R-3 Repository :: Browsing by Author "Rowley, Richard L."

Browsing by Author "Rowley, Richard L."

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Development of an augmented hard sphere equation of state
(1980) Casas, Alvaro, Jr.; Leland, Thomas W.; Kobayashi, Riki; Rowley, Richard L.
A new three-parameter generalized equation of state for application to mixtures and multicomponent equilibrium systems has been developed. The equation of state is developed from isothermal and isochoric behavior of pure fluids. This equation of state is based on the hard sphere equation of state and is made to favor vapor-liquid equilibrium computations, and also gives satisfactory prediction of other properties. It models the second order perturbation theory expansion in powers of 1/KT for which there is a theoretical base for the mixing rules. This is much more effective than a completely empirically derived set of mixing rules. Methane, Ethane, and Propane were selected for testing this approach. Satisfactory results in the calculation of densities, compressibility factors, vapor pressure and fugacity over a wide range of temperature and pressure demonstrates the applicability of this equation of state. The possibility of a completely analytical expression of the methods previously developed, such as the van der Waals' one-fluid theory and the original Hard Sphere Expansion theory on vapor-liquid equilibrium is in sight.
Diffusion thermoeffect in ternary liquid mixtures
(1980) Platt, Gerald Edwin; Rowley, Richard L.; McIntire, Larry V.; Leland, Thomas W.
The diffusion thermoeffect or Dufour effect, a heat flux induced by an isothermal chemical potential gradient, is usually characterized by the heat of transport. The heat of transport is defined as the ratio of the heat flux to the mass flux under isothermal conditions. Although heats of transport have been measured in binary liquid mixtures, no direct measurements have been made in ternary nonelectrolyte liquid mixtures. In this work, the two independent heats of transport for toluene-chlorobenzene-bromobenzene mixtures at 25°C were determined at various compositions using a withdrawable liquid gate cell. Values were obtained by fitting calculated to measured temperature differences via a weighted non-linear least squares fitting routine using heats of transport as adjustable parameters. Experimental temperature differences were measured at points symmetric about the initial diffusion interface. The diffusion thermoeffect can be described mathematically by the hydrodynamic equations into which fluxes, obtained using methods of nonequilibrium thermodynamics, have been substituted. The resulting set of coupled differential equations were solved using a perturbation scheme for the composition and temperature profiles as functions of time. Initial and boundary conditions used corresponded closely to the experimental configuration. In addition to heats of transport, the Onsager coefficients were determined. The effect of a third component on ternary solution thermal diffusion experiments was evaluated using Onsager reciprocity.
Effective molecular diameters for a conformal solution theory of hard sphere mixture
(1981) Kajiyama, Yohki; Leland, Thomas W.; Rowley, Richard L.; Kobayashi, Riki
The hard sphere expansion conformal solution theory is a very useful technique to predict the thermodynamic properties of a mixture. When we apply this theory, an important problem is the method of determining the effective diameters. Hwu developed a diameter evaluation method using pure component P-V-T data represented by accurate equation of state. This method requires a very time consuming iterative process. Consequently, if it is possible to obtain an analytical equation that expresses accurate diameter values in terms of known variables, we can shorten the computation time. In addition, one can simplify the prediction of derived thermodynamic properties from a single correlation of the optimal diameters for compressibility factor computation. Hard sphere diameters for light hydrocarbons (i.e., methane, ethane, and propane) were calculated using the hard sphere expansion conformal solution theory. The diameter correlation is presented in generalized form as a reduced temperature, reduced density, and acentric factor. Thermodynamic properties for methane-propane mixtures were calculated using the diameters from this diameter equation. The calculated results showed a good agreement with experimental values. The diameters for simple fluids were calculated and compared with those values reported by Bienkowski and Chao. Other than the same trend of temperature dependence, there was no agreement between them, indicating that the optimal values to accompany a particular method of determining the attractive contributions are not closely related to an actual hard molecular core.
Fixation of platelet aggregate size distribution
(1981) Goldblum, David K.; Hellums, Jesse D.; Solis, Robert Thomas; Rowley, Richard L.
An experimental study has been carried out on the use of aldehydes for fixation of human platelet aggregate size distributions. The objective of the work was to develop a methodology of stopping aggregation and disaggregation processes for subsequent analysis. The results are intended to facilitate study of rates of aggregation and disaggregation as influenced by various stimuli. Platelet aggregation was induced in citrate-anticoagulated platelet-rich plasma (PRP) by addition of adenine dinucleotide (ADP) in final concentration ranging from .5 to 2 yM. The aggregated PRP specimens were diluted (158.5 to 1) in a counting medium (isoton) for size distribution analysis. An electronic particle counter was used to study the aggregate size distributions in the range 13-11 urn in equivalent spherical diameter. Parameters used to monitor the size distributions were cumulative volume and cumulative population of the aggregates, mean aggregate size, and volume available for aggregation from free (unaggregated) platelets. In preliminary studies evidence was obtained that glutaraldehyde was a more promising fixative than formaldehyde. Glutaraldehyde in appropriate concentrations caused no important problems in resuspension or in aggregate size change for times of fixation of several minutes. Dilution of aggregated PRP specimens in isoton for counting induced rapid disaggregation. However, it was found that this disaggregation could be avoided by use of glutaraldehyde in the isoton counting diluent. Glutaraldehyde addition to both the aggregated PRP specimen and to the isoton counting diluent to final concentration of .48 wt% was selected as the recommended procedure. Detailed studies were made of aggregate size distributions fixed at various times in the aggregation process. The results indicate that the fixative stops the reactions and stabilizes the distribution for times of 3 to 5 minutes. Thus, the procedure should be useful in studies on rates of platelet aggregation.
Heats of transport in binary liquid mixtures
(1984) Hall, Mark D.; Rowley, Richard L.; Kilpatrick, John E.; Leland, Thomas W.
The diffusion thermoeffect or the heat flux induced by an isothermal chemical potential gradient can be characterized by the heat of transport; the ratio of the heat flux to the mass flux under isothermal conditions. The heat of transport, Q, for the carbon tetrachloridecyclohexane system was measured by Rowley and Home (198) and the ternary heats of transport, and Q2, were studied by Platt, Vongvanich, Fowler, and Rowley (1982) for the toluene-chlorobenzene-bromobenzene system. In this work, the binary heat of transport, Q, is determined for the toluene-chlorobenzene, chlorobenzene-bromobenzene, and toluenebromobenzene systems. The effect of temperature and composition on the binary heat of transport is examined and the Onsager and thermal diffusion coefficients calculated from Q. In addition, a qualitative view of the relationship between the ternary heats of transport of Platt, et al., and the binary heats of transport of this work is presented. The binary heats of transport are determined experimentally, using the boundary sharpening cell of Platt, Vongvanich, and Rowley (1982) by fitting experimentally measured temperature differences to the solution of the energy partial differential equation subject to appropriate boundary conditions. The composition dependence of the heat of transport, Onsager coefficient, and thermal diffusion coefficient are reported for the toluenechlorobenzene and chlorobenzene-bromobenzene systems at 298.15 K and 38.15 K and for the toluene-bromobenzene system at 38.15 K. The study of the relationship between the binary and ternary heats of transport indicate that there is indeed a definite relationship between the toluene-chlorobenzene-bromobenzene system and corresponding binaries, at least near the binary limits of the ternary system.
Heats of transport in toluene-chlorobenzene-bromobenzene mixtures
(1982) Vongvanich, Tevin; Rowley, Richard L.; Leland, Thomas W.; McIntire, Larry V.
The heat of transport is the transport property that characterizes the diffusion thermoeffect or Dufour effect, i.e., it relates the induced heat flux to an isothermal chemi cal potential gradient. It is formally defined as the ratio of heat flux to the mass flux under isothermal conditions. The heat of transport determined in binary liquid mixtures by Rowley and Home [1978] constituted experimental verification of the Onsager heat-mass reciprocal relations. However, an attempt to simultaneously determine the two independent heats of transport in a ternary system by Platt [198] was not completely successful due to coupling of parameters. This work represents the determination of heats of trans port (Q1 and Q2) in ternary liquid systems. The composition and temperature dependence of the two independent heats of transport are determined experimentally. This in turn allows computation of the Onsager coefficients associated with ternary mixtures. The toluene-chlorobenzene-bromobenzene system was chosen because of diffusion data availability. A new experimental cell was designed to provide much more versatility in initial interface creation. Experiments involved measurement of temperature differences between two positions symmetric about the initial sharp diffusional interface as a function of time. Experimental data were fitted to the solution of the energy partial differential equation, which had been solved subject to experimentally imposed boundary conditions by a double perturbation technique, using Q1 and Q2 as adjustable parameters. The problem of coupled parameters was circumvented by using two data sets both at the same mean composition but with different initial composition gradients. The heats of transport in the toluene-chlorobenzene-bromobenzene system were fitted to a polynomial in composition and temperature as were the corresponding Onsager coefficients. The resultant expressions are valid in the range .1^w^<.6 (i=l,2), w^>.1, and 298.15 K
Improvement of the effective hard sphere diameter and the intermolecular potential of lighter paraffin hydrocarbons, carbon dioxide and hydrogen sulfide
(1979) Jones, Lawley; Leland, Thomas W.; Kobayashi, Riki; Rowley, Richard L.
Effective hard sphere diameters for non-spherical molecules were obtained through use of the corresponding states principle and hard sphere expansion theory. The Weeks Chandler Andersen "blip" function technique, with an expanded form of the Verlet and Weis equation, was utilized to fit potential parameters for several models. In this manner, an equation was developed to predict effective hard sphere diameters. Intermolecular potential functions were developed with a three parameter Mie model and second virial coefficients. The numerical values of the Mie intermolecular potential model were compared to the more commonly used Lennard-Jones intermolecular potential model. Effective hard sphere diameters were evaluated from P-V-T data. Dimensionless plots of the effective hard sphere diameters were prepared.
New methods for activity coefficients correlations based on an improved prediction of pair distribution functions in mixtures
(1982) Zhang, Lingling (b. 1936); Leland, Thomas W.; Rowley, Richard L.; Kobayashi, Riki
Two new methods are examined for computing liquid phase activity coefficients at low pressures. The first is the Modified Regular Solution Theory (MRST), the second is a new group contribution method. These two methods are based entirely on the mean density approximation (MDA) to evaluate pair distribution functions in mixtures. The mean density approximation assumes that a pair distribution function in a mixture is the same as for this pair in a pure component at a composition dependent average density which is different from the mixture density. The original Regular Solution Theory of Scatchard and Hildebrand made some assumptions. The first is that the probability of finding a particular pair having a specified center-to-center separation distance in a mixture is independent of composition and is the same as the probability for the pair in the pure component. The second assumption is that the entropy change is the same as the ideal solution entropy change. In this work,we incorporate the mean density approximation and the Flory-Huggins entropy change into the Regular Solution Theory of Scatchard and Hildebrand instead of the unrealistic assumptions about pair distribution functions and the entropy change made in the original theory. The result is called the Modified Regular Solution Theory (MRST). In 197, Funk and Prausnitz have proposed the incorporation of an unlike pair coefficient in the original Regular Solution Theory to derive the Funic version of the Regular Solution Theory(RST). The unlike pair coefficient is used to relate the interactions between unlike molecules to those between like molecules. This work likewise incorporates an unlike pair coefficient in the MRST. In Chapter II,we predict excess thermodynamic functions and activity coefficients from the MRST, the incorporation of the ideal solution entropy change to the RST, the incorporation of the Flory - Huggins entropy change to the RST respectively. Each of these are compared with experimental data. Prom the predicted values, we observe that the results from the MRST is the best and results using the ideal solution entropy change with the RST are poorer. Unlike pair coefficients are necessary in all the theories test. With unlike pair coefficients the MRST is better in predicting excess thermodynamic functions and activity coefficients in mixtures with large differences in molecular size and shape. We also calculate activity coefficients for the MRST by a new analytical differentiation developed in this work and compare with a numerical differentiation.We find the results from these two differentiation methods are almost same. The mean density approximation is also used in this work to develop a new theory of group contributions. This new theory was tested by studying the effect of different molecular species on the inter-group parameters. The group contribution method results from an expansion of a mixture property about this property of a pure reference component conformal with the constituents of the mixture. The expansion is developed in terms of the deviations of the interaction parameters for the individual molecules of the mixture from those of the reference. These deviations constitute effective group contributions for liquid phase activity coefficients. In Chapter III, we predict activity coefficients based on this group contribution method in binary mixtures of acetone-methanol, methanol-ethanol, acetone-ethanol and ternary mixtures of acetone-methanol-ethanol and compare with experimental data. The predicted values are generally good but the errors from the binary mixtures are usually smaller than those from the ternary mixtures.
Thermal diffusion near a binary liquid azetrope
(1981) Peterson, Edward Ryan; Rowley, Richard L.; Kobayashi, Riki; McIntire, Larry V.
Induction of a mass flux by a temperature gradient is known as the thermal diffusion or Soret effect, and is characterized by the thermal diffusion factor. A thermogravitational column’was used to obtain thermal diffusion factors and steady state separations in the ethanol-water mixture at its azeotropic composition. The thermogravitational diffusion column was calibrated using the value of the thermal diffusion factor of the cyclohexane-benzene mixture, which had been previously determined at 25°C. The temperature dependence of the thermal diffusion factor was determined for the ethanol-water system within .5°C of the azeotropic point and in the range of 25° to 77.7°C. Within 1°C of the azeotropic point, the thermal diffusion factor shows an anomalous behavior. It appears to increase rapidly as the azeotrope temperature is approached. In addition to the thermal diffusion factor, the heat of transport and thermal diffusion coefficient were determined for the ethanol-water system as functions of temperature, based on the assumption of Onsager Reciprocity. These parameters also exhibit a divergent character as the boiling point is approached. Further studies are needed to determine the significance of this effect in terms of molecular models. Ethanol enriched fluid from the thermogravitational column operating in the continuous mode was used as feed to a packed distillation column. Further separation occurred via distillation. Thus, thermogravitational columns offer a convenient small scale intermediate to break the azeotropes which often arise in the separation of liquid mixtures by distillation.

Browsing by Author "Rowley, Richard L."

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