G. Kok, N. Pelevic, A. Chiribiri, X. Milidonis, M. Nazir, M. Capstick, S. Drost, C. Poelma, T. Schaeffter
A calibrated physical flow standard for medical perfusion imaging

In the medical sector, various imaging methodologies or modalities (e.g. MRI, PET, CT) are used to assess the health of various parts of the bodies of patients. One such investigation is the blood flow or perfusion of the heart muscle, expressed as the (blood) flow rate normalized by the mass of the volume of interest, with unit mL/min/g. Currently there is no physical flow standard for the assessment and validation of myocardial perfusion imaging methodologies, resulting in a large proportion of medical diagnoses being inaccurate and highly dependent on the scanner type, software used and the clinical operator. In the EMPIR 15HLT05 PerfusImaging project a phantom simulating myocardial perfusion has recently been developed with which imaging modalities can be tested. In this paper the construction and validation of the phantom is described which involved several iterations with design updates, computational fluid dynamics simulations, 3D printing of the phantom, ultrasound imaging velocimetry and magnetic resonance imaging (MRI). Dynamic contrastenhanced MRI was performed to image the passage of a tracer through the phantom and estimate perfusion. Two flow models and associated data analysis methods to relate the measurement data with the reference flow rates are presented and discussed.

I. B. S. Bispo, L. C. Pacifico, W. O. Chaves, N. M. Taira, P. J. S. Jabardo
Comparison of two different methods for calibration of Cole type Pitot tubes

The Cole type Pitot tubes (Pitot-Cole tubes) are widely used by water utility companies to map fluid flow velocity profile and thus measure the flow rate in pipelines. This technique is mainly used for on-site calibration of other kind of flow meters, such as electromagnetic or ultrasonic, particularly when removing the meter from the pipeline is somehow not feasible. Therefore, when using Pitot-Cole tubes for those purposes, the determination of the calibration coefficient (Cd) and its associated uncertainty contributes significantly to the results of such measurements.
This paper presents the description and comparison between the results of two different methodologies for calibration of Pitot-Cole tubes: in a wind-tunnel and in a towing tank. Comparisons were also performed for two configurations of the Pitot-Cole tube, with and without a central pin between the two pressure tips, in which the inclusion of this feature increases the measured differential pressure, leading to a set of more reliable measurements.
The obtained results demonstrate coherence and feasibility of the wind-tunnel calibration for normalized Reynolds numbers (RE/L) greater than 7×105. These results also show that a more precise value can be applied along distinct velocity ranges, individually for each Pitot-Cole tube, instead of employing the usual value of Cd = 0.869, used since Cole proposed this form of Pitot tube in 1896. Another major result shows that, for lower values of Re/L, a correction of the calibration coefficient is needed, in order to reduce the uncertainty associated to the measurement. This second result is especially important since the corresponding velocities are related to lower flow rates, in which their measurements are usually followed by larger uncertainty estimates.

N. Pedisius, A. Bertasiene
Reproduction of air velocity in the entrance region of the pipe

Information about the airflow development in pipes in the entrance region is still not thoroughly investigated due to the complexity and restricted access for experiments. However, the reproduction of air velocity values, as well as calibration of the devices, is usually made in free streams from the nozzles or in the entrance region of the channels (pipes). In this study, different flow regimes have been investigated using different air velocity measurement methods for mean velocity to define. Experimental and numerical results in the entrance region of the pipe and in the test chamber of higher dimensions give a broad spectrum of information about the developing flow. Ultrasonic anemometer (UA) installed into the entrance region of the aerodynamic test facility shows reliable and highly comparable results in a wide range of velocities with another non-intrusive method – laser Doppler velocimetry (LDA). Due to the fast response, it enabled to analyse fluctuations in the flow. The mean air velocity values were determined from the singe path sound propagation time in the pipe with a defined distance between the transducers placed at an angle of 45 degrees with the main axis. Local vortices identified in the flow might have influenced the low-frequency fluctuations and the scatter of measurement results. Moreover, high-frequency fluctuations found in the flow originated from the flow turbulence and the electronic or acoustic noise. The stabilisation of the entrance region and the boundary layer of the pipe influenced mean velocity value, velocity distribution and axial velocity development in different test sections of the pipe. Along with the recirculation zones in cavities of ultrasonic transducers they are the essential impact factors on velocity value defined.

J. D. Wright, S. D. Sheckels, J. T. Boyd
Automated Substitution Weighing Apparatus for Liquid Volume Measurement

The custody transfer of petroleum worth $1 x 1012 / year is traced to the volume delivered from provers and liquid test measures. Mistakes as small as 0.02 % in a custody meter calibration can lead to multi-million dollar corrections in bills. NIST presently uses the direct weighing method to measure the volume delivered from a test measure, by weighing (on a calibrated balance) the test measure when it is full of pure water and again after it has been drained. Recently, NIST reduced the uncertainty of its calibrations of volumes between 3.8 L and 40 L by constructing an automated substitution-weighing standard. The new standard reduces the mass measurement uncertainty by alternately placing 1) the test measure (unknown mass) and 2) approximately equal reference masses on the balance. Automated, pneumatically-driven hardware moves heavy liquid-filled volumes and reference masses on and off the weigh scale, thereby protecting the operator’s safety and comfort. We describe the system’s design, operation, uncertainty, and repeatability. The new standard was validated by comparison to NIST’s well established direct weighing approach and by repeated calibration of a 38 L pipette during more than 2 years. The results are fully consistent with the 95 % confidence level uncertainty estimate of 0.007 % for the substitution weighing standard. Correlation between temperature and the volume of the 38 L pipette shows the need for improved environmental temperature control in the laboratory. We also describe the design of a set of four pipettes with an overflow filling system that can be used as references in an automated volume transfer standard.

Chuanbo Zheng, Xingchuan Chen, Yiwen Liu, Wei Han, Zhe Liu
Study on Data Collection Methods of Natural Gas Flow Verification

Based on the different ways of data collection which adopted by the current domestic natural gas flow metering station, this paper first analyzes the theoretically applicability and limitations for two kinds of data collection methods: instantaneous flow and cumulative flow, and obtains the relation and distinction between these two ways. Then, the flow-meters with different diameters are actual tested in two data acquisition ways, instantaneous flow and cumulative flow, which performed by the work level standard device of substation in Guangzhou. The results show that the different methods of data collection have no evident impact on indication error but high effect on the repeatability of indication error.