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NATURAL CONVECTIONIN SHALLOW ENCLOSURES WITH DIFFERENTIALLY HEATED END WALLS AND NONADIABATIC HORIZONTAL WALLS

Description: Numerical studies of laminar natural convection at high Ra numbers in shallow enclosures are reported. In these studies the working fluid is allowed to interact with the horizontal walls. It is shown that even a small amount of heat loss from these walls can lead to a flow structure qualitatively different from the more commonly studied situation where the horizontal walls are adiabatic. This is particularly important in applications where the mass transfer and flow structure are of interest. The results highlight the difficulty in practice of both approximating the adiabatic horizontal wall condition, and interpreting experimental data.
Date: May 1, 1983
Creator: Gadgil, A. & Shiralkar, G.
Partner: UNT Libraries Government Documents Department

Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey

Description: Matrix diffusion is an important mechanism for solutetransport in fractured rock. We recently conducted a literature survey onthe effective matrix diffusion coefficient, Dem, a key parameter fordescribing matrix diffusion processes at the field scale. Forty fieldtracer tests at 15 fractured geologic sites were surveyed and selectedfor study, based on data availability and quality. Field-scale Dem valueswere calculated, either directly using data reported in the literature orby reanalyzing the corresponding field tracer tests. Surveyed dataindicate that the effective-matrix-diffusion-coefficient factor FD(defined as the ratio of Dem to the lab-scale matrix diffusioncoefficient [Dem]of the same tracer) is generally larger than one,indicating that the effective matrix diffusion coefficient in the fieldis comparatively larger than the matrix diffusion coefficient at therock-core scale. This larger value could be attributed to the manymass-transfer processes at different scales in naturally heterogeneous,fractured rock systems. Furthermore, we observed a moderate trend towardsystematic increase in the emDFmDDF value with observation scale,indicating that the effective matrix diffusion coefficient is likely tobe statistically scale dependent. The FD value ranges from 1 to 10,000for observation scales from 5 to 2,000 m. At a given scale, the FD valuevaries by two orders of magnitude, reflecting the influence of differingdegrees of fractured rock heterogeneity at different sites. In addition,the surveyed data indicate that field-scale longitudinal dispersivitygenerally increases with observation scale, which is consistent withprevious studies. The scale-dependent field-scale matrix diffusioncoefficient (and dispersivity) may have significant implications forassessing long-term, large-scale radionuclide and contaminant transportevents in fractured rock, both for nuclear waste disposal and contaminantremediation.
Date: March 28, 2005
Creator: Zhou, Quanlin; Liu, Hui Hai; Molz, Fred J.; Zhang, Yingqi & Bodvarsson, Gudmundur S.
Partner: UNT Libraries Government Documents Department

MASS TRANSFER TO ROTATING DISKS AND ROTATING RINGS IN LAMINAR, TRANSITION, AND FULLY DEVELOPED TURBULENT FLOW

Description: Experimental data and theoretical calculations are presented for the mass-transfer rate to rotating disks and rotating rings when laminar, transition, and fully developed turbulent flow exist upon different portions of the surface. Good agreement of data and the model is obtained for rotating disks and relatively thick rotating rings. Results of the calculations for thin rings generally exceed the experimental data measured in transition and turbulent flow. A y{sup +{sup 3}} form for the eddy diffusivity is used to fit the data. No improvement is noticed with a form involving both y{sup +{sup 3}} and y{sup +{sup 3}}.
Date: July 1, 1980
Creator: Law Jr., C.G.; Pierini, P. & Newman, J.
Partner: UNT Libraries Government Documents Department

Tracer Tests in a Fractured Dolomite: 4. Double Porosity, Multiple-Rate Mass Transfer Processes in Two-Well Convergent Flow Tests

Description: Two-well convergent-flow tracer tests conducted in the Culebra dolomite (Rustler Formation, New Mexico, USA) are analyzed with both single-and multiple-rate, double-porosity models. Parameter estimation is used to determine the mean and standard deviation of a Iog- normal distribution of diffision rate coefficients as well as the advective porosity and longitudinal dispersivity. At two different test sites, both mukirate and single-rate models are capable of accurately modeling the observed data. Estimated model parameters are tested against breakthrough curves obtained along the same transport pathway at a different pumping rate. Implications of the rnultirate mass-transfer model at time and length scales greater than those of the tracer tests include the instantaneous saturation of a fraction of the matrix ~d the possibility of a fraction of the matrix remaining unsaturated at long times.
Date: March 4, 1999
Creator: Haggerty, R.; McKenna, S.A. & Meigs, L.C.
Partner: UNT Libraries Government Documents Department

Gas-Liquid Mass Transfer in Agitated Tanks Containing Non-Newtonian Fluids

Description: The purpose of the tests was to investigate the effects of operating parameters, such as KTPB concentration, time, sodium molarity, temperature, salt composition, sludge concentration, and radiation dose, on benzene retention and release. This paper describes the results of the tests.
Date: November 6, 1998
Creator: Poirier, M.R.
Partner: UNT Libraries Government Documents Department

Investigation of Pore Scale Processes That Affect Soil Vapor Extraction

Description: Dense nonaqueous phase liquid (DNAPL) contamination in the vadose zone is a significant problem at Department of Energy sites. Soil vapor extraction (SVE) is commonly used to remediate DNAPLs from the vadose zone. In most cases, a period of high recovery has been followed by a sustained period of low recovery. This behavior has been attributed to multiple processes including slow interphase mass transfer, retarded vapor phase transport, and diffusion from unswept zones of low permeability.
Date: June 1, 2002
Creator: Valocchi, Albert J.; Werth, Charles J. & Webb, Andrew G.
Partner: UNT Libraries Government Documents Department

Test Plan for Solvent Extraction Data Acquisition to Support Modeling Efforts

Description: This testing will support NEAMS SafeSep Modeling efforts related to droplet simulation in liquid-liquid extraction equipment. Physical characteristic determinations will be completed for the fluids being used in the experiment including viscosity, density, surface tension, distribution coefficients, and diffusion coefficients. Then, experiments will be carried out to provide data for comparison to the simulation’s calculation of mass transfer coefficients. Experiments will be conducted with solutions used in the TRansUranic EXtraction (TRUEX) process extraction section. The TRUEX process was chosen since it is one solvent extraction system currently proposed for the separation of actinides and lanthanides from used nuclear fuel, it is diffusion limited, testing can be performed using non radioactive lanthanides to evaluate mass transfer. The extraction section involves transfer of one or more lanthanide species from an aqueous solution to an organic solvent. Single droplets rising by buoyancy will be studied first. Droplet size and number of species transferred will be varied independently to provide mass transfer coefficients as a function of each variable. An apparatus has been designed specifically for these experiments. In order to get more accurate measurements of droplet size, contact time, time of droplet formation, and possibly droplet breakup and coalescence, a high speed camera will be utilized for these experiments. Other potential experiments include examining the effects of jetted droplets and shear flow on the mass transfer coefficients.
Date: December 1, 2010
Creator: Rutledge, Veronica; Christensen, Kristi; Garn, Troy & Law, Jack
Partner: UNT Libraries Government Documents Department

Measurement and modeling of energetic material mass transfer to soil pore water :project CP-1227 FY03 annual technical report.

Description: Military test and training ranges operate with live fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low order detonations also disperse solid phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g., weather and geostratigraphy) contribute to groundwater pollution impacts. This report documents interim results of experimental work evaluating mass transfer processes from solid phase energetics to soil pore water. The experimental work is used as a basis to formulate a mass transfer numerical model, which has been incorporated into the porous media simulation code T2TNT. This report documents the results of the Phase III experimental effort, which evaluated the impacts of surface deposits versus buried deposits, energetic material particle size, and low order detonation debris. Next year, the energetic material mass transfer model will be refined and a 2-d screening model will be developed for initial site-specific applications. A technology development roadmap was created to show how specific R&D efforts are linked to technology and products for key customers.
Date: January 1, 2004
Creator: Phelan, James M.; Barnett, James L. & Kerr, Dayle R.
Partner: UNT Libraries Government Documents Department

Mass Transfer Testing of a 12.5-cm Rotor Centrifugal Contactor

Description: TRUEX mass transfer tests were performed using a single stage commercially available 12.5 cm centrifugal contactor and stable cerium (Ce) and europium (Eu). Test conditions included throughputs ranging from 2.5 to 15 Lpm and rotor speeds of 1750 and 2250 rpm. Ce and Eu extraction forward distribution coefficients ranged from 13 to 19. The first and second stage strip back distributions were 0.5 to 1.4 and .002 to .004, respectively, throughout the dynamic test conditions studied. Visual carryover of aqueous entrainment in all organic phase samples was estimated at < 0.1 % and organic carryover into all aqueous phase samples was about ten times less. Mass transfer efficiencies of = 98 % for both Ce and Eu in the extraction section were obtained over the entire range of test conditions. The first strip stage mass transfer efficiencies ranged from 75 to 93% trending higher with increasing throughput. Second stage mass transfer was greater than 99% in all cases. Increasing the rotor speed from 1750 to 2250 rpm had no significant effect on efficiency for all throughputs tested.
Date: September 1, 2008
Creator: Meikrantz, D. H.; Garn, T. G.; Law, J. D.; Mann, N. R. & Todd, T. A.
Partner: UNT Libraries Government Documents Department

Final Report - Advanced Hydraulic and Mass Transfer Models for Distillation Column Optimization and Design

Description: The project successfully developed a computational fluid dynamics (CFD) based simulation of the hydrodynamics of flow in a commercial structured packing element. This result fulfilled the prime objective of the research program. The simulation utilized commercial CFD code marketed by Fluent Inc. in combination with a novel graphical interface developed by Oak Ridge National Lab. The end product will allow the design of next generation column internals without the need for extensive experimental validation and will expand the fundamental understanding of the vapor-liquid contacting process.
Date: October 13, 2005
Creator: Eldridge, Robert, B.
Partner: UNT Libraries Government Documents Department

Estimating Heat and Mass Transfer Processes in Green Roof Systems: Current Modeling Capabilities and Limitations (Presentation)

Description: This presentation discusses estimating heat and mass transfer processes in green roof systems: current modeling capabilities and limitations. Green roofs are 'specialized roofing systems that support vegetation growth on rooftops.'
Date: April 1, 2011
Creator: Tabares Velasco, P. C.
Partner: UNT Libraries Government Documents Department

NUMERICAL CALCULATIONS FOR THE ASYMPTOTIC, DIFFUSION DOMINATED MASS-TRANSFER COEFFICIENT IN PACKED BED REACTORS

Description: For deep beds, the effective Sherwood number approaches a proportional relationship to the Peclet number as the Peclet number tends to zero. A sinusoidal periodically constricted tube model for the voids in the bed has been used to predict the constant of proportionality. This constant depends upon the dimensionless ratios of three lengths: the average tube radius, the oscillation amplitude, and wavelength.
Date: November 1, 1977
Creator: Fedkiw, Peter & Newman, John
Partner: UNT Libraries Government Documents Department

HIERARCHICAL METHODOLOGY FOR MODELING HYDROGEN STORAGE SYSTEMS PART II: DETAILED MODELS

Description: There is significant interest in hydrogen storage systems that employ a media which either adsorbs, absorbs or reacts with hydrogen in a nearly reversible manner. In any media based storage system the rate of hydrogen uptake and the system capacity is governed by a number of complex, coupled physical processes. To design and evaluate such storage systems, a comprehensive methodology was developed, consisting of a hierarchical sequence of models that range from scoping calculations to numerical models that couple reaction kinetics with heat and mass transfer for both the hydrogen charging and discharging phases. The scoping models were presented in Part I [1] of this two part series of papers. This paper describes a detailed numerical model that integrates the phenomena occurring when hydrogen is charged and discharged. A specific application of the methodology is made to a system using NaAlH{sub 4} as the storage media.
Date: December 22, 2008
Creator: Hardy, B & Donald L. Anton, D
Partner: UNT Libraries Government Documents Department

SOIL VAPOR EXTRACTION SYSTEM DESIGN: A CASE STUDY COMPARING VACUUM AND POREGAS VELOCITY CUTOFF CRITERIA

Description: Soil vapor extraction (SVE) systems are typically designed based on the results of a vadose zone pumping test (transient or steady state) using a pressure criteria to establish the zone of influence (ZOI). A common problem associated with pressure based SVE design is overestimating the ZOI of the extraction well. The vacuum criteria commonly used to establish the boundary of the ZOI results in large areas with very low pore velocities and thus long cleanup times. As a result, design strategies based upon critical pore gas velocity (CPGV) have increased in popularity. The CPGV is used in an effort to loosely incorporate the effects of mass transfer limitations into the design of SVE systems. Critical pore gas velocity designs use a minimum pore gas velocity rather than minimum vacuum to identify the extent of the treatment zone of an SVE system. The CPGV is typically much larger than the pore gas velocity at the perimeter of vacuum based (ZOI) designs resulting in shorter cleanup times. In this paper, we report the results of testing performed at the Savannah River Site (SRS) to determine the influence of a vapor extraction well based upon both a pressure and pore gas velocity design criteria. Results from this testing show that a SVE system designed based upon a CPGV is more robust and will have shorter cleanup times due to increased flow throughout the treatment zone. Pressure based SVE design may be appropriate in applications where soil gas containment is the primary objective; however, in cases where the capture and removal of contaminated soil gas is the primary objective, CPGV is a better design criteria.
Date: July 24, 2006
Creator: Dixon, K & Ralph Nichols, R
Partner: UNT Libraries Government Documents Department