We have developed a portable device, based on this infrared absorption method, that can measure in-situ micro flow rates from 0.2 to 20 mL/min using a simple diode laser and a photo detector. A 1450 nm laser absorbed in water was irradiated to form a hot spot and the temperature was measured upstream and downstream of the hot spot. Two diode lasers and two photodetectors were used to measure the water temperature in the tube upstream and downstream of the hot spot. The amount of laser diode light from 1550 nm to 1650 nm wavelength absorbed by the water varied with the temperature of the water. The flow rate was measured by the temperature difference obtained by the diode laser absorption upstream and downstream of the hot spot. The temperature difference measured upstream and downstream decreased exponentially with increasing flow rate. Thus, it was confirmed that the flow rate can be measured through the temperature difference gauged using a simple diode laser set. This method is used for various applications including biomedical and chemical processing without causing any contamination owing to the flow meter installation.

Coriolis meters have many advantages for mass flow and volumetric measurement in a wide variety of applications. Inherent reliability, linearity, and stable meter factor (MF) on a wide variety of products make them an ideal choice for pipeline transfer. With the recent introduction of high flow rate meters, Coriolis technology can now be used in line sizes up to 16”. Custody transfer of products is very common in these large pipelines; in many applications contractual requirements dictate that meters be proved in situ periodically to ensure accurate measurement over time and/or product changes.
Traditionally, large pipe provers have been employed at metering stations. The overall size of a pipe prover and the maintenance costs of the complex four-way valve integral to a bi-directional pipe prover can be a concern. Small volume “piston-type” provers are becoming more common because they have a much smaller foot-print and reduced maintenance costs. Even the largest small volume provers are small (as much as 10 times smaller) compared to pipe provers of similar flow capacity. Small volume provers tend to perturb the flow rate when the piston launches. Because the measuring volume of a small volume prover is so much smaller, this rate change caused by the operation of the prover becomes an integral part of the proving cycle that is measured by the metering device.
Proper sizing of a small volume prover to pair with a Coriolis meter(s) can result in greater proving efficiency, optimum prover size, and reduced maintenance on the prover. This selection and pairing process is especially important when using small volume provers to prove high-precision, high-flowrate Coriolis meters. Data collected to validate Coriolis meter performance with small volume provers in lab testing and field proving has been analyzed to determine which procedural and design factors yield the best results. This analysis has resulted in the development of the concept called “Total Prove Time” (TPT).
In addition, proving methods that apply incremental uncertainty analysis to determine when proving is completed will afford operators the opportunity to attain even greater efficiency. This method of proving involves continuing to collect runs until the repeatability that is equivalent to a meter factor random uncertainty of better than ±0.027% has been reached. This method is outlined in the American Petroleum Industry (API) Manual of Petroleum Measurement Standards (MPMS) Chapter 4.8, Second Edition, Operation of Proving Systems, Annex A, Evaluating Meter Proving Data.
The TPT concept is simple to apply and useful for selecting a small volume prover and Coriolis meter to achieve maximum freedom of choice between prover size selection and operational trade-offs including wear and tear. Diagnostic tools for enhancing overall measurement systems design, troubleshooting, and assessing future pipeline capacity expansions are another benefit that have resulted from this research.

The performance of Coriolis flow meters designed for use in hydrogen refuelling stations was evaluated in air and nitrogen by several National Metrology Institutes and Designated Institutes. Three meters were tested by members of the MetroHyVe consortium; NEL, METAS and CESAME EXADEBIT. A fourth meter was tested separately by KRISS and there was found to be a significant overlap in the test conditions and results from each experimental programme.
A wide range of conditions were tested overall, with gas flow rates ranging from 0.05 to 3.8 kg/min and pressures ranging from 10 to more than 40 bar. The densities encountered using air and nitrogen ranged from 11.5 to more than 52 kg/m³ (equivalent to hydrogen at approximately 125 bar and 875 bar respectively). There was also some investigation of the influence of temperature on flow meter performance, with selected points tested at temperatures as low as -40°C. The effect of pressure was studied separately using water and is presented in another paper.
When the flow meters were operated within the manufacturer's recommended flow rate ranges, errors were generally within ±1%. For some of the meters tested, errors approached ±0.5%.

In 2016, PTB introduced a function for the representation of the discharge coefficient cD of critical flow venturi nozzles (CFVN) (versus the Reynolds number Re) what covers the operating range with laminar boundary layers and with turbulent boundary layers as well. It contains the parameters a for the impact of the core flow, blam for the Re-dependency in case of laminar and bturb in case of turbulent boundary layers. These parameters are not independent to each other but have the fixed relation of bturb = 0.003654 b lam 1.736.
Furthermore, the parameter a and the parameter blam are both direct functions of the local curvature radius Rc,throat of the nozzle at the throat. These relationships to Rc,throat are described by theoretical models. Consequently, the overall dependency of the discharge coefficient cD on Reynolds number Re can be derived from only one parameter.
The paper describes how the relationships mentioned above can be used to extrapolate the calibration values of a CFVN determined with atmospheric air to high pressure gas flow applications covering a Reynolds range of about 1:60. It is shown in detail by examples and the reliability is demonstrated by comparison data for low and high pressure of 33 nozzles. Finally, aspects of preconditions for such extrapolation and uncertainties will be discussed.

The German national metrological institute, Physikalisch-Technische Bundesanstalt, is developing a new concept for volumetric primary standard to calibrate high pressure gas flow meters. The TUHH is supporting these R&D activities with its competence to elaborate computational models for detailed analysis of complex electromechanical systems including fluid flow aspects. The new primary standard is called Flow Comparator and uses an actively driven piston prover to measure the gas flow rate using the time the piston needs to displace a defined enclosed volume of gas in a cylinder. In Modelica a computational model is developed to investigate the Flow Comparator’s dynamic behaviour and interaction with the other components in the loop. Furthermore, it allows to gather detailed information about pressure and temperature development at arbitrary chosen locations in the system with high time resolution. The validation of the developed model shows good compliance with measured piston velocity and differential pressure at the piston. The model is used to optimize the frequency inverter’s control voltage trajectory to increase the available measuring time.