Coriolis flowmeters are recognised to give excellent performance of the mass flow measurement and independent density measurement of single-phase flow. However, the large measurement error of a Coriolis flowmeter under gas-liquid two-phase flow conditions makes it unsuitable for many industrial processes where gas-liquid two-phase flow is encountered. Although analytical models have been proposed to explain the reasons behind the large output error of a Coriolis flowmeter under two-phase conditions, none of the individual theories nor their combinations can match experimental results to within 10% difference. In particular, when the gas volume fraction (GVF) exceeds 15%, the existing analytical models are not suitable. In this paper, a semiempirical analytical model is established by combining existing analytical models with empirical terms and coefficients. The applicable range of this new analytical model is now extended to up to 40% GVF, which also better matches the experimental results. Comparisons between the modelling predictions and the experimental results for air-water two-phase flow on a two-inch Coriolis flowmeter (KROHNE OPTIMASS 6000) are made. Comparisons indicate that 2314 out of 2457 (94.2%) modelling predictions in mass flowrate fall within 10% relative error while 2403 out of 2457 (97.8%) predictions in GVF measurements fall within 5% absolute error. The outcome of this research contributes to an analytical approach to predict output error of Coriolis flowmeters under gas-liquid two-phase flow with improved accuracy and extended GVF range.

This paper is dedicated to the flow-rate measurement uncertainty calculation, considering the use of Pitot tubes inside closed conduits as the applied measurement method, according to the guidelines and procedures established by the current ISO 3966 standard. The performed study aims the comparison between measurement uncertainties obtained by the conventional error approach mentioned in the method’s standard and the results obtained from the application of the Monte Carlo Method (MCM). Using the same input data, a difference of 0,3% was obtained between the 95% relative expanded measurement uncertainties. The obtained probability density function of the compressibility correction factor showed a non-Gaussian asymmetric shape, however, not affecting the remaining quantities in the uncertainty propagation chain. The Pitot tube’s calibration factor and the turbulence and high frequency fluctuations were identified as the main uncertainty contributions for the combined measurement uncertainties.

In thermal power plants, flow meters are operated at high temperatures and pressures and often encounter disturbed flow profiles. This leads to an increased measurement uncertainty, which limits the save operating range of flow rates and hence the plant’s power output. Therefore, the laser optical flow rate standard (LFS) was developed. It is designed to allow the on-site calibration of industrial flow meters in power plants at high temperatures and pressures. It makes use of the metrologically traceable and non-invasive laser Doppler anemometry (LDA) to measure the velocity field simultaneously with two LDA systems. The volumetric flow rate is then determined by means of integration. Here, we present flow rate measurements for fully developed pipe flow and 6 pipe diameters downstream of a disturbance generator. The mean deviation in flow rate between the two LDA systems was 0.05 %, with a mean deviation from the gravimetrical reference flow rate of 0.12 %. The highest deviations from the reference were 0.21 % and 0.31 %, for the two systems respectively.

We will investigate the measuring principle of time-of-flight(TOF) ultrasonic level meter, related analysis and comparison of performance and modification method. Higher measuring precision of height at 0.1mm order of magnitude, and algorithm robustness in the case of weak surface movement, are expected. When using absolute transit time algorithm, the head of wave should be clear, by eliminate echo faster than that through main wave path. And in second trace echo case, ensure there are parts of two echo waves, can be located by theoretical arithmetic and waveform algorithm, have higher relevancy than 98%. In order to enhance the precision of ultrasonic level meter, a proper transit time algorithm will be selected and optimized. The systematic time deviation and delay, transit time in protective containment, cable delay and circuit running time, will be estimated, then adjusted in stable water. The speed of sound, to modify level results with high precision TOF, in objective experimental environment can be calibrated by manometer and thermometer, in pure water media, fluctuation of sound speed measured by ultrasonic apparatus and transfer from temperature is smaller than 0.01%. Finally, micrometer and pressure meter will be used, to compare and evaluate the precision, stability and linearity of level meter, in stable and moving water.

The paper describes an ultrasonic flow meter with an axial measuring path, which uses acoustic plane waves propagating through pipes with a sufficiently small diameter. The propagation of plane waves in a circular pipe depends on the pipe diameter and the wavelength of the acoustic signal. Therefor, the design of the meter has to consider the speed of sound for the gases intended to use, e.g. nitrogen, methane, hydrogen and any mixture of these. In order to measure low flow rates with small uncertainties, a great acoustic path length, i.e. a pipe with long length is advantageous. On the other hand, the signal attenuation increases proportionally with the length of the measuring pipe. The paper provides information about the basic conditions to reach plane waves in a pipe with small diameters.
The investigated prototype uses an inner pipe diameter of 4 mm and a path length of 320 mm. The ultrasonic transducers and the electronics are taken from a commercially available ultrasonic meter with two paths and a working frequency of 135 kHz. In this configuration, the signal quality is already very good with nitrogen under atmospheric conditions, but due to the acoustic attenuation, methane is only measurable with more than 2 bar absolute pressure. The results for nitrogen and methane show nearly linear behaviour over a flow range from 10 to 1,000 l/h. At the lower flow range of the meter the zero flow uncertainty is the limiting influence value. The protype has shown stabilities of lower than qz = 0.1 l/h. The meter may be used for quality assurance of test rigs such as checking small nozzles and as transfer standard for intercomparisons.