Heat flux temperature sensor probe for non-invasive process fluid temperature applications

Abstract

The heat flux temperature sensor probe (400) includes a first mineral insulated cable portion (402) and a second mineral insulated cable portion (404). The first mineral insulated cable portion (402) has a first metallic sheath (406) and a first plurality of thermocouple conductors (408, 410, 411) extending therethrough. The second metallic insulated cable portion (404) has a second metallic sheath (406) and a second plurality of thermocouple conductors (407, 409) extending therethrough. A first thermocouple (412) is formed between one of the first plurality of thermocouple conductors (408, 410, 411) and one of the second plurality of thermocouple conductors (407, 409) proximate a first end of the second mineral insulated cable portion (404). A second thermocouple (416) is formed between at least two of the second plurality of thermocouple conductors (407, 409) proximate the second end of the second mineral insulated cable (402). A sheath (418) is operatively coupled to and connected to the first (402) and second (404) mineral insulated cable portions, and a portion of the interior of the sheath (418) is filled with a non-conductive material.

Description

[Technical Field]

[0001] background In many industrial processes, process fluids are transported through pipes or other conduits. Such process fluids may include liquids, gases, and, in some cases, entrained solids. Flows of such process fluids can be found in any of a variety of industries, including, but not limited to, the manufacture of sanitary food and beverages, water treatment, the manufacture of high-purity pharmaceuticals, chemical processing, hydrocarbon extraction and processing, the hydrocarbon fuel industry, and hydraulic fracturing technologies that utilize erosive and corrosive slurries.

[0002] It is common practice to place a temperature sensor inside a thermowell and insert it into the process fluid flow through an opening in the conduit. However, this method is not always practical because the process fluid can be extremely hot, highly corrosive, or both. Furthermore, thermowells generally require threaded ports or other robust mechanical mountings / seals within the conduit and must therefore be designed to be in a defined location within the process fluid flow system. Thus, while thermowells are useful for providing accurate process fluid temperature, they have many limitations. Process fluid temperature is now estimated by measuring the temperature outside the process fluid conduit, such as a pipe, and using thermal flow calculations. This external method is considered non-invasive because it does not require a defined opening or port within the conduit. Therefore, such a non-invasive method can be placed at virtually any location along the conduit. [Overview of the Initiative]

[0003] overview The heat flux temperature sensor probe includes a first inorganic insulated cable section and a second inorganic insulated cable section. The first inorganic insulated cable section has a first metal sheath, a first plurality of thermocouple conductors extending inside thereof, and an inorganic insulating material that insulates the first plurality of thermocouple conductors from each other and from the first metal sheath. The second inorganic insulated cable section has a second metal sheath, a second plurality of thermocouple conductors extending inside thereof, and an inorganic insulating material that insulates the second plurality of thermocouple conductors from each other and from the second metal sheath. The first thermocouple is formed in close proximity to the first end of the second inorganic insulated cable section between at least one of the first plurality of thermocouple conductors and one of the second plurality of thermocouple conductors. The second thermocouple is formed in close proximity to the second end of the second inorganic insulated cable between at least two of the second plurality of thermocouple conductors. The sheath is operably coupled and connected to the first and second inorganic insulated cable sections, and a portion of the inside of the sheath is filled with a non-conductive material. [Brief explanation of the drawing]

[0004] [Figure 1] This is a schematic diagram of a temperature measuring assembly in which embodiments of the present invention are particularly useful. [Figure 2] This is a schematic diagram of a pipe skin measuring assembly in which embodiments of the present invention are particularly useful. [Figure 3] This is a block diagram of the device electronic circuit of a process fluid temperature measurement assembly. [Figure 4A] This is a schematic cross-sectional view of a heat flux sensor for a non-invasive process fluid temperature measurement system according to an embodiment of the present invention. [Figure 4B] This is a schematic cross-sectional view of a heat flux sensor for a non-invasive process fluid temperature measurement system according to an embodiment of the present invention. [Figure 5A] This is a modified example of a thermocouple configuration according to an embodiment of the present invention. [Figure 5B] This is a modified example of a thermocouple configuration according to an embodiment of the present invention. [Figure 5C] This is a modified example of a thermocouple configuration according to an embodiment of the present invention. [Figure 5D] This is a modified example of a thermocouple configuration according to an embodiment of the present invention. [Figure 6A] This is a schematic cross-sectional view of a heat flux sensor for a non-invasive process fluid temperature measurement system, according to another embodiment of the present invention. [Figure 6B] This is a schematic cross-sectional view of a heat flux sensor for a non-invasive process fluid temperature measurement system, according to another embodiment of the present invention. [Figure 7] This is a flowchart illustrating a method for manufacturing a heat flux sensor according to an embodiment of the present invention. [Modes for carrying out the invention]

[0005] Detailed description of exemplary embodiments Heat flow measurement has many applications that provide better methods for measuring process temperature. For example, the Rosemount X-Well® technology, available from Emerson Automation Solutions, can be used to measure process temperature in a non-invasive or non-intrusive manner. This technology uses temperature measurement of the pipe surface (skin), reference temperature measurement from a position spaced away from the pipe surface, known thermal relationships between each position of the temperature sensor (e.g., length and thermal conductivity), and heat flow calculations to estimate the internal surface temperature of a process fluid conduit and, from there, the temperature of the process fluid within the conduit. While heat flux sensors can provide skin temperature sensors as well as reference temperature sensors, the placement of the elements is crucial to ensure proper performance and a proper understanding of heat flow.

[0006] Figure 1 is a schematic diagram of a temperature measurement assembly in which embodiments described herein are particularly useful. The assembly 100 includes a sensor assembly 130 coupled to a process vessel wall 110. The coupling can be a pipe clamp 120, as shown in Figure 1. The sensor assembly 130 has a number of lead wires 150 extending to a transmitter 140, which may be locally connected to the sensor assembly 130 or remotely connected from the sensor assembly 130. The transmitter 140 includes a controller configured to perform heat flux calculations.

[0007] Figure 2 is a schematic diagram of a pipe skin measurement assembly in which embodiments of the present invention are particularly useful. The system 200 includes a pipe 110 coupled to a heat flux temperature probe 220 via the use of a pipe clamp 212. The heat flux temperature probe 220 is directly coupled to a transmitter 222. The transmitter 222 can be configured to calculate the heat flow based on the signal received from the heat flux temperature probe 220. The heat flux temperature probe 220 is biased against the outer diameter of the pipe 110 by a spring 208. Although the spring 208 is illustrated, those skilled in the art will understand that various techniques can be used to bias the heat flux temperature probe 220 to be in continuous contact with the pipe 110. The heat flux temperature probe 220 includes a plurality of temperature-sensing elements, such as thermocouples. These thermocouples are electrically connected to a transmitting circuit in a housing 210, which is configured to acquire temperature measurements from the heat flux temperature probe 220 and calculate an estimate of the process fluid temperature based on these measurements.

[0008] For example, basic heat flow calculations can be simplified as follows: T corrected = T skin + (T skin - T reference ) * (R pipe / R sensor )

[0009] In this equation, T skin This is the measured temperature of the outer surface of the conduit. Furthermore, Treference is the second temperature obtained for a position having a constant thermal impedance (R skin ) from a temperature sensor that measures T sensor . R pipe is the thermal impedance of the conduit and can be obtained manually by acquiring pipe material information and pipe wall thickness information. Additionally or alternatively, parameters related to R pipe can be determined during calibration and saved for later use. Thus, using an appropriate heat flux calculation as described above, the circuitry within housing 210 can calculate an estimate of the process fluid temperature (T corrected ) and communicate an indication regarding such process fluid temperature to an appropriate device and / or control room.

[0010] FIG. 3 is a block diagram of a device electronic circuit according to an embodiment of the present invention. The electronic circuit 300 can be housed within an electronic circuit housing 210. The electronic circuit housing 210 can be associated with a transmitter, such as transmitter 222 (shown in FIG. 2). Further, at least a portion of the electronic circuit 300 can form part of a sensor assembly, such as a sensor described herein. The electronic circuit 300, as one embodiment, includes a processor 350, one or more analog / digital (AD) converters 354, and a memory 356. The processor 350 can be a digital microprocessor. The memory 356 can include a digital data storage device electronically coupled to the processor 350. The electronic circuit 300 can be accessed locally via a local operator interface 366 that can display, for example, temperature or the status of the device.

[0011] The processor 350 is connected to a temperature sensor, such as a sensor described herein, by a connection between the A / D converter 354 and another sensor lead 342.

[0012] [[ID=As one embodiment, the electronic circuit 300 can also include a communication interface 358. The communication interface 358 provides communication between the electronic circuit 300 and a control or monitoring system 362. The electronic circuit 300 can transmit the calculated temperature of the process fluid in the process to the control system 362. Communication between the temperature measurement assembly 300 and the control system 362 can be performed via any suitable wireless connection or a wired connection. For example, the communication can be represented by an analog current via a two-wire loop in the range of 4 to 20 mA. Alternatively, the communication can be transmitted in digital form via a communication bus using a digital protocol such as a two-wire loop using the HART (registered trademark) digital protocol or the FOUNDATION (registered trademark) fieldbus.

[0013] The communication interface 358 can optionally include a wireless communication circuit 364 for communication by wireless transmission using a wireless protocol such as WirelessHART (IEC62591). Further, communication with the controller monitoring system 362 can be performed directly or via a network of any number of intermediate devices, for example, a wireless mesh network (not shown in FIG. 3). The communication interface 358 can assist in managing and controlling communication to and from the temperature measurement assembly 300. For example, the control or measurement system 362 can provide the configuration of the temperature measurement assembly 300, including input or selection of basic structure parameters, parameters of the wall of the process vessel, or selection of a heat transfer model for a particular application, by the communication interface 358.

[0014] According to embodiments described herein, a simplified heat flux temperature probe is provided along with a method for manufacturing the probe, which generally improves manufacturability, reduces manufacturing costs, and leverages existing manufacturing processes. Several embodiments described herein utilize commercially available mineral-insulated (MI) cables, also known as mineral-insulated metal sheath (MIMS) cables. MI cables generally have a generally cylindrical metal sheath through which a number of conductors pass. These conductors are insulated from each other and from the metal sheath by an inorganic powder such as magnesium oxide (MgO) or ceramic. MI cables can specify a variety of different materials for the metal sheath as well as for the conductors that pass through them. Furthermore, the conductors can also be specified as thermocouple metals. Examples of thermocouple metals include metals for J-type thermocouples (i.e., iron-constantan), K-type thermocouples, N-type thermocouples, E-type thermocouples, and T-type thermocouples (i.e., copper-constantan). Furthermore, the metal sheath can also be specified as, for example, 304 stainless steel, 310 stainless steel, 316 stainless steel, 321 stainless steel, and Inconel. A commercial supplier of MI cables is Omega Engineering in Norwalk, Connecticut.

[0015] Figures 4A and 4B are schematic cross-sectional views of a heat flux sensor for a non-invasive process fluid temperature measurement system according to an embodiment of the present invention. The heat flux sensor 400 is generally formed from a plurality of portions of MI cables 402, 404. Thus, each MI cable portion has a metal sheath 406 that includes a plurality of thermocouple conductors 408 insulated from each other and from the metal sheath 406 by an inorganic powder 410. As described above, the inorganic powder 410 is generally magnesium oxide or a ceramic. The first MI cable portion 402 is shown as having three thermocouple conductors 408, 410, 411. Of the three, conductors 408 and 410 are joined to each other at a thermocouple junction 412 at the low temperature end located between the first MI cable portion 402 and the second MI cable portion 404. Further, the second MI cable portion 404 has a plurality of thermocouple conductors 407, 409 that terminate at a sensor end cap 414 that forms a thermocouple junction 416 at the high temperature end.

[0016] As shown in FIGS. 4A and 4B, a portion of the conductors of the first MI cable portion is electrically coupled to the conductors of the second MI cable portion by welding or the like. In the illustrated example, the conductor 411 of the MI cable portion 402 is welded to the conductor 407 of the second MI cable portion 404 at location 424. Similarly, the conductors 408 and 410 of the MI cable portion 402 are welded to the conductor 409 of the MI cable portion 404 at location 426. When joining two conductors simply (i.e., without creating a thermocouple), by welding a thermocouple conductor wire within one MI cable portion to a thermocouple conductor wire within another cable, the two conductors must be of the same metal as each other.

[0017] Figures 4A and 4B also show that a support tube 418 is provided over the entire length of the second MI cable portion 404, similar to a portion of the first MI cable 402. The support tube 418 is fixed to the metal sheath 406 of the first MI cable 402 by a suitable process such as welding.

[0018] In the designs shown in Figures 4A and 4B, commercially available MI cables and MgO powder can be used, and the joint position (i.e., the position of the jointed thermocouple 412 at the low temperature end relative to the jointed thermocouple 416 at the high temperature end) can be made highly accurate. Preferably, the first MI cable section 402 and the second MI cable section 404 are welded to the outer support tube 418 after the thermocouple joint is formed. This support tube 418 includes a hole 420 (shown in Figure 4B) that allows a suitable insulator such as MgO or ceramic to be filled into the cavity 422 between the first MI cable section 402 and the second MI cable section 404 after the thermocouple joint is formed. Once the cavity 422 is filled, the hole 420 can be sealed by forming a weld to fill the hole 420. Depending on the distance of the conductors from the metal sidewall, air may be sufficient as an electrical insulator instead of the insulating material 410. In this case, the hole 420 may not be necessary. To make it easier to understand, various wiring combinations can be used according to the embodiments described herein by specifying a variety of numbers of conductors in the MI cable section.

[0019] Figures 5A to 5D show modified thermocouple configurations according to embodiments of the present invention. Figure 5A shows a three-wire MI cable joined to a two-wire MI cable. Figure 5B shows a four-wire MI cable joined to a two-wire MI cable. As shown, joints 412 and 416 share one conductor, and one wire remains unused. Figure 5C shows a first MI cable, which is a four-wire MI cable joined to a two-wire MI cable. Note that joints 412 and 416 do not share a conductor.

[0020] In Figure 5D, a single four-wire MI cable is used, and the material is simply removed at the second joint. The two conductors after the second joint are then not used. A similar configuration can also be made using a single three-wire MI cable with one shared conductor. In any such embodiment, the outer sheath 406 of the MI cable, or a portion thereof, is removed at the location of the second joint. The two wires of the four-wire MI cable are cut together at this location and welded, thereby forming the thermocouple joint 412 at the low-temperature end. The joint is then covered with a suitable sleeve, such as a sleeve 502 (shown in Figure 6A), and the sleeve is welded to the MI cable or otherwise connected. The opening in the sleeve can be used to fill and seal the joint as needed. This particular embodiment has the potential to allow for more precise positioning of the second joint thermocouple relative to the thermocouple joint at the high-temperature end. As mentioned above, the positioning of the thermocouple junction at the second end becomes more important when using algorithms or processing techniques that rely on the thermal impedance between these two locations. This thermal impedance is based on the material through which the heat flows (e.g., MI cables in general) and the length over which the heat must flow.

[0021] Figures 6A and 6B are schematic cross-sectional views of a heat flux sensor for a non-invasive process fluid temperature measurement system according to another embodiment of the present invention. The heat flux sensor 500 has several similarities with the heat flux sensor 400, and similar components are numbered similarly. One difference between the sensor 400 and the sensor 500 is that the support tube 502 does not extend over the entire length of one of the MI cable sections 402 and 404. Instead, the support tube 502 extends adjacent to the low-temperature thermocouple junction 412, simply covering portions of each of the MI cables 402 and 404. As shown in Figure 6B, the support tube 502 includes a filling opening 420 into which insulating material is supplied. In this embodiment, the insulating material may be an inorganic powder such as MgO or ceramic, but it is also explicitly assumed that a potting material such as epoxy may be introduced through the opening 420 to create an environmental seal.

[0022] In the embodiments shown in Figures 6A and 6B, the support tube 502 is attached to the first MI cable section 402 and the second MI cable section 404 at their respective interfaces 504 and 506. Welds can be provided at each of these attachment interfaces. However, instead of welding the interface 504, it is also explicitly intended to crimp the support tube 502 to the first MI section 402. This is especially true when potting material is used to create an environmental seal.

[0023] Another difference between sensor 500 and sensor 400 is that sensor 500 does not require an end cap coupled to the thermocouple 416 at the hot end. Instead, the thermocouple 416 at the hot end is grounded at position 508 to the sheath 406 of the second MI cable 404. However, in another embodiment, the thermocouple 416 at the hot end may also be grounded to an end cap attached to the end of the second MI cable 404 by welding or other means.

[0024] To make it clear, the embodiments described so far generally provide a pair of thermocouples spaced precisely apart using commercially available MI cables, but it is also explicitly intended that two or more thermocouples can be provided spaced apart simply by adding and coupling additional sections of MI cables, according to the various techniques described herein. Thus, a sensor comprising three or more thermocouples spaced apart along MI cables, each electrically coupled to a measuring circuit of a temperature measurement system using heat flux calculations, is explicitly intended.

[0025] Figure 7 is a flowchart of a method for manufacturing a heat flux sensor according to an embodiment of the present invention. Method 600 begins in block 602, where a first MI thermocouple cable section is provided. An example of such a cable is shown in Figure 4 by reference numeral 402. Next, in block 604, a second MI thermocouple cable is provided. An example of the second MI thermocouple cable is shown in Figure 4A by reference numeral 404. Next, in block 606, a first thermocouple is created between the first and second MI thermocouple cables. This first thermocouple is considered the thermocouple junction at the low-temperature end. Next, in block 608, a second thermocouple is formed at one end of the first and second MI thermocouple cables, opposite to the first thermocouple. An example of this second thermocouple is shown in Figure 4A by reference numeral 416. As illustrated, thermocouple 416 is at the end of the second MI cable 404 opposite to the low-temperature end thermocouple 412.

[0026] Next, in block 610, the sleeve is slid over the first thermocouple and coupled to the first and second MI thermocouple cables by welding or crimping. This sleeve can be a support sleeve 418 (shown in Figure 4A) or a support sleeve 502 (shown in Figure 6A). Next, in block 612, the sleeve is filled with insulating material. Step 612 can be arbitrary depending on the conductor spacing to the side wall. This insulating material can be MgO powder 614, ceramic powder 616, or potting material 618. Next, in block 620, the sleeve is sealed. In embodiments using MgO powder 614 or ceramic powder 616, the sleeve is sealed by welding the opening into which the powder is introduced. In embodiments where the insulating material is potting 618, the sleeve is sealed simply by the curing of the potting material.

Claims

1. A heat flux temperature sensor probe, A first inorganic insulated cable portion having a first metal sheath, a first plurality of thermocouple conductors extending inside the first plurality of thermocouple conductors, and an inorganic insulating material that insulates the first plurality of thermocouple conductors from each other and from the first metal sheath, A second inorganic insulated cable section having a second metal sheath, a second plurality of thermocouple conductors extending inside the sheath, and an inorganic insulating material that insulates the second plurality of thermocouple conductors from each other and from the second metal sheath. A first thermocouple is formed between at least one of the first plurality of thermocouple conductors and one of the second plurality of thermocouple conductors, adjacent to the first end of the second inorganic insulated cable portion. A second thermocouple is formed between at least two of the second plurality of thermocouple conductors, adjacent to the second end of the second inorganic insulated cable portion. A sheath that is operably coupled and connected to the first and second inorganic insulated cable portions, wherein a portion of the interior of the sheath is filled with a non-conductive material, and An end cap attached to the sheath is located near the second end of the second metal sheath. The heat flux temperature sensor probe, including the heat flux temperature sensor probe.

2. The heat flux temperature probe according to claim 1, further comprising at least one coupling portion of the same type of thermocouple conductor wire from the first plurality of thermocouple conductors to the second plurality of thermocouple conductors.

3. The heat flux temperature probe according to claim 1, wherein the inorganic insulating material is magnesium oxide powder.

4. The heat flux temperature probe according to claim 1, wherein the inorganic insulating material is ceramic.

5. The heat flux temperature probe according to claim 1, wherein the sheath is made of metal.

6. The heat flux temperature probe according to claim 5, wherein the sheath is welded to at least one of the first and second inorganic insulated cable portions.

7. The heat flux temperature probe according to claim 1, wherein the sheath has the non-conductive material sealed inside.

8. The heat flux temperature probe according to claim 1, wherein the sheath extends over the entire length of the second inorganic insulated cable portion.

9. The heat flux temperature probe according to claim 1, wherein the second thermocouple is electrically coupled to the sheath in close proximity to the second end of the second inorganic insulated cable portion.

10. The heat flux temperature probe according to claim 1, wherein the number of the first plurality of thermocouple conductors is greater than the number of the second plurality of thermocouple conductors.

11. The heat flux temperature probe according to claim 1, wherein the inorganic insulating material is air.

12. A heat flux temperature sensor probe, An inorganic insulated cable having a metal sheath, a plurality of thermocouple conductors extending inside the sheath, and an inorganic insulating material that insulates the plurality of thermocouple conductors from each other and from the metal sheath. At the joint where the metal sheath of the inorganic insulated cable has been removed, a first thermocouple is formed between two of the plurality of thermocouple conductors. A second thermocouple is formed between two of the plurality of thermocouple conductors, adjacent to the end of the inorganic insulated cable, A sheath operably welded to the inorganic insulated cable at the aforementioned joint position, wherein a portion of the interior of the sheath is filled with a non-conductive material, The heat flux temperature sensor probe, including the heat flux temperature sensor probe.

13. The heat flux temperature sensor probe according to claim 12, wherein the interior of the sheath is filled with a potting material.

14. The heat flux temperature sensor probe according to claim 12, wherein the second thermocouple is attached to the metal sheath of the inorganic insulated cable at the end of the inorganic insulated cable.

15. A temperature measurement assembly for process fluids, Transmitter's electronic circuitry, A heat flux temperature sensor probe coupled to the electronic circuit of the transmitter, First inorganic insulated cable section, At the joint position, the second inorganic insulated cable portion is operably coupled to the first inorganic insulated cable portion, At the aforementioned junction, a first thermocouple formed from a thermocouple conductor, On the opposite end of the first and second inorganic insulated cable sections, opposite to the aforementioned joint position, a second thermocouple formed from a thermocouple conductor is provided. The heat flux temperature sensor probe, Includes, The first and second thermocouples are operably coupled to the electronic circuit of the transmitter, and the electronic circuit of the transmitter is configured to perform heat flux calculations at least partially based on the known thermal impedance between the first and second thermocouples, and At least one of the first inorganic insulated cable section and the second inorganic insulated cable section is insulated by air. A temperature measurement assembly for the aforementioned process fluid.

Images