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Articles 721 - 750 of 757

Full-Text Articles in Chemical Engineering

Nitrogen Transformations In Coal During Pyrolysis, Simon R. Kelemen, Martin L. Gorbaty, P J. Kwiatek, Thomas H. Fletcher, Mathew Watt, Mark S. Solum, Ronald J. Pugmire Jan 1998

Nitrogen Transformations In Coal During Pyrolysis, Simon R. Kelemen, Martin L. Gorbaty, P J. Kwiatek, Thomas H. Fletcher, Mathew Watt, Mark S. Solum, Ronald J. Pugmire

Faculty Publications

X-ray photoelectron spectroscopy (XPS) was used to identify and quantify the changes in organically bound nitrogen forms present in the tars and chars of coals after pyrolysis. For fresh coal, pyrrolic nitrogen is the most abundant form of organically bound nitrogen, followed by pyridinic, quaternary, and amino types. Some of the quaternary nitrogen species initially present in coal are lost upon mild pyrolysis, prior to hydrocarbon devolatilization. These quaternary species are attributed to pyridinic or basic nitrogen species associated with hydroxyl groups from carboxylic acids or phenols. A portion of the quaternary nitrogen species is lost at the very earliest …

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Predicting The Viscosity Of Alkanes Using Nonequilibrium Molecular Dynamics: Evaluation Of Intermolecular Potential Models, Richard L. Rowley, William Allen Jun 1997

Predicting The Viscosity Of Alkanes Using Nonequilibrium Molecular Dynamics: Evaluation Of Intermolecular Potential Models, Richard L. Rowley, William Allen

Faculty Publications

Nonequilibrium molecular dynamics (NEMD) viscosity simulations of branched and linear alkanes at liquid densities were performed using both united-atom (UA) and all-atom (AA) intermolecular potential models in order to study the relative efficacy of the models in predicting fluid viscosity. Both models were used in conjunction with fixed bond lengths and bond angles, but different torsional potentials were investigated. The commonly used Ryckaert—Bellemans intermolecular potential model, which accurately predicts viscosities for short straight-chain alkanes, produced values for branched and long-chain alkanes that were significantly below experimental values. Likewise, a more complex UA model that uses transferrable site potentials and is …

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Effects Of Monomer Structure Ontheir Organization And Polymerizationin A Smectic Liquid Crystal, C. Allan Guymon, Erik N. Hoggan, Noal A. Clark, Thomas P. Rieker, David M. Walba, Christopher N. Bowman Jan 1997

Effects Of Monomer Structure Ontheir Organization And Polymerizationin A Smectic Liquid Crystal, C. Allan Guymon, Erik N. Hoggan, Noal A. Clark, Thomas P. Rieker, David M. Walba, Christopher N. Bowman

Faculty Publications

Photopolymerizable diacrylate monomers dissolved in fluid-layer smectic A and smectic C liquid crystal (LC) hosts exhibited significant spatial segregation and orientation that depend strongly on monomer structure. Small, flexible monomers such as 1,6-hexanediol diacrylate (HDDA) oriented parallel to the smectic layers and intercalated, whereas rod-shaped mesogen-like monomers such as 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) oriented normal to the smectic layers and collected within them. Such spatial segregation caused by the smectic layering dramatically enhanced photopolymerization rates; for HDDA, termination rates were reduced, whereas for C6M, both the termination and propagation rates were increased. These polymerization precursor structures suggest novel materials-design paradigms for gel …

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Soot In Coal Combustion Systems, Thomas H. Fletcher, Jinliang Ma, Jim Rigby, Alexander L. Brown, Brent W. Webb Jan 1997

Soot In Coal Combustion Systems, Thomas H. Fletcher, Jinliang Ma, Jim Rigby, Alexander L. Brown, Brent W. Webb

Faculty Publications

Soot is generated from coal when volatile matter, tar in particular, undergoes secondary reactions at high temperatures. A description of soot in coal flames allows better calculations of radiative transfer and temperatures in near-burner regions, which in turn allows more accurate predictions of NOx formation in coal-fired furnaces. Experiments are reviewed that examine the formation, agglomeration and properties of coal-derived soot, including pyrolysis experiments and combustion experiments. This review includes the types of experiments performed, the soot yields obtained, the size of the soot particles and agglomerates, the optical properties of soot, the relationship between coal-derived soot and soot …

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Release Of Inorganic Material During Coal Devolatilization, Larry L. Baxter, Reginald E. Mitchell, Thomas H. Fletcher Jan 1997

Release Of Inorganic Material During Coal Devolatilization, Larry L. Baxter, Reginald E. Mitchell, Thomas H. Fletcher

Faculty Publications

Experimental results presented in this paper indicate that coal devolatilization products convectively remove a fraction of the nonvolatile components of inorganic material atomically dispersed in the coal matrix. Results from three facilities burning six different coals illustrate this mechanism of ash transformation and release from coal particles. Titanium is chosen to illustrate this type of mass release from coal particles on the basis of its low volatility and mode of occurrence in the coal. During moderate rates of devolatilization (104 K/s heating rate), no significant loss of titanium is noted. At more rapid rates of heating/devolatilization (105 K/s) …

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The Effect Of Ultrasonic Frequency Upon Enhanced Killing Ofp. Aeruginosa Biofilms, Zhen Qian, Richard D. Sagers, William G. Pitt Jan 1997

The Effect Of Ultrasonic Frequency Upon Enhanced Killing Ofp. Aeruginosa Biofilms, Zhen Qian, Richard D. Sagers, William G. Pitt

Faculty Publications

It is widely recognized that the bacteria sequestered in a biofilm on a medical implant are much more resistant to antibiotics than their planktonic counterparts. Recent studies have shown that application of antibiotic along with low power ultrasound significantly increases the killing of planktonic bacteria by the antibiotic. Herein is reported a similar application of antibiotic and ultrasound to sessile bacteria in biofilms of Pseudomonas aeruginosa on a polyethylene substrate. Biofilm viability was measured after exposure to 12 μg/ml gentamicin sulfate and 10 mW/cm2 ultrasound at frequencies of 70 kHz, 500 kHz, 2.25 MHz, and 10 MHz. The results …

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Nitrogen Release During Coal Combustion, Thomas H. Fletcher, Larry L. Baxter, Reginald E. Mitchell, Robert H. Hurt Jan 1996

Nitrogen Release During Coal Combustion, Thomas H. Fletcher, Larry L. Baxter, Reginald E. Mitchell, Robert H. Hurt

Faculty Publications

Experiments in entrained flow reactors at combustion temperatures are performed to resolve the rank dependence of nitrogen release on an elemental basis for a suite of 15 U.S. coals ranging from lignite to low-volatile bituminous. Data were obtained as a function of particle conversion, with overall mass loss up to 99 % on a dry, ash-free basis. Nitrogen release rates are presented relative to both carbon loss and overall mass loss. During devolatilization, fractional nitrogen release from low-rank coals is much slower than fractional mass release and noticeably slower than fractional carbon release. As coal rank increases, fractional nitrogen release …

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Conversion Of Coal Tar To Soot During Coal Pyrolysis In A Post-Flame Environment, Thomas H. Fletcher, Jinliang Ma, Brent W. Webb Jan 1996

Conversion Of Coal Tar To Soot During Coal Pyrolysis In A Post-Flame Environment, Thomas H. Fletcher, Jinliang Ma, Brent W. Webb

Faculty Publications

Coal pyrolysis experiments were performed in the postflame region of a CH4/H2/air flat-flame burner operating under fuel-rich conditions, where the temperature and gas compositions were similar to those in the near-burner region of a large-scale coal-fired furnace. Volatiles released from the coal particles formed a cloud of soot particles at high temperatures in the absence of oxygen. The soot particles in the cloud were collected at different residence times using a water-cooled, nitrogen-quenched suction probe. Test variables included the reaction temperature and coal type. Soot yields in terms of weight percentage of dry ash-free coal were measured based on bulk …

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Chen, W., L. D. Smoot, S. C. Hill, And T. H. Fletcher, “Global Rate Expression For Nitric Oxide Reburning. Part 2,” Energy And Fuels, 10, 1046-1052 (1996)., Wei Chen, L Douglas Smoot, Scott C. Hill, Thomas H. Fletcher Jan 1996

Chen, W., L. D. Smoot, S. C. Hill, And T. H. Fletcher, “Global Rate Expression For Nitric Oxide Reburning. Part 2,” Energy And Fuels, 10, 1046-1052 (1996)., Wei Chen, L Douglas Smoot, Scott C. Hill, Thomas H. Fletcher

Faculty Publications

An investigation of a global reburning-NO reaction, sum(CiHj) + NO => HCN + . . ., which is a reduction pathway of nitric oxide (NO) by reaction with gaseous hydrocarbons, was conducted. The global reburning-NO rate expression was deduced from a combination of elemental reactions. The global rate expression and its rate constants were then determined by correlating predicted species profiles from simple hydrocarbon flames. This global reburning-NO rate constant can be expressed as 2.7x106 exp(-18,800/RT) (gmol/cm3 s). This expression and constants are applicable to atmospheric pressure with an equivalence ratio range of 1.0-2.08 …

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A Computational Method For Determining Global Fuel-No Rate Expressions. Part 1, Wei Chen, L Douglas Smoot, Thomas H. Fletcher, Richard D. Boardman Jan 1996

A Computational Method For Determining Global Fuel-No Rate Expressions. Part 1, Wei Chen, L Douglas Smoot, Thomas H. Fletcher, Richard D. Boardman

Faculty Publications

Global chemical reaction rates used in the modeling of NOx formation in comprehensive combustion codes have traditionally been obtained through correlation of experimental data. In this paper, a computational approach for obtaining global rates is presented. Several premixed flames were simulated, and sensitivity analysis of species concentration profiles was used to suggest global pathways in fuel-nitrogen conversion to NO. Based on these analyses, the global reaction rates were formulated. The predicted species concentration profiles and their derivatives were then used in the determination of the global rate constants. The correlation of rate constants for the two fuel-NO global rates …

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Effects Of Pyrolysis Heating Rate On Intrinsic Reactivities Of Coal Chars, Thomas K. Gale, Calvin H. Bartholomew, Thomas H. Fletcher Jan 1996

Effects Of Pyrolysis Heating Rate On Intrinsic Reactivities Of Coal Chars, Thomas K. Gale, Calvin H. Bartholomew, Thomas H. Fletcher

Faculty Publications

The main objective of this work was to determine the effects of pyrolysis heating rate on intrinsic O2 reactivity of coal chars. Relationships of intrinsic reactivity to other pyrolysis conditions and char physical and chemical structure were also investigated, and empirical correlations were obtained. Two different entrained flow reactors (a flat flame methane/air burner and a drop tube reactor) were used to prepare chars under a variety of different pyrolysis conditions at maximum particle temperatures and heating rates of 840-1627 K and 104 to 2x105 K/s, respectively. Intrinsic reactivities of a lignite and two bituminous coal chars …

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Combustion Modeling Of Rdx, Hmx And Gap With Detailed Kinetics, Jeffrey E. Davidson Jan 1996

Combustion Modeling Of Rdx, Hmx And Gap With Detailed Kinetics, Jeffrey E. Davidson

Theses and Dissertations

A one-dimensional, steady-state numerical model of the combustion of homogeneous solid propellant has been developed. The combustion processes is modeled in three regions: solid, two-phase (liquid and gas) and gas. Conservation of energy and mass equations are solved in the two-phase and gas regions and the eigenvalue of the system (the mass burning rate) is converged by matching the heat flux at the interface of these two regions. The chemical reactions of the system are modeled using a global kinetic mechanism in the two-phase region and an elementary kinetic mechanism in the gas region. The model has been applied to …

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Chemical Structure Of Coal Tar During Devolatilization, Thomas H. Fletcher, Mathew Watt Jan 1996

Chemical Structure Of Coal Tar During Devolatilization, Thomas H. Fletcher, Mathew Watt

Faculty Publications

Three coals of different rank were pyrolyzed in a drop-tube reactor at a maximum temperature of 900 K and a residence time of 160 ms. The coal and char were analyzed with solid-state 13C NMR. The tar was dissolved in deuterated methylene chloride. It was found that the tar was only partially soluble in CD2Cl2. The nonsoluble tar portion was analyzed in the same manner as the coal and char, while the soluble tar portion was analyzed using a recently developed high-resolution 13CNMRtechnique developed for liquid phases. The tar structure was found to be significantly …

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Kinetic Analysis Of The Fate Of Nitric Oxide Synthesized By Macrophages In Vitro, Randy S. Lewis, Snait Tamir, Steven R. Tannenbaum, William M. Deen Dec 1995

Kinetic Analysis Of The Fate Of Nitric Oxide Synthesized By Macrophages In Vitro, Randy S. Lewis, Snait Tamir, Steven R. Tannenbaum, William M. Deen

Faculty Publications

To investigate the fate of nitric oxide (NO) synthesized by activated macrophages, the concentrations of NO and its principal reaction products, nitrite (NO2-) and nitrate (NO3-), were measured as a function of time in suspension cultures of RAW264.7 macrophages attached to microcarrier beads. Synthesis of NO became evident 2-5 h after stimulation of the cells, and steady concentrations of NO were achieved after about 9 h. The appearance of NO in the extracellular fluid coincided with the appearance of NO2- and NO3-, which were formed thereafter at approximately equal and constant rates. Using a kinetic model based on rate constants …

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Decreases In The Swelling And Porosity Of Bituminous Coals During Devolatilization At High Heating Rates, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew Jan 1995

Decreases In The Swelling And Porosity Of Bituminous Coals During Devolatilization At High Heating Rates, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew

Faculty Publications

Concern about comparability and validity of different methods for producing coal chars for reactivity experiments has led to research on the effect of devolatilization conditions on the char physical and chemical structure. Particle diameter and porosity changes during devolatilization significantly affect char oxidation rates. In particular, physical properties of chars prepared in drop tube reactors differ greatly from chars prepared in flat flame burner experiments. Recent data indicate that the presence of oxygen in the gas atmosphere has no effect on swelling until char oxidation has begun. The present research concentrates on the effects of heating rate, particle temperature and …

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Thermophoretic Sampling Of Coal-Derived Soot Particles During Devolatilization, Jinliang Ma, Thomas H. Fletcher, Brent W. Webb Jan 1995

Thermophoretic Sampling Of Coal-Derived Soot Particles During Devolatilization, Jinliang Ma, Thomas H. Fletcher, Brent W. Webb

Faculty Publications

Thermophoretic sampling of soot particles formed during high-temperature coal devolatilization is performed in order to examine soot particle sizes and shapes. Coal particles are injected along the centerline of a laminar flow flat flame burner, where a fuel-rich methane-air flame is used as a heat source. Volatiles released from the coal particles form a cloud of soot particles at high temperatures in the absence of oxygen. A carbon-coated microscope grid is briefly inserted into the soot cloud, where the temperature gradient between the soot particles and the cold grid surface causes the migration of soot particles and results in deposition. …

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Effects Of Pyrolysis Conditions On Internal Surface Areas And Densities Of Coal Chars Prepared At High Heating Rates In Reactive And Non-Reactive Atmospheres, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew Jan 1995

Effects Of Pyrolysis Conditions On Internal Surface Areas And Densities Of Coal Chars Prepared At High Heating Rates In Reactive And Non-Reactive Atmospheres, Thomas K. Gale, Thomas H. Fletcher, Calvin H. Bartholomew

Faculty Publications

Concern about comparability and validity of different methods for producing coal chars for reactivity experiments has led to research on the effect of devolatilization conditions on the char physical and chemical structure. Particle diameter and porosity changes during devolatilization significantly affect char oxidation rates. In particular, physical properties of chars prepared in drop tube reactors differ greatly from chars prepared in fiat flame burner experiments. Recent data indicate that the presence of oxygen in the gas atmosphere has no effect on swelling until char oxidation has begun. The present research concentrates on the effects of heating rate, particle temperature and …

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Ultrasonic Enhancement Of Antibiotic Action On Gram-Negative Bacteria, William G. Pitt, Michael O. Mcbride, Jared K. Lunceford, Randall J. Roper, Richard D. Sagers Nov 1994

Ultrasonic Enhancement Of Antibiotic Action On Gram-Negative Bacteria, William G. Pitt, Michael O. Mcbride, Jared K. Lunceford, Randall J. Roper, Richard D. Sagers

Faculty Publications

The effect of gentamicin upon planktonic cultures of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and Staphylococcus aureus was measured with and without application of 67-kHz ultrasonic stimulation. The ultrasound was applied at levels that had no inhibitory or bactericidal activity against the bacteria. Measurements of the MIC and bactericidal activity of gentamicin against planktonic cultures of P. aeruginosa and E. coli demonstrated that simultaneous application of 67-kHz ultrasound enhanced the effectiveness of the antibiotic. A synergistic effect was observed and bacterial viability was reduced several orders of magnitude when gentamicin concentrations and ultrasonic levels which by themselves did not reduce …

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The Impact Of Coal Pyrolysis On Combustion, Peter R. Solomon, Thomas H. Fletcher Jan 1994

The Impact Of Coal Pyrolysis On Combustion, Peter R. Solomon, Thomas H. Fletcher

Faculty Publications

The pyrolysis process has impacts throughout coal combustion. The roles of pyrolysis in various aspectsof the coal combustion process are described, including the devolatilization yield, nitrogen release, softening and swelling, soot formation, and char reactivity. These processes can be understood and quantitatively predicted using recently developed network pyrolysis models that describe the transformation of the coal's chemical structure. The models are described and examples of their predictive ability for important coal combustion phenomena are presented.

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Overview Of Acerc Comprehensive Model Development, Thomas H. Fletcher, Scott C. Hill Jan 1993

Overview Of Acerc Comprehensive Model Development, Thomas H. Fletcher, Scott C. Hill

Faculty Publications

A major objective of the Advanced Combustion Engineering Research Center (ACERC) is the development of comprehensive combustion models to help in the solution of critical national combustion problems. Computer models incorporate research and technology results from center projects and from external research programs. The synergistic integration of scientific knowledge that is expected from the NSF engineering research centers is demonstrated to a great extent at ACERC by the development of these software tools. The transfer of technology from ACERC to industry is also accomplished in part by the implementation of the models at industrial firms. The effort to develop such …

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An Overview Of Acerc Research In Fuel Characterization And Reaction Mechanisms, Ronald J. Pugmire, Thomas H. Fletcher Jan 1993

An Overview Of Acerc Research In Fuel Characterization And Reaction Mechanisms, Ronald J. Pugmire, Thomas H. Fletcher

Faculty Publications

A major objective of the Advanced Combustion Engineering Research Center is the development and verification of data on fuel characterization and reaction mechanisms and rates that can be incorporated into submodels for use in the comprehensive combustion codes. As technology has advanced, the levels of analytical sophistication has also advanced, making it possible to augment the existing body of information with new data. From this new data it is possible to draw new insights regarding the complex nature of coal and the various processes associated with combustion. The ACERC program has made it possible to bring different disciplines together to …

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Swelling Properties Of Coal Chars During Rapid Coal Pyrolysis And Combustion,, Thomas H. Fletcher Jan 1993

Swelling Properties Of Coal Chars During Rapid Coal Pyrolysis And Combustion,, Thomas H. Fletcher

Faculty Publications

Coal devolatilization experiments are commonly conducted at moderate temperatures (800 to 1300 K) and heating rates (103 to 104 Ks−1) in inert environments in order to measure evolved species before secondary reaction in the gas phase. However, chars from these experiments exhibit different physical characteristics than chars obtained under typical combustion conditions (1500 to 2000 K, 105 Ks−1, and 3 to 10 mol% oxygen). Experiments were conducted in two laminar, entrained-flow reactors to determine characteristics of coal chars in inert and oxygen-rich environments. One flow reactor was heated electrically, with gas temperatures of …

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Progress In Coal Pyrolysis, Peter R. Solomon, Thomas H. Fletcher, Ronald J. Pugmire Jan 1993

Progress In Coal Pyrolysis, Peter R. Solomon, Thomas H. Fletcher, Ronald J. Pugmire

Faculty Publications

The heterogeneous nature of coal and the complexity of the pyrolysis process have made it very difficult to perform unambiguous experiments to determine the rates and mechanisms in coal pyrolysis. However, recent years have seen a number of new experimental and theoretical approaches which shed new light on the subject. This paper considers the recent progress on kinetics, the formation of volatile products, network models, cross-linking, rank effects, and the ‘two-component’ model of coal structure. Recent experiments which measured coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. These rates also agree with those derived …

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Chemical Structural Features Of Pyridine Extracts Of The Argonne Premium Coals Using 13c Nmr Spectroscopy, Thomas H. Fletcher, S Bai, Ronald J. Pugmire, Steven Wood, David M. Grant Jan 1993

Chemical Structural Features Of Pyridine Extracts Of The Argonne Premium Coals Using 13c Nmr Spectroscopy, Thomas H. Fletcher, S Bai, Ronald J. Pugmire, Steven Wood, David M. Grant

Faculty Publications

Soxhlet extractions were performed on the eight Argonne Premium coals using pyridine purged with argon and followed by a novel washing procedure to remove the pyridine. Mass closure (extracts plus residues) on duplicate experiments accounted for 94-96% of the original coal, repeatable to within 2%. Chemical structural features determined from 13C NMR analyses of the extracts and residues showed more attachments per aromatic cluster for the residues, indicating a greater degree of covalent bonding in the residue than in the extract. 1H NMR analysis of the extracts showed a gradual increase in the hydrogen aromaticity with rank, along …

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Note On The Number Dependence Of Nonequilibrium Molecular Dynamics Simulations Of The Viscosity Of Structured Molecules, Richard L. Rowley, James F. Ely Mar 1992

Note On The Number Dependence Of Nonequilibrium Molecular Dynamics Simulations Of The Viscosity Of Structured Molecules, Richard L. Rowley, James F. Ely

Faculty Publications

Nonequilibrium molecular dynamics simulations have been performed for a system of 512 four-site models representing n-butane molecules. The results are compared to simulations previously reported for 125 molecules to check a recently reported number dependence in such simulations. A small system size dependence was observed at low shear rates, but the rheological behavior is not affected. Considerably greater certainty is obtained using larger systems.

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Chemical Percolation Model For Devolatilization: Ii. Temperature And Heating Rate Effects On Product Yields, Thomas H. Fletcher, Alan R. Kerstein, Ronald J. Pugmire, David M. Grant Jan 1992

Chemical Percolation Model For Devolatilization: Ii. Temperature And Heating Rate Effects On Product Yields, Thomas H. Fletcher, Alan R. Kerstein, Ronald J. Pugmire, David M. Grant

Faculty Publications

The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite lattice. The chemical percolation devolatilization model described here includes treatment of vapor-liquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor pressure correlation for high molecular weight hydrocarbons, such as coal tar, is proposed based on data from coal liquids. …

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Chemical Structure Of Char In The Transition From Devolatilization To Combustion, Thomas H. Fletcher, Mark S. Solum, David M. Grant, Ronald J. Pugmire Jan 1992

Chemical Structure Of Char In The Transition From Devolatilization To Combustion, Thomas H. Fletcher, Mark S. Solum, David M. Grant, Ronald J. Pugmire

Faculty Publications

Coal devolatilization experiments are generally conducted separately from char oxidation experiments, and the relationship between the chars generated in the two types of research is often ignored. However, char is one of the most important products of coal devolatilization and must be characterized as a function of temperature and heating rate in a manner similar to that for gaseous devolatilization products. The chemical structure of the parent coal directly affects devolatilization behavior. In this work, the chemical structure of chars from five coals of different rank are examined, and implications on char reactivity are discussed. Chars were obtained as a …

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Molecular Dynamics Simulation Of Real-Fluid Mutual Diffusion Coefficients With The Lennard-Jones Potential Model, Richard L. Rowley, J. M. Stoker Sep 1989

Molecular Dynamics Simulation Of Real-Fluid Mutual Diffusion Coefficients With The Lennard-Jones Potential Model, Richard L. Rowley, J. M. Stoker

Faculty Publications

Mutual diffusion coefficients for selected alkanes in carbon tetrachloride were calculated using molecular dynamics and Lennard-Jones (LJ) potentials. Use of effective spherical LJ parameters is desirable when possible for two reasons: (i) computer time is saved due to the simplicity of the model and (ii) the number of parameters in the model is kept to a minimum. Results of this study indicate that mutual diffusivity is particularly sensitive to the molecular size cross parameter, σ12, and that the commonly used Lorentz–Berthelot rules are inadequate for mixtures in which the component structures differ significantly. Good agreement between simulated and experimental mutual …

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On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi Dec 1987

On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi

Faculty Publications

Recently reported thermal diffusion factors obtained from heats of transport have been used to test the ability of existing theories to predict thermal diffusivities using model parameters regressed from pure component transport data. None of the theories tested were able to provide even qualitative agreement with experiment. However, predictions using a square-well Enskog theory, modified here for consistency with normal experimental definitions, were found to be approximately correct using pure-component square-well parameters regressed from viscosity and thermal conductivity and an assumed mixing rule for cross terms. Predicted values are very sensitive to the energy mixing rule, and correlation of experimental …

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Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi Dec 1987

Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi

Faculty Publications

Measurements of heats of transport are reported for binary liquid mixtures containing carbon tetrachloride and benzene, toluene, 2-propanone, n-hexane, or n-octane at 298 K and ambient pressure. Additionally, measurements were made at 308 K for carbon tetrachloride with benzene, toluene, and 2-propanone. The corresponding heat-mass Onsager coefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. These data will be used in a companion paper to report a modified Enskog method for correlation and prediction of heats of transport.

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