Orifice Meter Research Articles

Determination of Kinetic Correction Coefficient of Fluid Flow Using a Generic Multiple Orifice Physical Scale Model Structure

Problem statement: Diesel particulate filters are fast becoming integral parts of diesel engines, light and heavy duty, due to their potential in the reduction of particulate matter from exhaust gases and their noise muffling property. Consequently, several researchers are developing mathematical models for the study of fluid flow through the filter substrate and in the aiding of filter systems design. Recently, some researchers developed a mathematical model known as the Multiple Orifice Mathematical (MOM) model for determining pressure gradients of gelcast ceramic foams. The MOM model was calibrated using fluid flow data from cellular foam filter structure similar to ceramic foams. However, there was need to improve on the method of calibrating the model. Approach: Following the conceptual model employed in the development of the MOM model, a physical scale model was designed using a CAD package and manufactured for the purpose of measuring pressure drops across the connecting windows of the cells. A new fluid flow rig was also designed from a CAD package and fabricated to adapt to the physical scale model. Applying the conservation theory, the flow rates across the windows were calculated and equated to the flow rate determined from an orifice meter, where the correction coefficients for the calibration of the MOM model were calculated. Results: A number of correction coefficients were calculated from the data collected from the experimental rig. The average correction coefficient which was used for the calibration of the MOM model was found to be 2.24. Conclusion/Recommendations: The result obtained from the new method of model calibration corroborated the value determined by earlier researchers. This new method reduced the computational time of calibrating the MOM model and eliminates the use of graphs and graph fitting. The new fluid flow rig and the physical scale model can be used in the study of fluid flow in other types of filter substrates.

Flow accelerated corrosion and its control measures for the secondary circuit pipelines in Indian nuclear power plants

A plain carbon steel feeder pipeline in the secondary circuit failed downstream of a flow measurement device (orifice meter) during operation at nuclear power plant. A detailed failure analysis done on the failed pipeline is described in this paper. The results established the fine surface pattern of ‘Horseshoe pits’ at the affected regions. X-ray diffraction analysis on the samples far from the failed regions showed presence of magnetite but on the sample from the failed region showed peaks due to base metal only, indicating dissolution of the oxide. Thickness profiling of the pipeline indicated reduction of thickness from the design 7.62 mm to a minimum of 0.4–1.4 mm at the location of the failure. These observations are characteristic of single phase flow accelerated corrosion. This paper details the extent of flow accelerated corrosion in various Indian power plants and the remedial measures for replacement and possible design and water chemistry changes to combat it.

Comparison of Primary Flow Measurement Techniques Used During Combined Cycle Tests

One of the most significant contributors to the overall uncertainty of a performance test of a combined cycle steam turbine is the uncertainty of the primary flow measurement. ASME performance test codes provide many alternative methods for determining flow. In two actual combined cycle tests performed in 2005, the following three alternate methods were used to determine the high-pressure (HP) steam flow into the combined cycle steam turbines: (1) Derivation from measured HP feedwater flow using calibrated PTC 6 throat tap nozzles, (2) derivation from low-pressure (LP) condensate using calibrated PTC 6 throat tap nozzles, and (3) derivation from LP condensate using calibrated orifice metering sections. This paper describes the design, calibration, and installation of each flow meter involved, the methods used to calculate the HP steam flow, the estimated uncertainty of the HP steam flow derived using each method, and the actual test results using each method. A comparison of the methods showed that there are distinct advantages with one of the methods and that very low uncertainties in HP steam flow can be achieved if sufficient attention is applied to the design, calibration, and installation of all flow meters involved. Note that the information in this paper was originally published in ASME Paper PWR2006-88074 and presented at the 2006 ASME Power Conference in Atlanta, GA. For detailed diagrams, figures, and tabulations of data and analysis, please refer to the published proceedings from that conference.

An experimental investigation and design of flow-conditioning devices for orifice metering

The problems associated with the use of flow conditioners usually relate to their ability to remove swirl and produce a fully developed mean velocity and turbulence profiles. In the present research, the mechanism for both swirl reduction and profile correction was suspected to be related to the action occurring within the turbulent mixing zone, which occurs within the first few diameters downstream of the flow straightener. A flow-conditioner device, which consists of a graded perforated plate with upstream vanes and short downstream tabs mounted on the plate has been designed, and demonstrated a good performance in terms of removing swirl and producing a fully developed flow within a short distance downstream of the flow conditioner. Furthermore, the flow conditioner produces good quality results in conjunction with an orifice plate meter. The vaned plate created a self-stabilizing mechanism for the time velocity profile and turbulence structure with respect to the axial position. Furthermore, the deviation on the discharge coefficient was low at around >0.2 per cent. Also the Zanker conditioner performs at its best when using the same design concept as the vaned plate (honeycomb followed by a perforated plate).

Analysis of the effect of body shape on annubar factor using CFD

Flow analysis around an annubar in a circular pipe has been carried out using computational fluid dynamics (CFD) code, ‘ FLUENT ’ to establish the effect of body shape on the annubar factor. It is found out that the annubar factor for elliptical shape with high slenderness ratio has the highest annubar factor and minimum permanent pressure loss. Rounding of the edges of a standard diamond shaped annubar improves its performance. The permanent pressure loss is comparatively lower than that for the orifice meter and the annubar factor is constant above a critical Reynolds number. The annubar factor reduces with increase in blockage factor.

Estimating Diaphragm Flow Coefficients for Nonstationary Gas Flow

A diaphragm is the most common flowmetering device on major pipelines, on which one often encounters flow-rate pulsations, which destabilize measurements. An experimental check on numerical calculations shows that the metrological characteristics of an orifice meter in unsteady flow can be determined by numerical simulation from full-scale experiments.

Design and development of variable area orifice meter

The variable area orifice meter indicates the flow rate as a linear displacement of a symmetrical body placed concentrically downstream of an orifice inside a constant area duct. Three shapes of symmetrical body namely, a frustum of cone, frustum of cone with hemispherical base, and frustum of cone with hemispherical base and parabolic apex are used downstream of an orifice to develop a variable area orifice meter. Experiments have been performed at different positions of the symmetrical bodies to evaluate the performance of the variable area orifice meter. The frustum of cone having hemispherical base and parabolic apex gives nearly linear variation of the flow rate with its position for a constant pressure differential.

A study of a pressure differential flow meter that is insensitive to inlet conditions

Orifice meters are a type of differential pressure flow meter widely used in industry and their behaviour is very well understood. The standard discharge coefficient can only be used if the flow approaching the meter is perfectly settled and fully developed. Thus the installation of these meters is subject to many constraints. Normally the required flow regime is established by the use of a combination of a flow conditioner and a settling length. This paper describes the initial work carried out to show the concept of an orifice meter whose performance is independent of the inlet conditions by the introduction of a standard swirl before the meter. These results show that a swirler renders the measurements independent of the influence of upstream disturbance. This is for both a partial blockage in the pipe and also upstream swirl, and is likely to be universal. A proposal for a new calibration equation is also made for the particular swirler employed. However, more data need to be acquired over a wide range of geometries, flow and operating conditions.

Qualification of a flow conditioning device according to the new API 14.3 procedure

The new AGA 3/API 14.3 standard on concentric square edged orifice meters suggests that if installation effects can be shown to be less than about 0.23%, then there is no need to apply any additional uncertainty to that of the basic discharge coefficient. This has revived interest in flow conditioners that can assure this performance, without the need for long straight up-stream lengths of pipe. A feature of the new standard is that it specifies performance acceptance tests for evaluating other flow conditioners, which were not included in the previous versions of the document. In this paper we will review this procedure, and show results for a device that has been qualified in this manner.

A Comparative Study of Two Flow Conditioners and Their Efficacy to Reduce Asymmetric Swirling Flow Effects on Orifice Meter Performance

The sensitivity of differential-pressure flow meters to the quality of the approaching flow continues to be a cause for concern to flowmeter manufacturers and users. Distortions to the approaching velocity profile generated by pipe fittings and installations located upstream of a flowmeter, can lead to considerable errors in flowmetering. This cannot be ignored because of the likely cost and process efficiency implications. This paper describes the effects of various entrance flow velocity profiles on the performance of an orifice flowmeter with and without flow conditioning. Asymmetric swirling velocity profiles were generated by a ball valve. These caused significant shifts to the meter's calibration. The use of a vaned-plate flow conditioner, consisting of six vanes attached to a 70% porosity plate, greatly improved the performance of the meter. Thus, the device can be used as part of a flowmetering package that will have considerably reduced installation lengths. The less sophisticated NEL plate proved to be a good flow straightener, i.e. a good swirl remover, but was not an efficient flow conditioner.

Performance of a tuyère gas distributor

The flow discharge coefficient of tuyere gas distributors with six radial holes was obtained as a function of the tuyere head holes diameter Reynolds number, with the holes to riser flow cross-sectional area ratio as parameter. The fraction of the pressure drop which occurred in the tuyere head holes, a significant parameter for satisfactory operation of a fluidized bed, was also determined. The flow phenomena in the thin-plate standard square-edged orifice meter and in the tuyere discharge holes were studied; the differences in the corresponding discharge coefficient values are discussed in the light of the flow pattern dissimilarities. The possibility of adopting the standard thin-plate square-edged orifice meter or perforated-plate discharge coefficients to calculate the tuyere coefficient was analyzed, as well as the influence of the presence or absence of a solids fluidized bed over the distributor plate.

Effects of cavitation and plate thickness on small diameter ratio orifice meters

High differential pressure drop is frequently required in the process line of electric power plants. However, cavitation produced by a high pressure drop could damage the pipe and pump blades. In these experiments, the effects of cavitation and plate thickness for small-bore diameter (d) to pipe diameter (D) ratio (β = d/D) orifice plates were evaluated in a 100 mm diameter test section of a water flow calibration facility. Three size orifice meters were tested with β = 0.10, 0.15, and 0.33 and no bevel on the throat. The cavitation number at inception was measured to be 1.0 to 1.2 for all experiments. Although cavitation occurred in all experiments, the discharge coefficient was affected by cavitation only for the smallest bore (β = 0.10) and thickest plate tested, 7.0 mm or t/d = 0.70 where t is the plate thickness. Thickness seemed to influence the discharge coefficient only for the β = 0.10 plate. But the trends in the results for thickness were not conclusive and could be attributed to edge sharpness.

FLOW OF SURFACTANT-STABILIZED OIL-IN-WATER EMULSIONS THROUGH WEDGE METERS AND SEGMENTAL ORIFICE METERS

The flow of surfactant-stabilized oil-in-water emulsions through wedge meters and segmental orifice meters was investigated experimentally. A flow loop consisting of wedge meters and segmental orifice meters of different shapes and sizes was designed and developed. The discharge coefficients were determined for various differently concentrated stable oil-in-water emulsions. The dispersed phase (oilrpar; concentration of emulsions was varied from 0 to 76,14° by volume. At low to moderate values of the dispersed phase concentration, the emulsions were Newtonian in nature. At high oil concentrations of 65.16° and 76.14° by volume, the emulsions were non-Newtonian pseudoplastic in nature. The single phase calibration curves of discharge coefficient versus Reynolds number are found to be applicable to surfactant stabilized oil-in-water emulsions, both Newtonian and non-Newtonian. However, in the latter case. one needs to use the power-law Reynolds number instead of the conventional one. Based on the experimental data obtained in this study, empirical expressions for the wedge and orifice discharge coefficients are given. These expressions can be used to predict the discharge coefficients for the emulsions provided that the emulsions are similar in nature to those investigated in the present work.

Numerical aspects of flow computation through orifices

The use of computational fluid dynamics (CFD) tools for modelling and analysing process systems has increased in recent years. A campaign has begun to investigate whether it is possible to simulate metering stations that include flow conditioners (FCs) and orifice meters. However, more information and validation are required in several areas before the technique can be fully exploited. This study was initiated prior to the start of full pipe simulation to investigate various grid effects, coordinate arrangements, wall boundary conditions, differencing schemes and turbulence models that can predict more accurate flow values through an orifice. The calculations were carried out in two-dimensional axisymmetric flow. The findings can be used in modelling both FCs and orifice plates.

Practical technologies for irrigation flow control and measurement

Practical technologies can encourage farmers to adopt practices that support sustainable irrigated agriculture. Important among these are convenient water measurement and control techniques. Many simple constructions or operating procedures are available that can bring considerable convenience to farmers and irrigation delivery system operators. Some are new technologies and some are improvements on older technologies. Many can be implemented with small expense. Some are superior replacements for current practices. The techniques and devices discussed included: (a) accurate and convenient zero setting for weirs and flumes (b) pressure-transducer field checks, (c) easy-to-use scales for orifice and Venturi meters, (d) flow-profile improvers to assist accurate meter operations in irrigation pipelines, (e) floor sills and wave suppressors for canals that usually flow at variable depths of flow, (f) water surface slope measurements–based on static-pressure tubes, and (g) field checks of flow velocity profiles to evaluate flow conditioning using rising-bubble techniques for flow-profile visualization. Many of the concepts are demonstrated in a summary illustration showing several items in a typical stilling well and broad-crested weir (long-throated flume) that need attention, and offers suggestions for correcting the deficiencies.

Flow measurement of two-phase oil-in-water emulsions using wedge meters and segmental orifice meters

The applicability of wedge meters and segmental orifice meters to monitor the flow rate of oil-in-water emulsions was investigated. A flow loop consisting of wedge meters and segmental orifice meters of various shapes and sizes was designed and developed. The discharge coefficients were determined for various differently concentrated oil-in-water emulsions. The oil concentration was varied from 0% to 75.18% by volume. The results indicate that wedge meters and segmental orifice meters are feasible flow-measuring devices for emulsions. The single-phase calibration curves (discharge coefficient vs. Reynolds number) are applicable to two-phase oil-in-water emulsions. The size and shape of the wedge element have a significant effect on the discharge coefficient.

Applications of Accurate Isentropic Exponent Determination for Fuel Gas Measurement

This paper discusses the determination and application of the isentropic exponent to the various thermodynamic processes found in a high-pressure natural gas transmission system. Increasing demands for more precise measurement of natural gas, coupled with the need for greater efficiency and accountability of transportation and processing operations, had led to our research and development efforts into the more precise measurement of gas flow, and the determination of gas thermodynamic properties including isentropic exponent. The isentropic exponent has many applications, some of which include: • the determination of the expansion factor ε, for calculation of flow using an orifice or venturi-type meter; • the volumetric efficiency in a reciprocating compressor; • the determination of the compression head for a centrifugal compressor; • the engine power required for the given conditions for a gas compressor; • the calculation of discharge temperatures for compressors; and • the direct measurement of gas density. As can be appreciated, the application of an incorrect value for the isentropic exponent represents an error in the parameter determined. For large volume gas flows, this can translate into a significant cost penalty.

Effects of upstream pipe fittings on the performance of orifice and conical flowmeters

It is difficult to get high accuracy over a broad measurement range from a flowmeter operating in ideal conditions, but when the device is placed in a hostile environment with highly disturbed flow profiles involving swirl caused by various pipe fittings such as pipe bends installed upstream of metering element, the task becomes even tougher. In this regard, the conical flowmeter seems to fare better than other pressure differential devices. In the present study, experiments were conducted to investigate the effect of upstream pipe fittings such as a single 90° mitre bend, double 90° mitre bends in-plane and double 90° mitre bends out-of-plane on the performance of a conical flowmeter and orifice meter. These measurements are carried out for Reynolds numbers ranging from 30000 to 494000 for a constant β ratio of 0.75 with air as the working medium. Further, static pressure distributions downstream of the orifice meter and conical flowmeter are measured to estimate the irrecoverable pressure drop due to the flowmeter in the line. Results indicate that the conical flowmeter is less sensitive to swirl when compared with the orifice meter. Further, the irrecoverable pressure drop in the conical flowmeter is 50% less than that for the orifice meter.

Experimental investigation of liquid accumulation effects during orifice gas metering of two-phase flow

A series of experiments was carried out to investigate the effect of liquid accumulation upstream of an orifice meter in a horizontal pipeline. The orifice meter was used to measure gas flow which contains small amounts of liquid. The experiments have verified that significant amounts of liquid will accumulate at low gas flow rates. The accumulated level is independent of the gas mass to total mass flow fraction within the investigated range from 0.91 to 0.95. The accumulated liquid will affect the form of the vena contracta. This will result in the observation of a lower differential pressure drop across the orifice for a given flow rate, and errors in the determination of gas mass flow will be introduced. An iterative method to quantify the effect of the accumulated liquid upstream of the orifice is suggested.

Beta ratio, axisymmetric flow distortion and swirl effects upon orifice flow meters

The objective of this study is to measure the response of the orifice meter to known upstream flow field disturbances generated by a concentric tube flow conditioner and a vane-type swirl generator. These disturbances are characterized by measuring the axial and tangential velocity profiles at the upstream flange tap with no orifice plate present. Two different flow rates are examined which correspond to Reynolds numbers of 91 100 and 120000 in a 50.8 mm diameter pipe. Eight orifice plates with β ratios of 0.43, 0.45, 0.484, 0.55, 0.6, 0.65, 0.7 and 0.726 are studied at both flow rates. The response of each orifice meter to the disturbance is characterized by measuring the axial wall pressure distribution near the orifice plate and the discharge coefficient. These data show that a nondimensionalized pressure does not change with varying axisymmetric flow distortions. However, the pressure distribution is very dependent upon the swirl. The axial momentum distribution is quantified by calculating the second-order moment of axial momentum ( R 2[ u] from the velocity profile data. Swirl is quantified by determining the centripetal acceleration flux of the flow (ψ), also from the velocity profile data. Surface fits indicating the variation of discharge coefficient as a' function of β ratio and R 2[ u] or ψ are developed.