate measuring tube 2 that is inserted into and fixed to the ultrasonic measuring device 1, the measuring tube 2 can be designed as a single-use component, in particular for single use.

[0091] The measuring tube 2 is manufactured under sterile conditions according to a precisely predetermined shape, template, or pattern. The manufacturing process can be carried out, for example, by injection molding or 3D printing. Other manufacturing methods are also possible. One advantage of this manufacturing method is that each manufactured single-use portion has exactly the same dimensions or measurements. This has the advantage that the same measuring conditions are provided when the measuring tube 2 is inserted into the housing 40 of the ultrasonic measuring device 1, ensuring, for example, a reliable and always consistent temperature measurement. Another advantage of the single-use portion of the measuring tube 2 compared to the conduit 100 is that, due to the always consistent dimensions of the measuring tube 2 as a single-use portion, the central axis M of the measuring tube 2 coincides with the central axis of the ultrasonic measuring device 1. This achieves an overall symmetrical structure of the ultrasonic measuring device 1. This means that the ultrasonic measuring device 1 has a symmetrical structure, which ensures that the measuring tube 2 is always enclosed by the housing 40 of the ultrasonic measuring device 1 in the same way.

[0092] The symmetrical structure of the housing 40 of the ultrasonic measuring device 1 ensures complete enclosure of the measuring tube 2. This results in the largest possible contact surface between the measuring tube 2 and the ultrasonic measuring device 1. This symmetrical and concentric structure ensures uniform thermal conditions in the ultrasonic measuring device 1. This means that thermal processes (e.g., temperature profiles) can be relatively easily represented using mathematical relationships based on the symmetry present in the structure of the ultrasonic measuring device 1. Thus, for example, temperature profiles that depend on the wall thickness of the measuring tube 2 can be easily calculated without substantial changes to the underlying mathematical calculation model. Therefore, isotherms, i.e., positions where the same thermal conditions prevail, can be determined, which results in, for example, the positioning of temperature sensors being easily changed. This is particularly true when the temperature sensor is changed on an isotherm, i.e., between positions with the same temperature.

[0093] However, on the other hand, it can also be appreciated that it is not trivial at which location in the ultrasonic measuring device 1 the temperature should be measured so that it can be suitable as an input variable for the calculation model.

[0094] Simpler variations of the temperature sensor in the ultrasonic measuring device 1 increase in particular the flexibility of the ultrasonic measuring device 1 in terms of the range of applications and the speed of the measurements, and also the adaptability of the measurements to new situations.

[0095] A further advantage of the symmetrical design is that the thermal conditions in the ultrasonic measuring device 1 are not subject to additional temperature gradients. As a result, non-uniform thermal conditions in the ultrasonic measuring device 1 are avoided. This has the advantage that the measurement is more accurate, but also that the influence on the measuring tube 2 and thus on the fluid flowing therein is reduced. Otherwise, additional temperature gradients may arise, for example, which may result in mechanical tensions and thus damage sensitive fluids and / or their components.

[0096] To be able to realize this desired symmetry of the ultrasonic measuring device 1, the cross section, i.e. the socket for the measuring tube 2 of the ultrasonic measuring device 1, can be designed hexagonally (see FIG. 6), however, other geometric cross sections, such as circular, elliptical or polygonal, are also possible.

[0097] The hexagonal cross-section of the ultrasonic measuring device 1 ensures increased accuracy and resolution during measurements. The hexagonal design makes it possible to measure along multiple measurement paths in the measuring tube 2 or in the fluid flowing in the measuring tube 2. As a result, for example, a higher tolerance to air bubbles in the fluid during measurements with the ultrasonic measuring device 1 is achieved.

[0098] The always identical enclosure of the measuring tube 2 by the ultrasonic measuring device 1 ensures, among other things, that an optimal and reproducible thermal interaction is possible between the ultrasonic measuring device 1 and the fluid flowing through the measuring tube 2. When using the ultrasonic measuring device 1 in a conduit 100 such as a hose, problems can arise at the enclosure point due to the different dimensions of the various conduits 100. The optimal thermal interaction, as well as the always identical positioning and always identical material properties of the measuring tube 2 as a single-use part, have the effect that the temperature measurement of the fluid is significantly more accurate and at the same time the response time of the measurement is improved, for example when the temperature of the fluid changes.

[0099] Another advantage of the measuring tube 2 as a single-use part compared to the clamped conduit 100 in the ultrasonic measuring device 1 is that the measuring tube is designed to be dimensionally stable as a single-use part. This means that attaching the ultrasonic measuring device 1 causes smaller deformations of the measuring tube 2, whereas if, for example, a hose is used as the conduit 100, a clamp-on ultrasonic measuring device can cause the hose to be squeezed and contracted at the attachment point, which means, on the one hand, that the fluid experiences a higher resistance than usual and, on the other hand, that, for example, the temperature measurement is not constant or that a calibration has to be performed before each measurement for an accurate determination of the temperature.

[0100] 3 also shows a control device 20, with which the ultrasonic transducers 11, 22 are controlled and with which the measurement signals 12, 21 received by the ultrasonic transducers 11, 22 are evaluated. Preferably, the control device 20 comprises an electronic printing device 25, also called PCB (printed circuit board), on which the electronic and / or electrical components of the control device 20 are arranged.

[0101] In particular, the arrangement of the two temperature sensors 61, 62 is also represented in Figure 3. The first temperature sensor 61 is arranged close to the measuring tube 2, so that the first temperature T1 measured thereby is determined very close to the fluid flowing in the measuring tube 2. The second temperature sensor 62 is arranged on the control unit 20, for example on the electronic printing device 25, so that the second temperature T2 determined by the second temperature sensor 62 represents the temperature of the control unit 20. It will be understood that both temperature sensors 61, 62 are signal-connected to the control device 20.

[0102] In a schematic cross-section, Figure 4 shows a further variant of the second embodiment of the ultrasonic measuring device 1 according to the invention. This variant is similarly designed similarly to the one shown in Figure 2, in that the line 100 is inserted into the measuring tube 2 so that the line 100 is clamped in the measuring tube 2 in the closed state of the housing 40.

[0103] The first temperature sensor 61 is arranged in the measuring tube 2 and is connected to the wall 101 of the conduit 100 via a thermally conductive layer 63. The second temperature sensor 62 is arranged in the control device 20, in this case on the electronic printing device 25, and is connected to the housing wall 401 that delimits the housing 40 via a thermally conductive layer 64. Due to the arrangement of the second temperature sensor 62 in the housing wall 401, the second temperature T2 represents the ambient temperature, which means the temperature of the environment in which the housing 40 is arranged. The thermally conductive layer 63 ensures a particularly good thermal connection between the conduit 100 or the measuring tube 2, on the one hand, and the first temperature sensor 61 on the other hand. The thermally conductive layer 64 ensures a particularly good thermal connection between the housing 40 and the second temperature sensor 62.

[0104] The thermally conductive layers 63 and 64 can be designed in any manner known per se. For example, the thermally conductive layers 63, 64 can be realized using a thermal potting compound into which the respective temperature sensors 61, 62 are applied. The thermally conductive layers 63, 64 can also be realized, for example, using a thermal pad, using a thermally conductive paste, or using a paint with good thermal conductivity. Of course, it is also possible for the first temperature sensor 61 to be placed directly on the wall 101 of the conduit 100. Furthermore, it is also possible for the second temperature sensor 62 to be placed directly on the housing wall 401.

[0105] Generally, it is preferred if the difference between the first distance D1 and the second distance D2 is as large as possible with regard to the placement of the two temperature sensors 61, 62. The first temperature sensor 61 is preferably placed as close as possible to the fluid, while the second temperature sensor 62 is placed as close as possible to the housing 40 and / or to the control unit 20 or is thermally coupled as well as possible to the housing 40, so that the second temperature T2 is a good representative of the ambient temperature.

[0106] FIG. 5 shows a schematic cross-sectional view of a third embodiment of an ultrasonic measurement device 1 according to the present invention.

[0107] In the following, only the differences from the two first embodiments will be described. Identical or functionally equivalent parts of the third embodiment are designated with the same reference signs as in the two first embodiments. In particular, the reference signs have the same meaning as those already explained in connection with the two first embodiments. It will be understood that all the preceding explanations also apply equally or similarly to the third embodiment.

[0108] In the third embodiment, the measuring tube 2 is designed as a separate component which can be inserted into the housing 40 of the ultrasonic measuring device 1 and fixed there, for example by means of a clamp connection. Apart from the two temperature sensors 61, 62, the basic structure of the ultrasonic measuring device 1 or measuring tube 2 of the third embodiment corresponds to the device disclosed in EP 3 770 561 A1.

[0109] In the third embodiment, a measuring tube 2 having a central axis M extends from a first end 110 to a second end 120 in the flow direction A, the length of the measuring tube 2 being dimensioned so that both the first end 110 and the second end 120 extend from the housing 40 of the ultrasonic measuring device 1. All ultrasonic transducers 11, 22 (not shown in FIG. 3 ) of the ultrasonic measuring device 1 are arranged within the housing 40 in the flow direction A between the first end 110 and the second end 120 of the measuring tube 2. In that case, the measuring tube 2 has at its first end 110 a first connector 115 designed for connection to the pipeline 100 and at its second end 120 a second connector 125 also designed for connection to the pipeline 100. The first and second connectors 115, 125 may be designed in any configuration known per se that is suitable for connecting the measuring tube 2 to the pipeline 100; they may, in particular, be designed to be flexible. The fluid enters the measuring tube 2 through the first connector 115 and the fluid leaves the measuring tube 2 through the second connector 125 .

[0110] A first chamber 30 in which a first ultrasonic transducer 11 (not shown) is disposed and a second chamber 50 in which a second ultrasonic transducer 22 (not shown) is disposed are provided. The first ultrasonic transducer 11 and the second ultrasonic transducer 22 define a linear measurement path 70 for the fluid. The first chamber 30 and the second chamber 50 are designed and arranged so that the fluid can flow around each of them. The first ultrasonic transducer 11 and the second ultrasonic transducer 22 are arranged so that the measurement path 70 extends in the flow direction A.

[0111] In the third embodiment, the ultrasonic sensors 11, 22 are therefore designed such that the measurement signals 12, 21 propagate parallel to the flow direction A. The main direction of propagation of the measurement signals 12, 21 therefore forms an angle of 0° or 180° with the flow direction A. As a result, the measurement signals 12, 21 are transmitted such that their main direction of propagation is equal to or exactly opposite to the flow direction A.

[0112] In a third embodiment of the ultrasonic measuring device 1 according to the invention, the first chamber 30 is designed on the side facing the first connector 115 in such a way that, when viewed in the flow direction A, it divides the fluid flow as gently as possible into two partial flows, one of which is guided in a circuitous manner above the first chamber 30 according to the indication and the other of which is guided in a circuitous manner below the first chamber 30 according to the indication. For this purpose, the first chamber 30 has, for example, a triangular cross section when viewed in the flow direction A. With this configuration, the fluid is divided into two substantially equally strong partial flows.

[0113] Preferably, the second chamber 50 is designed on the side facing the second connector 125 so that, when viewed in flow direction A, it rejoins the two partial flows as gradually as possible behind the second chamber 50. To this end, the second chamber 50 has, for example, a triangular cross section when viewed in flow direction A.

[0114] For further details of this embodiment of the ultrasonic measuring device, see EP 3770561 A1.

[0115] The two temperature sensors 61 , 62 and the control device 20 are disposed within the housing 40 , with the first temperature sensor 61 being disposed near the fluid and the second temperature sensor 62 being disposed near the housing 40 .

[0116] Naturally, such an embodiment is also possible and preferred, in which the measuring tube 2 is arranged rotated by 90° about its central axis M relative to the one presented in FIG.

[0117] As already explained, the first temperature sensor 61 is preferably arranged close to the fluid, such that the first temperature T1 depends primarily, but not exclusively, on the temperature of the fluid in the measuring tube 2. The second temperature sensor 62 is preferably arranged significantly further away from the fluid, in the control unit 20, for example on the electronic printing device 25 and / or on the housing wall 401 of the housing 40. The second temperature T2 therefore depends strongly on environmental influences, in this case the temperature at the electronic printing device 25 and / or the housing 40, more precisely the temperature of the housing wall 401, which in turn depends strongly on the ambient temperature, i.e. the temperature of the environment U in which the ultrasonic measuring device 1 is installed.

[0118] In the following, preferred regions for the first distance D1 (FIG. 6) and the second distance D2 (FIG. 7) will be explained with reference to FIGS.

[0119] In the operating state of the ultrasonic measuring device 1, the fluid flowing in the measuring tube 2 is delimited perpendicularly to the flow direction A by a wall W. In some embodiments, this wall W is the wall 101 of the conduit 100 or a wall delimiting the measuring tube 2. In embodiments in which the conduit 100 is inserted into the measuring tube 2 (see, for example, Figures 2 and 4), the fluid-delimiting wall W is the wall 101 of the conduit 100. In embodiments in which the conduit 100 is connected to the ends 110, 120 of the measuring tube 2 (see, for example, Figures 3 and 5), the fluid-delimiting wall W is the wall of the measuring tube 2. The following description applies to both embodiments. The fluid-delimiting wall, which is the wall 101 of the conduit 100 or the wall of the measuring tube 2, is therefore designated with the reference sign W.

[0120] 6 shows three variants for the design of the wall W that delimits the fluid flowing in the measuring tube 2 perpendicular to the flow direction A. The cross-sectional area represented in each case perpendicular to the flow direction A can be predetermined, for example, by the outer shape of the pipe 100 or the measuring tube 2, or it can be pressed in by the ultrasonic measuring device 1, for example, when the pipe is clamped in the ultrasonic measuring device 1 and its cross-sectional area is deformed as a result.

[0121] In the variant on the left side of FIG. 6, the wall W is designed with a ring-shaped profile, in particular a circular ring-shaped profile. In the variant in the middle of FIG. 6, the wall W is designed with a hexagonal profile. In the variant on the right side of FIG. 6, the wall W is designed with a rectangular profile, in particular a square profile, with the corners of the rectangle or square preferably being rounded. It is understood that the profile shown in FIG. 6 is a preferred profile, but is of an exemplary nature. However, other profiles are also possible, for example an n-sided profile, where n is a natural number other than 4 or 6.

[0122] The wall W has a wall thickness WS, which refers to the extent of the wall W in a direction perpendicular to the flow direction A. The first temperature sensor 61, which has a first distance D1 from the central axis M, has a vertical distance DF from the fluid and a vertical distance DW from the wall W. The distance DF of the first temperature sensor 61 from the fluid is therefore the sum DG+WS, i.e., the sum of the distance of the first temperature sensor 61 from the wall W and the wall thickness WS.

[0123] The first temperature sensor 61 is preferably positioned so that its vertical distance DF from the fluid in the measuring tube 2 is greater than or equal to the wall thickness WS and less than or equal to 20 times, preferably less than 10 times the wall thickness WS.

[0124] Particularly preferably, the first temperature sensor 61 is arranged on the wall W such that its distance DW from the wall W is zero. In this case, the distance DF of the first temperature sensor 61 from the fluid is equal to the wall thickness WS.

[0125] If it is not possible or desirable, e.g. due to construction, to position the first temperature sensor 61 directly on the wall W so that the distance DW is greater than zero, it is preferable to connect the first temperature sensor 61 to the wall W via a thermally conductive layer 63, as already explained in connection with Fig. 4. Materials with good thermal conductivity are particularly advantageous for the thermally conductive layer 63, e.g. metallic materials such as aluminum or copper, thermal pads or thermally conductive pastes.

[0126] A preferred arrangement of the second temperature sensor 62 will now be described with reference to Figure 7. Figure 7 shows a schematic cross-sectional view of an embodiment of the housing 40 of the ultrasonic measurement device 1, with a housing wall 401 separating the housing 40 from the environment U. In addition to the housing 40, only the control device 20 with the electronic printing device 25, as well as the second temperature sensor 62 for determining the second temperature T2, are represented in Figure 7, as it is sufficient for understanding.

[0127] The housing wall 401, at least in the area adjacent to the second temperature sensor 62, has a housing wall thickness GS, which refers to the extent of the housing wall 401 between the interior of the housing 40 and the environment U. The second temperature sensor 62 is arranged, for example, on the electronic printing device 25 of the control device 20. The second temperature sensor 62 is arranged at a vertical distance DU from the environment U. The second temperature sensor 62 has a vertical distance DG from the housing wall 401, more precisely from the inside of the housing wall 401. Therefore, the vertical distance DU of the second temperature sensor 62 from the environment U, i.e., the space outside the housing 40, is the sum of DG+GS, i.e., the sum of the distance DG of the second temperature sensor 62 from the inside of the housing wall 401 and the housing wall thickness GS.

[0128] The second temperature sensor 62 is preferably positioned such that its vertical distance DU from the environment U is greater than or equal to the housing wall thickness GS and less than or equal to 20 times, preferably 10 times, the housing wall thickness GS.

[0129] Particularly preferably, the second temperature sensor 62 is arranged in the housing wall 401, more precisely inside the housing wall 401, so that its distance DG from the inside of the housing wall 401 is equal to zero. In this case, the distance DU of the second temperature sensor 62 from the environment U is equal to the housing wall thickness GS.

[0130] If it is not possible or desirable, e.g., due to construction, to arrange the second temperature sensor 62 directly inside the housing wall 401 so that the distance DG is greater than zero, it is preferable to connect the second temperature sensor 62 to the housing wall 401 via a thermally conductive layer 64, as already explained in connection with Fig. 4. Materials with good thermal conductivity are particularly advantageous for the thermally conductive layer 64, e.g., metallic materials such as aluminum or copper, thermal pads, or thermally conductive pastes.

[0131] Another possibility for positioning the second temperature sensor 62 as close as possible to the environment U is to reduce the housing wall thickness GS of the housing wall 401 at the point where the second temperature sensor 62 is positioned. For example, a blind hole into which the second temperature sensor 62 is inserted can be provided in the housing wall 401. It is also possible to reduce the housing wall thickness GS of the housing wall 401 to zero at the point where the second temperature sensor 62 is positioned so that the second temperature sensor 62 is in direct physical contact with the environment U. For example, a perforation extending completely through the housing wall 401 can be provided in the housing wall 401. The second temperature sensor 62 can then be inserted into this perforation. The vertical distance DU of the second temperature sensor 62 from the environment U is then zero. Naturally, since the second temperature sensor 62 does not come into direct physical contact with the fluid in the measuring tube 2 by any means, the temperature measurement of the fluid remains non-invasive.

[0132] Furthermore, the invention proposes a method for determining the temperature of a fluid in an ultrasonic measuring device 1 according to the invention. In this method, a first temperature T1 is determined by a first temperature sensor 61 and a second temperature T2 is determined by a second temperature sensor 62. A correlation function with input and output variables is stored in the control device 20. The input variables of the correlation function include the first temperature T1 and the second temperature T2. The output variable of the correlation function is the temperature of the fluid in the measuring tube 2, denoted TM.

[0133] In the following, an embodiment of the method according to the invention will be described, in particular the determination of a correlation function that is stored in the control unit 20 of the ultrasonic measuring device 1 will be considered.

[0134] In a schematic diagram, FIG. 8 shows an embodiment of a measurement arrangement 300 suitable for determining the correlation function between a first temperature T1, a second temperature T2 and the temperature TM of the fluid in the measuring tube 2 or line 100.

[0135] The measurement arrangement 300 comprises a climate chamber 310 , a tempering device 320 , a pump 330 , a circulation line 340 as well as a number of temperature sensors 351 , 352 , 353 , 354 , 355 , 356 for determining the temperature at different points of the measurement arrangement 300 .

[0136] A predeterminable constant temperature TU may be set in the climate chamber 310 that is monitored by a temperature sensor 352. The temperature TU in the climate chamber simulates the ambient temperature.

[0137] In the temperature regulator 320, the fluid is thermostated to a predetermined temperature TM of the fluid. The predetermined temperature TM to which the fluid is thermostated in the temperature regulator 320 can be monitored by a temperature sensor 351.

[0138] In the climatic chamber 310, several ultrasonic measuring devices 1 designed according to the present invention, in this case three ultrasonic measuring devices 1, are arranged in a row one behind the other. All three ultrasonic measuring devices 1 are designed in the same way. In principle, a single ultrasonic measuring device 1 would be sufficient in the climatic chamber 310, but using several identical ultrasonic measuring devices 1 can improve the accuracy of the determined correlation function, for example, because the tolerances of the components of the ultrasonic measuring device 1 are averaged out. All ultrasonic measuring devices 1 are arranged in a row one behind the other in the climatic chamber 310. In each of the ultrasonic measuring devices 1, a first temperature sensor 61 for detecting a first temperature T1 and a second temperature sensor 62 for detecting a temperature T2 are arranged in each case. The temperature sensors 61, 62 are not shown in FIG. 8.

[0139] Furthermore, several temperature sensors 353, 354, 355, 356 are arranged in the climatic chamber 310 in the circulation line 340 in order to monitor the temperature of the fluid in the circulation line 340. Preferably, one temperature sensor 353, 354, 355 is arranged in each case upstream of each ultrasonic measuring device 1 in the climatic chamber 310 when viewed in the flow direction A, and one temperature sensor 356 is arranged downstream of the last ultrasonic measuring device 1.

[0140] The temperature regulator 320 , pump 330 and climate chamber 310 are connected by a circulation line 340 to form a flow circuit through which fluid is circulated by the pump 330 .

[0141] The fluid is thermostated in the temperature control device 320 to a predeterminable temperature TM and circulated by the pump 330 through the circulation line 340 and the climate chamber 310 back to the temperature control device 320. In the climate chamber 310, the fluid flows sequentially through three ultrasonic measuring devices 1, and a first temperature T1 and a second temperature T2 are determined in each case by temperature sensors 61, 62 (not shown) in each of the ultrasonic measuring devices 1. As shown in Fig. 8, if several ultrasonic measuring devices 1 are arranged in the climate chamber 310, the average value of the first temperature T1 measured by the various first temperature sensors 61 or the second temperature T2 measured by the various second temperature sensors 62 is used in each case for the individual measurement of the first temperature T1 or the second temperature T2, respectively.

[0142] For each individual measurement, the temperature TM of the fluid is set by a temperature regulation unit, while a temperature TU simulating the ambient temperature is set in the climate chamber 310. The temperature sensors 351 to 356 mainly serve to monitor the exact conditions during the measurement.

[0143] Since the thermal influence of the fluid on the ultrasonic measuring device 1 cannot and should not be underestimated, the fluid is preferably circulated at a volume or volumetric flow rate that ensures a significant degree of interaction between the fluid and the ultrasonic measuring device 1. In practice, a minimum volumetric flow rate of 100 ml / min has been shown to be sufficient. Naturally, the advantageous volumetric flow rate varies depending on the design and, in particular, the size of the ultrasonic measuring device 1. Depending on the specific design or size of the ultrasonic measuring device 1, the volumetric flow rate of the fluid is preferably in the range of 500 ml / min to 5000 ml / min. It has been determined that the volumetric flow rate of the fluid does not need to be varied for reliable determination of the correlation function. In particular, when the volumetric flow rate of the fluid is at least as high as the preferred minimum value of 100 ml / min, a constant, stable, and almost flow-rate-independent heat exchange is achieved between the ultrasonic measuring device 1 and the fluid.

[0144] In order to determine the correlation function between the first temperature T1, the second temperature T2 and the temperature TM of the fluid in the measuring tube 2 or conduit 100, different measurements are now carried out, which are carried out at different temperatures TM of the fluid and at different temperatures TU in the climate chamber 310 simulating different ambient temperatures, whereby the variation of the temperature TM of the fluid is carried out by the temperature adjustment device 320 and the variation of the temperature TU is carried out by the climate chamber 310.

[0145] In principle, the two temperatures TM and TU can be varied as desired. However, it is advantageous if the temperatures TM and TU encompass the range in which the ultrasonic measuring device 1 will later operate in operation. For example, if the fluid is water or a water-like liquid, it is preferable to vary the temperature TM of the fluid between approximately 2°C and 90°C. If the medium of the environment U is air, it is preferable to vary the temperature TU in the range of 5°C and 60°C.

[0146] After the temperature TM of the fluid or the temperature TU in the climate chamber 310 is set to a new value after each measurement, wait a sufficient time before the next individual measurement until the entire system of the measurement device 300 has settled and thermally stabilized.

[0147] A plurality of isotherms I1, I2, I3, and I4 are determined here by a plurality of individual measurements. As an example, FIG. 9 shows a plurality of four isotherms I1, I2, I3, and I4. In FIG. 9, the second temperature T2 determined by the measurements is measured by the second temperature sensor 62 of the ultrasonic measuring device 1 and is plotted on the horizontal axis. As already mentioned, each measured value of T2 is the average value of three values of T2 measured by different ultrasonic measuring devices 1. The first temperature T1 determined by the measurements is measured by the first temperature sensor 61 of the ultrasonic measuring device 1 and is plotted on the vertical axis. As already mentioned, each measured value of T1 is the average value of three values of T1 measured by different ultrasonic measuring devices 1. In FIG. 9, the black dots on the isotherms I1 to I4 indicate the values of T1 and T2 determined by the measurements.

[0148] On each isotherm I1 to I4, the temperature TM of the fluid is constant in each case, and four different points are assigned to different values of TU. This means that an isotherm I1 or I2 or I3 or I4 is determined by keeping the temperature TM of the fluid at a constant value and setting the temperature TU in the climate chamber 310 to different values, in this case four different values. Each isotherm I1 to I4 therefore shows the dependence of the first temperature T1 on the second temperature T2 when the temperature TM of the fluid is kept constant and the temperature TU is changed.

[0149] For example, isotherm I1 is assigned to a constant temperature TM of 10°C, isotherm I2 is assigned to a constant temperature TM of 20°C, isotherm I3 is assigned to a constant temperature TM of 30°C, and isotherm I4 is assigned to a constant temperature TM of 40°C.

[0150] The four measurement points on each of the isotherms I1 to I4 correspond to values of, for example, 10°C, 20°C, 30°C, and 40°C for the temperature TU from left to right in FIG.

[0151] Of course, these numbers should be understood as examples only and serve to explain how the desired correlation function is determined.

[0152] For a constant temperature TM of the fluid, all measurement points lie on a straight line in each case, i.e., each isotherm I1 to I4 has the form of a straight line. T1=a·T2+bt where a is the slope of the line and bt is the axis intercept where each line intersects the vertical axis.

[0153] It can be seen that for every temperature TM of the fluid, the associated isotherms I1, I2, I3, I4 each have the same slope a, i.e., all isotherms I1-I4 are parallel. This can also be seen in FIG. 9. The various isotherms I1-I4 therefore differ only in their axis intercepts bt, which depend on the temperature TM to which each isotherm I1-I4 belongs. The slope a of each isotherm I1-I4 is therefore a constant that depends on the respective ultrasonic measurement device 1. This constant must be determined anew for each embodiment of the ultrasonic measurement device 1, but is always the same for ultrasonic measurement devices 1 of the same design.

[0154] Once the individual isotherms I1-I4 have been determined, preferably so as to cover the entire desired operating range of the ultrasonic measurement device 1, the axis intercepts bt of the isotherms I1-I4 are determined. This is illustrated in FIG. 10. An associated axis intercept bt is determined for each isotherm I1-I4. The various axis intercepts are designated b1, b2, b3, and b4, where b1 is the axis intercept for isotherm I1 and is therefore assigned to the fluid temperature TM for which isotherm I1 was determined. Similarly, b2 is assigned to isotherm I2, b3 is assigned to isotherm I3, and b4 is assigned to isotherm I4.

[0155] Here, the correlation function between the fluid temperature TM and the axis intercept bt is determined. In Figures 11 and 12, the axis intercept bt of the isotherms I1 to I4 is plotted on the horizontal axis in each case, and the fluid temperature TM to which each axis intercept bt belongs is plotted on the vertical axis. These are the four sets of values represented as black dots in Figures 11 and 12.

[0156] From these sets of values TM, bt a decision function is now determined, which represents the temperature TM of the fluid in dependence on the axis intercept bt. The decision function therefore has exactly one variable, namely the axis intercept bt of the isotherm.

[0157] In practice, it has been found that a decision function that is at most a second order polynomial is sufficient for many applications. Of course, it is also possible to use an nth order polynomial, with n greater than 2 in the decision function.

[0158] In FIG. 11, the decision function is a straight line G, that is, a first-order polynomial, and the straight line G is expressed by the following function: TM=E·bt+F is expressed by

[0159] In FIG. 12, the decision function is a quadratic function P, i.e., a polynomial of second order, which is expressed by the following function: TM=E·bt 2 +F·bt+H is expressed by

[0160] The coefficients E, F and possibly H can be determined by approximation methods known per se.

[0161] Like the slope a, the coefficients E, F and H are model constants that depend on the respective ultrasonic measuring device 1. The coefficients E, F and possibly H must be determined anew for each embodiment of the ultrasonic measuring device 1, but are always the same for ultrasonic measuring devices 1 of the same construction.

[0162] By using the coefficients E, F and possibly H, and the slope a, the correlation function is now known with the first temperature T1 and the second temperature T2 as input variables and the temperature TM of the fluid in the measuring tube as output variable.

[0163] If the first temperature T1 and the second temperature T2 are determined in the operating state of the ultrasonic measuring device by the two temperature sensors 61, 62, the axis intercept bt is first calculated by the equation of the isotherm bt=T1-a T2 It can be calculated by:

[0164] Then, the temperature TM of the fluid in the measuring tube 2 is calculated by the linear decision function TM=E·bt+F By or quadratic decision function TM=E·bt 2 +F·bt+H can be determined with high accuracy by

[0165] Therefore, in the operating state of the ultrasonic measuring device 1, the temperature TM of the fluid in the measuring tube can be determined very precisely from the temperatures determined by the measurements, i.e. the first temperature T1 and the second temperature T2. In the process, this reliable temperature determination is non-invasive, i.e. neither the temperature sensors 61, 62 are in direct physical contact with the measuring tube 2 or the fluid flowing through the conduit 100.

[0166] Possibly, the input variables of the correlation function, i.e. the first temperature T1 and the second temperature T2, can be subjected to corrections. Since various components, such as the temperature sensors 61, 62 designed as thermocouples or infrared sensors or components for current or voltage measurement designed as integrated circuits, can be affected by component tolerances, it can be advantageous to adjust for the tolerances of such components.

[0167] This adjustment is preferably performed by allowing offset values T1off and T2off for the temperatures T1 and T2 to be constant for a particular ultrasonic measuring device 1, thereby adjusting the isotherm equation bt=T1-a T2 is carried out based on

[0168] The equation of the isotherm is therefore: bt=(T1-T1off)-a·(T2-T2off) is.

[0169] In this way, component tolerances in the temperature sensors 61, 62 can be specifically adjusted.

[0170] It is understood that such embodiments of the method according to the invention are also possible in which the correlation function, whose output variable is the temperature TM of the fluid in the measuring tube 2, has, in addition to the first temperature T1 and the second temperature T2, further input variables, for example additional temperatures, for example the temperature of the environment, or electrical operating variables or other operating parameters.

Claims

1. 1. An ultrasonic measuring device for determining the flow rate of a fluid flowing in a pipeline (100), comprising a measuring tube (2) with a central axis (M) defining a flow direction (A) of the fluid, at least two ultrasonic transducers (11, 22) arranged and aligned so as to be able to exchange measurement signals (12, 21) with each other, a control unit (20) for controlling the ultrasonic transducers (11, 22) and for evaluating the measurement signals (12, 21), characterized in that the ultrasonic device comprises a first temperature sensor (61) for determining a first temperature (T1) arranged in such a way that it is inaccessible to the fluid, and a second temperature sensor (62) for determining a second temperature (T2) arranged in such a way that it is inaccessible to the fluid.

2. 2. The ultrasonic measuring device of claim 1, wherein the first temperature sensor (61) has a first distance (D1) perpendicular to the central axis (M), the second temperature sensor (62) has a second distance (D2) perpendicular to the central axis (M), and the second distance (D2) is greater than or equal to the first distance (D1).

3. 3. The ultrasonic measuring device according to claim 1, wherein the first temperature sensor (61) is arranged in the measuring tube (2).

4. 4. The ultrasonic measuring device according to claim 1, wherein the control unit (20) comprises an electronic printing device (25), and the second temperature sensor (62) is arranged in the electronic printing device (25).

5. 5. The ultrasonic measuring device according to claim 1, wherein in an operating state, the fluid flowing in the measuring tube (2) is bounded perpendicular to the flow direction (A) by a wall (W) having a wall thickness (WS), and the first temperature sensor (61) has a vertical distance (DF) from the fluid in the measuring tube (2) that is equal to or greater than the wall thickness (WS) and is 20 times, preferably 10 times, the wall thickness (WS), or the first temperature sensor (61) is connected to the wall (W) via a heat-conducting layer (63).

6. 6. The ultrasonic measuring device according to claim 1, further comprising a housing (40) in which the measuring tube (2) and the control unit (20) are arranged, and the second temperature sensor (62) is arranged in the housing (40) or the control unit (20).

7. 7. The ultrasonic measuring device of claim 6, wherein the housing (40) is separated from the environment (U) by a housing wall (401), the housing wall (401) has a housing wall thickness (GS), and the second temperature sensor (62) is arranged at a vertical distance (DU) from the environment (U) that is equal to or greater than the housing wall thickness (GS) and is 20 times, preferably 10 times, the housing wall thickness (GS), or the second temperature sensor is connected to the housing wall (401) via a thermally conductive layer (64).

8. 8. The ultrasonic measuring device according to claim 1, wherein the measuring tube (2) is designed to receive the conduit (100) such that the conduit (100) is surrounded by the measuring tube (2).

9. 9. The ultrasonic measuring device according to claim 8, which is designed as a clamping device for a clamp connection with the line (100), so that the line (100) can be clamped in the measuring tube (2).

10. 8. The ultrasonic measuring device according to claim 1, wherein the measuring tube (2) extends in the flow direction (A) from a first end (110) to a second end (120), and the measuring tube (2) has at its first end (110) a first connector (115) designed for connection to the pipeline (100) and at its second end (120) a second connector (125) designed for connection to the pipeline (100).

11. 11. A method for determining the temperature of a fluid in an ultrasonic measuring device designed according to any one of claims 1 to 10, characterized in that a first temperature (T1) is determined by a first temperature sensor (61) and a second temperature (T2) is determined by a second temperature sensor (62), and a correlation function with input and output variables is stored in a control device, the input variables comprising the first temperature (T1) and the second temperature (T2), and the output variable is the temperature (TM) of the fluid in the measuring tube (2).

12. 12. The method of claim 11, wherein the correlation function is based on a plurality of isotherms (I1, I2, I3, I4), each of the isotherms being a linear equation having a slope (a) and an axis intercept (bt), the equation expressing the first temperature (T1) as a function of the second temperature (T2) for a constant temperature (T) of the fluid in the measuring tube (2).

13. 13. The method according to claim 12, wherein the temperature (TM) of the fluid in the measuring tube (2) is determined using a determination function having exactly one variable, said variable being the axis intercept (bt) of the isotherm (I1, I2, I3, I4).

14. The method of claim 13 , wherein the decision function is a polynomial of at most second degree.

15. 15. The method according to any one of claims 12 to 14, wherein specific offset values (T1off, T2off) for the input variables are determined for the ultrasonic measuring device based on the isotherms (I1, I2, I3, I4).

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