Flow coolers ensure that "real world" environments are very similar to "laboratory" environments for the proper performance of inferential flowmeters such as orifice, turbine, coriolis, ultrasonic etc.
Video Flow conditioning
Jenis aliran
Basically, the flow in pipes can be classified as follows -
- A fully developed stream (found in world class stream labs)
- A fully developed stream
- Non-swirling, non-symmetric flow
- Moderate stream is spinning, non-symmetric
- The flow is symmetrical and spins high
Maps Flow conditioning
The types of current conditioners
Flow conditioner shown in the picture. (A) can be grouped into the following three types -
- Those who just remove the vortex (bundle of tubes)
- Those who remove vortex and non-symmetry, but do not produce a fully developed false stream
- Those who remove vortex and non-symmetry and produce fully developed pseudo streams (high-performance current conditioners)
Aligning devices such as honeycomb and upstream propellers from the flow meter can reduce the length of the required straight pipe. However, they only result in marginal improvements in measurement accuracy and may still require significant straight pipe lengths, which may not be allowed to be installed in narrow installation locations.
Natural gas measurements
Natural gas that carries a lot of liquid with it is known as wet gas whereas natural gas produced without liquid is known as dry gas. Dry gas is also treated to remove all fluids. The effect of flow conditioners for the various popular meters used in the gas measurements is described below.
Pipeline conditions
The most important and most difficult to measure aspect of flow measurement is the flow conditions in the pipeline at the upstream meter. The flow conditions mainly refer to the flow velocity profile, the aberration in the profile, the degree of turbulence that varies in flow velocity or turbulence intensity profile, stir and other fluid flow characteristics which will cause the meter to register a different flow than expected. This will change the value of the original calibration state referred to as a reference condition that is free of installation effects.
Installation effects
Installation effects such as inadequate straight pipes, exceptional pipe roughness or smoothness, elbows, valves, tees and reductions cause flow conditions inside pipes to vary from reference conditions. How this effect of mounting impacts on the meter is critical because the device that creates the upstream effect is a common component of any standard measurement design. Flow Conditioning refers to an artificially created process of reference generation, a fully developed flow profile and is essential to enable accurate measurement while maintaining a standard cost meter design. The meter calibration factor is only valid for geometric and dynamic similarities between the measurement and calibration conditions. In fluid mechanics, this is often referred to as the Law of Equality.
Equal law
Legal Principles Equity is widely used for theoretical and experimental fluid engines. With respect to flowmeters calibration, the Law of Equality is the foundation for flow measurement standards. To satisfy the Law of Equality, the concept of a central facility requires geometric and dynamic similarities between the laboratory meter and the installed conditions of this same meter during the entire transfer period of the detainee. This approach assumes that the selected technology does not exhibit significant sensitivity to operating or mechanical variations between calibrations. The meter factor specified at calibration is valid if there is a dynamic and geometric similarity between the field installation and the artificial laboratory installation. The right producer experimental pattern places sensitive areas to be explored, measured and adjusted empirically. The manufacturer's recommended correlation method is the rational basis for performance prediction if physics does not change. For example, physics differs between subsonic and sonic streams. To fulfill the Equalization Law the in situ calibration concept requires geometric and dynamic equality between the calibrated meter and the installed conditions of this same meter during the entire transfer period of the detainee. This approach assumes that the selected technology does not exhibit significant sensitivity to operating or mechanical variations between calibrations. The meter factor specified at calibration is valid if both geometric and dynamic similarities are in "field meter installation" during the entire period of transfer of detention.
Speed ​​flow profile
The most common description of the flow conditions used in the pipeline is the flow velocity profile. Pictures. (1) shows a typical flow velocity profile for natural gas measurements. The shape of the flow velocity profile is given by the following equation, ---- (1)
The second explanation of the state of the flow field in the pipe is the intensity of turbulence. According to an experiment in 1994, measurement error may exist even when the speed flow profile is fully developed with perfect pipe flow conditions. Instead, it found zero measurement error at times when the speed profile was not fully developed. Therefore this behavior is called the turbulence intensity of the gas flow which can cause measurement bias error. This behavior account is partly for performance less than the conventional tube bundle.
Swirl
The third explanation of the condition of the swirling flow field. Swirl is a tangential flow component of the velocity vector. The speed profile should be referred to as the axial speed profile. Since the velocity velocity can be broken into three orthogonally interconnected components, the velocity profile represents only the axial velocity component. fig. (2) shows the Swirl Angle which explains the definition of swirl flow and vortex angle. Note that the vortex usually refers to the whole body rotation (in which the full pipe flow follows a vortex axle). In the actual pipe conditions, such as the downstream of the elbow, two or more rotation mechanisms may exist.
Effect on flow measurement devices
Stream conditions can affect the performance and accuracy of devices that measure flow.
The effect of flow conditioning on the Orifice meter
The second and best known option is the 19-tube tube-bundle flow conditioner. The majority of stream installations in North America contain tubular bundles. With the help of hot wire, pitot tube and laser-based computer measurement system that allows detailed measurement of speed profile and intensity of turbulence; we know that tube bundles do not provide a fully developed flow. Therefore, this device causes the orifice flow bias measurement. As a result of recent findings, some tube bundles are determined for flow measurement and reduced use of the device. Many available references provide performance results that show less than acceptable meter performance when using a conventional tube 19 test bundle. Individual results should be reviewed to ensure details such as beta ratio, meter tube length, Re condition and test.
Turbine gauges are available in various manufacturer configurations for common themes; turbine blades and configurable rotor devices. These devices are designed in such a way that when the gas stream passes through them, they rotate in proportion to the amount of gas passing through the blades repeatedly. Accuracy is then secured by calibration completion, showing the relationship between velocity and rotational volume, at various Reynolds Numbers. The fundamental difference between an orifice meter and a turbine meter is the derivation of the flow equation. Orifice meter flow calculations are based on fundamental fluid flows (Law 1 Thermodynamics derivation utilizes diameter pipe and vein contracta diameter for continuity equations). Deviations from theoretical expectations can be assumed under the Discharge Coefficient. Thus, a person can produce a meter of uncertainty known only with standard measurements in hand and access to a machine shop. The need for flow conditioning, and therefore, a fully developed velocity flow profile is driven from the initial determination of the fully developed developed Cd or 'reference profile' as described above.
In contrast, turbine gauge operation does not take root in thermodynamic foundations. This is not to say that the turbine meter is an inferior device. There are sound engineering principles that provide a theoretical background. This is basically a highly repeatable device that is then guaranteed to be accurate through calibration. Calibration provides accuracy. This is done in good flow conditions (free flow conditions of vortex and uniform flow velocity profile) is performed for every meter produced. Deviation from calibrated conditions will be considered as an installation effect, and the turbine's sensitivity to the effect of this installation is very interesting. The need for flow conditioning is driven from meter sensitivity to deviations from swirl calibration conditions and speed profiles. Generally, recent research shows that turbine meters are sensitive to vortex but not on the speed profile form. Uniform speed profiles are recommended, but there are no strict requirements for the fully developed flow profile shown. Also, no significant errors are seen when installing a single rotor turbine or a double-meter downstream of two out-of-plane elbows without a flow cooling device.
Effect of flow conditioner on ultrasonic meter
Due to the relative age of the technology, it may be useful to discuss the operation of multipath ultrasonic meters to illustrate the effects of distortion of flow profile and vortex. There are different types of flow measurements that utilize high frequency sound. The current resistance transfer measurement device utilizes the travel concept time. Flight time difference with flow compared to flight time against flow. This difference is used to infer the average flow velocity on the voice path. Picture. (5) indicates the sound path of the Ultrasonic Meter no flow illustrating this concept.
Persamaan aliran yang dihasilkan untuk kecepatan rata-rata yang dialami oleh jalur suara diberikan oleh,
---- (5)
Kasus tidak ada aliran memberikan jalur suara yang sebenarnya ketika ada aliran nol (dengan menyamakan persamaan. (5) ke nol). Dalam kasus profil aliran teoritis, katakanlah profil kecepatan aliran seragam di mana kondisi tanpa-slip pada dinding pipa tidak diterapkan, Gambar. (6) menunjukkan jalur suara Ultrasonic Meter - profil kecepatan seragam yang menggambarkan jalur suara yang dihasilkan.
A theoretical derivation of the average velocity equations for this sound path becomes much more complicated. In perfect perfect case perfect develop ultrasonic ultra meter profile shown in Fig. (7) shows possible sound tracks as a result of installation in a real stream.
Here the mathematical derivation for this ultrasonic meter also becomes very complicated. Developing a powerful flow algorithm to calculate the average flow velocity for the sound track can be very complicated. Now add this; reflection of the sound path from the pipe wall, multipaths to add degrees of freedom, vortex and departure from the fully developed axisymmetric flow profile and the problem of integrating the actual speed flow profile to produce the volume flow rate can be an achievement. Therefore the performance of real ultrasonic meter downstream disturbance, and the need for calibration is required.
Influence of flow conditioner on Coriolis meter
Coriolis meter is shown in the figure. (8) is very accurate in single-phase conditions but not accurate to measure the flow of two phases. This raises the problem of complex fluid structure interactions in the case of a two-phase operation. There is a dearth of theoretical models available to predict errors reported by Coriolis meters in the previously mentioned conditions.
The flow conditioner has no effect on meter accuracy when using wet gas due to the annular flow regime, which is not strongly influenced by the flow conditioner. In single-phase conditions, Coriolis meters provide accurate measurements even in the presence of severe flow interference. No precondition conditioning is required before the meter to get an accurate reading of it, which will be the case in other measurement technologies such as orifices and turbines. On the other hand, in a two-phase flow, the meter consistently gives a negative error. The use of flow conditioner clearly affects the meter reading in aerated fluid. This phenomenon can be used to obtain an approximate accurate flow rate in the liquid stream of low gas volume fraction.
Measurement of fluid flow
Flow conditioning makes a big effect on the accuracy of the turbine liquid meter which results in flow noise. This effect is mainly due to the debris on the filter screen, for various upstream plumbing geometries and different types of flow conditioners. The effectiveness of the flow conditioner can be demonstrated by the following two key measures:
- The percentage variation of the mean meter factor above the specified flow disturbance range for the specified flow rate and inlet piping geometry. The lower the percentage value variation of the mean meter factor above the range of flow noise, the better the performance of the flow conditioner.
- Repetition factor factor percentage for each flow disorder, at given flow rate and inlet plumbing geometry. The lower the repeatability value of the percentage meter factor in a given set of installation/operating conditions, the better the performance of the flow conditioner.
See also
- Flow measurements
- Orifice Gauge
- Turbine meter
- Ultrasonic flow meter
- Coriolis Metering
- Fluid dynamics
- Wet gas
- Dry gas
- Orifice Plates
- Bulk flow meter
- Bulk flow rate
- Volumetric flow rate
References
Source of the article : Wikipedia
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