Non-invasive display of process fluid flow using temperature difference

Abstract

The process fluid flow system (300) includes a first pipe skin sensor (306, 320, 322, 324) and a second pipe skin sensor (306, 320, 322, 324). The first pipe skin sensor (306, 320, 322, 324) is positioned at a first location on the process fluid conduit (100) to measure an external temperature of the process fluid conduit (100). The second pipe skin sensor (306, 320, 322, 324) is positioned at a second location on the process fluid conduit (100) to measure an external temperature of the process fluid conduit (100). A measurement circuit (238) is coupled to the first and second pipe skin sensors (306, 320, 322, 324). The controller (222) is coupled to the measurement circuit (238) and is configured to identify a state of the process fluid flow based on signals from the first and second pipe skin sensors (306, 320, 322, 324) and output an indication of the state of the process fluid flow.

Description

[Technical field]

[0001] background Many industrial processes transport process fluids through pipes and other conduits. Such process fluids may include liquids, gases, and in some cases, entrained solids. These process fluid flows may be found in any of a variety of industries, including, but not limited to, sanitary food and beverage production, water treatment, high purity pharmaceutical production, chemical processing, hydrocarbon extraction and processing, and the hydrocarbon fuel industry, including hydraulic fracturing techniques that utilize abrasive and corrosive slurries.

[0002] Measuring a property of a process fluid, such as pressure, flow rate, or temperature, typically requires the use of a measuring device that is extended into the process fluid. Extending the measuring device into the process fluid is an invasive measurement in that the process fluid conduit must have an opening through which the measuring device passes. Furthermore, the opening must be sealed to prevent the process fluid from leaking or spilling out. Furthermore, a measuring device that is exposed to the process fluid can be worn or damaged by the high velocity process fluid, which can sometimes be very abrasive. Summary of the Invention

[0003] The process fluid flow system includes a first pipe skin (exterior surface) sensor and a second pipe skin (exterior surface) sensor. The first pipe skin sensor is positioned to measure an exterior temperature of the process fluid conduit at a first location on the process fluid conduit. The second pipe skin sensor is positioned to measure an exterior temperature of the process fluid conduit at a second location on the process fluid conduit. A measurement circuit is coupled to the first and second pipe skin sensors. A controller is coupled to the measurement circuit and configured to identify a condition of the process fluid flow based on signals from the first and second pipe skin sensors and output an indication of the condition of the process fluid flow. [Brief description of the drawings]

[0004] [Figure 1] 1 is a schematic diagram of a heat flow measurement system to which embodiments of the present invention are particularly applicable; [Diagram 2] 1 is a diagram of a process fluid temperature estimation system to which embodiments of the present invention are particularly applicable; [Diagram 3] 1 is a schematic diagram of a system for estimating the temperature of a process fluid in accordance with an embodiment of the present invention; [Figure 4] 1 is a chart showing temperature at different pipe wall locations over time as the flow of a process fluid changes. [Diagram 5] FIG. 2 is a block diagram of a method for estimating the temperature of a process fluid in a flow conduit for various flow conditions according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] The embodiments disclosed herein generally provide important process fluid information without requiring that a measurement instrument or sensor pass through the process fluid conduit. Thus, the embodiments described herein are generally considered non-invasive in that they are not process damaging. However, important process fluid parameters can be determined and provided based on a number of temperature measurements at the external surface of the process fluid conduit. Examples can include an indication of whether process fluid is flowing in the conduit, and some degree of flow status in the process fluid conduit. Furthermore, this process fluid flow information can be provided to a heat flow calculation, or other suitable calculation, to provide an estimate of the temperature of the process fluid in the conduit that is adjusted or otherwise compensated for the determined process fluid flow. Much of the description presented below focuses on this synergistic effect, where it is expressly contemplated that the embodiments described herein can be implemented simply by providing an indication of process fluid flow based on a number of external temperature measurements.

[0006] It is common practice to place a temperature sensor in a thermowell and insert it into the process fluid flow through an opening in a conduit. However, as discussed above, this method is not always practical. Furthermore, a thermowell typically requires a threaded port or other robust mechanical mount / seal in the conduit, and therefore the process fluid flow system must be designed to be in a defined location. Thus, although thermowells are useful for providing accurate process fluid temperatures, they have many limitations.

[0007] Recently, the temperature of a process fluid has been estimated by measuring the external temperature of a process fluid conduit, such as a pipe, and using heat flow calculations. This external approach is considered non-invasive because it does not require any openings or ports to be defined in the conduit. Thus, such a non-invasive approach can be deployed virtually anywhere along the conduit.

[0008] As noted above, the temperature of the process fluid can be estimated by measuring the external temperature of a process fluid conduit, such as a pipe, and employing heat flow calculations. In such systems, it is common to estimate the pipe skin (external surface) temperature T skin and the reference temperature T reference and thermal impedance values ​​(relative to the pipe wall and relative to the thermal relationship between the location of the pipe skin and the location of the measurement of the reference temperature) are used in heat flow calculations to infer or otherwise estimate the temperature of the process fluid in the conduit. As the temperature of the process fluid changes (e.g., increases or decreases), the temperature profile of the system changes. This temperature difference between the skin temperature of the flowing piping and the reference temperature is the result of heat flowing between two locations. Combined with knowledge of the thermal impedance (or other similar constant related to heat flow) between the two locations, the temperature of the inside surface of the process fluid conduit can be estimated. Since the inside surface of the process fluid conduit is in direct contact with the process fluid, this inside surface temperature can be used to estimate the temperature of the process fluid.

[0009] The process fluid temperature estimates described above are generally based on the assumption that the temperature of the inner surface of the conduit is indicative of the entire cross-section of the process fluid flowing through the conduit. While this assumption is generally accurate for turbulent process fluids flowing through filled conduits, there are some process fluid flow conditions where this assumption is less accurate. For example, when the process fluid flow is laminar or partially turbulent, this assumption is less correct and the accuracy of the process fluid temperature estimate may be reduced. Additionally, when the process fluid conduit is not completely filled or when no process fluid is flowing through the conduit, the accuracy of the temperature estimate may also be affected.

[0010] FIG 1 is a schematic diagram of a process fluid temperature estimation system to which embodiments of the present invention are particularly applicable. As shown in the figure, the system 200 generally includes a pipe clamp 202 configured to clamp around a conduit or pipe 100. The pipe clamp 202 may have one or more clamping ears 204 to allow the clamping portion 202 to be positioned and clamped to the pipe 100. The pipe clamp 202 may replace one of the clamping ears 204 with a hinged portion such that the pipe clamp 202 can be opened to allow it to be positioned on the pipe, and then closed and secured by the clamping ears 204. While the clamp illustrated with respect to FIG 1 is particularly useful, any suitable mechanical arrangement for securely positioning the system 200 around the circumference of the pipe may be used in accordance with the embodiments described herein.

[0011] The system 200 includes a heat flow sensor capsule 206, or suitable surface sensor, biased by a spring 208 against the outer diameter 116 of the pipe 100. The term "capsule" is not intended to imply a particular structure or shape, and thus may be formed in a variety of shapes, sizes, and configurations. Although a spring 208 is illustrated, one skilled in the art will appreciate that a variety of techniques may be used to urge the sensor capsule 206 into continuous contact with the outer diameter 116. The sensor capsule 206 typically includes one or more temperature sensitive elements, such as a resistance temperature device (RTD) or a thermocouple. The sensor within the capsule 206 is electrically connected to a transmitter circuit within a housing 210, which is configured to obtain one or more temperature measurements from the sensor capsule 206 and calculate an estimate of the temperature of the process fluid based on the measurements from the sensor capsule 206 and a reference temperature, such as a temperature measured within the housing 210 or a temperature otherwise provided by the circuit within the housing 210.

[0012] As an example, a basic heat flow calculation can be simplified to: T corrected = T skin + (T skin -T reference ) * (R pipe / R sensor ).

[0013] In this formula, T skin is the measured temperature of the outer surface of the conduit. Furthermore, T reference is T skin The thermal impedance (R sensor ) is the second temperature obtained for the position having the reference is typically sensed by a dedicated temperature sensor in the housing 210. However, T referencecan be sensed or inferred in other ways as well. For example, a temperature sensor can be placed external to the transmitter to replace the measurement of the terminal temperature in the heat transfer calculations. This external sensor would measure the temperature of the environment surrounding the transmitter. As another example, industrial electronics typically have on-board temperature measurement capabilities. This electronics temperature measurement can be used as a proxy for the terminal temperature in the heat transfer calculations. As another example, if the thermal conductivity of the system is known and the ambient temperature around the transmitter is fixed or user controlled, then the fixed or user controllable temperature can be used as the reference temperature.

[0014] R pipe is the thermal impedance of the conduit, which can be obtained manually by obtaining pipe material information, pipe wall thickness information, etc. Additionally or alternatively, R pipe Parameters related to the temperature of the process fluid (T) can be determined during calibration or can be calculated and stored for subsequent use. Thus, using appropriate heat flux calculations such as those described above, the circuitry within the housing 210 can generate an estimate for the temperature of the process fluid (T corrected ) and communicate an indication of such process fluid temperature to appropriate devices and / or a control room. In the example illustrated in FIG. 1, such information may be communicated wirelessly via antenna 212.

[0015] 2 is a block diagram of circuitry within a housing 210 of a thermal flow measurement system 200 to which embodiments of the present invention are particularly applicable. The system 200 includes communication circuitry 220 coupled to a controller 222. The communication circuitry 220 may be any suitable circuitry capable of communicating information regarding an estimated process fluid temperature. The communication circuitry 220 enables the thermal flow measurement system 200 to communicate a process fluid temperature output over a process communication loop or segment. Suitable examples of process communication loop protocols include the 4-20 milliamp protocol, the Highway Addressable Remote Transducer (HART®) protocol, the FOUNDATION® Fieldbus protocol, and the WirelessHART protocol (IEC 62591).

[0016] The thermal flow measurement system 200 also includes a power supply module 224 that provides power to all of the components of the system 200, as indicated by arrow 226. In embodiments in which the thermal flow measurement system 200 is coupled to a wired process communication loop, such as a HART® loop or a FOUNDATION® Fieldbus segment, the power supply module 224 may include appropriate circuitry for conditioning the power received from the loop or segment to operate the various components of the system 200. Thus, in such wired process communication loop embodiments, the power supply module 224 may provide appropriate power conditioning so that the entire device can be powered by the loop to which it is coupled. In other embodiments, where wireless process communication is used, the power supply module 224 may include a power source, such as a battery, and appropriate conditioning circuitry.

[0017] The controller 222 includes any suitable arrangement capable of generating an estimate of the temperature of the process fluid based on the heat flow rate using measurements from the sensor in the capsule 206 and an additional reference temperature, such as a terminal temperature in the housing 210. In one embodiment, the controller 222 is a microprocessor. The controller 222 is communicatively coupled to the communication circuit 220.

[0018] Measurement circuitry 228 is coupled to controller 222 and provides a digital representation of measurements obtained from one or more temperature sensors 230. Measurement circuitry 228 may include one or more analog-to-digital converters and / or appropriate multiplexing circuitry to interface the one or more analog-to-digital converters with temperature sensors 230. Additionally, measurement circuitry 228 may include appropriate amplification and / or linearization circuitry as may be appropriate for the various types of temperature sensors used.

[0019] Temperature sensors 230 illustratively include a terminal temperature sensor 232, an electronics temperature sensor 234, and may include other items as well, as indicated by block 236. Electronics temperature sensor 234 is coupled to the electronics of system 200 and is used to determine the temperature of the electronics. Typically, electronics temperature sensor 234 is used to protect the electronics from overheating. For example, when the electronics reaches a predetermined temperature, a fan is turned on to reduce the temperature. In one embodiment, electronics temperature sensor 234 senses a reference temperature.

[0020] FIG. 3 is a schematic diagram of a process fluid temperature estimation system according to an embodiment of the present invention. System 300 has some similarities to system 200 (shown in FIG. 1), with like components being similarly numbered. In particular, system 300 includes a sensor capsule 306 that is biased into contact with an exterior surface of pipe 100 via a spring or other suitable mechanical element 308. Additionally, sensor capsule 306 is electrically coupled to electronics in housing 310 for generating an estimate of the process fluid temperature. However, as shown in FIG. 3, three additional temperature sensor capsules 320, 322, and 324 are positioned at different radial positions with respect to pipe 100 and coupled thereto by clamp 302. In the illustrated example, the four sensor capsules (306, 320, 322, and 324) are spaced approximately 90° apart. Thus, temperature sensor capsule 306 is positioned at the top of pipe 100, and temperature sensor capsule 324 is positioned at the bottom. Similarly, sensor capsule 320 is disposed on one side of the pipe 100 and sensor capsule 322 is disposed substantially diametrically opposite sensor capsule 320. Each sensor capsule is electrically coupled to measurement circuitry in transmitter housing 310 via a respective connection head, such as connection heads 326, 328, and 330, using wires (not shown) or wireless communication. As can be appreciated, each sensor capsule measures the pipe skin temperature at its respective location and can be used to generate an estimate of the temperature of the inner surface of the pipe 100 corresponding to the mounting location of the respective sensor capsule. The electronics controller 222 disposed in the transmitter housing 310 is programmed or otherwise configured to determine the flowing condition of the process fluid based on the difference between various estimates of the temperature of the inner surface at different locations. Additionally, as discussed above with respect to Figures 1 and 2, a reference temperature indication can be provided by a reference temperature sensor disposed in the transmitter housing 310, or communicated via process communication, such as via antenna 312, or by coupling to additional temperature sensors.In one embodiment, the temperature sensor is disposed within the transmitter housing 310 proximate the terminal junctions and is coupled to the measurement circuitry 228 .

[0021] By placing two or more sensor capsules at different locations about the pipe or conduit 100, the system 300 can determine whether the process fluid is flowing properly to accurately estimate the temperature of the process fluid provided. Additionally, the embodiments described herein can also determine whether the process fluid conduit 100 is only partially filled and / or whether process fluid is flowing through the process fluid conduit 100. These additional indications may be provided locally by the system 300 (such as via a local display) or may be communicated to a remote device, such as via process communications via antenna 312.

[0022] In some embodiments, it is important to know the mounting orientation of the various sensor capsules before determining what the sensor characteristics mean. In other words, the controller 222 in the transmitter housing 310 must know that the sensor capsule 306 is located at the top of the process fluid conduit 100, and similarly, must know that the sensor capsule 324 is located at the bottom side. Similarly, the controller must also know that the sensor capsules 320 and 322 are each located on opposite sides of the process fluid conduit. With this information, the controller 222 can generate and / or modify indications of changing process fluid flow conditions to provide a more accurate process fluid temperature estimate. Below are examples of flow conditions and how they can be identified by the controller 222:

[0023] If the gradient across the process fluid produces the highest temperature at the top sensor and the lowest at the bottom sensor, with both side sensors providing substantially the same indication, the controller 222 can determine that the process fluid is not flowing through the process fluid conduit 100. This is because the process fluid is in contact with all of the interior surfaces of the process fluid conduit and, since there is no fluid flow, the warmer fluid will move to the top of the process fluid conduit and the cooler fluid will remain at the bottom. If such a profile occurs, the controller 222 can provide an indication of a no-flow condition for the process fluid. Additionally, an average of the process fluid temperature can be provided by averaging the top and bottom sensors and comparing that estimate to the estimate provided by the two side sensors. In this example, the controller 222 can provide not only an estimate of the process fluid temperature, but also an additional indication that the process fluid is not flowing.

[0024] If the lower and side sensors all provide approximately equal temperatures, but the upper sensor (sensor capsule 306) is at a temperature between ambient and the side and lower sensor values, the controller 222 can indicate that the process fluid conduit is more than 50% full. Furthermore, if this condition occurs, the controller 222 can provide an estimate of the process fluid temperature based solely on the side and lower sensor capsule values, and can provide an indication that the conduit is more than 50% but less than 100% full.

[0025] If the top and side sensors are measured at temperatures between ambient and the bottom sensor temperature, but the top sensor value is closest to ambient, the controller 222 can indicate that the process fluid conduit is less than 50% full. Additionally, an indication of the process fluid temperature can be provided based solely on the temperature from the bottom sensor capsule 324, and the controller 222 can provide an indication that the conduit 100 is less than 50% full.

[0026] If the top and side sensors are at substantially the same temperature, but the bottom sensor capsule 324 registers different values, the controller 222 can determine that some material is present on the lower interior surface of the process fluid conduit. Examples of such material can include moisture, sediment, etc. In such an example, a process fluid temperature estimate can be provided based solely on the top and side sensors, and the controller 222 can provide an additional indication that material has been detected on the lower interior surface of the conduit 100.

[0027] Figure 4 is a chart showing the temperature at different locations on the pipe wall over time as the process fluid flow changes. The data shown in Figure 4 illustrates the condition when there is no process fluid flow. The data shows the difference between data from a side mounted sensor, such as 400, and a bottom mounted sensor, such as 402. At time t 1 At time t, the pump is activated to begin generating a flow of the process fluid. As can be seen, each sensor is subjected to a similar temperature measurement, the value of which varies with time t 2 It converges quickly.

[0028] While the embodiment illustrated for FIG. 3 shows multiple sensor capsules coupled to the clamping mechanism, one each coupled to a respective connection head, it is expressly contemplated that in other embodiments multiple sensor points may be incorporated directly into the clamping mechanism and various sensor lines may be routed to the transmitter housing 310 and directly coupled to the measurement circuitry 228. Additionally, while the embodiment illustrated for FIG. 3 utilizes a total of four sensor capsules, it is also expressly contemplated that by using three such sensor capsules (top, bottom, and one side sensor capsules), some process fluid variation information may be identified. Additionally, it is also expressly contemplated that by using four or more sensor capsules, additional information may be identified. Still further, it is expressly contemplated that multiple such systems 300 may be positioned at different longitudinal locations along the process fluid conduit, and one or both of the controllers in each system may be provided with additional information from other process fluid estimation systems so that temperature flow variations along the flow direction may be analyzed to determine additional process fluid flow conditions and / or modifications in the process fluid estimation system. For example, such information may indicate that the process fluid flow is turbulent, laminar, or transitional. Sectional slope may also be used to detect disturbances to the turbulent flow conditions as well as to indicate whether the flow is fully developed. Disturbances in the piping such as elbows, valves, reducers, etc. can destroy fully developed turbulent flow. Accurate temperature measurements (and flow measurements) often depend on the flow conditions being fully developed.

[0029] In embodiments employing additional temperature measurements on the exterior surface of the process fluid conduit, the linearity of the cross-sectional temperature can be determined. An indication of this linearity can help detect conditions such as scaling, thinning, the presence of deposits, or unwanted water in steam applications, and can also provide an indication for taking action. This can be important because in some cases, not taking action can lead to an impact on efficiency, an increase in pressure, or even permanent damage to the process fluid conduit.

[0030] While a steady state temperature difference may in some cases be all that is needed to determine an actionable condition, monitoring timing information with temperature changes can provide a better understanding of scaling or thinning levels. Thus, estimates of the various process fluids provided by the system 300 can be stored by an external device or stored internally and analyzed over time to identify trends that may indicate wear or other degradation of the system.

[0031] Although the embodiments described thus far have generally contemplated the use of a sensor capsule having a resistive temperature device (RTD) therein, any suitable temperature sensing structure or technique may be used in accordance with embodiments of the present invention. For example, sensor methods such as fiber optics may provide a technique that provides a higher density of temperature measurement points about the conduit 100.

[0032] FIG. 5 is a block diagram of a method for estimating the temperature of a process fluid in a flow conduit for various flow conditions, according to one embodiment of the present invention. Method 500 begins at block 502, where skin temperatures are measured at multiple locations on the process fluid conduit. For example, skin temperatures may be measured at top, bottom, and side locations as described above with respect to FIG. 3. Next, at block 504, any differences between the various temperature measurements are analyzed to identify a particular flow condition. Examples of flow conditions and the differences in measured temperatures that such flow conditions produce are described above. It is also expressly contemplated that the degree to which measurements must be different (or comparable) can be set as a user selected threshold or can be programmatically input via the manufacturer during assembly or construction of the process fluid temperature estimation system. Examples of various conditions that may be identified based on the measured temperature difference include a process fluid conduit that is 100% full and flowing, as shown at 506, no flow, as shown at 508, more than 50% full and flowing, as shown at 510, less than 50% full and flowing, as shown at 512, and the presence of material at the lower inner surface of the process fluid conduit, as shown at 514. As can be appreciated, if additional sensor capsules are positioned about the process fluid conduit (e.g., at 45° intervals), additional levels of fill of the process fluid conduit (e.g., 25% and 75%) may also be provided. The state of the process fluid flow may then be provided as an output in block 516 and / or used to adjust or otherwise compensate the process fluid temperature estimate. As discussed above, in certain embodiments, the estimate of the process fluid temperature may be based on data from less than all of the available sensors. For example, if the process conduit is less than 50% filled, the process fluid estimation is performed based solely on the skin temperature sensed by the lower sensor capsule (such as 324 shown in FIG. 3).In contrast, if the process fluid flow conditions indicate that material (such as deposits) is located proximate the lower surface of the process fluid conduit 100, but the process fluid conduit is otherwise full, then the process fluid temperature estimate will be based on measurements from the top and side sensor capsules, and values ​​received from the bottom sensor capsule will be omitted. Thus, an adjusted process fluid temperature estimate is provided based on the identified process fluid flow conditions. Next, in block 518, the system may optionally report the identified process fluid flow conditions.

[0033] Although the invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in the embodiments and details without departing from the spirit and scope of the invention.

Claims

1. 1. A process fluid flow system comprising: a first pipe skin sensor positioned to measure an external temperature of the process fluid conduit at a first circumferential location on the process fluid conduit; a second pipe skin sensor positioned at a second circumferential location on the process fluid conduit to measure an external temperature of the process fluid conduit; a measurement circuit coupled to the first and second pipe skin sensors; a controller coupled to the measurement circuit and configured to identify a state of flow of the process fluid based on signals from the first and second pipe skin sensors; and the controller is configured to obtain a reference temperature measurement having a fixed thermal relationship to the first and second pipe skin sensors, the reference temperature measurement differing from a measured external temperature of the process fluid conduit, and the controller is configured to provide a corrected process fluid temperature estimate output using the identified process fluid flow conditions and heat flow calculations. Process fluid flow systems.

2. The process fluid flow system of claim 1 , further comprising a clamp configured to mount the first and second pipe skin sensors on substantially opposite sides of the process fluid conduit.

3. 3. The process fluid flow system of claim 2, further comprising a third pipe skin sensor mounted in a clamp between the first and second pipe skin sensors.

4. 4. The process fluid flow system of claim 3, further comprising a fourth pipe skin sensor attached to said clamp diametrically opposite said third pipe skin sensor.

5. 5. The process fluid flow system of claim 4, wherein the first, second, third and fourth pipe skin sensors are positioned approximately 90 degrees apart about an exterior surface of the process fluid conduit.

6. The process fluid flow system of claim 1 , wherein the controller is configured to provide an estimate of the process fluid temperature as a local display.

7. 2 . The process fluid flow system of claim 1 , wherein the process fluid temperature estimate is generated using one of the first or second sensors based on a condition of the process fluid flow.

8. The process fluid flow system of claim 1 , further comprising a communications circuit coupled to the controller, wherein the process fluid temperature estimate is communicated to a remote device.

9. The process fluid flow system of claim 8 , wherein the controller is configured to communicate the identified process fluid flow status to the remote device.

10. 2. The process fluid flow system of claim 1, wherein the process fluid flow condition is a completely full process fluid conduit with process fluid flowing therethrough.

11. 2. The process fluid flow system of claim 1, wherein the process fluid flow condition is a completely full process fluid conduit with no process fluid flow.

12. 2. The process fluid flow system of claim 1, wherein the process fluid flow condition is a process fluid conduit greater than 50% full with process fluid flowing therethrough.

13. 2. The process fluid flow system of claim 1, wherein the process fluid flow condition is a process fluid conduit less than 50% filled with process fluid flowing therethrough.

14. 10. The process fluid flow system of claim 1, wherein the process fluid flow condition is indicative of material disposed on a lower surface of a process fluid conduit.

15. 1. A method for estimating flow characteristics of a process fluid in a flow path, comprising: obtaining surface temperature measurements at a plurality of locations about a circumference of the fluid conduit; analyzing the plurality of surface temperature measurements to identify flow conditions within the conduit; selecting a combination of surface temperature measurements based on the identified flow conditions; applying a heat flow calculation to the combination of the selected surface temperature measurements to generate an estimate of the temperature of the process fluid; and providing as an output an estimate of the temperature of the process fluid. The method includes:

16. 16. The method of claim 15, wherein analyzing the plurality of surface temperature measurements includes determining whether a difference between the surface temperature measurements exceeds a predetermined threshold indicative of the flow condition.

17. The method of claim 16 , wherein the predetermined threshold is provided by a user.

18. The method of claim 15 , further comprising generating an indication of the identified flow condition.

19. The method of claim 18 , wherein the representation is provided as a local display.

20. The method of claim 18 , wherein the indication is selected from the group consisting of laminar flow, transitional flow, and turbulent flow.

Images