WO2017194228A1 - Procédé pour déterminer un paramètre de débit d'un fluide et appareil de mesure du débit - Google Patents

Procédé pour déterminer un paramètre de débit d'un fluide et appareil de mesure du débit Download PDF

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Publication number
WO2017194228A1
WO2017194228A1 PCT/EP2017/056164 EP2017056164W WO2017194228A1 WO 2017194228 A1 WO2017194228 A1 WO 2017194228A1 EP 2017056164 W EP2017056164 W EP 2017056164W WO 2017194228 A1 WO2017194228 A1 WO 2017194228A1
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WO
WIPO (PCT)
Prior art keywords
fluid
flow
parameter
thermometer
time
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Application number
PCT/EP2017/056164
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German (de)
English (en)
Inventor
Ulf Hammerschmidt
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Bundesrepublik Deutschland, Vertreten Durch Das Bundesministerium Für Wirtschaft Und Energie, Dieses Vertreten Durch Den Präsidenten Der Physikalisch-Technischen Bundesanstalt
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Publication of WO2017194228A1 publication Critical patent/WO2017194228A1/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

Definitions

  • the invention relates to a method for determining a flow parameter of a fluid comprising the steps of (a) passing the fluid through a passageway, (b) pulse heating the fluid by means of a heating element, (c) measuring a time dependent temperature by means of a thermometer at a thermometer pitch is arranged from the heating element, (d) determining a maximum temperature time in the form of the time interval between the time of impulsformigen heating and the time of the temperature maximum in the thermometer distance and (e) calculating the flow parameter, in particular the flow rate, from the maximum temperature time.
  • the invention relates to a flowmeter for measuring a flow parameter of a fluid, comprising (i) a passage for passing the fluid, (ii) a heating element for pulsed heating of the fluid, (iii) a thermometer arranged at a measuring location for measuring a time-dependent temperature of the fluid and (iv) an electrical evaluation unit.
  • the invention solves the problem by a generic method in which the flow rate parameter is calculated from the maximum temperature time using the equation
  • the invention solves the problem by a generic flow meter configured to automatically calculate the flow parameter from this equation.
  • the flow parameter is understood in particular to mean a parameter which characterizes the flow through the passage.
  • the flow parameter is the flow velocity v, a flow D of flowing medium, for example in liters, amount of substance and / or mass per unit time At, or a quantity M, in particular a volume, an amount of substance and / or a mass of medium which has flowed through the passageway for a predetermined time unit ⁇ t.
  • v the flow velocity
  • M in particular a volume
  • an elongated heating element is understood, for example, an elongated heating element.
  • An elongated heating element is understood in particular to mean a heat source which, in a spatial dimension, has an extent which is at least ten times greater than the dimensions in the other two spatial directions.
  • the elongate heating element can thus be considered in good approximation as a linear heat source.
  • thermometer is understood in particular to mean a device by means of which the temperature and / or the temperature increase relative to an initial temperature can be determined. It is possible, but not necessary, for the thermometer to generate a reading that indicates the temperature in a unit of temperature, such as degrees Celsius, Fahrenheit, or Kelvin. In particular, it is sufficient that the absolute temperature and / or the temperature increase relative to an initial temperature can be determined in a unique manner from the temperature signal.
  • the pulse-shaped heating is understood in particular to mean a heating which takes place over such a short period of time that an approximation as a Dirac pulse leads to a measurement deviation of at most 5%.
  • heating takes less than a hundredth of a second, more preferably less than one millisecond.
  • the fluid is understood in particular a gas or gas mixture.
  • they are volatile hydrocarbons such as natural gas and / or biogas and / or hydrogen.
  • the fluid may be a liquid or a liquid mixture.
  • the flow rate parameter is calculated from the maximum temperature time
  • the maximum temperature time itself be used directly.
  • the calculation it is also possible for the calculation to use digital signals which encode the corresponding size.
  • a temperature such as the maximum temperature
  • a measured value is determined, which represents the temperature.
  • the temperature is represented by an electrical quantity, such as an electrical voltage.
  • the flow direction is usually indicated. Regardless of any explicit identification of this flow direction, for example by a graphical representation, which is mounted according to a preferred embodiment of the flow measuring device, the flow direction can also be clearly assigned to the flow meter, that the control unit is designed so that it the flow parameters is calculated using an equation which then gives a correct result when the fluid flows in the flow direction through the flow meter.
  • the flow measuring device is designed so that it can be flowed through in two directions.
  • the flow measuring device has at least two thermometers, wherein the heating element is arranged between the two thermometers. Since the temperature pulse always moves faster downstream than upstream at non-zero flow rates, the control unit can preferably be designed so that it automatically determines from the measurement results of the two thermometers, in which direction the fluid flows, and the flow conditions based on the measurement of stromabisserti Thermometer determined.
  • the flow parameter is calculated by means of an equation
  • mathematical operations are performed which correspond to this equation. It is possible, but not necessary, for the given equation to be written exactly as written. is used. If, for example, a factor is set equal to 1, then, of course, no multiplication by 1 must be carried out when applying the formula since such a multiplication does not change the result. It is also possible to add another term to the equation that will only marginally change the result. For example, it is possible to add any term as long as it changes the measurement uncertainty by less than 1%. It is also possible to use a mathematically equivalent equation for the calculation.
  • Calculating the flow parameter with the aid of the equation is understood in particular to mean calculation based on a calculation rule which is obtained by an approximation of this equation. Such an approximation is described below.
  • the evaluation unit is designed for automatically calculating the flow parameter is understood in particular to mean that the evaluation unit automatically calculates the flow parameter independently of any external intervention. It is possible and constitutes the preferred embodiment that the thus calculated flow parameter is output, for example in the form of an electrical or optical signal.
  • the flow parameter is determined using this equation:
  • the method comprises the steps of measuring the product F a from the thermal conductivity ⁇ of the fluid and the shape factor F and calculating the flow rate from the product Fa thus measured.
  • the thermal diffusivity a and the shape factor F always occur as a product so that both can be calibrated together.
  • Such a calibration can for example be performed automatically at regular intervals. This has the advantage that the measurement uncertainty remains low, even if the thermal conductivity of the fluid should change.
  • the method of the invention comprises the steps of measuring the thermal conductivity and / or the thermal conductivity of the fluid and reading calibration data associated with thermal diffusivity and / or thermal conductivity from a digital memory and calculating the flow rate from said calibration data.
  • the calibration parameters that is to say those parameters in the given formulas which, at least in a linear approximation, do not depend on the flow velocity, may depend on the type of fluid. In most applications, such as the flow measurement of natural gas, the properties of the fluid may change. This change can usually be characterized to a good approximation in a unique way on the basis of the thermal transport size, namely the thermal conductivity and / or the thermal conductivity.
  • thermal conductivity and / or the thermal conductivity on the calibration parameters can be connected.
  • the assignment between the thermal conductivity and / or the thermal conductivity on the one hand and the calibration parameter on the other hand can be stored, for example, in a map.
  • a map is a dataset that uniquely matches, for example, any combination of thermal conductivity and thermal conductivity Assigns set of caliber parameters. Such a map can be stored for example in a digital memory of the evaluation.
  • the maximum temperature time is additionally determined on at least one second measurement location, the flow rate parameter being calculated from the at least two maximum temperature times thus obtained.
  • the formula given above is applied to both maximum temperature times, and the mean value is determined from the two results thus obtained.
  • the mean value may be, for example, the optionally weighted arithmetic mean.
  • the temperature is measured at a distance from a wall of the passage which is less than 1 mm.
  • the flow of the fluid through the passage is particularly little affected, in particular, there is no significant additional turbulence.
  • the prevailing flow profile For flow measurement in or near the duct wall, the prevailing flow profile must be taken into account. For example, for a cylindrical channel with the diameter 2R is in place r.
  • n ⁇ 1, which means in particular that 0.9 ⁇ n ⁇ 1, 1.
  • this solution means that z. B. the sensor is not activated, or the flow channel has been evacuated.
  • equation (12) can also be used as a working equation in a further simplified form: For small values of k (measurement near the channel wall: k ⁇ 0), (12) is first developed into a Taylor series:
  • a gas sensor for the measurement method described above with several thermometers at different distances eg 100 ⁇ , 150 ⁇ , 200 ⁇ , 300 ⁇ , 500 [im) be equipped by the heat source. In this way, instead of a single value, a set of connected data is obtained for each measurement, with the aid of which the measurement uncertainty can be reduced.
  • the parameters of (1 1), c, k, p, F and a are generally dependent on the type of fluid flowing. As already mentioned, the product Fa can be determined in the respective stationary fluid (eg with the aid of a frit). The other three parameters must be calibrated.
  • the senor If the sensor is to measure the flow velocity of various gases and gas mixtures without interruption, it must first be individually calibrated for these fluids. The resulting parameters are stored separately for each fluid together with its values for the thermal conductivity and the thermal conductivity group by group so as to be available for the evaluation of a flow measurement available. During operation, the sensor will perform a gas analysis at regular intervals (eg before each flow measurement). For this he measures the thermal conductivity (patent
  • the evaluation program selects the respective required calibration data and loads it from the memory.
  • FIG. 1 shows a schematic cross-section through an inventive flowmeter for carrying out a method according to the invention
  • thermometer 2 shows a measuring element on which the thermometer and the heating segment are arranged.
  • FIG. 1 shows a schematic of a flow meter 10, which has a passage 12 for passing a fluid 14, in the present case in the form of a gas.
  • a measuring element 16 is arranged, by means of which a flow rate v can be measured, with which the fluid 14 flows through the passage 12.
  • the flow meter 10 has a branch drain 18, which, however, is only a preferred embodiment and is not necessary.
  • a partial flow of the fluid 14 is passed to a sensor 20, by means of which the thermal conductivity a and / or the thermal conductivity ⁇ can be measured.
  • the sensor 20 includes a frit 22, by means of which the velocity of the fluid 14 is reduced to such an extent that it can be considered to be close to zero to a good approximation.
  • the measuring element 30 is constructed as shown in FIG. The determination of the thermal diffusivity a and / or the thermal conductivity ⁇ when using a frit is described in DE 10 201 1 121 213.
  • FIG. 2 shows a schematic three-dimensional view of the measuring element 16.
  • a heating element 24 can be seen, which is electrically connected to an evaluation unit 26 by way of a not illustrated contacting.
  • the evaluation unit 26, which could also be referred to as a control and evaluation unit, is designed for automatically energizing the heating element 24, so that this emits a heat pulse.
  • the heating element 24 spans a channel 28, which is etched into a substrate 30 of the measuring element 16.
  • the heating element 24 has a distance c / from a wall 32 of the passage 12, which is represented in the present case by the channel bottom of the channel 28.
  • the measuring element 16 also has a first thermometer 34 and a second thermometer 36.
  • both thermometers span the channel 28. They are connected to the evaluation unit 26, which is designed for the current-free measurement of a respective electrical resistance R34, R34 of the thermometers 34, 36. Thus, from the electrical resistors R34, R34 to the temperature the thermometer 34, 36 are closed.
  • the distance xth is the distance to be used in the formulas given above.
  • the time t is less than 100 milliseconds, preferably less than 1 millisecond, in particular less than 0.5 milliseconds.
  • the temperature field around an instantaneously excited punctiform or linear heat source within a fluid, the thermal conductivity ⁇ , the thermal conductivity ⁇ and the volumetric specific heat capacity pc P is described in DE 10 2014 010 939.
  • Values for parameters k and F stored in calibration experiments are stored.
  • a distance of the thermometer 34 from the heating element 24 is stored.
  • the evaluation unit 26 is designed to calculate the flow rate v using an equation that incorporates the reduction of the flow rate v in an environment of the thermometer 34 and optionally the second thermometer 36.
  • the measuring element 16 is produced, for example, in that the channel 28 is etched out of a substrate 30 made of a semiconductor, for example silicon, such that the heating element 24 and the thermometers 34, 36 remain. Thereafter, an electrical contact is added to these elements, for example by applying metallic interconnects.
  • a first distance X34 between the first thermometer 34 and the heating element 24 is preferably at least 40 ⁇ , in particular 50 ⁇ , and 600 ⁇ , in particular 500 ⁇ .
  • a second distance X36 between the second thermometer 36 and the heating element 24 is preferably also at least 40 ⁇ , in particular 50 ⁇ , and 600 ⁇ , in particular 500 ⁇ .
  • the evaluation unit 26 is set up for energizing the heating element 24 with a pulse duration t.

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

Abstract

La présente invention concerne un procédé pour déterminer un paramètre de débit (v) d'un fluide, qui comprend les étapes consistant à : (a) diriger le fluide (14) dans une conduite (12), (b) chauffer de manière pulsée le fluide (14) au moyen d'un élément chauffant (24), (c) mesurer une température (T) en fonction du temps au moyen d'un thermomètre (34) qui est agencé dans un espace de thermomètre (xTh) à l'écart de l'élément chauffant, (d) déterminer un temps de température maximale (tmax) sous la forme du laps de temps entre le moment du chauffage pulsé et le moment du maximum de température dans l'écart de thermomètre (xTh) et (e) calculer le paramètre de débit (v) à partir du temps de température maximale (tmax). L'invention prévoit que le calcul du débit (v) s'effectue à l'aide d'une équation impliquant une réduction du débit au voisinage du thermomètre (34, 36).
PCT/EP2017/056164 2016-05-11 2017-03-15 Procédé pour déterminer un paramètre de débit d'un fluide et appareil de mesure du débit WO2017194228A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102016108688.6 2016-05-11
DE102016108688.6A DE102016108688B3 (de) 2016-05-11 2016-05-11 Verfahren zum Bestimmen einer Durchflussgeschwindigkeit eines Fluids und Durchflussmessgerät

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WO2017194228A1 true WO2017194228A1 (fr) 2017-11-16

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE112017008109A5 (de) * 2017-09-27 2020-06-25 Bundesrepublik Deutschland, Vertreten Durch Das Bundesministerium Für Wirtschaft Und Energie, Dieses Vertreten Durch Den Präsidenten Der Physikalischen Bundesanstalt Durchflussmessvorrichtung zum Messen eines Durchflussparameters eines Fluids und Verfahren zur Durchflussmessung

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19655001C2 (de) * 1995-09-06 2000-10-19 Gen Motors Corp Meßfühleranordnung
DE102011121213B3 (de) 2011-12-06 2013-03-28 Bundesrepublik Deutschland, vertr.d.d. Bundesministerium für Wirtschaft und Technologie, d.vertr.d.d. Präsidenten der Physikalisch-Technischen Bundesanstalt Verfahren zum Messen einer thermischen Gesamt-Transportgröße und Transportgrößen-Messvorrichtung
DE102012106657A1 (de) 2012-04-23 2013-10-24 Endress + Hauser Flowtec Ag Verfahren zum thermischen Bestimmen eines Massedurchflusses eines gasförmigen Mediums und thermischer Massedurchflussmesser
DE102012019657B3 (de) 2012-10-08 2013-10-31 Bundesrepublik Deutschland, endvertreten durch die Physikalisch-Technische Bundesanstalt Verfahren zum Ermitteln einer thermischen Transportgröße und einer Strömungsgeschwindigkeit in einem strömenden Medium und Thermotransportgrößen-Messanordnung
DE102012020147B3 (de) 2012-10-15 2014-01-30 Bundesrepublik Deutschland, endvertreten durch die Physikalisch-Technische Bundesanstalt (PTB) Verfahren zur Bestimmung einer thermischen Transportgröße und Thermotransportgrößen-Messanordnung
DE102014010939B3 (de) 2014-07-28 2015-10-08 Bundesrepublik Deutschland, vertr. durch das Bundesministerium für Wirtschaft und Energie, dieses vertreten durch den Präsidenten der Physikalisch-Technischen Bundesanstalt Verfahren zum Ermitteln einer thermischen Transportgröße und/oder einer zu einer Strömungsgeschwindigkeit in einem strömenden Medium proportionalen Größe und Durchfluss-Messanordnung

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Publication number Priority date Publication date Assignee Title
GB8903744D0 (en) * 1989-02-18 1989-04-05 Endress & Hauser Ltd Flowmeter

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19655001C2 (de) * 1995-09-06 2000-10-19 Gen Motors Corp Meßfühleranordnung
DE102011121213B3 (de) 2011-12-06 2013-03-28 Bundesrepublik Deutschland, vertr.d.d. Bundesministerium für Wirtschaft und Technologie, d.vertr.d.d. Präsidenten der Physikalisch-Technischen Bundesanstalt Verfahren zum Messen einer thermischen Gesamt-Transportgröße und Transportgrößen-Messvorrichtung
DE102012106657A1 (de) 2012-04-23 2013-10-24 Endress + Hauser Flowtec Ag Verfahren zum thermischen Bestimmen eines Massedurchflusses eines gasförmigen Mediums und thermischer Massedurchflussmesser
DE102012019657B3 (de) 2012-10-08 2013-10-31 Bundesrepublik Deutschland, endvertreten durch die Physikalisch-Technische Bundesanstalt Verfahren zum Ermitteln einer thermischen Transportgröße und einer Strömungsgeschwindigkeit in einem strömenden Medium und Thermotransportgrößen-Messanordnung
DE102012020147B3 (de) 2012-10-15 2014-01-30 Bundesrepublik Deutschland, endvertreten durch die Physikalisch-Technische Bundesanstalt (PTB) Verfahren zur Bestimmung einer thermischen Transportgröße und Thermotransportgrößen-Messanordnung
DE102014010939B3 (de) 2014-07-28 2015-10-08 Bundesrepublik Deutschland, vertr. durch das Bundesministerium für Wirtschaft und Energie, dieses vertreten durch den Präsidenten der Physikalisch-Technischen Bundesanstalt Verfahren zum Ermitteln einer thermischen Transportgröße und/oder einer zu einer Strömungsgeschwindigkeit in einem strömenden Medium proportionalen Größe und Durchfluss-Messanordnung

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