METHOD FOR DETERMINING A MEASURING SUBSTANCE TEMPERATURE AND MEASURING SYSTEM THEREFOR

Description

[0001] The invention relates to a method for determining a medium temperature, namely a temperature of a medium conveyed in a line, and a corresponding measuring system.

[0002] US-A 2017 / 0074701, US-A 2017 / 0074730, WO-A 2017 / 131546 and WO-A 2015 / 099933 each show measuring systems and methods for determining a medium temperature, namely a temperature of a medium flowing in a line, for example a pipe, for example a gas, a liquid or a dispersion, wherein in each case a temperature of a - typically metallic - wall surrounding the lumen of the line (wall temperature) is detected on a surface facing away from the lumen (shell surface) by means of one or more temperature sensors and, on the basis of temperature measurement signals generated thereby, medium temperature values representing the medium temperature are generated, for example calculated.

[0003] At least one of the temperature sensors of the respective measuring system is formed by a temperature sensor arranged outside the line, thus not contacted by the medium flowing in the lumen of the line during operation, and possibly also by a coupling body, for example made of a thermally conductive adhesive, that thermally connects the same temperature sensor to the wall. The temperature sensor is also configured to convert a wall temperature corresponding to a temperature at a temperature measuring point formed by the respective temperature sensor into a corresponding temperature measurement signal, namely an electrical measurement signal representing the respective wall temperature, for example with an electrical signal voltage dependent on the same wall temperature and / or an electrical signal current dependent on the same wall temperature.The temperature sensor can therefore be, for example, a platinum measuring resistor, a thermistor or a thermocouple or an electrical circuit formed by several such temperature-sensitive electrical or electronic components.

[0004] Each of the aforementioned measuring systems further comprises measuring system electronics configured to receive the at least one temperature measurement signal and to generate the measured medium temperature values using the same temperature measurement signal. Typically, the measuring system electronics are electrically connected directly to the at least one temperature sensor via appropriate connecting cables. In measuring systems used in industrial measurement and automation technology, the measuring system electronics are usually implemented using one or more microprocessors, possibly also designed as digital signal processors (DSPs), such that the measuring system electronics determines the respective temperature measurement values by numerically calculating digital sample values obtained from the measurement signals, not least the at least one temperature measurement signal, and provides them in the form of corresponding digital values.In addition, the measuring system electronics are typically housed within at least one comparatively robust, particularly impact-, pressure-, and / or weather-resistant, electronics housing. The electronics housing can, for example, be located away from the line or in its immediate vicinity, possibly even fixed to the line. The respective measuring system electronics can also be electrically connected via appropriate electrical lines to a higher-level electronic data processing system that is spatially remote from the respective measuring system or even spatially distributed, to which the measured values generated by the respective measuring system are transmitted promptly, for example, in real time, by means of at least one measured value signal that carries them accordingly.The data processing system can be formed, for example, by means of programmable logic controllers (PLCs) and / or process control computers installed in a control room as well as by means of corresponding data transmission networks, for example a fieldbus system and / or a radio network. Further examples of measuring systems for determining a medium temperature by means of temperature sensors arranged externally on a line carrying the medium can be found, among others, in DE-A 10 2018 132672, EP-A 919 793, US-A 2008 / 0127745, US-A 2008 / 0115577, US-A 2011 / 0113896, US-A 47 68 384, US-B 70 40 179, WO-A 95 / 08758, WO-A 01 / 02816, the.

[0005] WO-A 2009 / 051588, WO-A 2009 / 134268, WO-A 2012 / 018323, WO-A 2012 / 033504, WO-A 2012 / 067608 or WO-A 2012 / 115639.

[0006] As described in DE-A 10 2018 132672, US-A 2017 / 0074701, US-A 2017 / 0074730, EP-A 919 793, US-A 2008 / 0127745, US-A 2008 / 0115577, US-A 2011 / 0113896, US-A 47 68 384, US-B 70 40 179, WO-A 95 / 08758, WO-A 01 / 02816, WO-A 2009 / 051588, WO-A 2009 / 134268, WO-A 2012 / 018323, WO-A As shown in WO-A 2012 / 033504, WO-A 2012 / 067608 or WO-A 2012 / 115639, measuring systems of the type in question can also be designed to determine at least one further measured variable of the medium flowing in the line which differs from the temperature of the medium, in particular to generate measured values representing this.For example, such a measuring system can also be a vibronic measuring system that is used to measure one or more material parameters of the measuring medium, such as a density and / or a viscosity, and / or to measure one or more flow parameters of the measuring medium, for example a mass and / or volume flow and / or a flow velocity, and thus generates corresponding density measured values, viscosity measured values, mass flow measured values, volume flow measured values and / or flow velocity during operation.The structure and mode of operation of such vibronic measuring systems, formed by means of a vibration-type measuring transducer comprising the aforementioned line, typically designed as a (metal) pipe - for example also designed as Coriolis mass flow meters or as Coriolis mass flow / measuring systems - are known to the person skilled in the art and are described, for example, in US-B 65 133 393, US-B 66 51 513, US-B 70 17 242, US-B 74 06 878, US-B 87 57 007, US-B 86 71 776 or US-B 89 24 165 or also in the aforementioned US-A 2017 / 0074701, US-A 2017 / 0074730, EP-A 919 793, US-A 2008 / 0127745, US-A 2008 / 0115577, US-A 2011 / 0113896, US-A 47 68 384, US-B 70 40 179, WO-A 01 / 02816, WO-A 2009 / 051588, WO-A 2009 / 134268, WO-A 2012 / 018323, WO-A 2012 / 033504, WO-A 2012 / 067608 or WO-A 2012 / 115639.In such vibronic measuring systems, the line is specifically designed to be vibrated at least temporarily during operation to measure the material and / or flow parameter, and to be subjected to the flow of the measured material. Typically, the line is actively excited to useful vibrations, namely mechanical vibrations around a static rest position associated with the respective line, by at least one electromechanical exciter acting on it, for example, a permanent magnet fixed to the outside of the line pipe and an excitation coil interacting with it.also mechanical vibrations that are capable of inducing Coriolis forces in the flowing medium that are dependent on its mass flow, and / or that are capable of inducing frictional forces in the flowing medium that are dependent on its viscosity, and / or that are capable of inducing inertial forces in the flowing medium that are dependent on its density. To detect mechanical vibrations of the line, not least their useful vibrations, the respective (vibronic) measuring system further comprises at least one vibration sensor, for example an electrodynamic one, which is configured to convert at least one vibration signal, namely an electrical vibration measurement signal representing vibrational movements of the line, for example with an electrical signal voltage that is dependent on a speed of the vibrational movements of the line.The measuring system electronics of such vibronic measuring systems are - not least for the aforementioned case that density measured values representing the density of the measuring substance and / or viscosity measured values representing the viscosity of the measuring substance can be generated - further configured to generate measured values using both the at least one temperature measuring signal and the at least one vibration signal, for example in such a way that the measuring system electronics determines density measured values and / or viscosity measured values based on a useful frequency measured using the vibration signal, namely an oscillation frequency of the useful vibrations dependent on the material parameter to be measured, and for this purpose compensates for any dependence of the same useful frequency on a current measuring fluid temperature.In addition to evaluating the temperature measurement signals and the at least one vibration signal, the measurement system electronics of such vibronic measurement systems typically also serve to generate at least one driver signal, for example, a harmonic and / or clocked signal, for the at least one electromechanical vibration exciter. This driver signal can be regulated, for example, with respect to a current and / or voltage level.

[0007] Further investigations have shown that the medium temperature values determined by means of the above-mentioned methods and measuring systems deviate from the true or estimated temperature even at comparatively low flow velocities of the medium flowing in the pipe of approximately 0.1 m s -1< and / or at comparatively low Reynolds numbers of the medium flowing in the pipe of approximately 100.actual medium temperature can deviate considerably, for example in such a way that medium temperature values which represent a core temperature of the medium corresponding to a temperature of a partial volume of the medium located in the centre of the lumen can deviate by more than 4 K from the same core temperature; this is particularly the case when taking into account heat flows recorded by means of two or more temperature sensors within the wall and / or within an atmosphere surrounding the line, for example according to the aforementioned US-A 2017 / 0074701, US-A 2017 / 0074730, US-A 2008 / 0127745, US-B 70 40 179, WO-A 2017 / 131546 or WO-A 2015 / 099933.

[0008] Taking this into account, one object of the invention is to provide a method that enables the precise determination of a medium temperature of a medium flowing in a line, not least namely a core temperature of the medium, based on a measured wall temperature; this is particularly true for flow velocities of the medium flowing in the line of more than 0.1 m s -1< or for Reynolds numbers of the medium flowing in the line of more than 100 and / or such that the determined medium temperature or a medium temperature value representing it deviates from the true medium temperature by less than 3 K, in particular even less than 1 K. Furthermore, a further object of the invention is to provide a measuring system suitable for carrying out such a method.

[0009] To achieve the object, the invention consists in a method for determining a medium temperature TM according to claim 1 and a measuring system according to claim 20. Advantageous embodiments of the invention are defined in the dependent claims.

[0010] A basic idea of the invention is to determine an (additional) heating of the medium flowing in the line caused by the conversion of kinetic energy of the flowing medium into thermal energy due to friction processes within the medium flowing through the line or between the flowing medium and the wall of the line on the basis of further material and flow parameters of the medium, namely its density, its viscosity, its thermal conductivity, its heat capacity and the pressure difference, and to take this into account accordingly when determining the medium temperature on the basis of the wall temperature.

[0011] The invention and advantageous embodiments thereof are explained in more detail below using exemplary embodiments illustrated in the figures of the drawing. Identical or similarly acting or functioning parts are provided with the same reference numerals in all figures; where clarity requires it or it otherwise seems expedient, previously mentioned reference numerals are omitted in subsequent figures. Further advantageous embodiments or developments, in particular combinations of partial aspects of the invention initially explained only individually, will become apparent from the figures of the drawing and / or from the claims themselves.

[0012] In detail: Fig. 1 schematically shows an embodiment of a measuring system according to the invention for measuring a temperature of a fluid medium conveyed in the line; Fig. 2, 3 schematically shows a variant of a measuring system according to the invention according to Fig. 1; and Fig. 4 schematically shows a further variant of a measuring system according to the invention.

[0013] In Fig. 1 , 2 , 3and 4 respectively schematically depict a measuring system comprising a (fluid) line or a corresponding (measuring) arrangement, which serves to determine a medium temperature TM, namely a temperature of a fluid medium FL, for example a gas, a liquid or a dispersion, conveyed in the line 111. The line 111 has a lumen enclosed by a wall, for example a metallic wall, and can be designed, for example, as a (metal) tube. The medium temperature TM to be determined can be, for example, a core temperature of the same medium located on a longitudinal axis of the lumen or in its vicinity.According to one embodiment of the invention, the wall of the line is made of metal, for example a steel, a titanium alloy, a tantalum alloy or a zirconium alloy, and / or the wall of the line has a wall thickness which is not less than 0.5 mm, for example also more than 1 mm, and / or not more than 5 mm, for example also less than 3 mm. The line can furthermore be part of a (pipe) system and / or a measuring system which is used to determine the temperature TM, for example also a vibronic system and / or a measuring system which can be inserted into the course of a pipeline. Accordingly, the measuring system can, as also shown in . Fig. 2 or 3, for example also by means of one of the devices described in the above-mentioned EP-A 919 793, US-A 2008 / 0127745, US-A 2008 / 0115577, US-A 2011 / 0113896,

[0014] US-A 2017 / 0074701, US-A 2017 / 0074730, US-A 47 68 384, US-B 65 133 393, der US-B 66 51 513, der US-B 70 17 242, US-B 70 40 179, der US-B 74 06 878, US-B 87 57 007, US-B 86 71 776,

[0015] US-B 89 24 165, WO-A 95 / 08758, WO-A 01 / 02816, WO-A 2009 / 051588, WO-A 2009 / 134268, WO-A 2012 / 018323, WO-A 2012 / 033504, WO-A 2012 / 067608, WO-A 2012 / 115639,

[0016] WO-A 2015 / 099933 or WO-A 2017 / 131546 or also designed as a measuring device in compact design and / or vibronic, industrial measuring system, which in turn is set up to carry the measuring medium or partial volume thereof during operation, or the line can be part of a differential pressure measuring device and / or a Coriolis mass flow measuring device, in particular also a Coriolis mass flow / density measuring device, a Coriolis mass flow / density / viscosity measuring device, a Coriolis mass flow / density / differential pressure measuring device or a Coriolis mass flow / density / viscosity / differential pressure measuring device.

[0017] To determine the medium temperature TM, according to the invention the medium is flowed through the line in a predetermined flow direction, for example with a flow velocity U of more than 0.1 m / s and / or with a mass flow m of more than 0.01 kg·s -1< , and is, as in Fig. 1 shown schematically, at least one wall temperature T w , namely a temperature of the wall representing, for example, digital,

[0018] Wall temperature value X Tw is determined. The wall temperature T w to be determined can be, for example, a surface temperature, namely a temperature of the wall on a surface of the wall facing away from the lumen (lateral surface) or, for example, a temperature inside the wall or a temperature on a surface of the wall facing the lumen (inner surface). Alternatively or additionally, the wall temperature T w to be determined can also be, for example, the (wall) temperature of a hollow cylindrical segment of the wall of the line. Accordingly, according to a further embodiment of the invention, the wall temperature value X Tw represents the wall temperature T w , for example the surface temperature, of a hollow cylindrical segment of the wall and / or, according to a further embodiment of the invention, a surface temperature of the wall is detected to determine the at least one wall temperature value X Tw.According to a further embodiment of the invention, it is further provided that the wall temperature T w , for example the surface temperature of the wall and / or the temperature at a hollow cylindrical segment of the wall, is detected by means of a temperature sensor 21 and converted into a temperature measurement signal θ1, for example an electrical one, which follows a change in the same (wall) temperature with a change in at least one signal parameter, and in particular that the same temperature measurement signal θ1 is also used to determine the at least one wall temperature value X Tw . In particular, it is further provided for this purpose to use a temperature sensor that is thermally coupled to a lateral surface of the wall, for example fastened to the wall in a materially bonded or force-fitting manner, to generate the temperature measurement signal θ1.

[0019] Inevitable frictional processes within the medium flowing through the pipe or between the flowing medium and the pipe wall lead to the kinetic energy of the flowing medium being converted into thermal energy, thus causing (additional) heating of the medium flowing in the pipe through dissipation, for example in a partial volume of the flowing medium located close to the wall; this usually occurs in such a way that along one and the same radius of the pipe a temperature difference is established between the wall temperature and the medium temperature and / or that the wall temperature T w is higher than the temperature actually to be measured.

[0020] Medium temperature TM (TM < T w ). Not least in the above-mentioned case that the medium temperature TM to be determined is a core temperature of the medium, the above-mentioned dissipation can lead to this actually being more than 1 K lower than the (measured) wall temperature T w . The above-mentioned friction processes can be particularly pronounced, among other things, in the case that the medium flowing in the pipe has a flow velocity U that is greater than 0.1 m s -1< , in particular greater than 1 m s -1< , and / or that the medium flowing in the pipe has a mass flow mwhich is greater than 0.01 kg s -1< , for example also greater than 0.1 kg s -1< , and / or that the medium FL flowing in the line has a Reynolds number Re which is greater than 100, in particular greater than 1000. The Reynolds number Re of the medium flowing in the line is a dimensionless parameter for fluids, which is known to be defined as a ratio between inertial and viscosity forces in the flowing fluid and which depends, among other things, on a characteristic length L or A: Re = ρ ⋅ U ⋅ L μ = m ˙ A ⋅ μ Furthermore, the frictional processes described above could also be observed in particular in those media where the specific heat capacity cp is not less than 1 kJ kg -1< K -1< and / or the thermal diffusivity λ is not less than 0.1 W m -1< K -1< and / or the viscosity µ is greater than 1 mPa s, in particular greater than 10 mPa s, and / or the density ρ is greater than 500 kg m -3<.

[0021] Taking into account the aforementioned friction processes and the associated disspation, for the determination of the medium temperature TM according to the invention, at least one density value X ρ representing a density ρ of the medium flowing in the line, at least one viscosity value X µ representing a viscosity µ, in particular an effective dynamic viscosity, of the medium flowing in the line, at least one thermal conductivity value X λ representing a thermal conductivity λ of the medium, at least one heat capacity value X cp representing a specific heat capacity cp of the medium and at least one pressure difference Δp established within the medium flowing in the line in the flow direction, in particularnamely, a difference between a first static pressure p1 established in the flowing medium and a second static pressure p2 established downstream of the first static pressure p1 in the flowing medium, representing a pressure difference value X Δp. The viscosity µ of the medium can generally also be defined or determined, for example, as an effective viscosity µ, such that it corresponds to a consistency K of the medium flowing in the line, a shear rate . γ̇ of the medium flowing in the pipe and a flow index n of the medium flowing in the pipe dependent calculation formula: μ = K ⋅ γ ˙ n − 1 ⋅ 3 n + 1 4 n n ⋅ 8 n − 1 where the consistency K of the medium flowing in the pipe is again defined as a ratio between a shear stress τ in the medium and a shear rate γ̇ is defined in the measuring material, thus a calculation rule: K = τ γ ˙ corresponds.

[0022] The aforementioned density values X ρ , viscosity values X µ , thermal conductivity values X λ , heat capacity values X cp and / or pressure difference values X Δp can, for example, also each be digital values or digital measured values. In the aforementioned case that the measuring system is formed by a Coriolis mass flow meter or is designed as a component of such a Coriolis mass flow meter, the same Coriolis mass flow meter can further be configured to determine the aforementioned density value X ρ and / or the Coriolis mass flow meter can be configured to determine the aforementioned viscosity value X µ and / or the Coriolis mass flow meter can be configured to determine the aforementioned pressure difference value X Δp. The use of such a measuring system has, among other things, the advantage that the density value X ρ can be determined so precisely that it can be distinguished from the (true oractual) density ρ of the measuring substance by not more than 0.5% of the density ρ (. f ρ <0.5% ), or that the pressure difference value X Δp can be determined so precisely that it does not deviate from the (true or actual) pressure difference Δp by more than 15% of the pressure difference Δp (f Δp < 15%), and / or that the viscosity value X µ does not deviate from the (true or actual) viscosity µ of the medium by more than 15% of the viscosity µ ( fµ < 15%). In the other case mentioned, in which the measuring system is formed by means of a differential pressure measuring device or is designed as a component of such a differential pressure measuring device, the same differential pressure measuring device can, for example, also be used alternatively or in addition to the aforementioned Coriolis mass flow meter to determine the pressure difference value X Δp. The use of such a measuring system has, among other advantages, that the pressure difference value X Δp can be determined so precisely that it deviates from the (true or actual) pressure difference Δp by no more than 5% of the pressure difference Δp (f Δp < 5%). The thermal diffusivity value X λ and / or heat capacity value X cp specific for the respective medium, if applicable. also the aforementioned flow index n, in turn can, for example, be determined in advance accordingly and / or with knowledge of the respective measuring material from a specific thermal conductivity value (X λ ) orHeat capacity values (X cp ), if necessary also flow indices (n) are read out from a (value) table assigned to a respective measuring medium, if necessary also recurringly, for example regularly and / or due to a change or a change of the measuring medium in the line.

[0023] According to the invention, the density value X ρ , the viscosity value X µ , the pressure difference value X Δp , the thermal conductivity value and the heat capacity value are also used to determine at least one characteristic value XV for a medium characteristic number V, which characterizes a heating of the medium flowing in the line caused by dissipation, for example in a partial volume of the flowing medium located close to the wall. To process the density value X ρ , the viscosity value X µ , the pressure difference value X Δp , the thermal conductivity value and the heat capacity value X cp or to calculate the characteristic value XV, the measuring system can further have corresponding (measuring system) electronics 20, for example generating digital measured values and / or formed by a microprocessor, which can in turn be accommodated, for example, in a separate (electronic) protective housing 200.The (electronics) protective housing 200 can, for example, be designed to be impact- and / or explosion-resistant and / or configured to protect the (measuring system) electronics from dust and / or splash water. According to the invention, the (measuring system) electronics 20 is configured to determine the at least one measured medium temperature value X TM .

[0024] The (measuring system) electronics 20 can further comprise, for example, a non-volatile data memory (EEPROM) for storing digital data, in particular also digital (measured) values. According to a further embodiment of the invention, said data memory is configured to store the at least one thermal conductivity value X λ and / or the at least one heat capacity value X cp . Accordingly, the aforementioned (value) table for specific thermal conductivity values and / or the specific heat capacity value and / or the table for flow indices can also be stored in the data memory, such that at least one respective specific thermal conductivity value (X λ ) and / or at least one respective specific heat capacity value (X cp ) and / or a respective flow index (n) is assigned to an entry for a particular measured substance and can be read out in each case for calculating the characteristic value XV.In addition, the at least one wall temperature value X Tw , the at least one density value X ρ , the at least one viscosity value X µ and / or the at least one pressure difference value X Δp can also be stored in the non-volatile data memory and / or the at least one characteristic value XV and / or the at least one medium temperature value X TM can also be (temporarily) stored in the non-volatile data memory.In the aforementioned case that a temperature sensor 21 is provided for detecting the wall temperature T w and for generating the temperature measurement signal θ1 representing it, the (measuring system) electronics 20 can also be electrically connected to the temperature sensor, for example by means of an electrical connecting cable, and the (measuring system) electronics 20 can also be configured to receive and evaluate the temperature measurement signal θ1, for example to digitize it and / or to determine the wall temperature value X Tw based on the temperature measurement signal θ1.For the other aforementioned case that the measuring system is formed by means of a Coriolis mass flow meter, the (measuring system) electronics 20 can also be a component of the same Coriolis mass flow meter, just like the line, or for the aforementioned case that the measuring system is formed by means of a differential pressure meter, the (measuring system) electronics 20 can also be a component of the same differential pressure meter.

[0025] According to the invention, the aforementioned medium characteristic number V corresponds to a calculation formula determined by an Eckert number Ec of the medium flowing in the line, a Prandtl number Pr of the medium flowing in the line and a pressure loss coefficient ζ of the line as well as by a line-specific first exponent a, a line-specific second exponent b and a line-specific third exponent c: V = f Δ p , ρ , μ , λ , c p = Pr a ⋅ Ec b ⋅ ζ c

[0026] Typically, exponent a is more than 0.1 and less than 0.5, specifically 0.3. Exponent b and exponent c, in turn, can each be more than 0.8 and less than 1.2, for example, they can be equal to each other and / or each be 1.

[0027] Using both the aforementioned wall temperature value X Tw and the determined characteristic value XV, according to the invention at least one medium temperature value X TM representing the temperature TM of the medium, for example its core temperature, is subsequently determined; this, for example, in such a way that the medium temperature value X TM has a calculation rule that depends, among other things, on both the characteristic value XV and the wall temperature value X Tw: X TM = X TW − k 1 ⋅ X V + k 2 = X TW − X Δ T The aforementioned calculation rule for the wall temperature value X Tw can further be parameterized by a line-specific first coefficient k1 and a line-specific second coefficient k2. These coefficients k1, k2 can be (calibration) constants determined in advance for a respective measuring system, for example during calibration under reference conditions, wherein the coefficient k1 is typically not less than 0.5 K (Kelvin) and not more than 1.5 K and / or wherein the coefficient k2 is typically not less than as -0.2K and not more than 0.2 K, and can also be set equal to zero if necessary. According to a further embodiment of the invention, the characteristic value XV and the line-specific first and second coefficients k1, k2 are dimensioned such that, in particular when the medium is flowing and / or in the event that the medium temperature value X TM represents a core temperature of the medium, the medium temperature value X TM is smaller than the wall temperature value X Tw (X TM < X Tw ).

[0028] The Prandtl number Pr of the medium flowing in the pipe is a dimensionless parameter for fluids, which is known to be defined as a ratio between viscosity µ and thermal diffusivity λ, thus a calculation formula: Pr = c p λ ⋅ μ or when using the effective viscosity according to a calculation formula: Pr = c p λ ⋅ K ⋅ γ ˙ n − 1 ⋅ 3 n + 1 4 n n ⋅ 8 n − 1 The Eckert number Ec of the fluid flowing in the pipe is also a dimensionless parameter for fluids, which is defined as a ratio of the kinetic energy of the flowing fluid and an enthalpy difference established between the same fluid and the wall, or a calculation formula: Ec = U 2 c p ⋅ Δ T corresponds, whereby for the determination of the medium temperature TM according to the invention, the temperature difference ΔT to be used for this purpose can be assumed to be constant, for example, set at 1 K, so that the Eckert number Ec can also be calculated using a simplified formula: Ec = k 3 ⋅ U 2 c p can correspond to, for example, k3 = 1 K -1< . The aforementioned pressure loss coefficient ζ of the fluid flowing in the pipe is also dimensionless. In this case, it is a measure of the pressure loss in or along the pipe through which the fluid flows, whereby the pressure loss coefficient ζ - occasionally referred to as the pressure loss or resistance coefficient - corresponds to a calculation formula: ζ = Δp 0 , 5 ⋅ ρ ⋅ U 2 Accordingly, the measuring material characteristic number V can be calculated using a formula: V = c p λ ⋅ μ a ⋅ U 2 c p ⋅ Δ T b ⋅ Δp 0 , 5 ⋅ ρ ⋅ U 2 c = c p λ ⋅ μ a ⋅ k 3 ⋅ U 2 c p b ⋅ 2 ⋅ Δp ρ ⋅ U 2 c be defined.

[0029] To determine the characteristic value XV, according to a further embodiment of the invention, at least one velocity value XU is also determined, which represents a, for example, average or maximum, flow velocity U of the medium flowing in the line, and the characteristic value XV is determined based on the aforementioned calculation formula (11), such that the characteristic value XV has a calculation rule: X V = X cp ⋅ X μ X λ a ⋅ k 3 ⋅ X U 2 X cp b ⋅ 2 ⋅ X Δ p X ρ ⋅ X U 2 c is fulfilled, where a line-specific third coefficient k3 corresponds to the previously specified temperature difference ΔT (k3 = ΔT -1< = k Ec ).

[0030] For the already mentioned typical case that the exponent b can be set equal to the exponent c, the measured substance characteristic V corresponds accordingly to a calculation formula that is simplified compared to the calculation formula (11), in particular that is independent of the flow velocity U: V = c p λ ⋅ μ a ⋅ k 3 ⋅ Δp 0 , 5 ⋅ ρ ⋅ c p b for example, a further simplified calculation formula V = c p λ ⋅ μ a ⋅ k 3 ⋅ Δp 0 , 5 ⋅ ρ ⋅ c p or the measured substance characteristic value V can be defined by one of the simplified calculation formulas (13) or (14). Based on this, the characteristic value XV can also be determined in such a way that it uses a calculation rule - simpler than the aforementioned calculation rule (12): X V = X cp X λ ⋅ X μ a ⋅ k 3 ⋅ 2 ⋅ X Δ p X ρ ⋅ X cp b or X V = X cp X λ ⋅ X μ a ⋅ k 3 ⋅ 2 ⋅ X Δ p X ρ ⋅ X cp for example X V = X cp X λ ⋅ X μ 0 , 3 ⋅ k 3 ⋅ 2 ⋅ X Δ p X ρ ⋅ X cp fulfilled.

[0031] According to a further embodiment of the invention, it is further provided to detect a first static pressure p1 established in the medium FL flowing in the line 111 as well as a second static pressure p2 established downstream of it in the flowing medium and also to determine at least the pressure difference value X Δp , for example also the viscosity value X µ and / or the aforementioned velocity value XU , based on the detected first and second static pressures. The detection of the first and second static pressures p1, p2 or the pressure difference Δp (Δp = p1-p2) can, as in Fig. 4As indicated, this can be done, for example, by means of two pressure sensors 51, 52 embedded in the wall of the line at a distance from one another in the direction of flow, which can, for example, be electrically connected to the aforementioned (measuring system) electronics 20 and / or can also be part of the aforementioned differential pressure measuring device. Accordingly, the (measuring system) electronics 20 can also be configured to determine the pressure difference value X Δp , for example also the viscosity value X µ and / or the aforementioned velocity value XU , using pressure measurement signals generated by the aforementioned pressure sensors, possibly also digital ones.

[0032] As discussed in the above-mentioned US-B 87 57 007, US-B 86 71 776 and US-B 89 24 165, the above-mentioned pressure loss coefficient ζ of the medium flowing in the pipe can also be calculated using the formula: ζ = k 41 + k 42 ⋅ Re k 43 correspond or the pressure difference Δp also corresponds to a calculation formula: Δp = k 41 + k 42 ⋅ Re k 43 k 52 ⋅ k 51 ⋅ m ˙ 2 ρ or taking into account the above-mentioned calculation formula (1), for example, also a calculation formula: Δp = k 41 + k 42 ⋅ m ˙ A ⋅ μ k 43 k 52 ⋅ k 51 ⋅ m ˙ 2 ρ

[0033] In addition, the pressure difference value X Δp can be calculated based on the mass flow m , the density ρ and the viscosity µ and / or the Reynolds number Re of the flowing medium or the medium characteristic number V can also be determined using a calculation formula: V = c p λ ⋅ μ a ⋅ k Ec ⋅ U 2 c p b ⋅ 2 ρ ⋅ U 2 ⋅ k 41 + k 42 ⋅ m ˙ A ⋅ μ k 43 k 52 ⋅ k 51 ⋅ m ˙ 2 ρ c or with the same exponents b and c also by a calculation formula: V = c p λ ⋅ μ a ⋅ 2 ⋅ k Ec ρ ⋅ c p ⋅ k 41 + k 42 ⋅ m ˙ A ⋅ μ k 43 k 52 ⋅ k 51 ⋅ m ˙ 2 ρ b As a result, both the pressure loss coefficient ζ and the pressure difference Δp can also be determined using parameters that can be measured using a vibronic measuring system, such as a (conventional) Coriolis mass flowmeter.

[0034] Accordingly, according to a further embodiment of the invention, at least one mass flow m the mass flow value representing the medium flowing in the pipe X ṁ and / or to determine at least one Reynolds number value X Re representing the Reynolds number Re of the medium flowing in the line. The Reynolds number value X Re can be determined according to the calculation formula (1), for example, in such a way that it satisfies a calculation rule: X Re = k 61 ⋅ X ρ ⋅ X U X μ or a calculation formula: X Re = k 62 ⋅ X m ˙ X μ where the coefficient k61 corresponds to the previously specified characteristic length L and the coefficient k62 to the previously specified characteristic length A. Using the at least one Reynolds number value X Re and the previously specified mass flow value X ṁtogether with the density value X ρ, both the pressure loss coefficient value X ζ and the pressure difference value X Δp can then be calculated, for example, in such a way that the pressure loss coefficient value X ζ has a calculation rule: X ζ = k 41 + k 42 ⋅ X Re k 43 fulfilled and / or that the pressure difference value X Δp a calculation rule : X Δ p = k 51 ⋅ X m ˙ 2 X ρ ⋅ k 41 + k 42 ⋅ X Re k 43 k 52 If necessary, the velocity value XU can also be calculated based on the calculation rule using the at least one mass flow value X ṁ and at least one density value X ρ : X U = k 7 ⋅ X m ˙ X ρ be determined.

[0035] The aforementioned coefficients k41, k42, k43, k51, k52, k61, k62 and k7 are also line- or measuring system-specific (calibration) constants which, like the aforementioned coefficients k1, k2, can be determined in advance for a respective measuring system, for example by calibrating the measuring system under reference conditions, for example during calibration of the measuring system at the manufacturer's and / or (re-)calibration of the measuring system on site.

[0036] According to a further embodiment of the invention, it is further provided that the line for determining the density value X ρ and / or for determining the viscosity value X µ and / or for determining the pressure difference value X Δp and / or the aforementioned mass flow value X ṁand / or the aforementioned Reynolds number value X Re; this, for example, in such a way that the line 111 is actively excited to useful vibrations, namely mechanical vibrations around an associated static rest position with at least one vibration frequency that is inherent to the line, for example, also dependent on the density ρ of the fluid FL flowing in the line 111, or that only slightly deviates therefrom. The active excitation of mechanical vibrations of the line 111, thus the excitation of the useful vibrations, can, as in Fig. 3shown, for example by means of at least one electromechanical vibration exciter 31 acting on the line 111, which is designed to convert electrical power into a mechanical driving force causing vibrations of the line 111 and to introduce the same driving force into the line 111 and / or which, in the above-described case that the measuring system is formed by means of a Coriolis mass flow meter, can be a component of the same Coriolis mass flow meter just like the line 111.Alternatively or additionally, the at least one vibration exciter 31 can also be electrically connected to the aforementioned (measuring system) electronics 20, for example by means of an electrical connecting cable, and the (measuring system) electronics can be configured to feed the electrical power required to cause mechanical vibrations of the line into the vibration exciter 31 by means of an electrical excitation signal e1. Furthermore, it is further provided to detect the aforementioned mechanical vibrations of the line and, as shown in . Fig. 3 indicated, to convert into vibration signals s1, s2, for example, namely electrical vibration measurement signals representing vibration movements of the line, each with an electrical signal voltage dependent on a speed of the vibration movements of the line; this in particular in such a way that between the vibration signals s1, s2 a mass flow mof the medium FL flowing in line 111 is established and / or that each of the oscillation signals s1, s2 has a signal frequency dependent on the density ρ of the medium FL flowing in line 111. The detection of mechanical oscillations of the line, in particular the aforementioned useful oscillations, and for converting these oscillations into corresponding oscillation signals is carried out according to a further embodiment of the invention by means of two oscillation sensors 41, 42, which are arranged at a distance from one another in the direction of flow and are each arranged on the line or in its vicinity, for example electrodynamic or optical, which, in the aforementioned case that the measuring system is formed by means of a Coriolis mass flow meter, can also each be a component of the same Coriolis mass flow meter, just like the line.Alternatively or additionally, the vibration sensors can also be electrically connected to the aforementioned (measuring system) electronics 20, for example by means of an electrical connecting cable, and the (measuring system) electronics 20 can be configured to receive and evaluate the vibration signals of the vibration sensors 41, 42, for example to digitize them and / or to determine the density value X ρ and / or the viscosity value X µ and / or the pressure difference value X Δp and / or the aforementioned mass flow value based on the vibration signals s1, s2 or based on the vibration signals s1, s2 and the aforementioned electrical excitation signal. X ṁ and / or to determine the aforementioned Reynolds number value X Re.

[0037] As already mentioned, a particular aim of the invention is, among other things, that the measuring system according to the invention is suitable for achieving a higher degree of accuracy in determining the medium temperature TM compared to conventional measuring systems or measuring methods; this is particularly true in that a medium temperature value X TM determined according to the invention deviates from the actual or true medium temperature TM by less than 3 K, in particular less than 1 K, not least in the case that the medium temperature value X TM represents the core temperature. The method according to the invention also has the advantage, among other things, that the desired high degree of accuracy in determining the medium temperature TM can also be achieved if the density value X ρ deviates from the (true or actual) density ρ of the medium by no more than 0.5% of the density ρ ( fρ <0.5% ) and / or if the pressure difference value X Δp deviates from the (true or actual) pressure difference Δp by no more than 15% of the pressure difference Δp (f Δp < 15%), and / or if the viscosity value X µ deviates from the (true or actual) viscosity µ of the medium by no more than 15% of the viscosity µ ( f µ < 15%) and / or if the thermal diffusivity value X λ deviates from the (true or actual) thermal diffusivity λ of the measured material by not more than 50% of the thermal diffusivity λ ( f λ < 50%) and / or if the heat capacity value X cp deviates from the (true or actual) specific heat capacity cp of the measured substance by not more than 50% of the specific heat capacity cp ( f cp < 50%); this applies in particular if the density value X ρ deviates from the (true or actual) density ρ

[0038] of the medium by more than 0.1% of the density ρ (f ρ >0.1%) and / or the viscosity value X µ deviates from the (true or actual) viscosity µ of the medium by more than 2% of the viscosity µ ( f µ > 2%) and / or the pressure difference value X Δp deviates from the (true or actual) pressure difference Δp by more than 5% of the pressure difference Δp (f Δp > 5%) and / or the thermal diffusivity value X λ deviates from the (true or actual) thermal diffusivity λ of the medium by more than 5% of the thermal diffusivity λ ( f λ > 5%) and / or the heat capacity value X cp deviates from the (true or actual) specific heat capacity cp of the measured substance by more than 5% of the specific heat capacity cp ( fcp > 5%). It can also be advantageous for the determination of the medium temperature TM according to the invention, not least in the case that this is the aforementioned core temperature, that the specific heat capacity cp is not more than 5 kJ·kg -1< ·K -1< and / or that the thermal diffusivity λ of the medium is not more than 1 W·m -1< ·K -1< and / or that the density ρ of the medium is less than 2000 kg·m -3<.

Claims

1. A method for determining a measured substance temperature TM, that is to say a temperature, in particular a core temperature, of a measured substance (FL) conducted in a line (111), in particular a tube, wherein the line has a lumen enclosed by a wall, in particular a metal wall, said method comprising: - Allowing the measured substance to flow through the line in a predetermined flow direction, in particular with a flow velocity U of more than 0.1 m / s; - Determining at least one wall temperature value XTW representing a wall temperature TW, that is to say a temperature of the wall, in particular on a surface of the wall facing away from the lumen, on a surface of the wall facing toward the lumen, or from inside the wall; - Determining at least one density value Xρ representing a density ρ of the measured substance flowing in the line; - Determining at least one viscosity value Xµ representing a viscosity µ, in particular an effective dynamic viscosity, of the measured substance flowing in the line; characterized in that the method further comprises the steps: - Determining at least one thermal conductivity value Xλ representing a thermal conductivity λ of the measured substance; - Determining at least one thermal capacity value Xcp representing a specific thermal capacity Cp of the measured substance; - Determining at least one pressure difference value XΔp representing a pressure difference Δp established in the measured substance flowing in the line in the flow direction, that is to say, in particular a difference between a first static pressure p1 established in the flowing measured substance and a second static pressure p2 established in the flowing measured substance downstream of the first static pressure p1 - Using the at least one density value, the at least one viscosity value Xµ, the at least one pressure difference value XΔp, the at least one thermal conductivity value Xλ, and the at least one thermal capacity value Xcp to determine at least one characterizing number value XV for a measured substance characterizing number V, which characterizes heating of the measured substance flowing in the line caused by dissipation, in particular in a partial volume of the flowing measured substance located near the wall, wherein the measured substance characterizing number V corresponds to a calculation formula determined both by an Eckert number Ec of the measured substance flowing in the line, a Prandtl number Pr of the measured substance flowing in the line, and a pressure loss coefficient ζ of the line, as well as by a line-specific first exponent a, a line-specific second exponent b, and a line-specific third exponent c: V = f Δ p , ρ , μ , λ , c p = Pr a ⋅ Ec b ⋅ ζ c - and using the at least one characterizing number value XV and the at least one wall temperature value XTW to determine at least one measured substance temperature value XTM representing the measured substance temperature TM, in particular the core temperature of the measured substance, in particular in such a way that the measured substance temperature value XTM satisfies a calculation formula: X TM = X TW − k 1 ⋅ X V + k 2 = X TW − X Δ T 2. The method as claimed in one of the preceding claims, wherein the measured substance temperature value XTM satisfies a calculation formula which is dependent on both the characterizing number value XV and the wall temperature value XTW and is parameterized by a line-specific first coefficient k1 and a line-specific second coefficient k2: X TM = X TW − k 1 ⋅ X V + k 2 = X TW − X Δ T 3. The method as claimed in the preceding claim, - wherein the first coefficient k1 and the second coefficient k2 are (calibration) constants determined in advance; and / or - wherein the first coefficient k1 is not less than 0.5 K (Kelvin) and not more than 1.5 K; and / or - wherein the second coefficient k2 is not less than -0.2 K and not more than 0.2 K, in particular is equal to 0.

4. The method as claimed in one of the preceding claims, - wherein the first exponent a is more than 0.1 and less than 0.5, in particular 0.3; and / or - wherein the second exponent b is more than 0.8 and less than 1.2, in particular 1; and / or - wherein the third exponent c is more than 0.8 and less than 1.2, in particular 1; and / or - wherein the second exponent b is equal to the third exponent c, that is to say, in particular is equal to one.

5. The method as claimed in one of the preceding claims, wherein the characterizing number value XV satisfies a calculation formula: X V = X cp X λ ⋅ X μ a ⋅ k 3 ⋅ 2 ⋅ X Δ p X ρ ⋅ X cp b where k3 = 1 K-1.

6. The method as claimed in the preceding claim, wherein the second exponent b is equal to one.

7. The method as claimed in one of the preceding claims, - wherein the specific thermal capacity Cp of the measured substance is not less than 1 kJ kg-1 K-1 and not more than 5 kJ kg-1 K-1; and / or - wherein the thermal conductivity λ of the measured substance is not less than 0.1 W m-1 K-1 and not more than 1 W m-1 K-1; and / or - wherein the viscosity µ of the measured substance is greater than 1 mPa s, in particular greater than 10 mPa s; and / or - wherein the density ρ of the measured substance is greater than 500 kg m-3 and / or less than 2000 kg m-3; and / or - - wherein the measured substance flowing in the line has a flow velocity U, in particular an average or maximum flow velocity, which is greater than 0.1 m s-1, in particular greater than 1 m s-1; and / or - wherein the measured substance flowing in the line has a mass flow rh which is greater than 0.01 kg s-1, in particular greater than 0.1 kg s-1; and / or - wherein the measured substance flowing in the line has a Reynolds number Re which is greater than 100, in particular greater than 1000; and / or - wherein the density value Xρ deviates from the (true) density ρ of the measured substance by no more than 0.5% of the density ρ (fρ < 0.5%), in particular by more than 0.1% of the density ρ (fρ > 0.1%); and / or - wherein the pressure difference value XΔp does not deviate from the (true) pressure difference Δp by more than 15% of the pressure difference Δp (fΔp < 15%), in particular by more than 5% of the pressure difference Δp (fΔp > 5%); and / or - wherein the viscosity value Xµ does not deviate from the (true) viscosity µ of the measured substance by more than 15% of the viscosity µ (fµ < 15%), in particular by more than 2% of the viscosity µ (fµ > 2%); and / or - wherein the thermal conductivity value Xλ does not deviate from the (true) thermal conductivity λ of the measured substance by more than 50% of the thermal conductivity λ (fλ < 50%), in particular by more than 5% of the thermal conductivity λ (fλ > 5%); and / or - wherein the thermal capacity value Xcp does not deviate from the (true) specific thermal capacity Cp of the measured substance by more than 50% of the specific thermal capacity Cp (fcp < 50%), in particular by more than 5% of the specific thermal capacity Cp (fcp > 5%); and / or - wherein the wall temperature TW (TM < TW), is higher, in particular by more than 1 K, than the temperature TM of the measured substance, that is to say, in particular a core temperature of the measured substance; and / or - wherein the measured substance temperature value XTM is lower than the wall temperature value XTW (XTM < XTW); and / or - wherein the measured substance temperature value XTM represents a core temperature of the measured substance; and / or - wherein the wall temperature value XTW represents the temperature TW, in particular the surface temperature, of a hollow cylindrical segment of the wall; and / or - wherein, to determine the at least wall temperature value XTW a surface temperature of the wall, that is to say, in particular on a hollow cylindrical segment of the wall, is detected; and / or - wherein the wall of the line is made of metal, in particular a steel, a titanium alloy, a tantalum alloy or a zirconium alloy; and / or - wherein the wall of the line has a wall thickness which is not less than 0.5 mm, in particular more than 1 mm, and / or not more than 5 mm, in particular less than 3 mm; and / or - wherein the line for determining the density value and / or for determining the viscosity value and / or - for determining the pressure difference value XΔp is made to oscillate, that is to say, in particular is actively made to mechanically oscillate by means of an electromechanical oscillation exciter of a Coriolis mass flow / density meter.

8. The method as claimed in one of the preceding claims, further comprising: - Determining at least one mass flow value Xm representing a mass flow m of the measured substance flowing in the line; and - Determining at least one Reynolds number value XRe representing a Reynolds number Re of measured substance flowing in the line.

9. The method as claimed in the preceding claim, - wherein the pressure difference value XΔp satisfies a calculation rule: X Δ p = k 51 ⋅ X m ˙ 2 X ρ ⋅ k 41 + k 42 ⋅ X Re k 43 k 52 wherein k41, k42, k51, and k52 are line-specific or measuring system-specific (calibration) constants which are determined in advance for a respective measuring system, in particular by calibrating the measuring system under reference conditions, that is to say, in particular in the course of a calibration of the measuring system by the manufacturer and / or a (re)calibration of the measuring system on site; and / or - wherein the Reynolds number value XRe satisfies a calculation rule: X Re = k 62 ⋅ X m ˙ X μ wherein coefficient k62 is line-specific or measuring system-specific (calibration) constant which is determined in advance for a respective measuring system, in particular by calibrating the measuring system under reference conditions, that is to say, in particular in the course of a calibration of the measuring system by the manufacturer and / or a (re)calibration of the measuring system on site, and which corresponds to a characteristic length A; and / or - wherein a pressure loss coefficient value Xζ satisfies a calculation rule: X ζ = k 41 + k 42 ⋅ X Re k 43 wherein k41 and k42 are line-specific or measuring system-specific (calibration) constants which are determined in advance for a respective measuring system, in particular by calibrating the measuring system under reference conditions, that is to say, in particular in the course of a calibration of the measuring system by the manufacturer and / or a (re)calibration of the measuring system on site.

10. The method as claimed in one of the preceding claims, further comprising: Determining at least one velocity value XU representing a flow velocity U, in particular an average or maximum flow velocity, of the measured substance flowing in the line.

11. The method as claimed in the preceding claim, - wherein a pressure loss coefficient value Xζ satisfies a calculation rule: X ζ = X Δ p 0 , 5 ⋅ X ρ ⋅ X U 2 and / or - wherein the characterizing number value XV satisfies a calculation rule: X V = X cp ⋅ X μ X λ a ⋅ k 3 ⋅ X U 2 X cp b ⋅ 2 ⋅ X Δ p X ρ ⋅ X U 2 c where k3 = 1 K-1.

12. The method as claimed in one of the preceding claims, further comprising: - Determining a flow index n of the measured substance flowing in the line; and / or - Using the temperature measurement signal to determine the at least one wall temperature value XTw.

13. The method as claimed in one of the preceding claims, further comprising: Using a Coriolis mass flow / density meter to determine the density value Xρ and / or to determine the viscosity value xµ, and / or to determine the pressure difference value XΔp.

14. The method as claimed in the preceding claim, wherein the line is part of the Coriolis mass flow / density meter.

15. The method as claimed in one of the preceding claims, further comprising: Using a differential pressure measuring device to determine the pressure difference value XΔp.

16. The method as claimed in the preceding claim, wherein the line is part of the differential pressure measuring device.

17. The method as claimed in one of the preceding claims, further comprising: - Detecting a first static pressure established in the flowing measured substance and a second static pressure established in the flowing measured substance downstream of the first in the flow direction; - and determining the pressure difference value XΔp using the recorded first and second static pressures.

18. The method as claimed in one of the preceding claims, further comprising: - Detecting the temperature TW of the wall, in particular a surface temperature of a hollow cylindrical segment of the wall, - and generating a temperature measurement signal, in particular an electrical signal, following a change in said temperature TW with a change in at least one signal parameter.

19. The method as claimed in the preceding claim, further comprising: Using a temperature sensor (21) thermally coupled to an outer surface of the wall to generate the temperature measurement signal.

20. A measuring system, in particular a vibronic measuring system, adapted to carry out the method as claimed in the preceding claim, wherein said measuring system comprises: - The line (111), - the temperature sensor (21), - and measuring and operating electronics electrically connected to the temperature sensor, in particular formed by means of at least one microprocessor, wherein the measuring and operating electronics are set up to determine the at least one measured substance temperature value XTM.

21. The measuring system as claimed in the preceding claim, - wherein the measuring and operating electronics are set up to determine the at least one wall temperature value XTW; and / or - wherein the measuring and operating electronics are set up to determine the at least one characterizing number value XV for the measured substance characterizing number V.

22. The measuring system as claimed in one of the claims 20 to 22, further comprising: - An oscillation exciter (31) for initiating mechanical oscillations of the line (111) - and first and second oscillation sensors (41, 42) for detecting mechanical oscillations of the line (111) and for converting said oscillations into first and second oscillation signals (s1; s2).

23. The measuring system as claimed in the preceding claim, - wherein both the oscillation exciter (31) and the first and second oscillation sensors (41, 42) are electrically connected to the measuring system electronics, - and wherein the measuring system electronics are set up • to supply electrical power to the oscillation exciter (31) by means of an electrical excitation signal (e1) to cause mechanical oscillations of the line, • and to receive and evaluate the oscillation signals (s1, s2) of the oscillation sensors (41, 42), that is to say, in particular to digitize them and / or to determine the density value Xρ and / or the viscosity value Xµ, and / or the pressure difference value XΔp, and / or the mass flow value Xm, and / or the Reynolds number value XRe based on the oscillation signals (s1, s2) or based on the oscillation signals (s1, s2) and the electrical excitation signal (e1).

24. The measuring system as claimed in one of the claims 20 to 24, further comprising: First and second pressure sensors embedded in the wall of the line at a distance from each other in the flow direction to detect the pressure difference.

25. The measuring system as claimed in the preceding claim, wherein both the first pressure sensor and the second pressure sensor are electrically connected to the measuring system electronics (200) and wherein the measuring system electronics (200) are set up to determine the pressure difference value XΔp, that is to say, in particular also the viscosity value Xµ and / or the velocity value XU, using pressure measurement signals, in particular digital pressure measurement signals, generated using the aforementioned pressure sensors.