Papers by Keyword: Tracer

Abstract: Influence on the transient casting of large inclusions in steel were studied by means of tracer method, kinds of steel large inclusions content in transient casting is 1.5 times ~8 times to the steady casting, large inclusions principal from crystallizer mold powder entrapment, then the tundish slag and the ladle slag. Slag and refractory has a certain influence on high quality steel. Reducing fluctuations caused by transient casting is the key to improve the quality of the steel.

Abstract: In order to further research in porous media tracer mass transfer diffusion rule based on experiment, the conventional displacement experiment of natural long cores were carried out and the effect of the heterogeneity of microscopic pores structure to tracer mass transfer diffusion was compared. The experiment results show that, when injection rate is close, because the heterogeneity of low permeability core pore structure is stronger and small-scale dash is existed, the output time will be earlier, concentration will rise slowly, and mixed coefficient will be bigger. In terms of the same permeability, because injection rate is low, the pressure difference of two ends is small, the start of porosity is wider and its quantity is less. Therefore, if inject less pore volume of multiples displacement fluid, the output will be present tracer, the pore network of so-called "channeling the effect" will be formed, and mixed constant will be bigger. In homogeneous core, when permeability is close, due to the injection rate increases which exacerbate the actually existed part of microscopic heterogeneity features of the internal core, the output time will be earlier, concentration will rise slowly.

Abstract: This paper introduces a prototype multiphase flow metering system, named Uletech, for multiphase flow measurement. The Uletech Multiphase Flow Meter (UMFM) is based on the combination of particle recognition and the use of Laser Imaging Technology in the form of Particle Imaging Velocimetry (PIV). PIV uses tracer particles which follow the gas or liquid phase. The high resolution digital laser cameras identify/recognize all the different sizes of particle (gas, oil and water) in a multiphase flow. The cameras have sufficiently high resolutions (pixel size) to "see" the tracer particles. The prevailing conditions of high pressure and temperature of the flow regimes makes actual measurement a great challenge. The velocity differences between phases (hold up and slip) means unless the velocities of individual phases and concentrations are known, the true flow rate is practically impossible to obtain. The system comprised of two cameras, laser source, optical arrangement, computer data acquisition system, synchronizer and MATLAB based software. An algorithm that correlates the cameras view to the volume within the pipe has been developed through this research. The computer acquires image signals from the upstream and/or downstream cameras, and carries out the calculation of cross correlation between the two image frames so that the velocity of each pixel can be found. A Gas Liquid Chromatograph (GLC) provides the composition (concentration) of the gas and the liquid hydrocarbon (HC). The product of phase velocity and phase concentration provides the flow rate of the individual phase. This work provides theoretical analysis and experimental validations, and discusses the advantages of the system and its further development.

Abstract: The hydraulic characteristics of constructed wetland are vital to its performance for pollutant removal. Hydraulic characteristics of a pilot scale vertical flow constructed wetland were studied by tracer experiments with the method of moments (MoM) analyzing. From the residence-time distribution (RTD) of tracer during the experiment, the mean detention time, average water velocity and dispersion coefficients were obtained for the constructed wetland. The results showed that the mean residence time was approximately 15% shorter than nominal residence time indicating 85% of total available pore volume was active in pollutant removal processes. The two peaks observed on the RTD curves suggested short-circuiting flows or dead zones exist in the constructed wetland. The relatively large Peclet number of 11.8 suggested that dispersive processes dominated in the tracer movement. Comparison of tracer profiles at different sampling locations indicated that large amount of tracer transported through the upper portion of the constructed wetland.

Abstract: Oxidation mechanism of Alloy 690 has been investigated in Pressurised Water Reactor (PWR) primary coolant conditions (325°C, aqueous hydrogenated media). Experiments performed with gold marker and RBS technique reveal that the passive film formation is the consequence of an anionic mechanism. This result is confirmed by experiments achieved with two sequences of corrosion in a H2 16O media and in a mixed H2 16O/ H2 18O media. The localisation of 18O by SIMS analysis in the thin passive layer underlines an oxidation mechanism due to oxygen diffusion by short circuits (like grain boundaries) in the oxide scale. Moreover grain boundary diffusion coefficient in chromite like oxide was estimated to be in the range 2 10-18 – 1 10-17 cm2.s-1 and compared to values extrapolated from higher temperature.