THERMAL FLOWMETER

Abstract

A thermal flowmeter for measuring the mass flow rate of a medium in a measuring tube, includes: a measuring tube having a measuring tube wall; a sensor having four probes that project into the measuring tube from a main sensor body; and an electronic measuring/operating circuit designed to operate at least three probes and to generate and provide flow measurement values by operating the probes, each probe having a main probe body and an active probe body, the active probe body designed to heat the medium, to determine the temperature of the medium and/or to influence a flow of the medium in the measuring tube, wherein the main probe bodies span a rhombus on a surface of the main sensor body, and the rhombus is defined by centroid points of cross-sections of the main probe bodies.

Claims

1-11. (canceled)

12. A flow measuring device for measuring the mass flow of a medium in a measuring tube, the device comprising: a measuring tube including a measuring tube wall; a sensor including four probes that extend into the measuring tube from a main sensor body, wherein the probes are configured to heat the medium, to determine the temperature of the medium, or to influence a flow of the medium in the measuring tube; an electronic measuring/operating circuit configured to operate at least three of the probes and to generate and provide flow measurement values by operating the probes, wherein each probe has a main probe body and an active probe body, wherein each main probe body is disposed on a side of the corresponding probe adjacent the main sensor body, and wherein each active probe body is disposed on a side of the corresponding probe opposite the main sensor body, wherein each active probe body is configured to heat the medium, to determine the temperature of the medium, and/or to influence a flow of the medium in the measuring tube, wherein the main probe bodies are columnar, wherein the main probe bodies span a rhombus on a surface of the main sensor body, wherein the rhombus is defined by centroid points of cross-sections of the main probe bodies, the rhombus having a first diagonal and a second diagonal, wherein a first probe of the four probes is configured to measure the temperature of the medium, wherein a second probe and a third probe of the four probes are configured to heat the medium and to determine the temperature of the medium, wherein the first probe is arranged on a first side of the first diagonal, and wherein the third probe is arranged on a second side of the first diagonal, wherein the second probe and a fourth probe of the four probes are arranged on opposite sides of the second diagonal, wherein the first diagonal of the rhombus has an angle of rotation to a normal of a measuring tube cross-section, wherein the angle of rotation is greater than 1 degree.

13. The device of claim 12, wherein the angle of rotation is greater than 3 degrees.

14. The device of claim 12, wherein the angle of rotation is less than 20 degrees.

15. The device of claim 12, wherein the angle of rotation is less than 10 degrees.

16. The device of claim 12, wherein the fourth probe is configured to impede, at least partially, flow of the medium between the first probe and the third probe, wherein the active probe body of the fourth probe has a first width parallel to the first diagonal and a second width parallel to the second diagonal, wherein the second width is greater than the first width by a factor of at least 1.1, and wherein a geometric center of the active probe body of the fourth probe is offset in a direction of the second probe.

17. The device of claim 16, wherein an outer surface of the active probe body of the fourth probe is symmetrical with respect to the second diagonal.

18. The device of claim 12, wherein the first probe, the second probe, and the third probe each comprise a probe sleeve, the device further comprising resistance thermometers, wherein at least one resistance thermometer is disposed in an interior space of each respective probe sleeve of the first, second, and third probes, wherein the resistance thermometers are configured to detect a temperature or to emit thermal energy.

19. The device of claim 12, wherein the fourth probe is solid.

20. The device of claim 12, wherein an internal angle of the rhombus, belonging to the first probe, is less than 90°.

21. The device of claim 12, wherein a centroid point of a cross-section of the main probe body of the fourth probe is at a first distance from a centroid point of a cross-section of the main probe body of the second probe, wherein a minimum distance of an outer surface of the active probe body of the fourth probe from an outer surface of the active probe body of the second probe is less than 30% of the first distance.

22. The device of claim 21, wherein the minimum distance of the outer surface of the active probe body of the fourth probe from the outer surface of the active probe body of the second probe is less than 5% of the first distance.

23. The device of claim 12, wherein in an active region of the respective active probe body of each of the first probe, the second probe, and the third probe, an outer diameter of each respective active region is at least 1 mm and/or at most 7 mm.

24. The device of claim 23, wherein the outer diameter of each respective active region is at least 2 mm and/or at most 4 mm.

25. The device of claim 12, wherein a centroid point of a cross-section of the main probe body of the first probe is at a second distance from a centroid point of a cross-section of the main probe body of the third probe, wherein the second distance is at least two, first external diameters.

26. The device of claim 12, wherein cross-sections of the first probe, of the second probe, and of the third probe have a round contour, at least in regions of each respective active probe body.

Description

[0028] The invention will now be described with reference to schematic exemplary embodiments.

[0029] FIG. 1 shows active regions of two exemplary probe arrangements according to the invention of a thermal flowmeter and orientations of said probes in a measuring tube;

[0030] FIG. 2 a) shows a cross-section through an exemplary first, second, or third probe; and

[0031] FIG. 2 b) shows a side view of an exemplary fourth probe; and

[0032] FIG. 3 shows a side view of a sensor according to the invention; and

[0033] FIG. 4 sketches a structure of an exemplary schematic thermal flowmeter according to the invention.

[0034] FIG. 1 shows active regions of two probe arrangements according to the invention in a measuring tube 11 with a measuring tube wall 11.1 each having a first probe 12.21, a second probe 12.22, a third probe 12.23, and a fourth probe 12.24. The active regions are the regions in which active probe bodies W, (see FIGS. 2 a), 2 b), and 3)) are effective. The active probe bodies each connect to a main probe body G of the corresponding probe, which main probe bodies are connected to a main sensor body 12.1 (see FIGS. 2 a), 2 b), and 3)). The action of the active probe bodies is to heat the medium, to determine the temperature of the medium, and/or to influence a flow of the medium in the measuring tube.

[0035] The main probe bodies of a probe arrangement span a rhombus R, wherein the rhombus is defined by the centroid points of cross-sections of the main probe bodies and has a first diagonal D1 and a second diagonal D2. A first probe 12.21 is designed to measure the temperature of the medium,

wherein a second probe 12.22 and a third probe 12.23 are designed to heat the medium and to determine the temperature of the latter in each case,
wherein the first probe is arranged on a first side of the first diagonal, and wherein the third probe is arranged on a second side of the first diagonal, wherein the second and a fourth probe 12.24 are arranged on opposite sides of the second diagonal,

[0036] According to the invention, the first diagonal D1 of the rhombus has an angle of rotation q to a normal 11.3 of a measuring tube cross-section 11.2, wherein η is greater than 1 degree, and especially greater than 2 degrees and preferably greater than 3 degrees.

[0037] It has surprisingly been shown that a slight rotation of the main sensor body exhibits significantly better flow direction detection over a wide range of speeds. A rotation of the sensor has an advantageous effect, particularly at high flow velocities greater than 70 m/s.

[0038] In one embodiment, η is less than 20 degrees, and especially less than 15 degrees and preferably less than 10 degrees. It is important here that a probe located in a flow shadow, i.e., the first probe or the third probe, depending upon the flow direction, remain completely in the flow shadow formed from the second probe and the fourth probe.

[0039] An internal angle β associated with the first probe is less than 90 degrees, so that the probe arrangement has a low flow resistance.

[0040] In a first probe arrangement according to the invention, the fourth probe 12.24, like the other probes, has a round contour in its active region. In this way, a sensor with the probes can be manufactured cost-effectively. In a second probe arrangement according to the invention, the fourth probe 12.24 has a non-round contour in its active region, wherein the probe has a first width B1 parallel to the first diagonal D1 and a second width B2 parallel to the second diagonal D2, wherein the second width is at least 10% greater than the first width. A geometric center GS4 (see FIG. 2 b)) of the active probe body of the fourth probe is offset in the direction of the second probe. A partial blocking effect for a flow of a medium through the measuring tube in the active regions of the probes along the second diagonal D2 is thereby achieved. As a result, an influence on the first probe by the third probe 12.23 heating the medium can be reduced, and a measuring accuracy of the sensor can thus be increased. A centroid point of a cross-section of the main probe body of the fourth probe thereby is at a second distance from a centroid point of a cross-section of the main probe body of the second probe. A minimum distance of the outer surface of the active probe body of the fourth probe from an outer surface of the active probe body of the second probe is less than 30%, and in particular less than 15% and preferably less than 5%, of the second distance.

[0041] FIG. 2 a) shows a longitudinal section through an exemplary first, second, or third probe, wherein a probe sleeve SH defines an interior space IR of the probe, in which interior space the probe has a resistance thermometer WT. The resistance thermometer is thereby thermally and mechanically coupled to the probe sleeve via a contact means. The contact means can, for example, be a molten material that is melted during the production of the probe and, after solidification, subsequently processed.

[0042] FIG. 2 b) shows a plan view, perpendicular to a measuring tube cross-section, of an exemplary fourth probe, which is widened in its active region W, and thus has an enlarged outer surface AWK. A geometric center GS4 of the active probe body of the fourth probe is thereby offset from a longitudinal axis of the main body.

[0043] FIG. 3 shows a schematic side view of a sensor 12 of a thermal flowmeter, which sensor has a main sensor body 12.1 and probes 12.2, wherein the probes, as described in FIGS. 2 a) and b), each comprise a main probe body G and an active probe body W.

[0044] FIG. 4 outlines a schematic structure of a thermal flowmeter 10 according to the invention having a measuring tube 11 with a measuring tube wall 11.1, a sensor 12 with a main sensor body 12.1 and with probes 12.2, and an electronic measuring/operating circuit 13 for operating the sensor and providing flow measurement values. The main sensor body is attached in a medium-tight manner in the measuring tube wall. The active regions of the probes are preferably arranged in a flow region of the medium, in which flow region a local mass flow deviates less than 10%, and especially less than 5% and preferably less than 2%, from a mean value formed over a flow cross-section.

LIST OF REFERENCE SIGNS

[0045] 10 Thermal flowmeter [0046] 11 Measuring tube [0047] 11.1 Measuring tube wall [0048] 11.2 Measuring tube cross-section [0049] 11.3 Normal [0050] 12 Sensor [0051] 12.1 Main sensor body [0052] 12.2 Probe [0053] 12.21 First probe [0054] 12.22 Second probe [0055] 12.23 Third probe [0056] 12.24 Fourth probe [0057] 13 Electronic measuring/operating circuit [0058] G Main probe body [0059] W Active probe body [0060] SH Probe sleeve [0061] R Rhombus [0062] AWK Outer surface of active probe body [0063] D1 First diagonal [0064] D2 Second diagonal [0065] GS4 Geometric center of the active probe body of the fourth probe [0066] WT Resistance thermometer [0067] IR Interior space [0068] β Internal angle [0069] B1 First width [0070] B2 Second width [0071] η Angle of rotation