WO2019086899A2 - Procédé et système de détermination de débit dans un tuyau - Google Patents

Procédé et système de détermination de débit dans un tuyau Download PDF

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Publication number
WO2019086899A2
WO2019086899A2 PCT/GB2018/053197 GB2018053197W WO2019086899A2 WO 2019086899 A2 WO2019086899 A2 WO 2019086899A2 GB 2018053197 W GB2018053197 W GB 2018053197W WO 2019086899 A2 WO2019086899 A2 WO 2019086899A2
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WO
WIPO (PCT)
Prior art keywords
temperature
conduit
fluid
flow
pipe
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Application number
PCT/GB2018/053197
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English (en)
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WO2019086899A3 (fr
Inventor
Oliver PARSON
Ryszard MACIOL
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Centrica Hive Limited
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Publication date
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Publication of WO2019086899A2 publication Critical patent/WO2019086899A2/fr
Publication of WO2019086899A3 publication Critical patent/WO2019086899A3/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6847—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
    • G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/14—Supports; Fastening devices; Arrangements for mounting thermometers in particular locations
    • G01K1/143—Supports; Fastening devices; Arrangements for mounting thermometers in particular locations for measuring surface temperatures
    • 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
    • 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
    • G01K13/026—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow of moving liquids
    • 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
    • G01K7/42—Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/002—Investigating fluid-tightness of structures by using thermal means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
    • G01M3/28—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
    • G01M3/28—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds
    • G01M3/2807—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds for pipes

Definitions

  • the present invention relates to methods for determining a flow rate of a fluid through a pipe and for estimating the inlet temperature of the inlet fluid.
  • the present invention aims to detect a flow rate through pipes, and further to estimate the flow rate.
  • the estimation method uses various temperatures in determining a flow rate.
  • a further aim of the invention is therefore to provide a method for estimating the inlet flow temperature.
  • a method of determining rate of fluid flow through a conduit comprising: determining a first quantity representative of a difference between a temperature of the conduit and a temperature of the surroundings of the conduit; determining a second quantity representative of a difference between a temperature of the fluid entering the conduit and a temperature of the surroundings of the conduit; calculating a third quantity by dividing the first quantity by the second quantity; and estimating the flow rate of the fluid through the conduit based on the third quantity, wherein estimating the flow rate from the third quantity includes performing a non-linear conversion between the third quantity and the flow rate, wherein the non-linear conversion has a higher rate of change of the third quantity with respect to flow rate at lower flow rates than at higher flow rates.
  • the non-linearity of the conversion in this manner provides a high degree of sensitivity at low flow rates. This in turn allows the flow rate to be determined with higher accuracy at low flow rates, which are typical of the undetected situations often encountered in practice. For example, the very high flow rates encountered when a pipe (or conduit) bursts will usually be detected by other means because someone will likely notice flooding, water damage, etc. On the other hand, smaller leaks or dripping taps are less likely to come to a user's attention, but when left for a long time can represent a significant total loss.
  • the simple relationship set out above is easy
  • the method provides a convenient way of estimating the severity of a leak, as well as distinguishing between different types of leak, which may have characteristic flow rates. While a common example of a system in which this applies is a water supply system in a building, but the disclosure could apply equally to other fluids, e.g. a gas supply to a building.
  • the determination of the flow rate may be performed only once, continuously, or periodically, depending on the circumstances.
  • the method further comprises a calibration step in which the relationship between the flow rate and the third quantity is determined for the conduit.
  • the thermal response of typical systems can be quite complex and may depend on the size, wall thickness and material of the conduit; the specific fluid in the conduit and the fluid temperature and ambient temperature (i.e. temperature of the surroundings) of the conduit. While the exact response could be calculated, many of these quantities do not vary (or are relatively constant) during use of the system, so an in situ calibration can be performed.
  • the conduit (or pipe - the two terms will be used interchangeably herein) parameters are fixed, and the location of the pipe at the point at which temperatures are measured will often be sheltered so as not to vary much with time, particularly if it is located in a human-inhabited portion of a building where temperatures are typically held relatively constant at around 18-20°C, for comfort reasons. Consequently, the calibration in situ can be a valuable resource, which can be performed by an engineer when the monitoring system is installed, for example. Installation may include mounting sensors for measuring one or more of the quantities, for example, sensors for measuring the temperature of the conduit, the ambient air temperature (the temperature of the surroundings) and/or the temperature of the fluid entering the conduit.
  • installation may include setting up a monitoring unit to receive temperature measurements, compute the third quantity and/or perform the non-linear conversion.
  • a simple calibration would involve turning on a tap to cause fluid flow through the system. If the fluid flow rate from the tap is measured and the first, second and third quantities measured or calculated (as described herein), then a datum can be recorded for these values. Altering the flow rate for the tap can then be used to acquire further data points. In order to increase the flow rate beyond what is available from a single tap, multiple taps can be opened and the cumulative flow rate used in the recorded data points. Shutting off the entire flow through the system (e.g.
  • the calibration may be periodically performed or updated. This may involve a manual calibration described above. Alternatively, depending on the context, automatic control of a tap or other outlet may be provided to allow an automatic calibration. Lastly, one or more taps or outlets may have flow meters attached to them, which allows an estimation of the flow rate in the system, and consequently allows data to be collected to improve the calibration.
  • the calibration may include fitting received data related the first, second and/or third quantities to a mathematical formula.
  • Such received data may be individual temperatures of fluid, conduit or surroundings, or the received data may be the first or second quantity in the form of periodic measurements or continuous data streams.
  • the calibration may include populating a look-up table with received data.
  • the estimating step may include referring to data received in the calibration step. This provides a convenient manner in which to provide a user with a quick estimation of the current flow rate. In the event that a user is not expecting any flow rate (or indeed a flow rate of the current estimated magnitude), the estimated flow rate may serve to alert the user to an abnormal condition.
  • the method can be configured to detect abnormal flow conditions and provide a targeted alert to a user, e.g. by an audible or visible alarm, sending a message to a mobile telephone, etc.
  • the mathematical formula may include one or more of: a logarithmic term; an exponential term; a polynomial term; and/or a hyperbolic term.
  • a known function such as a sigmoid, an inverse reciprocal function, or an inverse tangent function may be used, for example.
  • the method may include allowing the conduit, fluid and/or surroundings temperatures to settle prior to the estimation step being performed. In some cases, the method includes waiting for the first, second or third quantity to settle prior to the estimate step being performed. This improves the stability of the system and therefore ensures that the estimated flow rate is as accurate as possible.
  • Settling in this context may mean that the relevant quantity does not change by more than a particular threshold for at least a certain amount of time, e.g. 0.5°C for at least 1 minute.
  • settling may mean that the rate of change of the relevant quantity is no larger than a threshold, e.g. no more than O.S'O/minute.
  • the rate of change may be required to remain below the threshold for a minimum amount of time (e.g.
  • the method may further comprise taking a measurement of a temperature of one or more of: the conduit; the surroundings of the conduit; and/or the fluid entering the conduit. Rather than relying on some other process or inferring the temperature of these quantities, the method may directly obtain some or all of them. Such measurements can then be used in deriving the first, second and/or third quantity. That is to say, the measurements can be used in performing the method described herein.
  • the system may estimate one or more of the temperature of: the conduit; the surroundings of the conduit; and/or the fluid entering the conduit. This allows the system to perform the calculations set out above irrespective of whether it has direct access to raw temperature data for one or more of the quantities.
  • Also described herein is a method of estimating the temperature of a fluid entering a conduit, the method comprising: periodically receiving measurements of the temperature of the conduit; determining an extremal temperature of the conduit over a preceding time period of predetermined length; and using the determined extremal temperature as an estimate for the fluid temperature.
  • the extremal pipe temperature i.e. the highest or lowest
  • the pipe temperature comes closer to the fluid temperature under these conditions.
  • the use of an extremal temperature over a preceding period allows changes in pipe temperature to be correlated with the fluid temperature.
  • the use of a preceding time period allows the system to select an extremal temperature over a reasonable period, in which enough flow to bring the pipe close to the fluid temperature is likely to have occurred.
  • the inlet temperature may change by around 0.5°C in a day.
  • a good balance between these two considerations is to use the extremal temperature from the preceding 3 days as the estimated inlet fluid temperature.
  • the method may include modifying the estimated fluid temperature based on a flow history of fluid through the conduit during the predetermined period.
  • the conduit will approach the fluid temperature and will settle at a value close to the fluid temperature. Exactly how close the temperature of the pipe is to the temperature of the fluid when the system has settled depends in part on how large the flow is and how long it occurs for. In cases where there has been little flow (i.e. only low flow rates, only very short flows, a low total cumulative amount of fluid passing through the system, etc.), it may be beneficial to adjust the estimated temperature to take account of the incomplete settling.
  • the estimated fluid temperature will always be higher than the true fluid temperature. Conversely when the ambient pipe temperature (the temperature of the pipe's surroundings) is cooler than the fluid temperature, then the estimated fluid temperature will always be lower than the true fluid temperature. It is easy to see whether the fluid temperature is higher or lower than the ambient temperature, since the measured pipe temperature will start to increase or decrease respectively when flow starts.
  • the true fluid temperature can be estimated.
  • the estimated term may remain uncorrected when the total flow, maximal flow rate, and/or total time of flow exceed a respective threshold. In cases where one or all of these thresholds are not exceeded, the correction may be applied. Making the correction conditional upon the severity of the discrepancy conserves computational power unless it is important to do so. This may be beneficial where the sensors and processing equipment are battery powered, for example. It should be noted that the non-linear conversion described above is particularly appropriate for making this correction.
  • the method may further comprise determining a no-flow condition during the preceding time period and using an alternative temperature in place of the extremal temperature during the preceding time period.
  • the alternative temperature is the most recent extremal temperature determined after a respective predetermined period had occurred in which flow was detected through the conduit.
  • an alternative to correcting the estimate may be to use a previously estimated value. This may be a value which has been determined following a predetermined preceding time period, i.e. by a previous iteration of the method described above in which the flow rate was high enough that the estimated temperature is deemed to be good enough. In effect, this means a value calculated after a period in which a no-flow determination was not made.
  • the previous value which is reverted to could be a corrected estimate as set out above.
  • Another method of providing an alternative temperature estimate is to use a rolling average of local air temperature over a second predetermined period.
  • the second predetermined period may be 10 days, for example, or it may be related to (e.g. the same as) the predetermined preceding time period.
  • the temperature of stored water typically matches the ground temperature at a certain depth, which warms and cools as the air temperature changes. However, given that the ground has a significant thermal mass, the supply temperature can be considered as a smoothed version of the external temperature. Consequently, the rolling average external air temperature is a good proxy measure of inlet water temperature. Similar arguments apply in respect of other fluids being supplied, since they will be affected by external temperatures in a similar way.
  • the no-flow condition may comprise the difference between the temperature of the conduit and the temperature of the surroundings of the conduit being less than a threshold for the duration of the predetermined period.
  • a threshold is 0.5 °C.
  • a no flow condition may take other values, e.g. 0.23 ⁇ 4 or even 0.1 °C.
  • a no-flow condition may comprise the rate of change of the temperature of the conduit being less than a threshold for the duration of the predetermined period.
  • a suitable threshold is 1 'O/minute.
  • a method of estimating the temperature of a fluid entering a conduit comprising: determining a rolling average of local air temperature over a preceding predetermined period; and using the determined rolling average of local air temperature as an estimate for the fluid temperature. As set out above, this provides a good proxy measurement of the inlet fluid temperature because the temperature of stored water typically matches the ground temperature at a certain depth, which warms and cools as the air temperature changes.
  • the supply temperature can be considered as a smoothed version of the external temperature. Consequently, the rolling average external air temperature is a good proxy measure of inlet water temperature. Similar arguments apply in respect of other fluids being supplied, since they will be affected by external temperatures in a similar way. It may be beneficial to control for natural temperature variations by always taking the temperature measurement at the same time of day (since days are typically hotter than nights, for example). In addition, since the temperature of a day is strongly affected by factors such as how sunny it is that day, it may be beneficial to wait until the night time to ensure that the net heating effect is captured, but short-timescale variances are controlled for.
  • both the rolling average air temperature and the extremal pipe temperature methods may be used together, e.g. to verify one another, or to provide correction terms to improve the estimate.
  • the system may include a learning algorithm to automatically improve the estimate based on historical data, for example.
  • the estimated fluid temperature is modified using a different temperature.
  • the rolling average air temperature may be modified with extremal pipe temperature data.
  • the rolling average air temperature method may be used to modify the estimate.
  • the ratiometric method set out above may be used to improve the estimate.
  • the method may further include making the temperature measurements to calculate the rolling average air temperature or the extremal pipe temperature. This means that the method can be self-contained and not rely on externally sourced data.
  • the methods of estimating the inlet fluid temperature set out above may be used to provide the inlet fluid temperature for the flow rate estimation method set out above.
  • the device may include, where appropriate, one or more temperature sensors; one or more flow rate detectors; one or more detectors for attaching to taps and/or outlets; one or more processors for receiving raw data and performing the calculations set out above; and/or one or more communications interfaces for communicating with remote devices (including sensors, servers, networks, etc.).
  • the device may be formed as a single unit, for example packaged into a housing, such that the housing is mountable on a pipe. In cases where there is a temperature sensor for sensing a temperature of the pipe, the housing may be provided with mounting means such as straps, clips, clamps, etc.
  • the system for providing the estimate of the flow rate may be distributed in the sense that there may be a device for taking temperatures readings (e.g. having a housing, means for attaching the housing to a pipe and a temperature sensor arranged to be in good thermal contact with the pipe when the housing is attached to the pipe).
  • the device for taking temperature readings may be configured to communicate with a second device, e.g. for performing the estimation.
  • the second device may be a remote server, for example.
  • Figure 1 shows a flow monitoring system installed on a conduit
  • Figure 2 shows an example of various temperatures changing over time in response to a flow condition
  • Figure 3 shows an example of a non-linear conversion between the flow rate and a temperature ratio
  • Figure 4 shows data on rolling extremal temperatures
  • Figure 5 shows data on rolling average external air temperatures
  • Figure 6 is a flow chart illustrating a method disclosed herein
  • Figure 7 is a flow chart illustrating another method disclosed herein.
  • Figure 8 is a flow chart illustrating a further method disclosed herein.
  • Figure 9 is a graph showing the results of several experiments.
  • FIG. 1 schematically shows a fresh water plumbing network 100 for a domestic dwelling.
  • a single supply pipe 102 enters the dwelling and branches into multiple branches 104, 106.
  • the pipe 102, 104, 106 we refer generically to the pipe 102, 104, 106 as 108, the pipe being a form of fluid conduit carrying clean water 1 10, a fluid, which flows into the property in the direction of the arrow labelled 1 12.
  • a flow determination apparatus In order to make a flow determination - typically to determine whether there is a leak from the plumbing network - a flow determination apparatus is used.
  • a single housing 1 14 is shown, but examples with multiple housings at different locations on the plumbing network are possible.
  • Each housing 1 14 may house first 1 16 and second 1 18 temperature sensors.
  • the first temperature sensor 1 16 is to measure the temperature of pipe 108
  • the second temperature sensor 1 18 measures the local ambient temperature (i.e. the temperature of the surroundings of the pipe).
  • the exact design of the housing 1 14 is not critical to the method or system, so long as the first sensor is in good thermal contact with the pipe 108, and the second sensor is able to accurately measure the ambient temperature.
  • Other desirable features include the attachment of the housing 1 14 to the pipe 108 not constituting too great a thermal load and ease of installation. By good thermal contact, it is meant that the heat flow path from the pipe 108 to the first sensor 1 16 has a low thermal impedance.
  • Each housing may also be provided with a transmitter - such as a Bluetooth (RTM) Low Energy transmitter - which can carry out some processing and/or transmits data elsewhere.
  • a transmitter - such as a Bluetooth (RTM) Low Energy transmitter - which can carry out some processing and/or transmits data elsewhere.
  • Each housing may also be provided with a power source (not shown), such as a battery, to power the transmitter and the temperature sensors.
  • the data collected by the sensors can be used to demonstrate how a flow determination can be made with this apparatus.
  • the apparatus relies on the fact that, if there is no flow in the pipe 108, then the temperature of the pipe - sensed by the first temperature sensor will converge with the ambient temperature - sensed by the second temperature sensor.
  • the temperature of the pipe 108 will diverge from the ambient temperature. This is most notable in domestic plumbing networks the closer to the point of entry of the supply pipe 102 into the premises. This is because the temperature of the fluid flowing through the pipe 108 - here, water - is likely to be different to the ambient temperature. In the domestic plumbing context, this is because pipes external to the dwelling are buried in the ground. In temperate climates such as the United Kingdom, it is likely that the water flowing into a dwelling will be significantly lower than ambient temperature and this explanation will be based on that assumption, although this embodiment will function well also with water significantly above ambient (for example, in an air-conditioned home in a hot climate).
  • the algorithm takes as an input the water supply temperature, which can also be estimated.
  • the sensing unit may be a battery-powered device with Wi-Fi (RTM) connectivity. Since powering up Wi-Fi (RTM) modules consumes a significant amount of battery, the device may connect to the leak platform only every 6 hours, unless a leak has started or ended in which case it may send an alert at that time, classifying the leak as small or large using the methods set out herein.
  • RTM Wi-Fi
  • a schematic example 200 of temperature measurements taken by the exemplary sensing apparatus of Figure 1 is shown in Figure 2. Specifically, the temperature of the pipe 220, its surroundings 222 and of the inlet temperature of the fluid 224 are plotted with respect to time.
  • the plot 200 encompasses a transition from a low- or no-flow situation to a (high) flow condition.
  • the times at which flow is occurring are indicated by arrow 226.
  • the time and temperature scales are arbitrary, the time scale is on a small enough scale that the ambient 222 and fluid 224 temperatures do not change significantly. Indeed, since this is a schematic, the plot is simplified to show no change in these quantities in order to clarify the desired effect.
  • the plot 200 also shows two derived quantities, a first quantity 228 obtained by subtracting the pipe temperature 220 from the ambient temperature 222 and a second quantity 230 obtained by subtracting the fluid temperature 224 from the ambient temperature 224.
  • a third quantity is obtainable by dividing the first quantity by the second quantity. It can be readily seen that the third quantity will be small (indeed, approaches zero) as the pipe 220 and the ambient 222 temperatures come close to one another (or even become equal). As described above, this occurs when the flow rate is low. Similarly, it is clear that the third quantity approaches the value of one when the pipe 220 and fluid 224 temperatures come close to one another. As set out above, this corresponds to a high flow condition.
  • a sample plot 300 comparing the flow rate to the third quantity i.e. the ratio of [the difference between the ambient 222 and pipe 220 temperatures] to [the difference between the ambient 222 and fluid 224 temperatures] is shown in Figure 3.
  • variable a can be used to uniformly scale the gradient of the function. Experimentally values of a at or close to 0.5 are seen to be reasonable in typical systems.
  • the ratio is used rather than absolute temperatures as it is more robust to varying differences between the ambient and supply temperature. For example, a flow rate of 1 L/h might achieve a pipe temperature of 16 degrees under an ambient temperature of 20 degrees and a water temperature of 10 degrees, while the same flow might achieve a pipe temperature of 18 degrees given the same ambient temperature but a water temperature of 15 degrees. As such, the difference between the pipe and the ambient temperature is 4 degrees in the first case and 2 degrees in the second case, but the ratio is 0.4 in both cases. Therefore, it is not necessary to adjust absolute temperature thresholds individually for each case, and instead can use the same ratio threshold in all situations.
  • the curve shown in Figure 3 will depend in general on the exact parameters of the system under consideration.
  • This calibration effectively means performing measurements and/or calculations to obtain a plot such as that shown in Figure 3, so that the two variables can be linked to one another.
  • Figure 4 shows a plot 400 of the ambient temperature 422 (shown in dark grey) and the pipe temperature 420 the (shown in light grey) over a period of a few months. The data points are close together and show as a solid mass in parts. Nonetheless, it is clear that the pipe temperature 420 drops below the ambient temperature 422 for large portions of the period being investigated. This is interpreted as being due to flow events, which cause inlet fluid to cool the pipe (as the inlet temperature is in this case cooler than the ambient temperature 422).
  • This line is shown in the plot as a thick black line 432, which considers the extremal temperature (lowest, in this case since the fluid is cooler than the ambient temperature 422) over the preceding three days.
  • This extremal temperature 432 can be used as an estimated inlet temperature.
  • the estimate derived in this way will be reasonably accurate. In any case, it may be possible to improve the estimated value in the various ways discussed above.
  • the supply temperature is estimated by taking a rolling 3 day minimum of the pipe temperature, although the exact period used can be changed according to circumstances.
  • the 3 day rolling window was chosen since it provides a good trade-off between assuring that the such a flow event has occurred in that window, and also the estimate stays up to date since the water temperature changes as the outside air temperature changes.
  • the minimum temperature is used since the pipe is assumed to reach the water supply temperature under a high flow rate water usage event (> 100 L/h) lasting a reasonable amount of time (> 5 minutes). Of course, in cases where the inlet water is warmer than the ambient temperature, it will be a maximum temperature which is reached in this way.
  • Figure 5 illustrates an alternative method of estimating the fluid temperature.
  • the temperature of stored water typically matches the ground temperature at a certain depth, which warms and cools as the air temperature changes. However, given that the ground has a significant thermal mass, the supply temperature can be considered as a smoothed version of the external temperature.
  • a plot 500 compares the external air temperature 534, a rolling 10-day average of the external air temperature 536 and the measured water from a tap 538 (having waited for the temperature to settle). It is clear that while the air temperature 534 (measured at midnight each night to minimise variability due to day/night and amount of sunlight) varies quite a lot from day to day, the rolling average of this quantity 536 smooths much of the detail out. Moreover, the rolling average 536 correlates well with the measured water temperature 538, albeit with an offset. Once more calibration could be used to bring these two values into closer alignment.
  • This alternative estimation can be used as well as or instead of the extremal temperature method. In some examples, both methods may be used in conjunction with one another to improve the accuracy.
  • a flow chart 600 is shown illustrating the method of estimating flow rate.
  • the method starts at step 640, in which a first quantity representative of a difference between a temperature of the conduit and a temperature of the surroundings of the conduit is determined.
  • a second quantity representative of a difference between a temperature of the fluid entering the conduit and a temperature of the surroundings of the conduit is determined.
  • a third quantity is then determined in step 644 by dividing the first quantity by the second quantity.
  • step 646 the flow rate of the fluid through the conduit is estimated based on the third quantity, wherein estimating the flow rate from the third quantity includes performing a non-linear conversion between the third quantity and the flow rate, wherein the non-linear conversion has a higher rate of change of the third quantity with respect to flow rate at lower flow rates than at higher flow rates.
  • This method allows for a simple estimation of the flow rate from some readily obtained or estimated temperature information.
  • Figure 7 shows a flow chart 700 illustrating a method of estimating the temperature of the fluid entering the system. Starting at step 748, periodically measurements of the temperature of the conduit are received.
  • an extremal temperature of the conduit over a preceding time period of predetermined length is determined. This period may be three days, for example, as described above.
  • the determined extremal temperature is used as an estimate for the fluid temperature. This provides a simple method of estimating a quantity which is often difficult to measure directly.
  • FIG. 8 shows a flow chart 800 illustrating an alternative method of estimating the inlet temperature.
  • the method determines a rolling average of local air temperature over a preceding predetermined period, this may be a ten day period, for example. Such information is readily obtained from e.g. weather services.
  • a system flush may be characterised by a short period of high flow rate, while a leak may be characterised by a long period of lower flow rate. Other events which are detectable in this way will be apparent to the skilled person.
  • the occurrence of the flush can be correlated with the third quantity during the time that the flush is planned, to check that the flow rate is indeed high in this time period, thereby helping a user ensure that the flush has been correctly implemented.
  • the occurrence of high and low flow occurrences can be monitored over time. These can be collated and compared with expected use patterns, which can be used to detect abnormal usage which may indicate an error of some kind, such as a leak or a malfunctioning device (washing machine, dishwasher, etc.), for example where such a device is drawing water irregularly, or at times when it should not be drawing water at all.
  • a leak or a malfunctioning device washing machine, dishwasher, etc.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Measuring Volume Flow (AREA)
  • Details Of Flowmeters (AREA)

Abstract

L'invention concerne un procédé de détermination du débit dans un tuyau, comprenant les étapes consistant à mesurer une différence de température entre le tuyau et la température de l'environnement du tuyau et à diviser cette différence par la différence entre la température du fluide entrant dans le tuyau et la température de l'environnement du tuyau. Une conversion non linéaire entre le rapport dérivé de cette manière et le débit est utilisée pour estimer le débit. L'invention concerne également des procédés d'estimation de la température du fluide entrant dans le tuyau.
PCT/GB2018/053197 2017-11-02 2018-11-02 Procédé et système de détermination de débit dans un tuyau WO2019086899A2 (fr)

Applications Claiming Priority (2)

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GB1718195.9 2017-11-02
GB1718195.9A GB2559836B (en) 2017-11-02 2017-11-02 Method and system for Determining flow rate in a pipe

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WO2019086899A2 true WO2019086899A2 (fr) 2019-05-09
WO2019086899A3 WO2019086899A3 (fr) 2019-06-27

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GB2553681B (en) 2015-01-07 2019-06-26 Homeserve Plc Flow detection device
GB201501935D0 (en) 2015-02-05 2015-03-25 Tooms Moore Consulting Ltd And Trow Consulting Ltd Water flow analysis

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DE19858307C2 (de) * 1998-12-17 2003-05-15 Viterra Energy Services Ag Verfahren und Vorrichtung zur Bestimmung des Volumenstromes oder der Strömungsgeschwindigkeit und/oder der Temperatur eines durch ein Rohr strömenden Mediums
GB2546126B (en) * 2016-01-06 2022-04-13 Homeserve Plc Flow detection device
AU2017100989A4 (en) * 2015-01-07 2017-08-17 Leakbot Limited Flow detection device
GB2553681B (en) * 2015-01-07 2019-06-26 Homeserve Plc Flow detection device
GB201501935D0 (en) * 2015-02-05 2015-03-25 Tooms Moore Consulting Ltd And Trow Consulting Ltd Water flow analysis
GB2546018A (en) * 2015-03-13 2017-07-05 Flowgem Ltd Flow determination

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GB2559836A (en) 2018-08-22
GB201718195D0 (en) 2017-12-20
GB2559836B (en) 2019-05-29
WO2019086899A3 (fr) 2019-06-27

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