A gaseous diffusion column was designed, constructed, and its operation tested with a system of electrolytic hydrogen and carbon dioxide. The column contained one diffusion unit with two 6-inch diameter barrier areas. In the preliminary tests the flow rates of the hydrogen-carbon dioxide mixture were varied from 0 to 15 cubic feet per hour. Vacuum on the system was varied from 0 to 25 inches of mercury. Composition of the feed mixture was held constant at 50 mol per cent hydrogen and 50 mol per cent carbon dioxide. Temperature of the system varied with the surroundings from 75 to 85 °F. Barrier materials were of 0.008 inch thick fiber glass called Dexiglas mat obtained from Dexter and Sons, and 0.018-inch thick fiber glass Ultra Efficient Filter media mat obtained from Mine Safety Appliance Company. It was found that the hydrogen permeated at a rate greater than could be explained by diffusion alone, but which could be closely accounted for when adsorption and adsorbed flow were taken into account. The separation of a system of carbon dioxide and hydrogen by means of a fiber glass barrier could be adequately represented as a combination of gaseous diffusion and of adsorbed flow. Agreement of observed values was within five per cent with an estimate of gaseous diffusion using Weller and Steiner's equation plus a value for adsorbed flow from a modified version of Russell's equation. The separation of hydrogen from carbon dioxide in the equipment as constructed increased as the pressure increased from 10 to 20 inches of mercury for flow rates of one to ten cubic feet per hour for the gaseous mixture which is contrary to that predicted by pure gaseous diffusion. A permeability apparatus was constructed and operated with a system of .carbon dioxide and hydrogen. Composition of the feed mixture was either pure electrolytic hydrogen, pure carbon dioxide, or a mixture of 50 mol per cent hydrogen and 50 mol per cent carbon dioxide. Temperature of the system varied with the surroundings from 25 to 28 °C. Barrier materials of 0.008-inch thick fiber glass called Dexiglas obtained from Dexter and Sons, 0.001-inch thick polystyrene from Dow Chemical Company, 0.001-inch thick cellulose acetate supplied by Celanese Corporation, and silicone rubber obtained from General Electric Company, Silicone Division, were used in this investigation. The permeation of hydrogen and carbon dioxide checked previous work⁽⁶⁹⁾ which listed these barriers as having selective permeability to the gases used. The permeation of a mixture of carbon dioxide and hydrogen is in direct relationship with the adsorption of that mixture onto a powdered sample of the barrier material. / Ph. D.

The transient effects of the breakup and atomization of liquid jets in a crossflow on the size of droplets within the spray plume was experimentally determined. Water and water/methanol mixtures were injected normal to a high velocity air stream at Mach numbers of 0.48 and 3.0 with ambient stagnation temperature and respective stagnation pressures of 1.4 and 4.3 atm. The liquids were injected at liquid-to-gas momentum flux ratios ranging from 4 to 12. Droplet size distributions were obtained using a Fraunhofer diffraction technique at sampling rates of up to 9 kHz. Liquid mass flow rates were inferred from measurements of the extinction of a laser beam traversing the plume. The droplet sizes were found to fluctuate with frequencies of the order of 1 to 10 kHz. The fluctuations were characterized by a sudden and relatively brief increase in the mean diameter of the droplets caused by the passage of fractured clumps through the spray plume. Also evident in the droplet size distributions was the very small size of the droplets that had been sheared off the windward surfaces of the jet. The jet fracture frequency was related to the frequency of waves propagating along the initial jet column. The column waves are postulated to have been caused by jet perturbations created by vortices in the air flow around the jet column. / Ph. D.

Creation of vacuum is very slow, energetically and technologicaly demanding process. Closing of valve is very simple and fast process which produces pressure surges when moving cylinder of fluid is stopped. The goal of this thesis is to find out, if it is possible to combine these processes. To reach this goal, 1D model of compressible gas flow and pressure surges in direct pipeline was made. Then follows experimental measurement evaluation and assessment of potential that the technology offers.

The subject of the diploma thesis is research of the testing process exhaust clamps. There is a description of a testing device designed to provide simulations of the real operating conditions on an exhaust assembly. The testing device is named the Hot Gas Test Bench. The thesis solves the optimization process of the test setup by determining the optimal fuel ratio, which is given by air flow as oxidizer and flow of natural gas as fuel. The input parameters which provide flow of mentioned fluids are speeds of blowers. In diploma thesis is created a design of initialization and control process to ensure the optional combustion ratio during the entire length of the test.

A medical ventilator is a life-sustaining device that helps critically ill patients with complete or partial breathing support. It provides a patient with the right amount of air and/or oxygen as per requirement. It is therefore essential to have a highly accurate device controlling the flow of these essential gases. In ventilators developed by Maquet, an electro-mechanical device called Gas-Module is used for gas flow control. The Gas-Module is the heart of the ventilator since it is responsible for providing the patient with the right amount of gas at the right time. The focus of this thesis is on improving the accuracy of the gas flow control in these Gas-Modules. This is done through identifying various factors that influence the accuracy of gas flow control, and then finding an efficient method to calibrate the Gas-Modules. Calibration of a Gas-Module is done by tuning values of components in the analog electronic circuit. In this thesis, an electrical model of the circuit is built to simulate various modes of operation. A new trimming method is proposed that with a few measurements, and a simulation model, can be predict the optimal calibration parameters. This method helps to improve accuracy at various flow rates. Predicting the calibration parameters in advance avoids many iteration cycles of measure-adjust-measure which would otherwise be required to calibrate the Gas-Module. The new trimming method proposed in this thesis also has the potential to save calibration time of each Gas-Module and thus save production cost. / Medicinsk ventilator är en livsupphållande apparat som hjälper kritiska sjuka patienter med helt eller partiellt andningsstöd. Den förser en patient med rätt mängd luft eller syre efter individuellt behov. Det är därför viktigt att ha en mycket noggranna anordning som styr flödet av dessa viktiga gaser. I ventilatorer från Maquet görs detta med hjälp av gasmoduler som är en elektromekanisk enhet som styr flödet. Denna modul kallas också hjärtat i en ventilatorn eftersom den ansvarar för tillförseln av rätt mängd gas vid rätt tidpunkt. Arbetet som beskrivs i denna avhandling fokuseras på att förbättra noggrannhet för gasflödeskontroll i dessa gasmoduler. Detta görs genom att identifiera olika faktorer som påverkar flödeskontrollens noggrannhet och sedan hitta en effektiv metod för kalibrering av gasmodulerna. Kalibrering av gasmodul görs genom att justera värdet på elektriska komponenter i kontroll kretsen. I denna avhandling buggdes upp en elektrisk modell av kretsen för att simulera olika driftfall. En ny trimmningsmetod föreslås att med hjälp av ett fåtal mätningar och en funktions modell kan de mest optimala kalibrerings parametrarna prediceras. Denna metod hjälper till att förbättra noggrannheten vid olika flödesbehov.Att förutsäga kalibreringsparametrarna i förväg undviker många mätjusteringscykler som annars skulle krävas för att kalibrera en gasmodul. Med denna nya metod reduceras caliberingstid för varje gasmodul vilket kan bidra till minskade produktions kostnader.

A gas-diffusion tracer experiment was conducted at the ChemNuclear, Inc., nuclear waste burial site near Barnwell, South Carolina, on June 1-10; 1981, testing a new methodology to measure the in situ gaseous diffusion characteristics of unsaturated porous media for the purpose of estimating the diffusive flux of volatile contaminants from the burial ground. The tracers used were CClBrF₂ and SF₆. They were released in the subsurface from permeation devices that closely approximate an ideal point-diffusion source. The permeation devices contain the tracer in liquid form and allow the tracer to escape at a constant rate by diffusion through a Teflon membrane. The release rates for CClBrF₂ and SF6 during the test were 105 and 3.3 nanograms/second, respectively. These compounds were selected on the basis of their compatabi1ity with the permeation-release device, their absence in the subsurface, and detectability in the part-per-tri11ion range in soil gas. Analyses were made in the field on a Varian 3700 series gas chromatograph equipped with an electron-capture detector. The instrument was modified to introduce soil gas through sampling valves and a Nafion tube desiccant. The diffusion sources were placed in the unsaturated soil at depths of 2 meters and 13 meters below land surface. Diffusive movements of tracer were monitored for a period of 7 days and tracer breakthrough was observed at points up to 3.5 meters away. Diffusion was modeled using a three-dimensional, continuous point source, transient-state, analytical model which allowed estimation of the effective diffusion coefficient of the porous media, and an independent assessment of the media's sorptive effects on the tracer gas. The model was calibrated using least squares and curve matching techniques, the latter of which enables a field technician to quickly interpret observed field data. Field values obtained for effective diffusion coefficient ranged from 0.026 to 0.037 cm²/sec. The average tortuosity factor observed for test site was 0.705.

The focus of this work is to present in detail the implementation of a three dimensional direct simulation Monte Carlo methodology on unstructured Delaunay meshes (U-DSMC). The validation and verification of the implementation are shown using a series of fundamental flow cases. The numerical error associated with the implementation is also studied using a fundamental flow configuration. Gas expansion from microtubes is studied using the U-DSMC code for tube diameters ranging from 100Æ’ÃÂ�m down to 100nm. Simulations are carried out for a range of inlet Knudsen numbers and the effect of aspect ratio and inlet Reynolds number on the plume structure is investigated. The effect of scaling the geometry is also examined. Gas expansion from a conical nozzle is studied using the U-DSMC code for throat diameters ranging from 250 Æ’ÃÂ�m down to 250 nm. Simulations are carried out for a range of inlet Knudsen numbers and the effect of inlet speed ratio and inlet Reynolds number on the plume structure is investigated. The effect of scaling the geometry is examined. Results of a numerical study using the U-DSMC code are employed to guide the design of a micropitot probe intended for use in analyzing rarefied gaseous microjet flow. The flow conditions considered correspond to anticipated experimental test cases for a probe that is currently under development. The expansion of nitrogen from an orifice with a diameter of 100Æ’ÃÂ�m is modeled using U-DSMC. From these results, local ¡¥free stream¡¦ conditions are obtained for use in U-DSMC simulations of the flow in the vicinity of the micropitot probe. Predictions of the pressure within the probe are made for a number of locations in the orifice plume. The predictions from the U-DSMC simulations are used for evaluating the geometrical design of the probe as well as aiding in pressure sensor selection. The effect of scale on the statistical fluctuation of the U-DSMC data is studied using Poiseuille flow. The error in the predicted velocity profile is calculated with respect to both first and second-order slip formulations. Simulations are carried out for a range of channel heights and the error between the U-DSMC predictions and theory are calculated for each case. From this error, a functional dependence is shown between the scale-induced statistical fluctuations and the decreasing channel height.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO. / Includes bibliographical references. / by Yoshiaki Kuwano. / M.S.

A methodology to measure in-plane permeability of fibrous media using a transient one dimensional air flow is developed. The method, based on the measurement of gas pressure at the boundaries throughout the transient flow, is convenient, clean and fast, avoids usage of a gas flow meter and offers a way to study the gas transport within fibrous media. The gas transport through fibrous porous media is described by several models to comply with different flow regimes. The permeability, only depending on the fibrous structure, is determined by inverse method, fitting the simulation results to the experimental data obtained using rising or dropping pressure methods. The results of viscous permeability Kv of Glass/Carbon Twill Woven fabrics (viscous permeability Kv ranging from 10-11 to 10-10 m2) measured using gas match well the permeability measured with liquid compression and injection techniques from previous works. The deviation from Darcy's law caused by gas sliding effect on low permeability Carbon Uni-Directional fabrics (Kv from 10-14 to 10-12 m2) is analyzed and a related parameter of fabric material shows a dependence in permeability, with a similar trend as the Klinkenberg sliding parameter in soils and rocks.The experimental errors due to dimensions, thermal effect, pressure variation, sample handling, and trapped gas at boundaries are analyzed. It comes out that the sensitivities of pressure sensors and trapped gas volumes at the boundaries have the most important effects. A design for 2D measurement using gas to obtain 2D permeability tensor in one single test is proposed to avoid the issues of trapped gas at boundaries. Simulated experiments show that the measurements based on pressure measured at three proposed locations could provide robust and accurate results for fabrics of anisotropic permeability ratios (K1/K2) ranging from 0.1 to 10, with various principal permeability direction orientations.

The accurate description of fluid flow through porous media allows an engineer to properly analyze past behavior and predict future reservoir performance. In particular, appropriate mathematical models which describe fluid flow through porous media can be applied to well test and production data analysis. Such applications result in estimating important reservoir properties such as formation permeability, skin-factor, reservoir size, etc. "Real gas" flow problems (i.e., problems where the gas properties are specifically taken as implicit functions of pressure, temperature, and composition) are particularly challenging because the diffusivity equation for the "real gas" flow case is strongly non-linear. Whereas different methods exist which allow us to approximate the solution of the real gas diffusivity equation, all of these approximate methods have limitations. Whether in terms of limited applicability (say a specific pressure range), or due to the relative complexity (e.g., iterative character of the solution), each of the existing approximate solutions does have disadvantages. The purpose of this work is to provide a solution mechanism for the case of timedependent real gas flow which contains as few "limitations" as possible. In this work, we provide an approach which combines the so-called average pressure approximation, a convolution for the right-hand-side non-linearity, and the Laplace transformation (original concept was put forth by Mireles and Blasingame). Mireles and Blasingame used a similar scheme to solve the real gas flow problem conditioned by the constant rate inner boundary condition. In this work we provide solution schemes to solve the constant pressure inner boundary condition problem. Our new semi-analytical solution was developed and implemented in the form of a direct (non-iterative) numerical procedure and successfully verified against numerical simulation. Our work shows that while the validity of this approach does have its own assumptions (in particular, referencing the right-hand-side non-linearity to average reservoir pressure (similar to Mireles and Blasingame)), these assumptions are proved to be much less restrictive than those required by existing methods of solution for this problem. We believe that the accuracy of the proposed solution makes ituniversally applicable for gas reservoir engineering. This suggestion is based on the fact that no pseudotime formulation is used. We note that there are pseudotime implementations for this problem, but we also note that pseudotime requires a priori knowledge of the pressure distribution in the reservoir or iteration on gas-in-place. Our new approach has no such restrictions. In order to determine limits of validity of the proposed approach (i.e., the limitations imposed by the underlining assumptions), we discuss the nature of the average pressure approximation (which is the basis for this work). And, in order to prove the universal applicability of this approach, we have also applied this methodology to resolve the time-dependent inner boundary condition for real gas flow in reservoirs.