Method for determining the gas fraction in a medium flowing through a Coriolis mass flowmeter

Abstract

The invention shows and describes a method (1) for determining the gas content in a medium (3) flowing through a Coriolis mass flowmeter (2), wherein the Coriolis mass flowmeter (2) has at least one measuring tube (4), at least one oscillation generator (5), at least two oscillation receivers (6) and at least one control and analysis unit (7), wherein the method is characterized in that 100 ‑In step (8), obtain the density of the medium without gas#imgabs1# 100 , in #imgabs2# 测量 ‑Measure the density value of the medium (3) flowing through the measuring tube (4) in step (9)#imgabs3# 测量 , in GVQ-step (10), use the density value #imgabs4# 100 and density value#imgabs5# 测量 A measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4) is calculated and the measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4) is output.

Description

Technical Field

[0001] The invention relates to a method for determining the gas content in a medium flowing through a Coriolis mass flowmeter, wherein the Coriolis mass flowmeter has at least one measuring tube, at least one oscillation generator, at least two oscillation absorbers and at least one control and analysis unit. The invention also relates to a Coriolis mass flowmeter related thereto, which carries out the method during operation. Background Art

[0002] Coriolis mass flowmeters and methods for operating Coriolis mass flowmeters have been known for decades in various designs. With Coriolis mass flowmeters, high measurement accuracies can be achieved, which are sometimes better than 0.1% of the measured value, so that Coriolis mass flowmeters can also be used in calibration-obligated transactions, for example.

[0003] Coriolis mass flowmeters belong to the category of oscillating measuring instruments. Their mode of operation is based on the fact that at least one measuring tube through which the medium flows is excited to oscillate by an oscillation generator. This oscillation generator is often an electrical drive, which is usually present as an electromagnetic drive. In such an electromagnetic drive, a current flows through a coil as an electrical excitation signal, wherein a force is directly applied to the measuring tube by the coil current in combination with the coil power. The mode of operation of the Coriolis mass flowmeter is based on the fact that the massive medium reacts to the wall of the measuring tube due to the Coriolis inertial force caused by two orthogonal movements, namely the movement of the flow and the movement of the measuring tube. This reaction of the medium to the measuring tube causes a change in the measuring tube velocity compared to the oscillating state of the measuring tube without the flow flowing through it. By detecting this characteristic of the oscillation of the Coriolis measuring tube through which the flow flows (the phase shift between the measuring tube oscillations on the inflow side and the outflow side), the mass flow through the measuring tube can be determined with high accuracy.

[0004] Of particular importance is the natural frequency of the oscillating part of the Coriolis mass flowmeter, i.e., essentially the natural frequency of the measuring tube through which the flow passes as an oscillating element, since the operating point of the Coriolis mass flowmeter is usually at the natural frequency of the measuring tube, so that the oscillations required for inducing the Coriolis force can be memorized with minimal energy consumption. The oscillations implemented by the measuring tube have a specific form, which is called the natural vibration mode of the corresponding excitation. Another reason for the special significance of the natural frequency in the Coriolis mass flowmeter is the direct physical connection between the natural frequency of the measuring tube through which the flow passes in the corresponding natural vibration mode and the effectively deflected oscillating mass (mass of the measuring tube and the mass of the medium in the measuring tube). Through this correlation, the density of the medium in the measuring tube can be determined, which is important for the present invention, even if it is not the primary measurement variable of the flowmeter.

[0005] If the mass of the oscillating element changes, i.e. the mass of the measuring tube through which the medium flows, the resonant frequency of the oscillation mode that is excited or under investigation also changes; if the measuring tube is excited to oscillate at a constant frequency, the excited oscillations are damped due to the shifting resonance point. Various methods for operating a Coriolis mass flowmeter are therefore used to identify the variable resonance frequency and also to track the frequency of the excitation to the resonance point at the variable resonance frequency; for this purpose, reference is made, for example, to DE 10 2016 190 952 A1 or DE 10 2013 020 603 A1.

[0006] A particular challenge in operating a Coriolis mass flowmeter is the occurrence of multiphase flows that have a gaseous component. This is also usually referred to as a two-phase flow, where this term is based on the understanding that the flow has a gaseous phase and a non-gaseous phase, which can itself have liquid and solid components. In this general sense, the term "two-phase flow" should also be used here.

[0007] The occurrence of two-phase flows (i.e. the transition from a single-phase flow with a liquid component or a liquid-solid component to a flow with a gas phase) is therefore problematic, since entrained gases can strongly affect the measurement accuracy and also make safe operation of the Coriolis mass flowmeter difficult or even impossible. The same problem also occurs when the gas content in the flowing medium changes. In this case, for example, in applications in the food industry, entrained gases in the medium can be completely desired, where the processed medium can have, for example, a foamy consistency.

[0008] Regardless of whether the medium contains entrained gas intentionally or unintentionally, the measurement accuracy is subject to the fact that the entire mass of the flowing medium is no longer deflected completely by the vibrating measuring tube, but only partially deflected. This may be caused, for example, by the fact that the less dense components in the medium flow around the more dense components, which also applies to the motion components orthogonal to the flow direction, which are necessary for the Coriolis measurement. Compression or decompression of gaseous components in the medium, for example due to the inertia of heavier liquid or solid medium components, may also be important. Depending on the form of the entrained gas and the shape of the flow regime (stratified, wavy, bubble-shaped, droplet-shaped), entrained gas may also lead to interruptions in the measurement operation, since continuous measurement is no longer guaranteed.

[0009] In the past, most efforts have been directed to identifying two-phase flows and reacting to the identified two-phase flows by suitable control measures so that the measuring operation can still be continued. DE 10 2005 012505 A1, DE 10 2006 031 198 A1 and DE 10 2008 039 012 A1 are mentioned as examples. These measures differ in the component of the so-called "traffic gas management" of the applicant.

[0010] For pure detection of two-phase flow, DE 10 2006 017 676 A1 is mentioned by way of example, in which various state variables and their changes are partly statistically evaluated in order to obtain a two-phase signal which indicates the presence or absence of a two-phase flow with greater accuracy but does not reliably quantify it. Summary of the invention

[0011] Against the background described, there is a need to include during a measuring operation not only a conclusion as to whether a two-phase flow is possible, but rather also to obtain quantitative information about the gas proportion in a medium flowing through a measuring tube of a Coriolis mass flowmeter.

[0012] The previously introduced tasks are solved by different method steps, which are usually implemented in the control and analysis unit of the Coriolis mass flow meter. The control and analysis unit is functionally connected to the elements of the Coriolis mass flow meter, so that the oscillation generator can be controlled and the signal provided by the oscillation receiver can be received. Here, the control and analysis unit typically refers to a digital signal processor. Of course, there are also switching circuits for signal processing, such as analog / digital converters, digital / analog converters and possibly electronic power components, but this is not important in detail within the framework of the present invention.

[0013] It is important to first find the density of the medium without gas 100 ( 100 - step). If the medium does not contain a gaseous component, knowledge of the density of the medium flowing through the measuring tube is essential for calculating the gas content in the medium, provided that the medium contains a gas content. Density values ​​for gas-free media 100 In this case, density values ​​which are already theoretically ascertainable and can ultimately be based on measurements can be predetermined and stored in the control and evaluation unit.

[0014] In a further step, the density value of the medium flowing through the measuring tube is measured, for example, in the following manner: 测量 ( 测量 - step), namely determining the resonant frequency of the system consisting of the measuring tube and the medium flowing through it.

[0015] In a further method step, the density value of the gas-free medium is used 100 And the density value of the medium currently flowing through the measuring tube 测量 The measurement GVQ of the gas fraction of the medium flowing through the measuring tube (GVQ step) is calculated, and thus a meaningful variable about the gas fraction in the medium is also present. This variable represents a quantitative conclusion about the gas fraction in the medium and is much more than a pure indicator variable about the presence or absence of gas in the medium flowing through the measuring tube.

[0016] Finally, a measure GVQ of the gas fraction of the medium flowing through the measuring tube is output, so that the GVQ value can be used for other calculations, also within the measuring device, or output externally, for example via a display output or via a communication link (fieldbus) and can thus be used for process monitoring; this is an exemplary, but not exhaustive, enumeration.

[0017] According to a further development of the method according to the invention, provision is made for determining in the indicating step an indicating variable I which indicates the presence of entrained gas in the medium flowing through the measuring tube. 二相 This indicator variable only indicates whether a two-phase flow is present or not. In the operation of the Coriolis mass flow meter, the indicator variable I is preferably determined continuously. 二相 Coriolis mass flowmeters therefore always have knowledge of the state of the medium flowing through the measuring tube with respect to the presence of a gaseous phase.

[0018] The aforementioned measures now enable a further development of the method to be achieved when the indicator variable I 二相 The density of the medium flowing through the measuring tube is measured to indicate that there is no entrained gas in the medium flowing through the measuring tube. 100 -step. This improved method thus makes use of the fact that the density of the gas-free medium is determined most recently when there is a gas-free medium flow. This also makes it possible to respond to a changing density of the gas-free medium. Preferably, provision is made for the last determined density value of the gas-free medium to be used in the GVQ step. 100 , so that the latest density value of the gas-free medium is always used for the calculation of the gas fraction.

[0019] In another embodiment of the method, the indicator variable I 二相 trigger 测量 - step, and that is, just at the indicated parameter I 二相 This indicates that the medium flowing through the measuring tube has entrained gas. In this case, it is clear that the density determination does not result in a new density value for the gas-free medium. 100 , but more precisely the density value of the medium containing the gas 测量 On the basis of this density value, a new value for the measure GVQ of the gas fraction of the medium flowing through the measuring tube can then be calculated.

[0020] In one embodiment of the method, a gas volume ratio GVR (gas volume ratio or void ratio) is calculated as a measure of the gas portion GVQ of the medium flowing through the measuring tube, which corresponds to the quotient of the gas volume and the volume of the non-gaseous medium portion and is therefore calculated from 100 and 测量 The difference between 测量 The quotient of 100- 测量 ) / 测量 In a further embodiment of the method, a gas volume fraction GVF (gas volume fraction or void fraction) is calculated as a measure of the gas fraction GVQ of the medium flowing through the measuring tube, for which the gas volume fraction is referred to the total volume under consideration and is therefore determined by the density 100 and density 测量 Difference and density 100 The quotient of 100- 测量 ) / 100 ) calculated.

[0021] A preferred embodiment of the method provides that in the GVQ step, a measure GVQ of the gas fraction of the medium flowing through the measuring tube is calculated under the assumption that the density of the gas fraction is negligible, in particular zero. The above-mentioned calculations for the gas volume ratio and the gas volume fraction are based on this assumption.

[0022] In a further development of the method, provision is made for measuring the medium pressure p of the medium flowing through the measuring tube. m , and the measured medium pressure p of the medium flowing through the measuring tube m and the measured density value 测量 Get the corrected density value 测量 (p m ), where the corrected density value 测量 (p m ) as the measured density value 测量 It is the basis of other methods. Here we can experimentally find the relationship 测量 (p m ), but the relationship can also be derived based on theoretical considerations. The relationship can be stored in the form of a numerical table, or alternatively expressed by a mathematical relationship. In detail, the relationship 测量 (p m ) is not important; what is important is whether the relationship is taken into account in the design.

[0023] In another embodiment of the method, a response can be made to a limit value of the gas portion of the medium flowing through the measuring tube. This is achieved in one embodiment by comparing the calculated measure GVQ of the gas portion of the medium flowing through the measuring tube with the limit value GVQ of the gas portion of the medium flowing through the measuring tube. 极限 By comparison, and after determining the calculated measure GVQ with the limit value GVQ 极限The status notification is output in the event of a deviation. This deviation may be zero or non-zero. The status notification may consist simply in setting a byte in a register of the control and analysis unit or writing a memory cell with a corresponding value. The status notification may be output in the form of a bus message via a bus interface. The status notification may also be displayed via a display of the Coriolis mass flow meter. Many other possibilities for the output of the status signal can be considered here. In one embodiment of the aforementioned method, hysteresis is achieved, that is, the calculated measurement GVQ is hysteresized relative to the limit value GVQ. 极限 The determined deviation is selected to be not equal to zero, for example, GVQ 公差 When the limit value GVQ is exceeded 极限 Add tolerance value GVQ 公差 If the total value is less than the limit value GVQ, the status notification is output. 极限 and tolerance value GVQ 公差 If the difference is found, the status notification is deleted.

[0024] The object introduced at the outset is achieved in the Coriolis mass flowmeter described here in that the method steps described above are carried out during operation of the Coriolis mass flowmeter. Most of the steps are carried out by a control and analysis unit. This means in particular that the control and analysis unit is designed such that it performs the following steps during operation of the Coriolis mass flowmeter: 100 - Step 1: Obtain the density of the medium without gas 100 ,exist 测量 -Measure the density of the medium flowing through the measuring tube in the step 测量 , in the GVQ-step, with the density value 100 and density value 测量 A measure GVQ of the gas fraction of the medium flowing through the measuring tube is calculated and output. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Specifically, there are now several possibilities for designing and improving the method shown for determining the gas fraction in a medium flowing through a Coriolis mass flow meter and the corresponding Coriolis mass flow meter. This is explained below with the aid of the accompanying drawings. The drawings show:

[0026] Figure 1A Coriolis mass flowmeter is schematically shown in which a method for determining the gas fraction in a medium flowing through its measuring tube is implemented;

[0027] Figure 2a A method for determining the gas fraction in a medium flowing through a measuring tube of a Coriolis mass flowmeter is schematically shown;

[0028] Figure 2b A further embodiment of a method for determining the gas fraction in a medium flowing through a Coriolis mass flowmeter is schematically shown;

[0029] Figure 3 A method for determining the gas fraction using an indicator variable of a two-phase flow is schematically shown;

[0030] Figure 4 A further variant of a method for determining the gas portion using an indicator variable for a two-phase flow is shown;

[0031] Figure 5 Another embodiment of the above method using medium pressure is shown; and

[0032] Figure 6 A configuration of the method is shown using a limit value for the measure GVQ of the gas fraction of the medium flowing through the measuring tube. DETAILED DESCRIPTION

[0033] exist Figures 1 to 6 1 shows a method 1 for determining the gas content in a medium 3 flowing through a Coriolis mass flowmeter 2 in various aspects. The Coriolis mass flowmeter 2 is Figure 1 In the embodiment shown in FIG. , there are two curved measuring tubes 4 , an oscillation generator 5 , two oscillation receivers 6 and a control and analysis unit 7 . Figure 1 Only the measuring tube 4 can be seen in this view, the second measuring tube being covered by the first measuring tube 4. In principle, it is not important in the invention whether the Coriolis mass flowmeter has straight or curved measuring tubes, and the number of measuring tubes is also insignificant in terms of the practice of the method 1 concerned here.

[0034] During operation, the measuring tube 4 is excited to resonance in a fundamental oscillation mode by means of an oscillation generator 5. When there is a flow of the medium 3 through the measuring tube 4, opposing Coriolis forces act on the measuring tube 4 on the inlet side and the outlet side, thereby generating overlapping higher oscillation modes. The phase difference between the overlapping oscillations on the inlet side and the outlet side of the measuring tube 4 is a measure of the mass flow through the measuring tube 4.

[0035] As explained at the outset, the presence of a two-phase flow, i.e. a flow with a gas portion and a liquid and / or solid fluid portion, is problematic because damping and noise effects impede the measurement. In addition, the variable gas portion also causes changes in the density of the medium 3 and thus also changes in the resonant frequency of the oscillating element consisting of the measuring tube 4 and the medium 3 flowing in the measuring tube 4. By means of various control measures, the operating point of the Coriolis mass flowmeter 2 can be tracked in such a way that the excitation frequency of the oscillation generator 5 tracks the variable resonant frequency.

[0036] The control and analysis unit 7 is Figure 1 The exemplary embodiment of comprises a digital signal processor and corresponding I / O interfaces for controlling the oscillation exciter 5 and for reading out the oscillation signal of the oscillation receiver 6. The aforementioned control measures are implemented in terms of programming on the digital signal processor.

[0037] It is known in the prior art that the occurrence of a two-phase flow is detected by analyzing state variables of a Coriolis mass flowmeter 2 and represented by a corresponding indicator variable signal, wherein this indicator variable does not contain reliable quantitative conclusions about the gas fraction in the medium 3, but rather makes a binary conclusion about whether the medium 3 has a gas fraction or does not have a gas fraction.

[0038] exist Figure 2a , 2b 1 shows a method 1 by which the gas content in a medium 3 flowing through a Coriolis mass flow meter 2 can be determined. For this purpose, it is provided that 100-In step 8, first calculate the density of the medium without gas 100 .exist 测量 - In step 9, the density value of the medium 3 flowing through the measuring tube 4 is measured 测量 The measurement is done here by determining the resonant frequency of the system. In addition, in GVQ step 10, the density value 100 and density value 测量 The measure GVQ of the gas fraction of the medium 3 flowing through the measuring tube 4 is calculated. Finally, the measure GVQ of the gas fraction of the medium 3 flowing through the measuring tube 4 is output. Figure 2a and 2b The differences should be clarified and the implementation 100 - Step 8 and 测量 - The order of step 9 is not important. Two values, namely the density value 100 and density value 测量 This is necessary to determine the measure GVQ of the gas fraction in the medium 3 .

[0039] In press Figure 2a In the embodiment, the density value of the medium without gas is 100 Simply pre-given as a fixed value, the density value 100 It is therefore known in this case that the density value of the gas-free medium can be practically excluded. 100 However, in other cases, it is also possible to determine the density of a medium without gas by measuring, for example 100 , when the density of the medium without gas is desired 100 This makes sense when changes also occur on the fly.

[0040] exist Figure 3 and 4 4 shows that the use of the indicator variable I indicates the presence of entrained gas in the medium 3 flowing through the measuring tube 4 二相 The common feature of the embodiments is that firstly in the indication step 11 an indication variable I indicating the presence of entrained gas in the medium 3 flowing through the measuring tube 4 is determined. 二相 In the exemplary embodiment shown, this indicator variable I is determined continuously during operation of the Coriolis mass flowmeter 2. 二相 . Indicator parameter I 二相 Now the answer is given as to whether a gas phase is present or not in the medium 3. The indicator variable is therefore only a binary signal here. In any case, the indicator variable I is determined in the indicator step 11 to indicate the presence of entrained gas in the medium 3 flowing through the measuring tube 4. 二相 . Figure 3 In the embodiment of the present invention, the method 1 is designed so that only when the indicating parameter I 二相 When it is indicated that the medium 3 flowing through the measuring tube 4 is free of entrained gas, the density of the medium 3 flowing through the measuring tube 4 is measured. To implement 100 -Step 8. Therefore, only when the indicator parameter I 二相 When this is shown, it triggers 100 - Step 8, otherwise calculate the density value when there is entrained gas 测量 of 测量 - Step 9. In the GVQ step 10, the last determined value of the gas-free medium 3 is then always used 100 .

[0041] In press Figure 4 In the embodiment of the present invention, in general steps 8 and 9, the density value of the medium 3 is obtained. The embodiment shows that when the indicating parameter I 二相 It shows that when medium 3 has no gas content, this density value Refers to the density value of medium 3 without gas 100 The medium 3 has a gas content and this is therefore indicated by the indicator variable I 二相 In the case of display, the density value Corresponds to the density value of the medium 3 flowing through the measuring tube 4 测量 In the combined steps 8, 9, the density of the medium 3 is therefore usually always measured. , and according to the indicated parameter I 二相 As density value 100 or as density value 测量 be stored.

[0042] exist Figure 5 The development of the method 1 for determining the gas content in a medium 3 flowing through a Coriolis mass flowmeter 2 is characterized in that a medium pressure p of the medium flowing through the measuring tube 4 is measured 12 m , and the measured medium pressure p of the medium 3 flowing through the measuring tube 4 m and the measured density value 测量 Get the corrected density value 测量 (p m ), where the corrected density value 测量 (p m ) as the measured density value 测量 It is the basis for the further method, namely in particular in the GVQ step 10 for determining the gas proportion.

[0043] Finally, in Figure 6 4 shows the calculated measurement GVQ of the gas fraction of the medium 3 flowing through the measuring tube 4 compared to the limit value GVQ of the gas fraction of the medium 3 flowing through the measuring tube 4. 极限 and compare the calculated measure GVQ with the limit value GVQ 极限Output status notification in case of deviation.

[0044] exist Figure 1 , the control and analysis unit 7 is schematically shown to be connected to the display unit 13. The measurement GVQ of the gas content in the medium 3 can be directly displayed on the display unit 13. However, the measurement GVQ of the gas content can also be output to a higher-level control room (Leitwarte) via the fieldbus interface 14, for example. In another embodiment, the measurement GVQ is simply output to the control and analysis unit 7 and stored there. Then, the value of the GVQ measurement can also be used further internally, for example for control technology or diagnostic purposes.

[0045] Reference numerals list

[0046] 1 Methods

[0047] 2 Coriolis mass flow meter

[0048] 3 Medium

[0049] 4 Measuring tube

[0050] 5 Oscillation generator

[0051] 6 Oscillator Receiver

[0052] 7 Control and analysis unit

[0053] 8 100 -step

[0054] 9 测量 -step

[0055] 10 GVQ-Steps

[0056] 11 Instructions

[0057] 12 Measuring medium pressure p m

[0058] 13 Display unit

[0059] 14 Fieldbus interface

[0060] 15 Obtain the corrected density value 测量 (p m ).

Claims

1. A method (1) for determining the gas content in a medium (3) flowing through a Coriolis mass flowmeter (2), wherein: The Coriolis mass flow meter (2) comprises at least one measuring tube (4), at least one oscillation generator (5), at least two oscillation receivers (6) and at least one control and analysis unit (7). Among them, in ρ 100 - In step (8), the density value ρ of the medium without gas is obtained 100 , Among them, in ρ 测量 - In step (9), the density value ρ of the medium (3) flowing through the measuring tube (4) is measured 测量 , In the GVQ step (10), the density value ρ is used 100 and density value ρ 测量 Calculating a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4), Therein, a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4) is output, In the indicating step (11), an indicating variable I is determined which indicates the presence of entrained gas in the medium (3) flowing through the measuring tube (4). 二相 ,and Wherein, when the indicating parameter I 二相 When it is indicated that the medium (3) flowing through the measuring tube (4) is free of entrained gas, the ρ is implemented by measuring the density of the medium (3) flowing through the measuring tube (4). 100 -Step (8).

2. The method (1) according to claim 1, characterized in that: During operation of the Coriolis mass flowmeter (2), the indicator variable I is continuously determined. 二相 .

3. The method (1) according to claim 1, characterized in that: The last density value ρ of the medium without gas is used in the GVQ step 100 .

4. The method (1) according to claim 1, characterized in that: When the indicated parameter I 二相 When it is indicated that the medium (3) flowing through the measuring tube (4) has entrained gas, the ρ 测量 -Step (9).

5. The method (1) according to any one of claims 1 to 4, characterized in that A gas volume ratio GVR or a gas volume fraction GVF is calculated as a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4).

6. The method (1) according to any one of claims 1 to 4, characterized in that In the GVQ step (10), a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4) is calculated, assuming that the density of the gas fraction is negligible, in particular zero.

7. The method (1) according to any one of claims 1 to 4, characterized in that Measuring (12) the medium pressure p of the medium (3) flowing through the measuring tube (4) m , and the measured medium pressure p of the medium (3) flowing through the measuring tube (4) m and the measured density value ρ 测量 Obtain the corrected density value ρ of (15) 测量 (p m ), where the corrected density value ρ 测量 (p m ) as the measured density value ρ 测量 It is the basis of other methods.

8. The method (1) according to any one of claims 1 to 4, characterized in that The calculated measurement GVQ of the gas portion of the medium (3) flowing through the measuring tube (4) is compared with a limit value GVQ of the gas portion of the medium (3) flowing through the measuring tube (4). 极限 and compare the calculated measure GVQ with the limit value GVQ 极限 Output status notification in case of deviation.

9. A Coriolis mass flow meter (2) comprising at least one measuring tube (4) through which a medium (3) can flow, at least one oscillation generator (5), at least two oscillation receivers (6) and at least one control and analysis unit (7), characterized in that: The control and analysis unit (7) is designed in such a way that, during operation of the Coriolis mass flowmeter (2), it 100 - In step (8), the density value ρ of the medium without gas is obtained 100 , In ρ 测量 - In step (9), the density value ρ of the medium (3) flowing through the measuring tube (4) is measured 测量 , In the GVQ step (10), the density value ρ is used 100 and density value p 测量 calculating a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4), and outputting a measure GVQ of the gas fraction of the medium (3) flowing through the measuring tube (4), In an indication step (11), an indication variable I is determined which indicates the presence of entrained gas in the medium (3) flowing through the measuring tube (4). 二相 ,and When the indicator parameter I 二相 When it is indicated that the medium (3) flowing through the measuring tube (4) is free of entrained gas, the ρ is implemented by measuring the density of the medium (3) flowing through the measuring tube (4). 100 -Step (8).

10. The Coriolis mass flow meter (2) according to claim 9, characterized in that: The control and analysis unit (7) is designed in such a way that at least one of the method steps according to the characterizing portion of at least one of claims 2 to 8 is carried out.

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