Measuring device for determining a distribution of a heat transfer medium and method for determining a distribution of a heat transfer medium

Abstract

Measuring device (100) for determining a distribution of a heat transfer medium (150) on an inner wall (130) of a shaftless container (120) which rotates during its intended use and which is designed in particular for heating the heat transfer medium (150) with concentrated solar radiation (112) in a solar thermal power plant or as a rotary kiln, comprising a distance measuring device (10) for determining a thickness (156) of a film (152) of the heat transfer medium (150) on the inner wall (130) of the container (120), wherein the distance measuring device (10) comprises at least one optical device (30) for detecting at least one height profile along at least one measuring line (40) projected onto the inner wall (130) and at least one position sensor (50) for determining a current rotational position of the respective measuring line (40) on the inner wall (130), characterized in that the position sensor (50) has a magnetic tape (52) and a sensor (54) and the magnetic tape (52) or the sensor (54) is attached to the container (120) and the position sensor (50) detects a rotational position of the container (120).

Description

Prior ArtThe invention relates to a measuring device for determining a distribution of a heat transfer medium in a receiver device for solar radiation in a solar thermal power plant and to a method for determining a distribution of a heat transfer medium.DE 102010062367 A1 describes a device for receiving solar radiation. The apparatus comprises a container having an inner wall and a rotary drive device by which the container is rotated about a rotation axis. The container has an axis oriented parallel or at an acute angle to the direction of gravity. A heat transfer medium is guided along the inner wall through the container, forming a heat transfer medium film. As heat transfer medium in DE 102010062367 A1, particles or a liquid are proposed, for example.JP 2018-9807 A describes an optical cutting apparatus for inspecting welds on the inside of a tank, comprising: a measurement head part having a line-shaped light source for irradiating line-shaped light to a tank inner surface from the vicinity of a cylindrical axis of a tank, a focus lens that is located at a position separated in the direction of the cylindrical axis and is for obliquely photographing a line irradiated to the tank inner surface, a camera; a rotating mechanism for rotating the tank or the measurement head; and a linear mechanism for moving the tank or the measurement head part in the axial direction.EP 2 431 734 A1 describes a tire inspection apparatus having a plurality of cameras which are arranged at relatively offset circumferential positions and are also set differently in the axial direction of the tire for the respective recording positions. Thus, the images of the inner circumferential surface of the tire are captured by the plurality of cameras while the tire is rotated in the circumferential direction relative to the plurality of cameras. During this process, markers are simultaneously inserted into the images captured by all cameras. The images thus captured by all the cameras are synthesized using these marks as reference positions in the orientation of the captured images in accordance with the relative displacements of the cameras in the circumferential direction.In experiments with the described device, there were indications of an inhomogeneous distribution of the film and thus of the heat transfer medium on the inner wall of the device. One possible cause of this may be that the surface of the inner wall of the container can change during operation as a result of the high thermal load in the case of solar radiation and thermal cycles between times with solar radiation and without solar radiation, so that a homogeneous distribution of the film may no longer be present.In order to identify this, a simulation of the film thickness of the heat transfer medium is usually carried out, but this is subject to many simplifications and assumptions which are not fully validated.Disclosure of the InventionAn object of the invention is to provide a measuring device for determining a distribution of a heat transfer medium in a receiver device for solar radiation in a solar thermal power plant, which device supplies meaningful data.A further object of the invention is to specify methods for determining a distribution of a heat transfer medium using such a measuring device.The objects are achieved by the features of the independent claims. Advantageous embodiments and advantages of the invention are evident from the further claims, the description and the drawing.A measuring device is proposed for determining a distribution of a heat transfer medium on an inner wall of a shaftless container rotating when used as intended, which is designed in particular for heating the heat transfer medium with concentrated solar radiation in a solar thermal power plant or as a rotary kiln. The measuring device comprises a distance measuring device for determining a thickness of a film of the heat transfer medium on the inner wall of the container. The distance measuring device comprises at least one optical device for detecting at least one height profile along at least one measurement line projected onto the inner wall and at least one position transmitter for determining a current rotational position of the respective measurement line on the inner wall with respect to a rotational position of the container. The position transducer has a magnetic tape and a sensor. The magnetic tape or the sensor is attached to the container and the position sensor detects a rotational position of the container.The container is in particular a so-called particle receiver in a solar thermal power plant. In a particle receiver, solar rays are concentrated in the interior and a particulate heat carrier is heated, the particles of which are distributed along the inner wall of the particle receiver when the particle receiver is set in rotation. The particles form a particle film substantially parallel to the inner wall of the particle receiver. The particle film moves from an inlet into the particle receiver to an outlet from the particle receiver.Advantageously, the film thickness can be measured. A possibly erroneous calculation or simulation of the film thickness may be omitted. The film thickness can be assessed not only qualitatively as to whether gaps are present in the film, for example, but a reliable statement can be made about the film thickness on the inner wall of the container in the measured region.The measuring device is particularly suitable for so-called centrifugal receiver, also known as particle receiver, in receiver devices for solar radiation in solar thermal power plants and for rotary kilns.According to a favorable embodiment of the measuring device, the distance measuring device can be designed to acquire distance data directly on the inner wall of the container along the measuring line in order to generate the height profile.A statement about the height profile on the entire surface of the inner wall or on regions of interest of the inner wall can be obtained if, for example, a multiplicity of measurement lines lying next to one another are detected successively. Expediently, the container can be set in rotation for this purpose, so that a region or the entire surface of the inner wall can be measured.According to a favorable embodiment of the measuring device, the distance measuring device can be designed to acquire distance data directly on the film of the heat transfer medium on the inner wall of the container along the measuring line in order to generate the height profile.A statement about the height profile of the film of the heat transfer medium on the entire surface of the inner wall or on regions of interest of the inner wall can be obtained if, for example, a multiplicity of measurement lines lying next to one another are recorded successively. Expediently, the container can be set in rotation for this purpose, so that a region or the entire surface of the inner wall can be measured.Advantageously, a light section can be used to record the height profile. The light section is a method known per se of optical 3-D measurement technology, with which the measurement of a height profile along a projected line of light can take place and is based on the principle of triangulation. The optical device can be, in particular, a light section sensor which comprises a line projector, usually with a laser as light source, which projects a line which is as narrow and bright as possible onto the measurement object, and an electronic camera which records the projection of the measurement line on the object, in this case the pure inner wall or the film on the inner wall. The displacement of the measurement line in the camera image can be converted into 3-D coordinates using the methods of photogrammetry which are known per se. Measuring devices which use this method are known, for example, as so-called profile scanners.Profile scanners measure a height profile along a projected line of light, which represents the measurement line. In this case, the distance is not measured continuously. Along the height profile there is a certain number of measurement points, which each generate a separate measurement value for the distance.In the case of film thickness measurement in the solar radiation receiver, a profile scanner can be held in the container by means of a holder and a height profile of the particle film along the longitudinal axis of the container, also known as receiver, can thus be measured. This height profile is initially only a 2D profile. If the container now additionally rotates and the measurement of the previously measured height profile is continuously repeated, a 3D height profile of the film of the heat transfer medium is produced.In the case of a perfect cylinder, the thickness of the particle film could be calculated from the 3D height profile and the determined distance of the profile scanner from the receiver inner wall. However, since the container is not a perfect cylinder, the measurement of the 3D profile alone does not give any information about the actual thickness of the particle film.In order to determine these, a reference measurement of the empty container without heat transfer medium can additionally be carried out. In this case, the inner wall of the container, also referred to as an inliner, is measured in the same way as the film of the heat transfer medium on the inner wall and a 3D height profile of the inner wall is created in the process. Subsequently, the two height profiles can be subtracted from one another. As a result, the actual thickness of the film of the heat transfer medium follows.In order to be able to subtract the two height profiles correctly from one another, the information about the rotational position of the two height profiles or of the respective measurement line with respect to this rotational position of the container is additionally also necessary. The rotational position of the measurement line correlates closely with the rotational position of the container; in particular, the rotational position of the measurement line can be equal to the rotational position of the container. The measurement points of both height profiles can thus relate to the same real point in the container.This information can be provided by the position transmitter, also known as an encoder or a rotary encoder. This is a sensor for the angle of rotation, with which the rotational position of the container can be determined.This rotational position can be transferred to the profile scanner so that the individual measurement points along the respective measurement line can be stored with the information about the associated rotational position of the container. Alternatively or additionally, the rotational position of the container can be transferred to a computing device which can correspondingly perform an assignment of the measurement points with the information about the rotational position and the height profile of the associated measurement line.A transfer to the profile scanner can take place via an interface, for example via an RS-422 interface, which can be connected directly to the profile scanner from the position transmitter. The measurement data about the rotational position can then be stored simultaneously with the measurement data about the distance and transmitted to the computing device and processed.Advantageously, the heat transfer medium can consist of particles, for example bauxite particles. The height profile is measured on a surface of a film of the heat transfer medium in the form of a particle bed. It has been found that even a porous bed with the absorptive material of the bauxite particles reflects sufficient light.According to a favorable embodiment of the measuring device, the measuring line can extend parallel to a longitudinal axis of the container. The measurement line consists of a number of individual measurement points along the length of the measurement line, in which the optical device determines the distance between the measurement object and the sensor for each measurement point, for example via a transit time measurement.The profile scanner can have a variable measurement range transversely to the longitudinal axis in the direction of the surface normal of the inner wall of the container. Depending on how different the distances to be measured are, for example due to non-round running or eccentricity of the container, the measurement range can be adapted. In the case of small changes in distance, the measurement range can be very small. If there are larger differences, the range may be chosen larger, for example in the case of imperfect concentricity or eccentricity.The measurement frequency of the profile scanner depends on the size of the measurement range. The smaller this is, the fewer measurement points have to be read out on the sensor and the faster it is possible to measure. Accordingly, it is desirable to keep it low.An eccentrically running, rotating component can be problematic in this case, since the measurement range would actually have to be selected to be quite large in order to be able to detect everything precisely. This can be solved by software by evaluating the data of the position transmitter, which can be connected to the profile scanner and / or to the computing unit, together with the data of the height profiles of the profile scanner.In this case, a reference measurement can first be carried out in order to detect deviations in the circulation of the container. Subsequently, the information from the reference measurement can be used to shift the measurement range in height profile in accordance with the imperfect runout of the container. This has the advantage that the measurement range can be selected to be quite small, resulting in a higher measurement frequency. Nevertheless, the distance information can be sufficiently accurately recognized because the measurement range is shifted according to the lack of roundnessAccording to a favorable embodiment of the measuring device, the position transmitter can be coupled to the container, in particular attached to the container, and can detect a rotational position of the container. The profile scanner can record a rotational position of the container, which is supplied by the position transmitter, synchronously with the projected measurement line. Alternatively or additionally, the position transmitter can forward the rotational position to a computing unit, which combines the projected measurement line and the respective rotational position. Advantageously, the position transducer can comprise a magnetic tape which is placed around the container. In particular, the rotational position of the container can be determined via a magnetic tape having a number of magnetic poles, which are read out by a sensor of the position sensor which travels over the magnetic tape.A container, in particular a particle receiver, for heating the heat transfer medium of a receiver device for solar radiation or a rotary kiln usually does not have a shaft about which the container can rotate. Instead, it is driven via a chain. Therefore, conventional position sensors cannot be used to determine the rotational position of the particle receiver. The determination of the rotational position can advantageously take place via a magnetic tape placed around the container and having a specific number of poles, which can be read by a sensor. By means of this combination of sensor and magnetic tape, the rotational position of a container without a rotary shaft, in particular a particle receiver, can then be determined with high accuracy.It is particularly advantageous to use a combination of a magnetic tape placed around the container and a sensor arranged above it for detecting a rotational position of a shaftless rotating particle receiver in a solar thermal power plant or in a rotary kiln. The sensor may be disposed at a fixed angular position with respect to the container. As the container rotates, the sensor does not rotate. The distance between the sensor and the magnetic tape is advantageously between about 1 mm and about 3 mm. Optionally, the sensor can be mounted in a radially displaceable manner in order to ensure a uniform distance from the receiver or the magnetic tape. This is advantageous if the container runs out of round or is eccentric, for example, or fluctuating distances can occur between the magnetic tape and the sensor.According to a favorable embodiment of the measuring device, a computing device can be coupled to the distance measuring device and / or the position transmitter.Advantageously, the computing device can make a corresponding assignment of the measurement points with the information about the rotational position of the container and the distance corresponding to the height profile of the associated measurement line. In particular, height profile data can be processed there from a measurement of the inner wall of the empty container without heat transfer medium and from a measurement with a film of the heat transfer medium. Thus, the two height profiles can be subtracted from one another. As a result, the actual thickness of the film of the heat transfer medium follows.According to a favorable embodiment of the measuring device, the distance measuring device can protrude into the container on a holder. In particular, a plurality of the optical devices of the distance measuring device can project into the container on a holder. If the distance measuring device has only one optical device, in particular in the form of a profile scanner, it can be arranged so as to be displaceable along and / or with the holder, so that the container can be measured over its entire length.If the distance measuring device has a plurality of optical devices, in particular in the form of profile scanners, the number thereof can expediently be selected such that the entire axial extent of the container can be detected with mutually adjoining measurement lines.According to a further aspect of the invention, a method is proposed for determining a distribution of heat transfer medium on an inner wall of a shaftless container rotating when used as intended, in particular in which the heat transfer medium of a receiver device for solar radiation is heated in a solar thermal power plant or a rotary kiln, by means of a measuring device which comprises at least one optical device for detecting at least one height profile along at least one measurement line projected onto the inner wall and at least one position transmitter for determining a current rotational position of the respective measurement line on the inner wall.The distance measuring device detects at least one height profile along at least one measurement line projected onto the inner wall by means of the at least one optical device, and the at least one position sensor determines a current rotational position of the container and thus the rotational position of the respective measurement line on the inner wall. A magnetic tape or sensor of the position transducer is attached to the container. A rotational position of the container is detected by the position transmitter.According to a favorable embodiment of the method, a rotational position of the two height profiles with and without heat transfer medium on the inner wall of the container can be determined with respect to a rotational position of the container. By subtracting the data, the film thickness of the heat transfer medium on the inner wall of the container can thereby be determined in a positionally accurate manner.According to a favorable embodiment of the method, the distance measurement can be carried out without solar radiation into the container. It is advantageously possible to use customary components which do not tolerate high temperatures.According to a favorable embodiment of the method, a difference between distance data of the film and distance data of the inner wall can be formed and a location-dependent distribution of the film of the heat transfer medium on the inner wall of the container can be determined therefrom. As a result, reliable measured values can be provided.According to a favorable embodiment of the method, a measurement frequency of the position transmitter can be adapted to a length of the measurement line in the direction of the longitudinal axis of the container. This enables an accurate measurement to be made even in the case of large changes in distance, i.e. in the case of a profiled surface with a correspondingly pronounced height profile.According to a favorable embodiment of the method, a reference measurement can be carried out for determining an eccentricity and / or a lack of concentricity of the container and a length of the measurement lines can be adjusted in the direction of the longitudinal axis of the container. Advantageously, the determination of the distribution of heat transfer medium on the inner wall of the container can be adapted to the real state of the container.According to a favorable embodiment of the method, the determination of the distribution of heat transfer medium on the inner wall can be carried out repeatedly and changes in the distribution can be detected. This allows reliable quality testing to be carried out during the operating period of the solar radiation receiver.According to a favorable embodiment of the method, if permissible tolerances of the changes are exceeded, a maintenance requirement indication can be made. By means of timely maintenance or repair, reliable operation of the solar radiation receiver can be advantageously made possible.According to a further aspect of the invention, a use of a measuring device for determining a distribution of a heat transfer medium on an inner wall of a container which is designed for heating the heat transfer medium with concentrated solar radiation in a solar thermal power plant, comprising a distance measuring device for determining a thickness of a film of the heat transfer medium on the inner wall of the container, wherein the distance measuring device comprises at least one optical device for detecting at least one height profile along at least one measurement line projected onto the inner wall and at least one position transmitter for determining a current rotational position of the respective measurement line on the inner wall, wherein the position transmitter has a combination of a magnetic tape and a sensor arranged above it for detecting a rotational position of the shaftless rotating container.The container is in particular a particle receiver, also known as a centrifugal receiver, in a solar thermal power plant. Optionally, the combination can also be used for detecting a rotational position of a rotary kiln.The magnetic tape is disposed on the container and rotates with the container while the sensor is disposed over the magnetic tape. The magnetic tape can surround the container, in particular on the outer circumference, and the sensor can be arranged at a small radial distance therefrom. The sensor may be disposed at a fixed angular position with respect to the container. As the container rotates, the sensor does not rotate. The distance between the sensor and the magnetic tape is advantageously between about 1 mm and about 3 mm. Optionally, the sensor can be mounted so as to be displaceable in the radial direction in order to ensure a uniform distance from the receiver or the magnetic tape. This can be advantageous if the container runs out of round or is eccentric, for example, or fluctuating distances can occur between the magnetic tape and the sensor.Optionally, the magnetic tape can also be arranged in the interior, in particular on the inner wall, of the container and the sensor can accordingly be arranged in the interior of the container at a small radial distance therefrom.Optionally, the sensor is disposed on the container and rotates with the container while the magnetic tape is disposed over the container and the magnetic tape, respectively. The sensor can be arranged on an outer side of the container, in particular on the outer periphery, and the magnetic tape can be arranged at a small radial distance therefrom. Optionally, the sensor can also be arranged in the interior, in particular on the inner wall, of the container and the magnetic tape can be arranged in the interior of the container at a small radial distance therefrom.Optionally, the two alternative configurations can also be combined on a container, wherein the measurement accuracy can be increased by two such combinations of sensor and magnetic tape.According to a further aspect of the invention, a use of a combination of a magnetic tape and a sensor arranged above it is proposed for detecting a rotational position of a shaftless rotating container. The container is in particular a particle receiver, also known as a centrifugal receiver, in a solar thermal power plant. Optionally, the combination can also be used for detecting a rotational position of a rotary kiln.According to a favorable embodiment, the magnetic tape can be arranged on the container and rotate with the container, while the sensor is arranged above the magnetic tape. The sensor may be disposed at a fixed angular position with respect to the container. As the container rotates, the sensor does not rotate. The distance between the sensor and the magnetic tape is advantageously between about 1 mm and about 3 mm. Optionally, the sensor can be mounted so as to be displaceable in the radial direction in order to ensure a uniform distance from the receiver or the magnetic tape. This can be advantageous if the container runs out of round or is eccentric, for example, or fluctuating distances can occur between the magnetic tape and the sensor.The magnetic tape can surround the container, in particular on the outer circumference, and the sensor can be arranged at a small radial distance therefrom. Optionally, the magnetic tape can also be arranged in the interior, in particular on the inner wall, of the container and the sensor can be arranged in the interior of the container at a small radial distance therefrom.According to a favorable alternative embodiment, the sensor can be arranged on the container and rotate with the container, while the magnetic tape is arranged above the sensor. The sensor can be arranged on an outer side of the container, in particular on the outer periphery, and the magnetic tape can be arranged at a small radial distance therefrom. Optionally, the sensor can also be arranged in the interior, in particular on the inner wall, of the container and the magnetic tape can be arranged in the interior of the container at a small radial distance therefrom.Optionally, the two alternative configurations can also be combined on a container, wherein the measurement accuracy can be increased by two such combinations of sensor and magnetic tape.DRAWINGFurther advantages are evident from the following description of the drawings. Exemplary embodiments of the invention are illustrated in the figures. The figures, the description, and the claims contain numerous features in combination. The skilled person will expediently also consider the features individually and summarize them to form meaningful further combinations.The following are shown by way of example: FIG. 1 shows an embodiment of a container of a solar radiation receiver which is driven by a chain; FIG. 2 shows a schematic illustration of a detection of a height profile on a measurement line; FIG. 3 shows a schematic illustration of a detection of a height profile at a region of measurement lines which follow one another in a circumferential direction, corresponding to FIG. 2 ; FIG. 4 shows a measuring device according to an exemplary embodiment of the invention, in which a distance measuring device has a displaceable optical device; FIG. 5 shows a measuring device according to an exemplary embodiment of the invention, in which a distance measuring device has a plurality of optical devices; FIG. 6 shows a perspective view of a container in a framework with a position transmitter on a container according to an exemplary embodiment of the invention; FIG. 7 shows a detailed view of an arrangement of a magnetic tape of the position transmitter according to FIG. 6 on a bearing flange of the container; FIG. 8 shows a detailed view of an arrangement of the position transmitter with sensor and magnetic tape according to FIG. 6 ; FIG. 9 shows a detailed view of a magnetic tape of a position transmitter on a flange of a container according to an exemplary embodiment of the invention; FIG. 10 shows a detailed view of the position transmitter on a flange of a container according to FIG. 9 ; FIG. 11 is a cut-away perspective view of a container in a framework with an optical device on a holder according to an exemplary embodiment of the invention; FIG. 12 shows a flow chart for carrying out a method according to an exemplary embodiment of the invention.Embodiments of the InventionIn the figures, components of the same type or having the same effect are denoted by the same reference numerals. The figures merely show examples and should not be understood as limiting.Before describing the invention in detail, it should be understood that it is not limited to the particular components of the apparatus, as well as the particular method steps, as these components and methods may vary.The terms used herein are intended to describe particular embodiments only and are not used in a limiting sense. Moreover, when the singular or indefinite articles are used in the specification or claims, this also refers to the plurality of these elements unless the overall context clearly indicates otherwise.Directional terminology used in the following with terms such as "left", "right", "top", "bottom", "front", "behind", "after" and the like is merely used for better understanding of the figures and is in no case intended to represent a limitation of generality. The components and elements illustrated, their design and use can vary within the meaning of the considerations of a person skilled in the art and be adapted to the respective applications.FIG. 1 shows an embodiment of a container 120 of a solar radiation receiver driven by a chain (not shown).The container 120 is of double-walled design and has an inner wall 130, on which a film 152 of a heat transfer medium 150, for example bauxite particles, moves through the container 120 during intended operation. Along the axial extent 162 of the container 120, the film 152 is strongly heated by the solar radiation 112 entering through the radiation entrance aperture 126. The heat transfer medium 150 is supplied, for example, via the medium inlet 124 on the opposite side of the container 120 in a manner known per se and is distributed on its inner wall 130 by the rotation of the container 120.The container 120 can be inclined with its longitudinal axis 160 by an angle 114 with respect to the gravity g of the earth.In order to determine the thickness of the film 152, a distance measuring device 10 is used, which comprises at least one optical device 30 with a transmitter 32 and a receiver 34. Advantageously, the optical device 30 is designed as a profile scanner, with which a measurement line 40 (FIG. 2 ) is directed onto the object to be measured, for example the inner wall 130 with or without film 152.FIG. 2 shows a schematic illustration of a detection of an elevation profile using a distance measuring device 10 on a measurement line 40, while FIG. 3 shows a schematic illustration of a detection of an elevation profile on a region 42 of measurement lines 40 following one another in a circumferential direction 140 in accordance with FIG. 2.The transmitter 32 is expediently a laser, the receiver 34 is expediently an electronic camera. The transmitter 32 of the optical device 30 radiates a laser beam onto the inner wall 130, and the receiver 34 measures the distances between the optical device 30 and points on the measurement line 40 point by point along a measurement line 40.The optical device 30 is rigidly mounted during the measurement, while the container 120 can move in the direction of rotation 170 below the measurement line 40. If the measurement line 40 or the region 42 of measurement lines 40 lies above a step in the film 152, the height difference 154 is recognized, so that a height profile can be detected with the measurement line 40.In this case, a height profile of the inner wall 130 without film 152 and a height profile of the inner wall 130 with film 152 of the heat transfer medium 150 can be detected. From the difference of the values, the thickness of the film 152 can be determined. In this case, a rotational position of the container 120 is determined for each measurement line 40, so that a positionally accurate determination of the thickness of the film 152 is possible.FIG. 4 shows a measuring device 100 according to an exemplary embodiment of the invention, in which a distance measuring device 10 has an optical device 30 which can be displaced on or with a holder 20.The distribution of heat transfer medium 150 on the inner wall 130 of the container 120 can be determined with the measuring device 100. The measuring device 100 comprises the distance measuring device 10, which in this exemplary embodiment comprises an optical device 30 for detecting at least one height profile along at least one measuring line 40 projected onto the inner wall 130, and at least one position transmitter 50 for determining a current rotational position of the respective measuring line 40 on the inner wall 130 with respect to the rotational position of the container 120.The measurement line 40 extends parallel to a longitudinal axis 160 of the container 120. If the container 120 rotates, measurement lines 40 lying next to one another form a region 42, as schematically depicted in FIG. 3.The position transducer 50 is attached to the container 120 and detects the rotational position of the container 120 in particular synchronously with the projected measurement line 40 in a measurement position. The position transmitter 50 can pass the position values on to the distance measuring device 10 or, as is indicated in the figure, to a computing device 90 which links the distance measuring values and the position values.It is understood that the transmission of the measured values from the position transmitter 50 to the optical device 30 and / or to the computing unit 90, as indicated by dash-dot lines in FIGS. 4 and 5, can take place via data lines or also wirelessly.Since the container 120 cannot be driven by a shaft whose angular position could be detected during the rotation of the container 120, the position transducer 50 has a magnetic tape 52 which is laid around the container 120. For determining the rotational position, the magnetic tape 52 has a number of magnetic poles which are read out by a sensor 54 of the position transducer 50.In order to detect the distribution of the heat transfer medium 150 on the entire inner wall 130 of the container 120 also in the direction of the longitudinal axis 160, the optical device 30 can be displaced parallel to the longitudinal axis of the container 120 to a new measurement position.FIG. 5 shows a measuring device 100 according to an embodiment of the invention, in which, in contrast to the embodiment in FIG. 4, a distance measuring device 10 has a plurality of optical devices 30, in this example three optical devices 30. the number of optical devices 30 can expediently be selected such that their measuring lines 40 projected onto the inner wall 130 or the film 152 adjoin one another in the direction of the longitudinal axis 160 of the container 120 and cover the entire axial extent 162 thereof. The optical devices 30 can then remain at their respective measurement point when determining the distribution of the heat transfer medium 150 on the inner wall 130.FIG. 6 shows a perspective view of a container 120 in a framework 200 with a position transmitter 50 on the container 120 according to an exemplary embodiment of the invention. FIG. 7 shows a detailed view of an arrangement of a magnetic tape 52 of the position transmitter 50 according to FIG. 6 on a bearing flange 132 of the container 120. FIG. 8 shows a detailed view of an arrangement of the position transmitter 50 with sensor 54 and magnetic tape 52 according to FIG. 6.For rotating the container 120 during intended operation, the container 120 does not have a shaft. The container 120 is driven, for example, by a chain drive, for which purpose the container 120 in this example has a flange 134 with a toothed ring 136, in which a chain (not shown) can engage in order to set the container 120 in rotation. Axially spaced therefrom is a bearing flange 132 disposed on the container 120.The container 120 is mounted and guided in the framework 200 by the bearing flange 132. For example, the container 120 has the bearing flange 132 at one axial end and the flange 134 with the toothed ring 136 at the opposite axial end.The magnetic tape 52 may be arranged on the bearing flange 132 of the container 120, with which the container 120 is mounted in the framework 200.The magnetic tape 52 may be attached to the support flange 132 on an outer side of a suitably bent support plate 60, for example made of aluminum, and may enclose the container 120 on its outer side. The holding plate 60 can be arranged, for example, in a free space on the inner side of the bearing flange 132.The holding plate 60 can consist of individual parts which are bent on a bite machine. The holding plate 60 can then be fastened, for example adhesively bonded, to the inner side of the bearing flange 132. The magnetic tape 52 can then be fastened to the holding plate 60, for example glued on, or fixed with a tension band, or in another suitable manner.The sensor 54 is mounted at a short distance from the magnetic tape 52. A favorable distance is in particular between 1 mm and 3 mm. For this purpose, the sensor 54 can be arranged on a holding arm 56 facing the magnetic tape 52, which is fixed to the frame 200 (FIG. 6 ). In this way, the sensor 54 can be positioned stably and reproducibly with respect to the magnetic tape 52.Advantageously, the connections of the holding arm 56 and the sensor 54 to the framework 200 can be releasable and can be designed, for example, as screw connections.FIG. 9 shows a detailed view of a magnetic tape 52 of a position transmitter 50 on a drive flange 134 of a container 120 according to an exemplary embodiment of the invention. FIG. 10 shows a detailed view of the position transmitter 50 on the drive flange 134 of the container 120 according to FIG. 9.The drive flange 134 is part of the container 120 itself. In this embodiment, the magnetic tape 52 is attached, for example adhesively bonded, to the outer side of the drive flange 134.The sensor 54 is mounted at a short distance from the magnetic tape 52. A favorable distance is in particular between 1 mm and 3 mm. For this purpose, the sensor 54 can be arranged on a holding arm 56 facing the magnetic tape 52, which is fixed to the frame 200 (FIG. 10 ). In this way, the sensor 54 can be positioned stably and reproducibly with respect to the magnetic tape 52.Advantageously, the connections of the holding arm 56 and the sensor 54 to the framework 200 can be releasable and can be designed, for example, as screw connections.It is understood that the magnetic tape 52 may be disposed elsewhere on the container 120.FIG. 11 shows a cut-away perspective view of a container 120 in a framework 200 with an optical device 30 of a distance measuring device 10 on a holder 20 according to an exemplary embodiment of the invention.The holder 20 projects with an arm 22 pointing in the axial direction of the container 120 into the interior of the container 120. The optical device 30 is fastened to the arm 22, for example screwed, firmly bound, clamped or the like.The arm 22 is attached to a cross strut 24 that is located in front of the aperture 126 of the container 120 and is attached to the frame 200. Typically, in operation of the container 120, solar radiation is directed through the aperture 126 into the container 120.In this case, the cross strut 24 can extend from one side of the framework 200 to the other and cover the aperture 126.The optical device 30 may be slidably disposed along the arm 22. Alternatively or additionally, the arm 22 can be arranged displaceably on the transverse strut 24.Alternatively or additionally, the arm 22 can also be designed as a telescopic arm.Expediently, all connections of the arm 22 are designed as releasable connections, so that the aperture 126 can be released again after the measurements.FIG. 12 shows a flow chart for carrying out a method according to an exemplary embodiment of the invention.The method for determining a distribution of heat transfer medium 150 on an inner wall 130 of a container 120 starts in step S 100.In a first sequence S 200, a first measurement is carried out, in which the inner wall 130 of the container 120 is measured. The optical device 30 of the distance measuring apparatus 10 measures the distances between the optical device 30 and points on the measurement line 40 on the inner wall 130 point by point along a measurement line 40 in step S 202, while the position transmitter 50 measures the rotational position of the container 120 (step S 204). By linking the distance and the rotational position, a first three-dimensional point cloud is generated in step S 206. In this case, the respective distance relative to the respective measurement line 40 produces a height profile of the inner wall 130 both in the direction of the longitudinal axis 160 of the container 120 and, since the container 120 rotates, in the circumferential direction 140.In a second sequence S300, a second measurement is carried out, in which the film 152 of the heat transfer medium 150 distributed on the inner wall 130 is measured. The optical device 30 of the distance measuring apparatus 10 measures the distances between the optical device 30 and points on the measurement line 40 on the film 152 point by point along a measurement line 40 in step S 302, while the position encoder 50 measures the rotational position of the container 120 (step S 304).By linking the distance and the rotational position, a further three-dimensional point cloud is generated in step S 306. In this case, the respective distance relative to the respective measurement line 40 produces a height profile of the film 152 on the inner wall 130 both in the direction of the longitudinal axis 160 of the container 120 and, as the container 120 rotates, in the circumferential direction 140.It is understood that the measurement on the inner wall 130 can also be carried out after the measurement on the film 152, so that the two sequences S 200 and S 300 can be interchanged.In the sequence S 400, in step S 402, for each measurement point, a difference is formed between the distance from measurement on the inner wall 130 of the container 120 without the heat transfer medium 150 and the distance from measurement on the film 152 on the inner wall 130. In step S 404, a corrected point cloud is provided.After the sequence S 400, in step S 500, measurement values for the thickness of the film 152 corresponding to the distribution of the heat transfer medium 150 on the inner wall 130 are provided at a defined number of measurement points. The thickness of the film 152 or the distribution of the heat transfer medium 150 on the inner wall 130 can be determined with high spatial resolution.The method ends in step S 600.The distance measurements are made without solar radiation into the container 120. The measurements are expediently carried out at comparable temperatures.Further, corrections may be made to the film 152 in a reference measurement and in the measurement if the container 120 has deviations from runout and / or eccentricity. In this case, in particular the measurement lines 40 can be adapted.The determination of the distribution of heat transfer medium 150 on the inner wall 130 can be carried out repeatedly with a time interval for quality control and any changes in the distribution can be detected. If permissible tolerances of the changes are exceeded, a maintenance requirement indication can be made.Reference numerals denote reference numerals10 Distance measuring device 20 Holder 22 Arm 24 Cross strut 30 Optical device 32 Transmitter 34 Receiver 40 Measuring line 42 Region 50 Position transmitter 52 Magnetic tape 54 Sensor 56 Arm 60 Holding plate 90 Computing device 100 Measuring device 112 Solar radiation 114 Angle 120 Container 122 Housing 124 Medium inlet 126 Aperture 130 Inner wall 132 Bearing flange 134 Drive flange 136 Toothed ring 140 Circumferential direction 150 Heat carrier medium 152 Film 154 Height difference 160 Longitudinal axis 162 Axial extension 170 Rotational direction 200 Framework

Claims

Measuring device (100) for determining a distribution of a heat transfer medium (150) on an inner wall (130) of a shaftless container (120) rotating when used as intended, which container is designed in particular for heating the heat transfer medium (150) with concentrated solar radiation (112) in a solar thermal power plant or as a rotary kiln, comprising a distance measuring device (10) for determining a thickness (156) of a film (152) of the heat transfer medium (150) on the inner wall (130) of the container (120), wherein the distance measuring device (10) comprises at least one optical device (30) for detecting at least one height profile along at least one measuring line (40) projected onto the inner wall (130) and at least one position transmitter (50) for determining a current rotational position of the respective measuring line (40) on the inner wall (130), characterized in that, the position sensor (50) having a magnetic tape (52) and a sensor (54), and the magnetic tape (52) or the sensor (54) being attached to the container (120), and the position sensor (50) detecting a rotational position of the container (120).Measuring device according to claim 1, wherein the distance measuring device (10) is configured to acquire distance data directly on the inner wall (130) of the container (120) along the measuring line (40) in order to generate the height profile.Measuring device according to claim 1 or 2, wherein the distance measuring device (10) is configured to acquire distance data directly on the film (152) of the heat transfer medium (150) on the inner wall (130) of the container (120) along the measuring line (40) in order to generate the height profile.The measuring device according to any one of the preceding claims, wherein the measuring line (40) extends parallel to a longitudinal axis (160) of the container (120).Measuring device according to one of the preceding claims, wherein the position transducer (50) detects a rotational position of the container (120) synchronously with the projected measuring line (40).Measuring device according to one of the preceding claims, wherein the position transducer (50) has a magnetic tape (52) which is placed around the container (120), in particular wherein a determination of the rotational position takes place via a magnetic tape (52) having a number of magnetic poles which are read out by a sensor (54) of the position transducer (50).Measuring device according to one of the preceding claims, wherein a computing device (90) is coupled to the distance measuring device (10) and / or the position transducer (50).Measuring device according to one of the preceding claims, wherein the distance measuring device (10) protrudes into the container (120) on a holder (20), in particular wherein a plurality of the optical devices (30) of the distance measuring device (10) protrudes into the container (120) on a holder (20).Method for determining a distribution of a heat transfer medium (150) on an inner wall (130) of a shaftless container (120) rotating when used as intended, in particular in which the heat transfer medium (150) is heated with concentrated solar radiation (112) in a solar thermal power plant or a rotary kiln, by means of a measuring device (100) according to one of the preceding claims, wherein the distance measuring device (10) detects at least one height profile along at least one measuring line (40) projected onto the inner wall (130) by means of at least one optical device (30) and at least one position transmitter (50) determines a current position of the respective measuring line (40) on the inner wall (130), wherein a magnetic tape (52) or a sensor (54) of the position transmitter (50) is attached to the container (120) and a rotational position of the container (120) is detected by the position transmitter (50).Method according to claim 9, wherein a position of the two height profiles with and without heat transfer medium (150) on the inner wall (130) of the container (120) is determined with respect to a rotational position of the container (120).The method of claim 9 or 10, wherein the distance measurement is performed without solar radiation into the container (120).Method according to one of Claims 9 to 11, wherein a difference is formed between distance data of the film (152) and distance data of the inner wall (130), and a location-dependent distribution of the film (152) of the heat transfer medium (150) on the inner wall (130) is determined therefrom.Method according to one of Claims 9 to 12, wherein a measurement frequency of the position transmitter (50) is adapted to a length of the measurement line in the axial direction (162) of the container (120).Method according to one of Claims 9 to 13, wherein a reference measurement is carried out in order to determine an eccentricity and / or lack of concentricity of the container (120), and a length of the measurement lines is adapted in the direction of the longitudinal axis (160) of the container (120).Method according to one of Claims 9 to 14, wherein the determination of the distribution of heat transfer medium (150) on the inner wall (130) is carried out repeatedly and changes in the distribution are detected, in particular wherein a maintenance requirement indication takes place if permissible tolerances of the changes are exceeded.Use of a measuring device (100) for determining a distribution of a heat transfer medium (150) on an inner wall (130) of a container (120), which is designed in particular for heating the heat transfer medium (150) with concentrated solar radiation (112) in a solar thermal power plant or in a rotary kiln, comprising a distance measuring device (10) for determining a thickness (156) of a film (152) of the heat transfer medium (150) on the inner wall (130) of the container (120), wherein the distance measuring device (10) comprises at least one optical device (30) for detecting at least one height profile along at least one measurement line (40) projected onto the inner wall (130) and at least one position transmitter (50) for determining a current rotational position of the respective measurement line (40) on the inner wall (130), wherein the position transducer (50) comprises a combination of a magnetic tape (52) and a sensor (54) arranged above it for detecting a rotational position of the shaftless rotating container (120), characterized in that the magnetic tape (52) is arranged on the container (120) and rotates with the container (120) and the sensor (54) is arranged above the magnetic tape (52), or in that the sensor (54) is arranged on the container (120) and rotates with the container (120) and the magnetic tape (52) is arranged above the sensor (54).Use of a combination of a magnetic tape (52) and a sensor (54) arranged above it for detecting a rotational position of a shaftless rotating container (120) in a solar thermal power plant or a rotary kiln.The use of claim 17, wherein the magnetic tape (52) is disposed on the container and rotates with the container (120), and the sensor (54) is disposed over the magnetic tape (52).The use of claim 17, wherein the sensor (54) is disposed on the container (120) and rotates with the container (120), and the magnetic tape (52) is disposed over the sensor (54).

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