Non-invasive temperature measuring method with thermal conductivity compensation

Abstract

The invention relates to a method (100) for non-invasively detecting a temperature (25) of a fluid (15) and comprises a first step (110) in which a first temperature measurement value (22) is detected. In a second step (120), a second temperature measurement value (24) on a surface (26) of a thermal coupling element (30) is detected. This is followed by a third step (130), in which a correction value (42) is determined on the basis of the first and / or second temperature measurement value (22, 24). The method (100) also comprises a fourth step (140), in which the temperature (25) of the fluid (15) is determined on the basis of the first temperature measurement value (22), the second temperature measurement value (24) and the correction factor (42) and output. According to the invention, the correction factor (42) is determined on the basis of a temperature-dependent thermal conductivity value (43) for a material of the thermal coupling element (30). The invention also relates to a corresponding computer program product (50), to a corresponding evaluation unit (40), to a corresponding non-invasive temperature measuring device (10), to a temperature measuring arrangement (60) and to a correspondingly equipped automation system (80).

Description

[0001] 202409558 Foreign version

[0002] 1

[0003] Description

[0004] Non-invasive temperature measurement method with thermal conductivity compensation

[0005] The invention relates to a method for non-invasively detecting the temperature of a fluid and a computer program product designed for this purpose. The invention also relates to a corresponding evaluation unit and a non-invasive temperature measuring device with such an evaluation unit. Furthermore, the invention relates to a temperature measuring arrangement with such a non-invasive temperature measuring device and a correspondingly equipped automation system.

[0006] International patent application WO 2023 / 066541 A1 discloses a temperature measuring device comprising a first and a second temperature sensor integrated into a thermal coupling element. The thermal coupling element is essentially S-shaped and configured to axially reverse a heat conduction path.

[0007] Patent DE 10 2022 200 354 B3 discloses a self-monitoring sensor designed as a non-invasive temperature measuring device. The self-monitoring sensor comprises sensor elements designed as temperature sensors and integrated into a thermal coupling element.

[0008] From US 2022 / 260432 A1, a non-invasive temperature measuring device is known, comprising a first and a second sensor arranged in thermal contact with a pipe wall. When calculating a fluid temperature, the thermal conductivity of the pipe wall material is taken into account, among other factors. The thermal conductivity is assumed to be a constant.

[0009] Non-invasive temperature measurements are used in a variety of applications, such as automation systems in the process industry. The goal is to achieve precise and rapid temperature measurement of liquids and gases in pipes and containers. Simultaneously, the objective is to manufacture suitable devices cost-effectively. Therefore, there is a need for a precise, robust, and cost-effective method for non-invasive temperature measurement. The invention aims to provide a solution that offers an improvement in at least one of the outlined aspects. 202409558 Foreign version

[0010] 2

[0011] The problem is solved by a method according to the invention for the non-invasive detection of the temperature of a fluid. The fluid is contained in a pipe or a container, for example, a tank. In a first step of the method, a first temperature measurement is taken at a wall of the pipe or container. This first temperature measurement can be taken by means of a first temperature sensor, which is part of a corresponding temperature measuring device. The first temperature measurement can essentially correspond to the temperature of the wall itself.

[0012] The process also includes a second step in which a second temperature measurement is taken at the surface of a heat coupling element. The heat coupling element is thermally coupled, either directly or indirectly, to the pipe or container, i.e., its wall. The second temperature measurement can be taken with a second temperature sensor, which is also part of the corresponding temperature measuring device. This second temperature sensor can be positioned on the surface of the heat coupling element.

[0013] A third step in the inventive method follows, in which a correction factor is determined based on the first and / or second temperature measurement. The correction factor is suitable for use as a coefficient in a temperature equation that defines a relationship between the fluid temperature to be determined and the first and second temperature measurements. The correction factor can preferably be a mathematical factor.

[0014] The method also includes a fourth step in which the fluid temperature is determined based on the first temperature measurement, the second temperature measurement, and the correction factor, which are determined or recorded in the first, second, and third steps, respectively. For this purpose, the first temperature measurement, the second temperature measurement, and the correction factor can be inserted into the temperature equation. Furthermore, in the fourth step, the determined fluid temperature is output to a user and / or a data interface. The fluid temperature can, for example, be displayed to the user by means of a display device that is directly or indirectly connected to the temperature measuring device with which the method according to the invention is carried out.The data interface can be configured to establish a connection to a computer program that controls an underlying process, for example, in an automation system. 202409558 Foreign version.

[0015] 3

[0016] In the method according to the invention, the correction factor is determined in the third step based on a temperature-dependent thermal conductivity value for a material of the heat coupling element. The correction factor can be determined, in particular, based on a temperature-dependent thermal conductivity value for each material that influences the thermal conductivity of the heat coupling element from the wall of the pipe or container to the surface where the second temperature measurement is taken. The steps outlined above can be carried out, at least partially, by an evaluation unit that is directly or indirectly connected to a suitably designed temperature measuring device.

[0017] The method according to the invention is suitable for dynamically determining the correction factor as a function of the temperature range in which the fluid temperature is currently located. Accordingly, the correction factor can be automatically adjusted, at least within arbitrarily narrow temperature intervals. This allows a temperature measuring device to be precisely calibrated for a wide temperature range. In particular, measurement inaccuracies can be reduced at the upper and / or lower end of a temperature measuring range. The claimed method is based, among other things, on the finding that thermal conductivity values, and thus the correction factors derived therefrom, are temperature-dependent. A further finding is that the thermal conductivity values, and thus the correction factors, are only temperature-sensitive to such an extent that the claimed method is computationally stable.A spiraling effect leading to significantly deviating measured fluid temperatures does not occur. Due to its computational stability, the method according to the invention is both robust and reliable. This allows for a greater utilization of the technical potential theoretically provided by the first and second temperature sensors.

[0018] In one embodiment of the claimed method, the correction factor comprises at least one geometry factor that at least partially models the thermal behavior of the heat coupling element. The correction factor itself can therefore be calculated based on at least one other factor. For example, the geometry factor characterizes the thermal conductivity within the heat coupling element from the point of thermal contact between the wall and the surface where the second temperature measurement is taken. The geometry factor can, in particular, be an empirical value determined by the shape, i.e., the geometry, of the heat coupling element. Such a geometry factor can be precisely and reliably determined through testing.Alternatively or additionally, the geometry factor can also be designed as a geometry function, which also characterizes a time-related coupling between the first and second temperature measurements. In the claimed method, the geometry is thus 202409558 Foreign version.

[0019] 4. The influencing factor for determining the fluid temperature can be considered separately. Consequently, a precise measurement of the fluid temperature can be achieved in a simple manner using the claimed method.

[0020] Furthermore, in the claimed method, the temperature-dependent thermal conductivity value can be determined using a formula, a characteristic curve, a table, and / or an algorithm. For a large number of materials, there is a simple relationship between the ambient temperature and the resulting temperature-dependent thermal conductivity value. Determining the value based on a formula, a characteristic curve, or a table allows for a computationally simple calculation of the temperature-dependent thermal conductivity value. In particular, with a table, the temperature-dependent thermal conductivity value can also be derived by interpolation. An algorithm, in turn, allows the determination of the temperature-dependent thermal conductivity value even for materials with a complex profile.

[0021] Furthermore, the temperature-dependent thermal conductivity value can be determined as a function of an arithmetic or geometric mean of the first and second temperature measurements. This essentially allows for the rapid determination of the effective thermal conductivity value for the thermal coupling element. The greater the difference between the first and second temperature measurements, the greater the variation in thermal conductivity within the thermal coupling element. The claimed method thus makes it possible to easily and with sufficient precision account for the temperature distribution within the thermal coupling element and the resulting distribution of its thermal conductivity. This eliminates the need for a detailed simulation of the thermal behavior of the thermal coupling element.

[0022] In a further embodiment of the claimed method, the first temperature measurement can lie between -120°C and +600°C, preferably between -50°C and +250°C, and particularly preferably between -30°C and +150°C. The claimed method is suitable for precisely covering a wide temperature range with a suitable temperature measuring device. Overall, the claimed method achieves increased measurement accuracy over a wide temperature range without modification of the temperature measuring device used. 202409558 Foreign version

[0023] 5

[0024] Furthermore, in the claimed method, the correction value can also be determined based on a temperature-dependent thermal conductivity value of a wall material. Alternatively or additionally, the correction factor can also be determined based on a heat transfer coefficient that describes contact-based heat transfer from the wall to the heat coupling element. Accordingly, the thermal connection of the heat coupling element to the wall can also be taken into account in the claimed method. Particularly with pipes, a standardized system is often available, so that corresponding data for a large number of pipes can be provided in a database. This makes it possible, for example, to characterize the rate at which a change in the actual fluid temperature present in the pipe or container affects the fluid temperature determined by the method according to the invention.The slower the change in the actual fluid temperature affects the measured fluid temperature, the lower the frequency at which the claimed method can be performed. This avoids excessively energy-intensive operation of a corresponding temperature measuring device. Consequently, the claimed method is particularly suitable for battery-operated temperature measuring devices.

[0025] In the claimed method, the thermal coupling element can, for example, be at least partially made of stainless steel, carbon steel, or Cr-Ni steel, particularly austenitic Cr-Ni steel. Alternatively, the thermal coupling element can also be made of a combination of the aforementioned materials. Stainless steels, carbon steels, and Cr-Ni steels, particularly austenitic Cr-Ni steels, exhibit a precisely defined relationship between the temperature and their thermal conductivity. Furthermore, for these materials, the proportionality between the temperature and the corresponding thermal conductivity is low over a wide temperature range.Consequently, a simplified determination of the thermal conductivity value of the heat coupling element based on the first and / or second temperature measurement is also possible, without resulting in excessively large deviations between reality and the model underlying the method. This further increases the computational stability of the claimed method and, as a result, its robustness.

[0026] Furthermore, the first and / or second temperature reading in the claimed method can be measured using a resistance thermometer or a thermocouple. Resistance thermometers and thermocouples allow for reliable and precise temperature measurement. In particular, the first 202409558 Foreign version

[0027] The first and / or second temperature readings can be measured by contact. Accordingly, the resistance thermometer or thermocouple can be in thermal contact with the wall of the pipe or container, or with the surface of the heat-coupling element, to measure the first or second temperature reading. Furthermore, resistance thermometers and thermocouples respond sufficiently quickly to temperature changes and allow for a predefined sampling rate, i.e., a frequency, at which measurement signals for temperature readings can be generated. Therefore, the claimed method can be implemented advantageously overall.

[0028] The underlying problem is solved by a computer program product according to the invention, which is designed to operate a non-invasive temperature measuring device. The computer program product can be stored in retentive memory and comprise program code that is executable by a processor. The computer program product is designed to receive and process at least a first and a second temperature measurement. According to the invention, the computer program product is designed to execute a method according to one of the embodiments outlined above. For this purpose, the program code can be designed to perform corresponding method steps during execution. The claimed method can advantageously be carried out using the computer program product according to the invention. The computer program product can be monolithic, i.e., executable on a single hardware platform.Alternatively, the computer program product can be modular and comprise a plurality of subprograms that can be executed on separate hardware platforms. The subprograms can be configured to interact via a communicative data connection to provide the functionality of the claimed computer program product. The features of the claimed method and the resulting technical advantages are readily transferable to the claimed computer program product.

[0029] In one embodiment of the claimed computer program product, it may comprise a digital twin of a temperature measuring device, in particular a non-invasive temperature measuring device, on which the underlying method is carried out. The digital twin may be configured according to US 2017 / 0286572 A1. The disclosure content of US 2017 / 0286572 A1 is incorporated by reference into the present application. 202409558 Foreign version

[0030] 7

[0031] The problem set out above is solved by an evaluation unit according to the invention for a non-invasive temperature measuring device. The evaluation unit comprises a memory, in particular a retentive memory, and a processor. The memory and the processor are configured to execute a computer program for operating the non-invasive temperature measuring device to which the evaluation unit belongs. The computer program, which is stored in an executable form on the evaluation unit, is configured according to one of the embodiments described above. The features of the claimed computer program and the resulting technical advantages are readily transferable to the claimed evaluation unit.

[0032] Furthermore, the problem outlined above is solved by a non-invasive temperature measuring device according to the invention, which comprises a first temperature sensor, a second temperature sensor, a thermal coupling element, and an evaluation unit. The non-invasive temperature measuring device is designed to be attached to the wall of a pipe or to a container. The non-invasive temperature measuring device is further designed to measure the temperature of a fluid in the pipe or container non-invasively. According to the invention, the evaluation unit of the non-invasive temperature measuring device is configured according to one of the embodiments described above. The features of the underlying evaluation unit and the associated advantages are transferable to the claimed non-invasive temperature measuring device.

[0033] The problem set out at the outset is also solved by a temperature measuring arrangement according to the invention and a correspondingly equipped automation system. The temperature measuring arrangement comprises a pipe or container having a wall. Furthermore, the temperature measuring arrangement according to the invention includes a non-invasive temperature measuring device that is attached to the wall of the pipe or container. According to the invention, the temperature measuring device is configured according to one of the embodiments sketched above. The automation system according to the invention comprises a control unit and a plurality of field devices connected to the control unit. The automation system can, for example, be configured as a chemical plant, a petrochemical plant, a manufacturing plant, or a power plant. According to the invention, the automation system has a temperature measuring arrangement configured according to one of the embodiments described above.The features of the underlying non-invasive temperature measuring device are readily transferable to the claimed temperature measuring arrangement. Furthermore, the features of the claimed temperature measuring arrangement are transferable to the claimed automation system. 202409558 Foreign version.

[0034] 8

[0035] The invention is explained in more detail below with reference to individual embodiments shown in the figures. The figures are to be read as complementary to one another, such that identical reference numerals in different figures have the same technical meaning. The features of the individual embodiments can also be combined with one another. Furthermore, the features of the embodiments shown in the figures can be combined with the features outlined above. Specifically, the figures show:

[0036] FIG 1 shows a schematic setup of an embodiment of the claimed temperature measuring arrangement, on which an embodiment of the claimed method is carried out;

[0037] FIG 2 shows a flowchart of an embodiment of the claimed method.

[0038] FIG. 1 schematically shows an embodiment of the claimed temperature measuring arrangement 60, which is connected to an automation system 80 and comprises an embodiment of the claimed non-invasive temperature measuring device 10. The temperature measuring arrangement 60 includes a tube 21 or a container 23, on the wall 20 of which the non-invasive temperature measuring device 10 is attached. A fluid 15, having a temperature 25, is contained in the tube 21 or container 23. The fluid 15 can be stationary or flowing. The non-invasive temperature measuring device 10 comprises a first and a second temperature sensor 12, 14, which are coupled to an evaluation unit 40. The first temperature sensor 12 is in substantially direct thermal contact with the surface 26 of the wall 20. For this purpose, an end of the first temperature sensor 12 facing the wall 20 can be in contact with the wall 20.Alternatively, a housing or encapsulation of the non-invasive temperature measuring device 10 (not shown in detail in FIG. 1) can be designed as a thermal window in the area of ​​the first temperature sensor 12, thus offering a substantially negligible thermal resistance. For this purpose, the housing or encapsulation in the area of ​​the first sensor 12 can, for example, be thin-walled. The first temperature sensor 12 is designed to detect a first temperature measurement 22 on the surface 26 of the wall 20, which can be transmitted to the evaluation unit 40.

[0039] The second temperature sensor 14 is connected to a thermal coupling element 30, which is also in thermal contact with the wall 20. The thermal coupling element 30 has a thermal resistance that is determined by the material of the thermal coupling element 30 and its geometry. The material of the thermal coupling element 30 has 202409558 Foreign version

[0040] 9 exhibits a temperature-dependent thermal conductivity value 43. The temperature-dependent thermal conductivity value 43 is illustrated by a diagram in FIG. 2. Due to the thermal resistance provided by the thermal coupling element 30, a heat flow 35 is established from the wall 20 to the second temperature sensor 14, which results from a temperature difference to the wall 20. The second temperature sensor 14 is in thermal contact with a surface 32 of the thermal coupling element 30, located on a region of the thermal coupling element 30 facing away from the wall 20. The second temperature sensor 14 is configured to generate a second temperature measurement 24 and transmit it to the evaluation unit 40.

[0041] In the intended operation of the non-invasive temperature measuring device 10, a method 100 for detecting the temperature 25 of the fluid 15 in the pipe 21 or in the container 23 can be carried out. The method 100 comprises a first step 110 in which the first temperature measurement 22 is detected by the first temperature sensor 12 on the surface 26 of the wall 20. The method 100 also comprises a second step 120 in which the second temperature measurement 24 is detected on the surface 32 of the heat coupling element 30, with which the second temperature sensor 14 is in direct or indirect thermal contact. The first and second steps 110 and 120 can be carried out sequentially or at least partially simultaneously.

[0042] The first and / or second temperature measurements 22, 24 are further processed in a third step 130 of the procedure 100. A correction factor 42 is determined based on the first and / or second temperature measurements 22, 24. The correction factor 42 is determined, at least partially, based on the temperature-dependent thermal conductivity value 43 of the heat coupling element 30. For example, the first and / or second temperature sensor 12, 14 is used to estimate, i.e., determine, the expected temperature range 25 of the fluid 15, and thus also the expected temperature range of the heat coupling element. For example, an arithmetic mean or a geometric mean can be calculated between the first and second temperature measurements 22, 24, and the temperature-dependent thermal conductivity 43 of the heat coupling element 30 can be determined based on such a mean.The first temperature measurement 22 lies between -120°C and +800°C, preferably between -50°C and +250°C, and particularly preferably between -30°C and +150°C. Furthermore, in the third step 130, a geometry factor 46 of the heat coupling element 30 is used to determine the correction factor 42. The geometry factor 46 can, for example, be a fixed value, a table of values, or a foreign version.

[0043] 10

[0044] The algorithm or function may be stored. The geometry factor 46 can be temperature-independent and merely describe thermal behavior at the surface 32 with which the second temperature sensor 14 is in thermal contact.

[0045] Method 100 further comprises a fourth step 140 in which the temperature 25 of the fluid 15 is determined based on the first temperature measurement 22, the second temperature measurement 24, and the correction factor 42. The determined temperature 25 of the fluid 15 is output as a fluid temperature measurement 55 in the fourth step 140 to a data interface 44 and / or to a user via a display device 45. For the execution of method 100, the evaluation unit 40 is equipped with a computer program 50 that can be executed from the evaluation unit 40. The evaluation unit 40 has suitable retentive memory and a suitable processor for this purpose.

[0046] The non-invasive temperature measuring device 10, and thus the temperature measuring arrangement 60, is coupled to a control unit 65 of the automation system 80 via the data interface 44. The control unit 65 is configured to use the received fluid temperature measurement 55 to control an underlying production process. For this purpose, the control unit 65 is coupled to a plurality of field devices 66 via a communication system 67, for example, a fieldbus system. From the perspective of the control unit 65, the non-invasive temperature measuring device 10 also represents a field device. Furthermore, a simulation program product is stored in an executable form on the control unit 65, which includes a digital twin 70 of the non-invasive temperature measuring device 10 or the temperature measuring arrangement 60. The simulation program product, i.e., the digital twin 70, is configured to simulate the operating behavior of the non-invasive temperature measuring device 10 or the temperature measuring arrangement 60.to replicate the temperature measurement arrangement 60.

[0047] An embodiment of the claimed method 100 is shown as a flowchart in FIG. 2. The method 100 begins with a first step 110 in which a first temperature measurement 22 is acquired in a non-invasive temperature measuring device 10 with a first temperature sensor 12. The first temperature measurement 22 corresponds essentially to a temperature on a wall 20 of a pipe 21 or container 23 to which the non-invasive temperature measuring device 10 is attached. Essentially simultaneously, a second step 120 is carried out with the non-invasive temperature measuring device 10 in which a second temperature measurement 24 is determined. The second temperature measurement 24 corresponds essentially to a temperature on a surface 32 of a heat coupling element 30.

[0048] 11, which is in thermal contact with the wall 20. The first and second temperature measurements 22, 24 are used in a third step 130 to determine a correction factor 42. For this purpose, the temperature-dependent thermal conductivity value 43 of the heat coupling element 30 is determined in the third step 130. Based on this, at least, the correction factor 42 is determined. Furthermore, in a fourth step 140, a fluid temperature measurement 55 is determined based on the first temperature measurement 22, the second temperature measurement 24, and the correction factor 42, which corresponds to the temperature 25 of the fluid 15. The determined fluid temperature measurement 55 is output in the fourth step 140 to a data interface 44 and / or to a user via a display device 45. After the fourth step 140, a feedback loop 150 of the process 100 is performed, so that the first and second steps 110,

[0049] The process 120 is initiated again. The procedure 100 according to FIG. 2 thus runs cyclically and essentially represents the operation of the non-invasive temperature measuring device 10.

Claims

202409558 Foreign version 12 Patent claims 1. Method (100) for non-invasively detecting the temperature (25) of a fluid (15) contained in a tube (21) or a container (23) using a non-invasive temperature measuring device (10) comprising a first and a second temperature sensor (12, 14), comprising the steps of: a) detecting a first temperature reading (22) on a wall (20) of the tube (21) or container (23) using the first temperature sensor (12); b) detecting a second temperature reading (24) on a surface (26) of a heat coupling element (30) connected to the wall (20) of the tube (21) or container (23).a) the container (23) is thermally coupled indirectly or directly to the second temperature sensor (14); c) determining a correction factor (42) based on the first and / or second temperature measurement (22, 24); d) determining the temperature (25) of the fluid (15) based on the first temperature measurement (22), the second temperature measurement (24) and the correction factor (42) and outputting the determined temperature (25) of the fluid (15) to a user and / or a data interface (44); characterized in that the correction factor (42) is determined based on a temperature-dependent thermal conductivity value (43) for a material of the thermal coupling element (30).

2. Method (100) according to claim 1 , characterized in that the correction factor (42) comprises at least one geometry factor (46) by which a thermal behavior of the heat coupling element (30) is at least partially represented.

3. Method (100) according to claim 1 or 2, characterized in that the temperature-dependent thermal conductivity value (43) is determined using a formula, a characteristic curve, a table and / or an algorithm.

4. Method (100) according to one of claims 1 to 3, characterized in that the temperature-dependent thermal conductivity value (43) is determined as a function of an arithmetic mean or a geometric mean of the first and second temperature measurement values ​​(22, 24). 202409558 Foreign version 13 5. Method (100) according to one of claims 1 to 4, characterized in that the first temperature measurement (22) is between -120°C and +600°C, preferably between -50°C and +250°C, particularly preferably between -30°C and +150°C.

6. Method (100) according to one of steps 1 to 5, characterized in that the correction value (42) is also determined based on a temperature-dependent thermal conductivity value (43) of a material of the wall (20).

7. Method (100) according to one of claims 1 to 6, characterized in that the heat coupling element (30) is at least partially made of stainless steel, carbon steel or Cr-Ni steel, in particular austenitic Cr-Ni steel.

8. Method (100) according to one of claims 1 to 7, characterized in that the first and / or second temperature measurement (22, 24) is measured with a resistance thermometer or a thermocouple.

9. Computer program product (50) for operating a non-invasive temperature measuring device (10), which is configured to receive and process at least one first and one second temperature measurement value (22, 24), characterized in that the computer program product (50) is configured to perform a method (100) according to one of claims 1 to 8.

10. Computer program product (50) according to claim 9, characterized in that the computer program product (50) comprises a digital twin (70) of the non-invasive temperature measuring device (10).

11. Evaluation unit (40) for a non-invasive temperature measuring device (10), comprising a memory and a processor configured to execute a computer program product (50) for operating the non-invasive temperature measuring device (10), characterized in that the computer program product (50) is configured according to claim 9 or 10.

12. Non-invasive temperature measuring device (10) comprising a first temperature sensor (12), a second temperature sensor (14), a heat coupling element (30) and an evaluation unit (40), characterized in that the evaluation unit (40) is configured according to claim 11. 202409558 Foreign version 14 13. Temperature measuring arrangement (60) comprising a tube (21) or a container (23), wherein a non-invasive temperature measuring device (10) is attached to a wall (20) of the tube (21) or the container (23), characterized in that the non-invasive temperature measuring device (10) is designed according to claim 12.

14. Automation system (80) comprising a control unit (40) and a plurality of field devices (66) connected to the control unit (40), characterized in that the automation system (80) has a temperature measuring arrangement (60) according to claim 13.

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