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Page 11 of 907 Results 101 - 110 of 9067

S. Neuhaus, H. Bissig, B. A. Bircher, M. de Huu
Presentation of the METAS pipe viscometer

Calibration of flow devices is important in several areas of pharmaceutical, flow chemistry and HPLC applications where dosage of process liquids or accurate measurement of the flow rate are important. The process-oriented liquid itself might influence the performance of the flow device. Therefore, the calibration of the flow meter or microfluidic device with the process-oriented liquid is important and the simultaneous determination of the dynamic viscosity under flow conditions is a valuable information for viscosity dependent flow metering methods or other process parameters. To offer the simultaneous calibration of the dynamic viscosity of the process-oriented liquid at the corresponding flowrate, METAS has built a pipe viscometer for the traceable in-line measurement of the dynamic viscosity in the current flow facilities for low flow rates from 1 L/min to 150 mL/min and pressure drops up to 10 bar. To guarantee the tracability, the most challenging part remain the determination of the inner diameter of the micro tube. This can be determined by measuring the pressure drop as a function of flow rate and applying the law of Hagen-Poiseuille with a well known liquid (water) or perform the measurements with the μ-CT at METAS, which determines the inner diameter by x-ray diffraction. The setup of the facility, the uncertainty calculation for the in-line measurement of the dynamic viscosity and the validation measurements are discussed in this paper.

H. Bissig, O. Büker, K. Stolt, E. Graham, L. Wales, A. Furtado, S. Moura, Z.Metaxiotou, S. H. Lee, S. Kartmann, J. Groenesteijn, J. C. Lötters
First comparison of inline measurements of dynamic viscosity

Microfluidic devices are gaining importance in various fields of pharmacy, flow chemistry and healthcare. In the embedded microchannel, the flow rates, the dynamic viscosity of the transported fluids and the fluid dynamic properties play an important role. Various auxiliary functional components of microfluidic devices such as flow restrictors, valves and flow meters need to be characterised with liquids used in several microfluidic applications. However, calibration with water does not always reflect the behaviour of the fluids used in the different applications. Therefore, several National Metrology Institutes (NMI) have developed micro pipe viscometers for traceable in-line measurement of the dynamic viscosity of liquids used in flow applications as part of the EMPIR 18HLT08 MeDDII project. These micro pipe viscometers allow the calibration of any flow device at different flow rates and the calibration of the dynamic viscosity of the liquid or liquid mixture used under actual flow conditions. The traceability of the micro pipe viscometer, the validation of the stated measurement uncertainty with eight liquids as well as dynamic viscosity measurements with in-line sensors are presented in this paper.

Yuan Liu, Wenrui Gao, Lei Wang, Heming Hu
Experimental Investigations of Boundary Layer Thickness Using Ultrasonic Transit Time Method

The widely used investigation method of fluid boundary layer is to record or simulate the current profile distributions near boundary, and then the loss of velocity can be estimate by integration. A directly measuring method of boundary layer displacement thickness by using ultrasonic transit time instrument is proposed. The problem of boundary layer measurement can be simplified to a easier measurement process of current velocity calibration, and the verification experiments are carried out by taking smooth plate as an example. An experimental platform of towing tank facility is established, the towing velocity is taken as the standard value of the outflow speed. The device for flat plate boundary layer measurement is regarded as an ultrasonic current meter. The inner side of the pair of plates equipped with ultrasonic probes can be considered as smooth surface, when the concave at the end of probes, installed by path axial angle, is filled with the material, which acoustic impedance is approximately equal to water. The measured value of ultrasonic current meter is equivalent to the difference between the outflow velocity and the loss caused by boundary layer. The accuracy of measurement result is ensured through high-precision geometric measurement, time delay calibration and sufficient zero-offset correction. In order to improve the time measurement resolution of the current meter, the range of flow velocity is set higher than 100mm/s. By changing the towing velocity and the characteristic position of ultrasonic probe installation, the Reynolds number range is 5e4 to 5e5. By analyzing the principle of ultrasonic current meter and towing tank facility, the uncertainty of displacement thickness measurement results can be properly evaluated. The measurement results of these experiments are close to the integration of flow field record by LDA.

S. Dixon, D. Greenshields, Z. Li, W. Sun, L. D. Smith
Ultrasonic anemometry from very to low to high air flow speeds using a cw or long pulse ultrasonic wave

Ultrasonic anemometers have a wide dynamic range, no moving parts and potentially high accuracies for measuring wind speed, but can also be used for indoor air flow monitoring. Some designs of ultrasonic anemometer already use flexural ultrasonic transducers (FUTs)- a sensor that is used extensively in car parking sensors as they are low cost, robust and reliable. Ultrasonic anemometers often use a method called transit time difference, where the different transit time generally with or against the air flow gives rise to a transit time difference, that can be used to calculate air flow speed. In most conventional ultrasonic anemometers, each transducer in a pair is pulsed in turn, with one generating whilst the other detects, and then the roles are reversed by multiplexing. The ADC captured signals and are processed using cross-correlation (or similar). Arranging pairs of transducers at different angles facilitates 2D and 3D measurements of air flow speed - the most common being 2D anemometers. Both air flow speed and direction (velocity) can be calculated. Challenges with this approach include that ADC and signal processing needed are relatively power-hungry and expensive.

Zheng Zhang, Miao Miao, Wenjia Li
Study on the influence of installation angle on pitot tube in wind tunnel

Pitot tube is a standard instrument commonly used in wind speed measurement, which generally needs to be used in conjunction with wind tunnel. On the premise that the pitot tube coefficient is determined and the performance of other related supporting equipment (digital pressure gauge, temperature and humidity sensor) is stable, it is found that the horizontal installation angle of pitot tube in the wind tunnel will have a significant impact on the measurement of wind speed. This paper designs an experimental method for this kind of phenomenon, summarizes the experimental data, and analyzes the possible impact of this kind of phenomenon on wind speed traceability, in order to improve the accuracy and effectiveness of pitot tube wind speed measurement.

A. Iwai, T. Funaki
Uncertainty Evaluation of Fluid Density at High Air Speed Standard in NMIJ

The National Metrology Institute of Japan (NMIJ) maintains high air speed standard and its calibration facility is capable of a relative expanded uncertainty (k = 2) of 0.63 % in the air speed range 40 m/s to 90 m/s. The model equation for measurement uncertainty in the high air speed calibration wind tunnel, which is the working standard, employs a method that cancels out the density term of the fluid. This is due to the fact that the density on the wind tunnel and DUT side is considered to be the same, i.e., the air speed values on the wind tunnel and DUT side are based on the same Bernoulli's principle. Therefore, the calibration environment of this standard is registered in the KCDB (CIPM MRA database) as ambient, which is independent of temperature and pressure changes throughout the year. However, there is a need to develop a calibration method for anemometers which are not based on Bernoulli's principle, as calibration targets. In this presentation, the reproducibility of air speed values in the wind tunnel is experimentally discussed, especially in the calibration environment, as the density of air changes throughout the year. In addition, the relative uncertainty of the density due to the difference of air density derivation formulas will be compared. Finally, the measurement uncertainty with the corrective coefficient of the anemometer under calibration due to the density change of air will be discussed.

Yang You-Tao, Chen Hai-Lin, Liu Kai
Research on Flow sensor of Ultrasonic Gas Meter

By reviewing the development of gas meter, the application prospect of ultrasonic gas meter is forecasted, the key technology and research and development difficulties of ultrasonic flow sensor, as well as the key application technology problems to be solved are discussed.The paper focuses on the design and selection of timing scheme of flow sensor, design of flow field characteristics of flow channel of flow sensor, electro-acoustic performance of flow sensor, linearity and repeatability of gas flow sensor. Through the exchange of theoretical research and practical application experience, the promotion of ultrasonic sensing technology, so as to promote the batch production and application of ultrasonic gas meters.

Nguyen Ngoc Hai, Nguyen Xuan Thai, Phan Lac Tuan, Duong Hong Son
Evaluation results of the new standard gas flow system at VMI: Piston prover system

Currently many National Metrology Institute (NMIs) as well as advanced calibration laboratories are using piston gas flow standards with mercury sealing method for gas flow calibration in the low pressure range. The flow in the small range is about cc/min. In this work, the low pressure gas flow calibration system at VMI is presented, designed and manufactured by the Taiwan National Metrology Institute, CMS/ITRI. The flow range is within (0.002 - 24) L/min. The uncertainty of the reference system is assessed against the ISO/IEC Guide 98-3:2008 document, Uncertainty is evaluated from individual influence sources such as category A and B assessments. The standard uncertainty/relative standard uncertainty and degrees of freedom of the sources can be evaluated individually and then combined to produce a composite standard uncertainty/combined relative standard uncertainty and an effective degree of freedom. Finally, the relative expanded uncertainty is obtained by multiplying the relative standard uncertainty associated with a coverage factor at the 95 % confidence level of the measurement result.

W. Kang, S. Im, N. D. Trang, J. Shin, Y-M Choi
Smokestack Gas Velocity Measurements using 3-D Pitot tubes in a Coal-Fired Power Plant

The fossil carbon dioxide (CO2) emissions from the combustion of fossil fuels and energy generators prevail over total greenhouse gas (GHG) emissions. Therefore, accurately estimating GHG emissions from stationary sources such as coal-fired power plants is also one of the efforts to mitigate the global rise in emissions. The GHG volumetric flow rates in stacks are measured mostly with the S-type Pitot tubes in Korea. But the S-type Pitot tube introduces error when it is operated under the presence of non-axial flows in stacks. In contrast, the three-dimensional (3D) Pitot tubes, which can determine all three-directional velocity components of the flow, are expected to surmount the restriction of the S-type Pitot tube. In this research, the flue gas velocity in the smokestack is measured with the 3D Pitot tubes to investigate the three-dimensional velocity profile and patterns inside the smokestack. The axial and off-axial velocity components of the flue gas in the smokestack are measured with two kinds of 3D Pitot tubes which are prism and spherical 3D Pitot tubes. They are compared with the TMS velocity which is measured with the S-type Pitot tube. The axial velocity components measured by the 3D Pitot tubes are well agreed with the TMS velocities by the S-type Pitot tube, and the velocity distribution and flow patterns inside the smokestack are investigated.

Ping Chen, Mei Chen, Miyue Zhao
Research of large diameter gas flow rate measurement method

To solve the hard problem of large diameter Pitot Pipe flow meter source tracing and parameter obtaining, we propose the similarity principle, which means making one (set) model that has same geometric structure but scaling down of the actual applied flow meter (prototype for short). We calibrate the model with gas flow standard facility, determine the mathematical formula and characteristic parameters of flow calculation, then applied on prototype. Base on DN4000 pipe air flow rate measurement project, we design a differential pressure flow meter based on the principle of Pitot static tubes for prototype. Models of DN1200, DN800 and DN400 are made at the same time. In order to verify the correctness and feasibility of the solution, this project is carried on in two steps. In first step, we make the models of DN600, DN300 and DN150, then test them with gas low standard facility, figure out the relationship of parameter of different diameter. In second step, we test the models of the flow meter actually in used. Base on the two groups of test results, we can find out the parameter of the flow meter actually in used. This essay is a phase summary of step one. The result shows that the Pitot tube flow meter with same geometric structure and similarity ratio is 2, their flow coefficient difference would not be larger than 5 %.

Page 11 of 907 Results 101 - 110 of 9067