RU8475U1 - HIGH TEMPERATURE - Google Patents

Abstract

1. A high-temperature thermocouple, comprising a coaxial assembly of thermoelectrodes, housed in a sealed fixture containing a high-temperature part and a low-temperature part with a spring unit for tensioning the internal thermoelectrode, characterized in that the thermoelectrode assembly is equipped with a fusible element with a reference melting point installed in the electric assembly circuit and made with the possibility of replacing it after melting, and the high-temperature part of the reinforcement is removable and contains a cavity for collecting the melt Stalls elementa.2. Thermocouple according to claim 1, characterized in that the fusible element is made in the form of a rod mounted in the cross section of the assembly and mounted on its hot end by tensioning the internal thermoelectrode. Thermocouple according to claim 1, characterized in that the fusible element is made as part of an external thermoelectrode. Thermocouple according to claim 1, characterized in that the fusible element is made as part of an internal thermoelectrode. A thermocouple according to claim 1, characterized in that the low-temperature part of the valve is made with channels for supplying an inert gas medium into the cavity of the high-temperature part.

Description

SHOCK CRAFT

The invention relates to the field of thermoelectric converters and can be used to measure temperature-temperature reflux high-temperature technological processes, in particular, when studying the processes of melting refractory materials of the active zone of a nuclear reactor in the range of 2500-2700 ° C,

Known high-temperature thermocouple containing two tungsten-fired thermoelectrodes, the first of which is made in the form of a rod or wire sheathed inside a ceramic tube and the second in the form of rectilinear and spring sections with a ratio of lengths satisfying the tightening // / L, where: D is the straight length linear section, 1, is the length of the spring section. When the thermocouple is heated, its working junction moves, while the first thermoelectrode moves freely through the vacuum motion input and inside the ceramic case, and the second thermoelectrode moves due to the extension of its spring QQQP

L 1379646, 6-OIK7 / 02, claimed 12/29/85),

A disadvantage of the known thermocouple is that it does not allow measuring the temperature above, since above this temperature the ceramic materials of the cover become electrically conductive. In addition, it is technologically difficult to manufacture a spring section of an external thermoelectrode with a small diameter of coils (several millimeters) from a refractory wire, which complicates the manufacture of the thermocouple as a whole.

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2400-2500 0. The thermocouple contains a tungsten cover filled with an inert gas environment, inside of which there is an assembly of wire thermoelectrodes made of refractory metal materials (tungsten, tungsten alloy). Using a tungsten disk, a hot junction of thermoelectrodes is connected to a drawing wire of refractory metal, a parrimer made of wokframing alloy, the ends of which are mounted on an asbestos-cement sleeve inserted inside a flange located in the low-temperature zone of the furnace. The cold sheath of thermoelectrodes is mounted on a movable block, which is connected to a pull-out spring placed on the opposite side behind the furnace body. The initial tension of the retracting spring is selected from such a calculation that, as the thermoelectrodes elongate during heating, they are maintained in a taut state to prevent their sagging and contact with the walls of the heater and with each other. In this case, the tensile force should not exceed the tensile strength of thermoelectrodes at high temperatures (see High-temperature thermocouples. Danishevsky S.K., Swede-Shvets N.y., M., Metallurgy, 1977, SL75 “177; a.s. USSR L 199449, 6-OIKI5 / 00, claimed 19,10.63).

The disadvantages of the known thermocouple are the complexity of its design, excluding its use directly in any technological process, since a hot junction of thermoelectrodes is located between the cold sections of the 1st thermocouple. The known thermocouple cannot be used, for example, as an immersion thermocouple or as a surface thermocouple fixed by hot end at the measurement object.

- 2 containing a coaxial assembly of thermoelectrodes, the outer ones of which are made in the form of a carborundum tube, and the inner one is made of molybdenum wire placed in an alumina insulating tube (or beads) connected to a steel spiral shell mounted by insulating sleeves on the cold end of the outer thermoelectrode and providing a tightness of the internal thermoelectrode. When operating in molten salts and other aggressive environments, the thermocouple is placed in a MaTfpe ceramic or metal arg, which ensures its tightness during measurements (see USSR AS L 564546, OIK7 / 06, application 18.03.76),

The known thermocouple can also not be used at temperatures higher than the presence of ceramic materials in it (carborundum tube and alumina electrical insulation) .In addition, it is technologically difficult to ensure the density of the hot junction by coating with carborundum powder and additional protection of the hot end by coating with carborundum-alumina paste, with subsequent drying and heat treatment at a temperature of 10C10-1200 C.

An analysis of the state of the art in the field of high-temperature thermo-pairs shows that there are currently no thermocouples capable of providing accurate and reliable temperature measurements above. This is due to the use of ceramic materials in well-known thermocouples, as well as to the structural and technological complexity of thermocouple assemblies, while thermoelectrodes made of refractory metals and alloys themselves are able to operate at temperatures higher in neutral, reducing, and vacuum media (see the indicated book Vksokotemperaturnye thermocouples, pp. 80-97)

"" To solve the posed problem and achieve the objective of the invention, the author proposes an extra-coke temperature thermocouple, including a coaxial assembly of thermoelectrodes placed in a pressure fitting containing a high-temperature part and a low-temperature part with a spring unit for tensioning the internal thermoelectrode, which differs from the known analogs in that the assembly is equipped with fusible element with a reference melting point installed in the electrical circuit of the assembly and made with the possibility of its replacement after races melting, and the high-temperature part of the reinforcement is removable and contains a cavity for collecting the melt of the fusible element. The fusible element may be hollow in the form of a rod mounted in the cross section of the assembly and fixed to its hot end by tensioning the internal thermoelectrode. In addition, the fusible element can be made in the form of part of the external or internal thermoelectrodes. And also, the low-temperature part of the reinforcement can be made with canals for supplying an inert gas medium into the cavity of the high-temperature part. The placement in the assembly of thermoelectrodes of a fusible element with a reference melting point, which is installed in the electrical circuit of the assembly, allows you to record the temperature by changing the properties of the reference material at the stage of its melting, the temperature of which is known exactly. For benchmarks, it is advisable to use metals or alloys, since high-temperature compounds such as oxides, carbides, borsch, nitrides, etc. can partially decompose before reaching their melting point. Available metals with a high melting point, from which benchmarks can be made, include, for example, hafnium (t pl. 2230 ° С), ruthenium (), irvdium С 2447 ° С), niobium ( 2469 ° C), molybdenum (2620 ° C), osmium (), tantalum (2990 ° C). - 4

When the benchmark is melted, the electrical resistance of the assembly of thermoelectrodes changes with their opening or with the preservation of the hot junction (passive benchmark of the rod type) or open circuit (active benchmark in the form of a part of the outer tube or part of the inner wire thermoelectrode). The reference melt is collected in the cavity of the high-temperature part of the arvyatura so that then it does not have a hive effect on the thermoelectrodes (in the case of an active reference), if the active reference is made as part of the internal wire thermoelectrode forming a hot junction with an external tubular thermoelectrode, the change in electrical resistance will be monitored (up to the breaking of the chain) at the stage when the melting point of the local section of the wire reference is reached

The tension force transmitted to the benchmark (passive or active) from the spring assembly through the internal wire thermoelectrode provides, on the one hand, the reliable contact of the benchmark with the hot junction during the entire thermocouple operation, until the benchmark melts, and on the other hand, it provides the mechanical force necessary to quickly release the hot junction from the passive benchmark at the time of its melting and to quickly break the chain at the time of melting of the active benchmark. As a result, an abrupt change in the electric signal occurs in the EHP pair, which makes it possible to record the temperature value reached at the moment, which exactly corresponds to the previously known melting point of the reference material.

The implementation of the high-temperature part of the reinforcement removable allows you to disconnect it from the low-temperature part of the valve to replace the benchmark (passive or active), reconnect both parts to each other and reuse the thermocouple.

- 5 - due to an inert gas medium into the cavity of the high-temperature part, it allows to create reliable) protection of thermoelectrodes and benchmarks from the effects of oxygen or other aggressive gases and increases the stability of their operation at high temperatures, ensuring the accuracy of measurements of a gas-filled genetic thermocouple. These channels can also be used for fast pumping of gases from the thermocouple cavity, if it is used for measurements in a vacuum sealed volume. It follows from the above arguments that the use of the proposed thermocouple allows us to solve the problem posed by the authors and achieve the goal of the invention, that is, to create a thermocouple that allows accurate and reliable measurement of temperatures above, mainly up to 2650 -2700 ° C, where known thermocouples do not work. As a result, the scope of high-temperature thermocouples can be significantly expanded. The proposed thermocouple is shown in the following drawings: the diagram of a thermocouple is shown, a general sectional view; figure 2 - place a figL, option I (with a passive benchmark); in Fig. 3, place A of Fig. L, variant II (with a passive benchmark); in - place And figure 1, option P1 (with an active benchmark); in FIG. 5th place A, option 17 (with an active benchmark). The thermocouple includes sealed fittings consisting of a high-temperature part I and a low-temperature part 2 connected to each other using a collapsible connection 3 having an electrical insulator 4. The coaxial assembly of the thermoelectrodes is formed by an external tubular thermoelectrode 5 and an internal wire thermoelectrode 6, between which a hot junction is formed 7, containing a reference 8, which is connected to the internal thermoelectrode and due to the tension of the latter from the central part 9 installed in the low-temperature part, is fixed to end (hot) part of the assembly Thermoelectrodes through the insulator 10 are hermetically removed from the low-temperature part 2 and connected to the compensation wires II.

The high-temperature part I has a cavity 12, which serves to collect the reference melt, the high-temperature part has channels 18, which serve to supply an inert gas medium into the cavity of the high-temperature part through a central hole in the insulator 4, through which the internal wire thermoelectrode is passed.

Figure 2 shows an embodiment I of a passive frame in the form of a rod 8, which is freely mounted in diametrically opposite holes at the end of the external tubular thermoelectrode 5 and is fixed therein by tension of the internal wire thermoelectric of genus 6, which is in turn connected with the spring 9. tension forces in FIG. 2 is conventionally indicated by arrow 14.

In Fig. 3, an embodiment II of a passive frame in the form of a rod 8 is shown, which is freely installed in the diametrical recess at the end of the lid 15, by means of which a hot junction between the thermoelectrodes is formed, and together with it is pressed against the end of the external thermoelectrode 5 (force along arrow 14 )

Figure 4 shows a variant III of the active frame in the form of an end crumb 16 connected to the end face of the external thermoelectrode 5 and from the end-inside thermoelectrode 6,

In FIG. 5 shows an embodiment 1U of an active frame in the form of a wire part 17 connected to the rest of the internal thermoelectrode 6 and fixed to the end face 18 of the external thermoelectrode having through holes 19 that serve to flow through them

- 7 -

When assembling, using pruction 9, a predetermined tension force is set for the inner wire thermoelectrode 6, which secures the passive frame 8 at the end of the assembly (Figs. 2, 3) or the tension of the active frame 17 C | Ig.5) The casing I is put on c6op: f, which with the help of compound 3 is hermetically connected to the case 2 and inert gas, for example, argon, is supplied into the thermocouple cavity through the channel 13. Then, the thermocouple is vertically installed in the object under study. When heated, the temperature elongations of the assembly compensate | they are spring 9. When the temperature on the hot junction of thermoelectrodes reaches the melting temperature of the reference material, depending on its options, the following processes occur.

Option I (see figure 2)

The rod reference 8 begins to melt, loses its strength, and due to the force 14 is cut by the internal thermoelectrode 6, which leads to the destruction of the hot junction and the abrupt termination of the thermocouple signal. The molten material of the rod 8 flows into the “cavity 12. The temperature-temperature schedule of changes in the electrical signal allows you to accurately record the value of the achieved temperature. After that, the thermocouple is removed from the object, the cover is disconnected from the cover 2, a new rod reference is installed, the thermocouple is assembled and reused. Such a benchmark replacement can be made repeatedly, including for benchmarks from various materials.

Option II (see Fig. 3)

The rod reference 8, as in version I, is cut by the force 14 and the melt flows into the cavity 12. However, the destruction of the hot junction does not occur, since the internal wire thermoelectrode 6, due to tension by the spring 9, continues to contact

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Adjusting the shift 15. Moving power of cutting the reference 8 leads to an abrupt change in the signal of the thermocouple and allows you to precisely set the reached temperature for || and Еоо, after which the thermocouple can continue to work. Replacement of the benchmark is carried out similarly to option I.

Option III C, see FIG. 4)

The active benchmark, made in the form of an end cap 16 connected to the end face of the external thermoelectrode 5, is under the influence of a small current passing through the thermoelectrode, which makes it possible to control the change in the resistance of the electric circuit and accurately record the moment when the cap 16 is cut by the internal thermoelb) (trod 6 from the force 14, an abrupt discontinuity occurs in the circuit 11. The melt of the lid 16 flows into the cavity 12, releasing the end face of the thermoelectrode 5.

Option 1U (see Fig. 5)

The operation of the thermocouple with an active benchmark 17 proceeds similarly to variant III, but a jump-like breaking of the circuit occurs when the wire 17 is melted, the melt of which flows through the holes 19 in the end face 18 into the cavity 12.

In options III and 1U, the replacement of benchmarks is carried out according to the scheme described in I.

Example

The thermocouple was used in a facility designed to study the physicochemical processes of the interaction of the steel body of the nuclear reactor core with the molten core material containing uranium oxide (UOa,) and zirconium oxides (, () x) under a temperature gradient. The range of controlled melt temperature is 2500-26500С, protective cover I of the hot part

- 9 fittings in the form of a tungsten tube with a diameter of 14.5 mm, length 500 mm. “An external thermoelectrode-tantalum tube with a diameter of 9 mm, a wall thickness of 0.2 mm, a length of 450 mm, inside of which there is an active a reference in the form of a molybdenum wire with a diameter of 1.2 mm, one end of a tantalum tube soldered to the bottom (hot junction), and the other end connected to a wire thermoelectrode from BP-2Q alloy (tungsten alloy with 20 rhenium) with a diameter of 0.2 mm. The cover 2 of the cold part of the valve is made in the form of a tube made of I2XI8HIOT steel. Covers I and 2 are connected to each other by means of an adapter 3 having an intermediate electrical insulator 4 of alsinium oxide. The wire thermo-electrode is freely passed through the central hole in the insulator and inside the steel spring 9 and is connected to its free end. At the other end, the spring rests || on the end face of the insulator. The end face of the tantalum thermoelectrode 5 is fixed in an insulator 4 and connected to a 0.2 mm thick BP-20 alloy wire passed through a snarro of a dinner 9. The ends of both wires are then hermetically passed through an aluminum oxide end insulator 10 and connected to compensation wires II.

Previously, the inertia of the thermocouple was studied at a bench installation, it was calibrated in a protective cover, the effect of heat leaks in the protective cover was investigated, the service life of the thermocouple was estimated. In addition, the thermopower of the control thermocouples ВР5 / 20 and the temperature of the outer surface of the thermocouple cover and the crucible were measured using the ZhP-66 pyrometer (error 0.4SS) from the thermoelectric power of the thermocouple under study.

- 10 2 sec., Spread of thermoelectric power not more than 0.4 mV (not more than 1), resource - more than 2.5 hours. The calibrated thermocouple was immersed vertically at a depth of 100 tum in a tungsten crucible with core material and filled with argon at a pressure of 0.2 MPa. The crucible was heated in an argon medium with a tungsten heater placed inside the inductor of the setup. During measurements, the response of the active molybdenum reference was recorded by an abrupt decrease in the value of the thermocouple thermocouple from 41.4 mV to 31.4 mV, which corresponds to the value of the temperature according to the pyrometer reading of $ 2630 $ 10. Thus, the thermocouple readings make it possible to accurately judge the achieved melt temperature core materials at the time of melting of the molybdenum benchmark, the melting point of which is known in advance and equal to 2620 ° C. After the reference has been triggered, the thermocouple is removed from the crucible, disassembled and, after installing a new reference, is reused. In comparison with the prototype, the proposed thermocouple is used as a more accurate and reliable means of indicator control of temperature changes higher, i.e., in the high temperature range, where the prototype and other known thermocouples are not operable. JOO l Octave Authors: LUZHIN V.N., Grechkin A.T. - II Dyakov E.K.

Claims (5)

1. A high-temperature thermocouple, comprising a coaxial assembly of thermoelectrodes, housed in a sealed fixture containing a high-temperature part and a low-temperature part with a spring unit for tensioning the internal thermoelectrode, characterized in that the thermoelectrode assembly is equipped with a fusible element with a reference melting point installed in the electric assembly circuit and made with the possibility of replacing it after melting, and the high-temperature part of the reinforcement is removable and contains a cavity for collecting the melt bench element.  2. The thermocouple according to claim 1, characterized in that the fusible element is made in the form of a rod mounted in the cross section of the assembly and mounted on its hot end by tensioning the internal thermoelectrode.  3. The thermocouple according to claim 1, characterized in that the fusible element is made as part of an external thermoelectrode.  4. The thermocouple according to claim 1, characterized in that the fusible element is made as part of an internal thermoelectrode. 5. A thermocouple according to claim 1, characterized in that the low-temperature part of the valve is made with channels for supplying an inert gas medium to the cavity of the high-temperature part.