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Petrochemical and electric power plants are using flow meters, of which capacity is larger than 1000 m3/h. They require the accuracy of flow meters better than ±0.3% if the flow meters are being used for custody transfer or allocation measurement. However, the number of national metrology institutes, which can handle this issue, is very limited, including PTB (Germany), NMIJ/AIST (Japan), MIKES (Finland), CEESI-NIST (USA), and TÜV-NEL (UK). Large-capacity flow measurement standards are also needed to make better quality control for process engineering in the Republic of Korea. This study aims at establishing the water flow measurement standards up to 2000 m3/h with uncertainty better than 0.06%. How to evaluate the measurement uncertainty is discussed for establishing the large-capacity water flow standards at KRISS.

Master meter method is an efficient way to calibrate flow meters with less time and costs. The master meter method has simpler flow configuration than the gravimetric flow measurement method requires. Maintenance efforts of the master meter method are easier than the gravimetric method. However, the guidelines of master meter method have not been established completely. It is because the notion of relative deviations, which are used as a measure and for comparison calibration, is not clearly understood. On the other hand, the system uncertainty, which is typically used as the calibration and measurement capability of the gravimetric flow standards, are understood very well. In this study, a complete explanation on the master meter method is attempted. First, appropriate calibration conditions are assumed. Second, a suitable calibration procedure is suggested. Third, a mathematical model for the relative deviations is described. Fourth, uncertainty factors of the relative deviations are evaluated. Finally, two examples of the comparison calibration are explained in detail. The master meter method is compatible with the guide to the expression of uncertainty in measurement (GUM, ISO/IEC Guide 98-3:2008). In the examples, it is found that the master meter method can achieve the measurement uncertainty as low as 0.20%.

First-order partial derivatives of a mathematical model are an essential part of evaluating the measurement uncertainty of a liquid flow standard system according to the Guide to the expression of uncertainty in measurement (GUM). Although the GUM provides a straight-forward method to evaluate the measurement uncertainty of volume flow rate, the first-order partial derivatives can be complicated. The mathematical model of volume flow rate in a liquid flow standard system has a cross-correlation between liquid density and buoyancy correction factor. This cross-correlation can make derivation of the first-order partial derivatives difficult. Monte Carlo simulation can be used as an alternative method to circumvent the difficulty in partial derivation. However, the Monte Carlo simulation requires large computational resources for a correct simulation because it considers the completeness issue whether an ideal or a real operator conducts an experiment to evaluate the measurement uncertainty. Thus, the Monte Carlo simulation needs a large number of samples to ensure that the uncertainty evaluation is as close to the GUM as possible. Unscented transform can alleviate this problem because unscented transform can be regarded as a Monte Carlo simulation with an infinite number of samples. This idea means that unscented transform considers the uncertainty evaluation with respect to the ideal operator. Thus, unscented transform can evaluate the measurement uncertainty the same as the uncertainty that the GUM provides.

In the study, we developed a flowmeter to be mounted on fishing vessels to measure their fuel consumption in the sea, and evaluated the performance of the flowmeter under the dynamic conditions of a fishing vessel. In order to analyze the dynamic behavior of the fishing vessel in the sea, dynamic motions (pitch and heave) based on the speed of the fishing vessel were obtained through simulation and field test. In the presence of vibration, the uncertainty of the ultrasonic flowmeter increased from 0.12% to 0.5%. The measurement error of the ultrasonic flowmeter also increased from 0.5% up to 2% when dynamic behavior motions (pitch and heave) increased with the speed of the fishing vessel. The results confirmed that the measurement errors of ultrasonic flowmeter were consistent at the same flow rate and speed of the fishing vessel in the dynamic test bed and sea field test. Additionally, to confirm the long-term stability of the developed flowmeter, a long-term test of the flowmeter was performed for three days in actual fishing conditions. The results indicated that the ultrasonic flowmeter developed in the study can measure the fuel consumption of an actual fishing vessel. To the best of the authors’ knowledge, this is the first study to measure the fuel consumption in the sea via mounting a flowmeter on an actual fishing vessel.

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, it indicates flow rates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow metering amounts as low as ±1% if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be increased greater than ±2% if the flow velocity is lowered smaller than 0.5 m/s. Inner pipe diameter can be also an influential factor in flow metering when the exact value of the inner diameter is not known. The inner pipe diameter cannot be found if the pipe is too large to measure or if there are erosions or adhesions on the inner pipe surface due to small particles in the flow. These shortcomings of the clamp-on ultrasonic flow metering can be overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is termed combined V/Z clamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performance between the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths. Notably, the combined technique showed better performance (expanded uncertainty less than 0.76%, k = 2) than the two flow metering techniques (1.61% and 1.17%, k = 2) in the flow range of (100–400) m3/h with pipe diameter of 250 mm.

A liquid flow standard system is used to calibrate liquid volume of fuel–oil flow meters at small flow rates between 50 L/h and 700 L/h. However, the system has not been used to calibrate volume flow rate because the system is only operated with the standing-start-and-finish mode. In this study, the liquid flow standard system was rebuilt to provide a calibration service of volume flow rate by attaching two flow diverters, which can operate the system with the flying-start-and-finish mode. To evaluate its performance for volume flow metering, several techniques were introduced. First, diverter timing errors were estimated by linear regression. Second, covariance between buoyancy correction factor and water density was obtained to consider interdependency between the two measurands. Third, calibration and measurement capability (CMC) was evaluated by setting a fixed value of collected weight or elapsed time for flow diversion. Finally, several CMCs were compared to find the best measurement condition. As a result of the above approach, the CMC of the liquid flow standard system was found to be (0.10–0.52)% (k = 2) for (50–700) L/h with a minimum collected weight at 10 kg.

Flow disturbances can significantly affect flow metering because the downstream flow of flow disturbances can become unstable and asymmetric, thus resulting in measurement errors in the flow meter. A clamp-on type ultrasonic flow meter is an example of a flow meter that is susceptible to flow disturbances given its diametrical configuration of ultrasonic paths. Several flow rate correction formulas have been suggested to mitigate the effect of flow disturbance for improved flow metering. As a novel method, a multi-dimensional non-linear correction formula is suggested to overcome limitations in flow metering that are attributed to the non-linearity of flow disturbances. The non-linear correction formula comprises n-th order polynomials with multiple variables. To validate the usefulness of the non-linear correction formula, the standard error of estimate (SEE) is introduced. Four types of flow configurations, namely, downstream of a contraction pipe, an expansion pipe, a single elbow joint, and a tee joint, are used to show the effect of the non-linear correction formula. The expanded uncertainty based on the SEE indicates estimated values of 1.29%, 11.14%, 1.07%, and 6.31% for the four upstream flow configurations, respectively. Thus, the effect of the non-linear correction formula is limited according to the upstream flow conditions. In the downstream flow of the contraction pipe and of the single elbow joint, the non-linear correction formula not only harmonizes the distribution of the flow rate deviations but also removes the biases of flow rate deviations with respect to the flow velocity, the installation location, and the diameter ratio.

Heat flowmeters are expected to be reasonably priced, be very reliable, and have high measurement accuracy. Various types of heat flowmeters have been developed and they are widely used in large residential and industrial buildings. In this study, three types of heat flowmeters (turbine, electromagnetic and ultrasonic) were tested for accuracy, effect of installation position and vibration, durability and performance in the field for several installation positions and in the presence of vibration. We used a liquid flow standard system and a customized durability test system in accordance with the International Organization of Legal Metrology (OIML) R 75-2 heat meter testing method. The field test was conducted in eight different locations from winter to summer. All flowmeters were calibrated before and after the field test, and the measurement deviation and the relative expanded uncertainty were calculated. The mean deviations obtained were–0.21%,–0.07%, and 0.11%, with the relative expanded uncertainties 0.48%, 0.17%, and 0.40% for turbine, electromagnetic, and ultrasonic flowmeters, respectively. The results of position and rotation tests, mean deviations by rotation angles at 90°, 180°and 270°relative to 0°(horizontal position) were–1.24%,–1.07% and–0.80%, respectively. For the vibration tests at 1 m/s 2 and 5 m/s 2 vibration acceleration, the turbine flowmeter, the electromagnetic flowmeter and the ultrasonic flowmeter showed deviations that ranged from −0.2% to −0.5%, −0.6% (2.6 m 3 /h), and 0.0% (negligible), respectively. In the durability tests, the accuracy of all three types of heat flowmeters remained at ±1% or less, showing sufficient durability. In the field test, the deviation of the turbine flowmeter and the ultrasonic flowmeter showed ±2.5% or less deviation. However, the electromagnetic flowmeter seems to be inaccurate below 6.9% of the maximum flow rate.

For an accurate flow metering without considering the influences of flow control devices such as valves and elbows in closed conduits, velocity distribution in the cross-sectional area must be integrated. However, most flow meters, including multi-path ultrasonic, electromagnetic or Coriolis mass flow meters, require assumptions on the fully-developed turbulent flows to calculate flow rates from physical quantities of their own concern. Therefore, a long straight pipe has been a necessary element for accurate flow metering because the straight pipe can reduce flow disturbances caused by flow control devices. To reduce costs due to the installation of long straight pipes, another flow metering technique is required. For example, flow rates can be estimated by integrating velocity distributions in the crosssection of conduits. In the present study, ultrasound tomography was used to find the velocity distribution in the cross-section of a closed conduit where flow was disturbed by a Coriolis mass flow meter or a butterfly valve. A commercial multi-path ultrasonic flow meter was installed in the pipeline to measure the line-averaged velocity distribution in the pipe flow. The ultrasonic flow meter was rotated 180° at intervals of 10° to construct line-averaged velocity distributions in Radon space. Flow images were reconstructed by using a backprojection algorithm (inverse Radon transform). Flow diagnostic parameters were defined by calculating statistical moments, i.e., average, standard deviation, skewness, and kurtosis, based on the normalized velocity distribution. The flow diagnostic parameters were applied to flow images to find whether the parameters could discern flow disturbances in the reconstructed velocity distribution.

In order to improve the characteristics of MgO-C brick applied to RH lower vessel, several originally-prescribed specimens were prepared by changing the amount of additives with different size distributions. These specimens were tested on their durabilities with an experimental rotary type electric furnace and a practical 2RH in a manufacturing line. Following are the major results:1) Specimens prepared with 3-7% expanded carbon and anti-oxidation agents exhibited excellent spalling durability.2) Specimens containing both metallic Al and metallic Si had higher elasticity than those containing only metallic Al and those with a higher Si content retained excellent durability against corrosion and oxidation.3) Corrosion at a high temperature was suppressed by removing SiC from the low C-content MgO-C specimen.4) Durability against spalling was improved by shifting the size distribution of specimen from fine one to coarse one.

Swirl flows are either tumbling motions of main flows or circulating secondary flows in the cross-section of pipe, which makes accurate flow metering difficult without installing a long straight pipe upstream of a flow meter. However, there are many situations, where such long upstream/downstream pipelines cannot be installed due to limited space in the installation site for flow metering. The relative deviations of flow rates between the testing and the reference flow meters can be reduced by introducing a correction formula. The correction formula considers flow parameters such as curve number, swirl factor, Reynolds number and two non-dimensional numbers regarding installation of flow meters. Nonetheless, there are certain flows where the correction formula is not effective due to strong swirl flows. Two-dimensional curve fitting is introduced in the present study to solve some of difficulties in compensating flow rates due to swirl flows upstream/downstream of flow control elements, i.e., a contraction pipe, an expansion pipe, a single elbow and a butterfly valve. This method minimizes the gap between the measured and the estimated flow rates by applying the Levenberg-Marquardt algorithm. 2nd or 4th order polynomials with two independent variables, i.e., Reynolds number and a non-dimensional location of testing flow meter, are chosen to test their ability to compensate flow rates. From this study, the relative deviations were maintained within ±2% by applying the two-dimensional curve fitting.Copyright © 2011 by KSME

Flow meters, which are used for transferring water or crude oil through pipelines, require well‐defined flow conditions for accurate flow rate monitoring. Even though all the installation conditions for the flow meters are satisfied, there could be unexpected flow disturbances, such as abrupt increase of upstream pressure, affecting on the performance of flow meters. To investigate any differences between measured and actual flow rates, flow velocity profiles inside the pipeline must be known. Ultrasound tomography is a means of reconstructing flow profiles from line‐averaged velocities by Radon transformation. Diagnostic parameters are then extracted from the reconstructed flow profiles to give information whether the flow conditions are appropriate for accurate flow metering. In the present study, flow profiles downstream of a mass flow meter and a butterfly valve are reconstructed. Flow diagnostic parameters are defined using statistical moments such as mean value, standard deviation, skewness and kurtosis. The measured diagnostic parameters in the above‐mentioned flow conditions are compared with those of fully‐developed laminar and turbulent flow profiles to validate their usefulness.

This study selected a total of 24 heat flowmeters consisting of three types: impeller, electromagnetic and ultrasonic, 8 meters each. The diameter was 0.05 m (9 meters), 0.08 m (9 meters), and 0.15 m (6 meters). In accordance with the OIML R 75 testing method accuracy, installation position, external environment, and durability were tested, and the flowmeter property field test was conducted in the field where of heat supply from winter to summer in order to select the type of heat flowmeter best suited for the circumstances in Korea. According to the test result, all 3 types of flowmeters met the OIML Recommendation, but the result of the field test showed that the electromagnetic flowmeters displayed a deviation at the low flow rate during summer. The impeller flowmeters showed accuracy suggested by the OIML Recommendation, but the ultrasonic flowmeter, a next‐generation flowmeter, which is strong against contamination, low in maintenance‐rate, and high in accuracy as it has no moving part, was found to be the best choice.