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A gas flow unified measurement system (UMS-G) for sequential measurement of gas diffusion and gas permeability of geosynthetic clay liners (GCLs) under applied stress conditions (2 to 20 kPa) is described. Measurements made with the UMS-G are compared with measurements made with conventional experimental devices and are found to give similar results. The UMS-G removes the need to rely on two separate systems and increases further the reliability of the gas properties' measurements. This study also shows that the gas diffusion and gas permeability reduce greatly with the increase of both gravimetric water content and apparent degree of saturation. The effect of applied stress on gas diffusion and gas permeability is found to be more pronounced at gravimetric water content greater than 60%. These findings suggest that at a nominal overburden stress of 20 kPa, the GCL used in the present investigation needs to be hydrated to 134% gravimetric water content (65% apparent degree of saturation) before gas diffusion and gas permeability drop to 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] and 8.0 x [10.sup.-13] m x [s.sup.-1], respectively, and to an even higher gravimetric water content (apparent degrees of saturation) at lower stress. Key words: geosynthetic clay liner, gas flow, diffusion, advection, gravimetric water content. Dans le cadre de cette etude, on decrit un systeme de mesure du flux gazeux unifie (UMS-G) afin de mesurer sequentiellement la diffusion gazeuse et la permeabilite au gaz des membranes geosynthetiques d'etancheite d'argile (GCL) soumises des conditions de contrainte (2 20 kPa). Les mesures prises au moyen de l'UMS-G sont comparees aux mesures obtenues au moyen de dispositifs experimentaux courants et il s'avere que les resultats sont semblables. En utilisant l'UMS-G, il n'est plus necessaire d'avoir deux systemes separes et la fiabilite des mesures des proprietes des gaz augmente davantage. De plus cette etude demontre que la diffusion gazeuse et la permeabilite au gaz diminuent considerablement lorsqu'a la fois la teneur en eau gravimetrique et le degre de saturation apparent augmentent. Lorsque la teneur en eau gravimetrique est superieure 60%, on constate que l'effet de la contrainte appliquee sur la diffusion gazeuse et la permeabilite au gaz est plus prononce. Ces resultats suggerent que sous une surcharge de 20 kPa, la GCL utilisee aux fins de cette investigation doit subir une hydratation jusqu'a une teneur en eau gravimetrique de 134% (degre de saturation apparent de 65%) avant que la diffusion gazeuse et la permeabilite au gaz ne baissent jusqu'a 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] et 8.0 x [10.sup.-13] m x [s.sup.-1], respectivement, et jusqu'a une teneur en eau gravimetrique encore plus elevee (degre de saturation apparent) a des contraintes plus faibles. [Traduit par la Redaction] Mots-cles: membrane geosynthetique d'etancheite d'argile (GCL), flux gazeux, diffusion, advection, teneur en eau gravimetrique., Introduction Evaluation of gas migration is important in engineered cover systems of waste containment facilities to prevent or minimize possible contamination of the environment following their closure due to gas [...]

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted A high-pressure stainless steel rupture tube (internal diameter = 38.1 mm and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33-37 MPa-a and a temperature range of 21-68[degrees]C. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng--Robinson, Soave--Redlich--Kwong, and Groupe Europeen de Recherches Gazieres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7% (conservative) and -11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13% and -20% of the rupture tube predicted values, while PIPEDECOM with a 1[degrees]C temperature delay provides fracture arrest values that are within 0% and -20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case. [DOI: 10.1115/1.4001438] Keywords: gas pipelines, rupture, rich gas, decompression wave speed, GASDECOM, PIPEDECOM, expansion waves, dynamic pressure measurements

The gas-liquid two-phase slug flow regime phenomenon is commonly encountered in the chemical engineering industry, particularly in oil and gas production transportation pipelines. Slug flow regime normally occurs for a range of pipe inclinations, and gas and liquid flowrates. A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flowrates at the outlet. Therefore, the monitoring of slugs and the measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. In this paper, a correlation between gas void fraction, absolute acoustic emission energy, and slug velocities in a two-phase air/water flow regime was developed using an acoustic emission technique. It is demonstrated that the gas void fraction can be determined by measurement of acoustic emission. [DOI: 10.1115/1.4000463] Keywords: acoustic emission, slug flow, gas void fraction, slug velocity, process monitoring

Computational simulations of flow and heat transfer in heat recovery steam generators (HRSGs) of vertical-and horizontal-tube designs are reported. The main objective of the work was to obtain simple modifications of their internal configuration that render the flow of combustion gas more spatially uniform. The computational method was validated by comparing some of the simulation results for a scaled-down laboratory model with experimental measurements in the same. Simulations were then carried out for two plant HRSGs--without and with the proposed modifications. The results show significantly more uniform combustion gas flow in the modified configurations. Heat transfer calculations were performed for one superheater section of the vertical-tube HRSG to determine the effect of the configuration modification on heat transfer from the combustion gas to the steam flowing in the superheater tubes. [DOI: 10.1115/1.2751505]

A preconditioned numerical method for gas-liquid two-phase flows is applied to solve cavitating flow. The present method employs a finite-difference method of the dual time-stepping integration procedure and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The present density-based numerical method permits simple treatment of the whole gas-liquid two-phase flow field, including wave propagation, large density changes and incompressible flow characteristics at low Mach number. Two-dimensional internal flows through a backward-facing step duct, convergent-divergent nozzles and decelerating cascades are computed using this method. Comparisons of predicted and experimental results are provided and discussed. [DOI: 10.1115/1.1777230]

The application of pneumatic metrology to control dimensional accuracy on machined parts is based on the measurement of gas flow resistance through a restricted section formed by a jet orifice placed at a small distance away from a machined surface. The backpressure, which is sensed and indicated by a pressure gauge, is calibrated to measure dimensional variations. It has been found that in some typical industrial applications, the nozzles are subject to fouling, e.g., dirt and oil deposits accumulate on their frontal areas, thus requiring more frequent calibration of the apparatus for reliable service. In this paper, a numerical and experimental analysis of the flow behavior in the region between an injection nozzle and a flat surface is presented. The analysis is based on the steady-state axisymmetric flow of an incompressible fluid. The governing equations, coupled with the appropriate boundary conditions, are solved using the SIMPLER algorithm. Results have shown that for the standard nozzle geometry used in industrial applications, an annular low-pressure separated flow area was found to exist near the frontal surface of the nozzle. The existence of this area is believed to be the cause of the nozzle fouling problem. A study of various alternate nozzle geometries has shown that this low-pressure recirculation area can be eliminated quite readily. Well-designed chamfered, rounded, and reduced frontal area nozzles have all reduced or eliminated the separated recirculation flow area. It has been noted, however, that rounded nozzles may adversely cause a reduction in apparatus sensitivity. [DOI: 10.1115/1.1598991]

A new probe technique is introduced for the measurement of concentration in binary gas flows. The new technique is demonstrated through application of the probe in a Mach 4 nonreacting jet of hydrogen injected into a nominally quiescent air environment. Previous concentration probe devices have mostly used hot wires or hot films within an aspirating probe tip. However, the new technique relies on Pitot pressure and stagnation point transient thin film heat flux probe measurements. The transient thin film heat flux probes are operated at a number of different temperatures and thereby provide stagnation temperature and heat transfer coefficient measurements with an uncertainty of around [+ or -] 5 K and [+ or -] 4% respectively. When the heat transfer coefficient measurements are combined with the Pitot pressure measurements, it is demonstrated that the concentration of hydrogen within the mixing jet can be deduced. The estimated uncertainty of the reported concentration measurements is approximately [+ or -] 5% on a mass fraction basis. [DOI: 10.1115/1.1595671]

Studies of wavy stratified and stratified/atomization two-phase flow in horizontal pipes are outlined. Notable features of this flow regime include the appearance of disturbance waves, the atomization onset and the drastic change of the gas/liquid interface profile from flat to 'concave.' Liquid-to-wall shear stress tends to decrease circumferentially. A computational procedure for predicting main flow characteristics, which takes into account the above results in its design relations, is first assessed with detailed experimental data and is then combined with a CFD code, aiming at enhancing the predictive capability. [DOI: 10.1115/1.1576265] Keywords: Gas/Liquid Flow, Stratified Flow, Horizontal Pipes, Liquid Holdup, Pressure Drop, Shear Stress, Computational Method.

The mechanistic model of Taitel and Dukler [1] has previously been reported to exhibit a region in which three solutions exist for the height of the gas-liquid interface in the stratified/wave flow regime. Most laboratory studies have not dealt with flow rates in the ranges where the multiple solutions occur. An experimental study has been carried out at the University of Calgary to obtain such data. The object of this work is to review the relevant theory, investigate situations where theory suggests that multiple solutions should exist, and attempt to show whether or not such solutions do physically exist. [DOI: 10.1115/1.1521710]

Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness. [DOI: 10.1115/1.1576264] Keywords: Friction Factor, Turbulent Flow, Wall Roughness, Pressure Drop, Natural Gas

An experimental procedure was developed for determining both the density and flow rate of a gas from measurements of pressure drops caused by an abrupt flow area contraction in a cylindrical pipe. Experiments were carried out by varying the density and flow rate of a light gas mixture of air and helium, spanning a Reynolds number range from 0.2 x [10.sup.4] to 3.4 x [10.sup.4]. From experimental results, a procedure was then proposed for evaluating the density from pressure change measurements in the scope of light gas extraction experiments. [DOI: 10.1115/1.2953294]

The thrust measurement of a miniature electrothermal thruster is conducted by using microwave-excited microplasmas. The results have shown that the pressure thrust has contributed to the total thrust at low gas flow rates and that the micronozzles have an isothermal wall rather than an adiabatic.

Images show how an ionization cloud forms at the needle electrode, how the cloud evolves into a shell, and how one or more streamers emerge from this shell and propagate. Index Terms--Gas discharges, pulsed corona, streamer inception, streamer propagation.

The high-voltage (HV) nanosecond discharge in wide pressure range develops in the form of the streamer discharge. Intensified charge-coupling device images of the discharge development and propagation in pure air are presented. For cathode-directed streamer, the area of streamer branching is obtained as well as dependence between branching intensity and discharge parameters. The streamer structure has been measured when the streamer was initiated by a long HV pulse. Index Terms--Branching, nanosecond pulsed discharge, streamer.

A direct simulation Monte Carlo method (DSMC) solver, adapted to the subsonic microflow, is developed under the object-conception language (c++). Some technical details critical in these DSMC computations are provided. The numerical simulations of gas flow in a microchannel are carried out using the developed DSMC solver. Streamwise velocity distributions in the slip flow regime are compared with the analytical solution based on the Navier-Stokes equations with the velocity slip boundary condition. Satisfactory agreements have been achieved. Furthermore, the domain of the validity of this continuum approach is discussed. Simulations are then extended to the transitional flow regime. Streamwise velocity distributions are also compared with the results of the numerical solutions of the linearized Boltzmann equation. We emphasize the influence of the accommodation coefficient on the velocity profiles and on the mass flow rate. The simulation results on the mass flow rate are compared with the experimental data, which allow us to validate the 'experimental' technique of the determination of the accommodation coefficient. [DOI: 10.1115/1.3026733]

Researchers have figured out a new way to accelerate crude oil flow using electric and magnetic pulses, which could help harvest crude oil buried in fields deep below the seafloor. The new method d is based on the simple concept of sending a magnetic or electric pulse through the pipeline and into the oil that causes the wax-like molecules in the crude oil to cluster together into a smaller number of large particles, which makes it flow more easily.