GB2065969A - Thermoelectric Temperature Measurement - Google Patents
Thermoelectric Temperature Measurement Download PDFInfo
- Publication number
- GB2065969A GB2065969A GB8038811A GB8038811A GB2065969A GB 2065969 A GB2065969 A GB 2065969A GB 8038811 A GB8038811 A GB 8038811A GB 8038811 A GB8038811 A GB 8038811A GB 2065969 A GB2065969 A GB 2065969A
- Authority
- GB
- United Kingdom
- Prior art keywords
- components
- junction
- leads
- temperature
- tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000009529 body temperature measurement Methods 0.000 title description 2
- 229910052751 metal Inorganic materials 0.000 claims abstract description 17
- 239000002184 metal Substances 0.000 claims abstract description 17
- 150000002739 metals Chemical class 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 9
- 230000007704 transition Effects 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 12
- 239000012530 fluid Substances 0.000 claims description 9
- 238000012544 monitoring process Methods 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 5
- 238000005259 measurement Methods 0.000 abstract description 3
- 238000001514 detection method Methods 0.000 abstract description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000004044 response Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000003466 welding Methods 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910000619 316 stainless steel Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 229910001055 inconels 600 Inorganic materials 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K13/00—Thermometers specially adapted for specific purposes
- G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
- G01K7/04—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples the object to be measured not forming one of the thermoelectric materials
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
The measuring of temperature or the detecting of changes in temperature is achieved by using components (18, 16 or 16, 24 or 18, 16, 24) of dissimilar metals to form a thermoelectric junction (22 or 28 or 22, 28 combined, respectively). The components have leads (40, 38, 36) of materials of compatible thermoelectric properties, which leads are used to form a circuit with the components and a device responsive to current flow in the circuit in dependence upon the temperature difference between the junction formed by the components and a second junction (which may be at a reference temperature). During said measurement or detection, the components are subject to another operation or perform a further function; for example, the components are a transition assembly in a heat exchanger. <IMAGE>
Description
SPECIFICATION
Temperature Measurement
The invention relates to measuring temperature or detecting changes in temperature.
The measurement of temperature or the detection of changes in temperature is often effected by using a thermocouple temperaturemeasuring apparatus. The thermocouple can be merely secured to the surface of a component.
Alternatively, the thermocouple can be in the form of a probe which can be positioned in fluid whose temperature is to be measured or in a pocket in a solid component whose temperature is to be measured.
However, such devices, except in those applications where the probe is in direct contact with a fluid, tend to be relatively slow in their response owing to their physical relationship with the item whose temperature is to be measured.
According to the invention, a method of measuring temperature or detecting change in temperature at a junction of components of dissimilar metals while the components are subject to or perform an operation or function not part of the method, the method comprising monitoring current flowing in an electric circuit including said junction, which current depends on the temperature difference between said junction and a second junction in the circuit, and determining the temperature corresponding to the monitored current or using changes in the monitored current to detect said change.
According to the invention also, apparatus for measuring temperature or detecting changes in temperature comprises at least two components of dissimilar metals which form a first junction, leads having first ends electrically connected respectively to the components, each lead being of a material having thermoelectric properties compatible with the respective component, second ends of the leads being located at a second junction and a device completing an electric circuit with the leads and the components, the device being responsive, in use, to the current flowing in the circuit in dependence upon the temperature difference between the junctions.
For example, the components form at least part of a tube through which fluid can flow, the device measuring the temperature of the fluid. Typically, the tubular components form a transition assembly in a heat exchanger, the fluid being hot water or steam, for example.
In other applications the components may be other shapes, e.g. flat in a plate-type heat exchanger, or form parts ofother structures such as an enclosure or vessel.
It is preferred that the components are joined together by, for example, welding, brazing or a similar process. However, in some applications it may only be necessary to effect a screw-threaded, compression or similar joint provided that intimate contact of the components is achieved.
Generally, the leads are of the same material as their respective components. However, in some applications it may be desirable to use leads of materials which have the same thermoelectric properties as the metals of the respective components but which are made of less expensive materials.
The reference temperature is maintained by an ice and water mixture for example.
The device is, for example, a potentiometer linked to converting means which converts the measured potential difference directly into a temperature which can be read off a scale, printed on a print-out device; or the temperature can be recorded on a recording device. Such a link-up would involve preliminary calibrations of the converting means.
Apparatus incorporated in a heat exchanger will now be described to illustrate the invention by way of example with reference to Figure 1, which is cross-section through a threecomponent transition assembly forming part of a boiler tube, Figure 1 being the only figure of the accompanying drawing.
The boiler tube 10 is typically a tube forming part of a heat exchanger in an AGR power plant.
Owing to temperature requirements, the tube has sections of different materials which have to be joined by fusion welding. Owing to the types of materials used in the tube, the joint has to be effected by using a transition assembly.
The higher-temperature section of the tube 10 is formed of a tube component 12. The tube component 12 is made of an austenitic steel designated as 316 stainless steel and primarily contains 65% iron, 17% chromium and 13% nickel.
The lower-temperature section of the tube 10 is formed of a tube component 14. The steel of the tube component 14 is primarily iron with 9% chromium and 1% molybdenum.
The tube components are joined by a three component transistion assembly 1 6, 1 8 and 24.
The transition-tube component 1 6 is made of a metal known as Alloy 600 and that consists primarily of 73% nickel, 1 6% chromium and 10% iron.
As shown, the tube components 12 and 14 are of different diameters and consequently the second transition-tube component 18, made of the same metal as tube component 14, has portions of different diameters and is interposed between the tube component 14 and the first transition-tube component 1 6. The component 1 8 is welded to those components 14 and 1 6 at 20 and 22, respectively.
The third transition-tube component 24, made of 31 6 stainless steel, is interposed between the tube component 12 and the first transition-tube component 1 6 and is welded thereto at 26 and 28, respectively. The third transition-tube component 24 has a boss 30 in which is sunk a bore 32 parallel to the tube axis 34 into which a conventional thermocouple probe can be placed, if desired. That type of construction is used owing to the tube 10 being pressurisable to relatively high pressures making it undesirable to make the tube wall thinner at a given point.
Leads in the form of wires 36, 38 and 40 are spot welded at respective first ends to the transition-tube components 24, 1 6 and 1 8 and are made of the same metals as the respective transition-tube components.
Second ends (not shown) of the wires 36, 38 and 40 are located at a second junction at which appropriate means (not shown) maintain them at a reference temperature. Copper wires (not shown) connect the second ends of the wires 36, 38 and 40 in pairs to respective potentiometers or to switches which allow pairs of the wire to be connected across a potentiometer. The second ends of the wires 36, 38 and 40 and the copper wires form the second junction.
The or each potentiometer is connected to a converting means which converts the measured current into a temperature signal which can be recorded by a print-out or other device or which can give a reading on a scale.
in use, the apparatus can be used to determine the temperature of fluid in the tube 10 by monitoring the potential difference between the pair of wires 36 and 38 or 38 and 40.
Alternatively, the potential difference between the pair of wires 36 and 40 could be monitored.. It is, in fact, preferred to monitor the potential difference between the wires 36 and 40. That is because the double junction formed by the three types of dissimilar metals results in a greater potential difference to be measured for a given temperature.
Tests showed that the apparatus responded to a stepped change in temperature in approximately 8 seconds as compared to approximately 30 seconds for a conventional thermocouple located in the bore 32. It is understood that even a "fast response" thermocouple, i.e. one located in a pocket extending through the tube wall into the fluid stream, only has a response time of approximately 10 seconds.
Where the metals are suitable to be joined directly together, only those two dissimilar metals are required to form a junction.
Although three wires 36, 38 and 40 have been shown, in practice only one pair of the wires is necessary. However, in case one wire should break all three wires could be provided, if desired.
In the particular application described, it is desirable to monitor the temperature of the fluid in the tube 10 in order to determine whether a malfunction has resulted in water entering the tube component 12 in the place of steam, the metal of the tube component 12 being susceptible to stress corrosion in the presence of water. If that condition is detected the power plant is shut down as a safety precaution.
Consequently, it is preferable to have a relatively fast response.
The invention is also applicable to similar situations in other types of boiler where the temperature has to be monitored.
In a modification, the second ends of the leads may be joined at the second junction and the device, i.e. the potentiometer, located in the one of a pair of leads. In that instance, the second junction can still be kept at a reference temperature. Alternatively, the second junction can be located at a position, whose temperature is accurately monitored and differs by relatively small amounts (e.g. 1 OOC) from the temperature of the components, such that the temperature difference between the components and that position can be relatively accurately monitored as compared to determining the temperatures of the components and that position to obtain the difference by, for example, thermocouples.
It is also envisaged that the invention would be applicable in a number of other areas; for example flowrate measurement by determining the rate of cooling of a tube by temperature monitoring, heat flux monitoring, heat transfer testing, or monitoring the temperature of a weld pool during a welding process joining two components of dissimilar metals both for quality control purposes and for providing a feed-back signal to influence the welding process.
Claims (14)
1. A method of measuring temperature or detecting change in temperature at a junction of components of dissimilar metals while the components are subject to or perform an operation or function not part of the method, the method comprising monitoring current flowing in an electric circuit including said junction, which current depends on the temperature difference between said junction and a second junction in the circuit and determining the temperature corresponding to the monitored current or using changes in the monitored current to detect said change.
2. A method according to Claim 1, in which the second junction is maintained at a reference temperature.
3. A method according to Claim 1, in which the second junction is located at a position relative to the components such that the temperature difference between the components and said position can be monitored.
4. Apparatus for measuring temperature or detecting changes in temperature comprising at least two components of dissilimilar metals which form a first junction, leads having first ends electrically connected respectively to the components, each lead being of a material having thermoelectric properties compatible with the respective component, second ends of the leads being located at a second junction and a device completing an electric circuit with the leads and the components, the device being responsive, in use, to the current flowing in the circuit in dependence upon the temperature difference between the junctions.
5. Apparatus according to Claim 4, in which the device is- connected across the second ends of the leads, said second junction being maintainable, in use, at a reference temperature.
6. Apparatus according to Claim 4, in which the second ends of the leads are joined together, the device being inserted in one of said leads, said second junction being maintainable, in use, at a reference temperature.
7. Apparatus according to Claim 6, in which the second ends of the leads are joined together, the device being inserted in one of said leads, said second junction being locatable, in use, at a position relative to the components such that the temperature difference between the components and said position can be monitored.
8. Apparatus according to Claim 4, in which the components form at least part of a tube through which fluid flows.
9. Apparatus according to Claim 8, in which the tube is part of a heat exchange apparatus.
10. Apparatus according to Claim 8 or Claim 9, in which the components form a transition assembly between tube parts of dissimilar metals.
11. Apparatus according to Claim 10, in which three components form the transition assembly, the two components adjacent the tube parts are of the same material as the adjacent tube parts and the component intermediate said two components being of a metal compatible with said dissimilar metals.
12. Apparatus according to Claim 11, in which said first junction is formed between one of said two components and said intermediate component, the first wends of the leads being connected to said one component and said intermediate component.
13. Apparatus according to Claim 11, in which said first junction is a combination of junctions formed between each of said two components and said intermediate component, the first ends of the leads being connected to said two components.
14. Apparatus according to Claim 11, in which first junctions are formed between each of said two components and said intermediate component and by a combination of said junctions between each of said two components and said intermediate components, the first ends of the leads being connected to each of the components so that, in use, the potential difference across one or more pairs of leads can be used.
1 5. A method according to Claim 1 substantially as hereinbefore described with reference to the accompanying drawing.
1 6. Apparatus according to Claim 4 substantially as hereinbefore described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8038811A GB2065969B (en) | 1979-12-05 | 1980-12-03 | Thermoelectric temperature measurment |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7941948 | 1979-12-05 | ||
| GB8038811A GB2065969B (en) | 1979-12-05 | 1980-12-03 | Thermoelectric temperature measurment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2065969A true GB2065969A (en) | 1981-07-01 |
| GB2065969B GB2065969B (en) | 1984-06-27 |
Family
ID=26273796
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8038811A Expired GB2065969B (en) | 1979-12-05 | 1980-12-03 | Thermoelectric temperature measurment |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2065969B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2140206A (en) * | 1983-05-20 | 1984-11-21 | British Petroleum Co Plc | Thermoelectric power generator associated with oil pipelines |
-
1980
- 1980-12-03 GB GB8038811A patent/GB2065969B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2140206A (en) * | 1983-05-20 | 1984-11-21 | British Petroleum Co Plc | Thermoelectric power generator associated with oil pipelines |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2065969B (en) | 1984-06-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |