Biomedical subjects

KK Mohanty

Publications and source records attributed to KK Mohanty.

5 recordsLinked to original sources

PubMed2000

Mixing Properties of Two-Dimensional Lattice Solutions of Amphiphiles.

Lattice Monte Carlo simulations of two-dimensional amphiphile solutions are used to examine the accuracy of the mixing properties predicted by lattice theories such as the Flory-Huggins theory, random-solution approximation, and quasichemical approximation. The internal energy, Helmholtz free energy, and entropy of mixing have been calculated from the configurational energy data obtained from the simulations, and the effect of nonrandom mixing on these properties has been determined. The quasichemical approximation predicts the entropy and Helmholtz free energy of mixing accurately for the amphiphile solution, but fails to predict the energy of mixing, due to the presence of microphase (self-aggregation) separation, which is beyond the reach of the quasichemical approximation, a mean-field theory. Helmholtz free energy of mixing is predicted accurately, and the shielding of the solvophobic segments in the microphase leads to small energies of mixing compared to the entropy of mixing. Copyright 2000 Academic Press.

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PubMed1999

Critical Condensate Saturation in Porous Media.

The understanding of gas and condensate flow in porous media is critical to the optimum exploitation of gas-condensate reservoirs. Critical condensate saturation and relative permeabilities are the key parameters for the evaluation of possible recovery strategies. This work is aimed at developing a mechanistic network model for the critical condensate saturation in which phase trapping and connectivity in the pore corners are critically examined. Porous media are modeled by networks of pore bodies interconnected by pore throats. Bodies and throats are characterized by their connectivity, shapes, and radii distributions. Pore-level laws are identified from micromodel experiments with near-critical fluids. A nonzero critical condensate saturation can be obtained in the absence of contact angle hysteresis due to the converging-diverging nature of the throats. The critical saturation at which the condensate flows is found to be a function of pore geometry, water saturation, and interfacial tension (or the Bond number). The modified sphere-pack model underpredicts the critical condensate saturation of typical sandstones. The cubic model adequately predicts the critical saturation and its experimentally observed trends. Copyright 1999 Academic Press.

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PubMed1997

Interfacial Tension Measurement in DNAPL/Aqueous Surfactant Systems

Spinning drop tensiometry has been used in the past to determine low interfacial tension between aqueous surfactant solutions and organic phases that are lighter than water. In this work, we extend the use of the technique to measurement of low interfacial tension between aqueous surfactant solutions and organic phases that are denser than water by altering the wettability of the spinning glass tube. The interfacial tensions of water-SDS-PCE and water-SDS-TCE are determined using this new method. Copyright 1997 Academic Press. Copyright 1997Academic Press

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PubMed1997

Monte Carlo Simulations for Micellar Encapsulation

The solubilization of solutes in surfactant aggregates (micelles) is studied using lattice-based Monte Carlo simulations. Various properties such as the size and shape of the micelles, the critical micelle concentration, the locus of solubilization, and the partition coefficient of the solute are obtained, and the implications of the results for the thermodynamics of solubilization are examined. The presence of contaminants in the solution affects micellar properties by promoting micellization and stabilizing micelles. The ratio of head group size to tail group size for the surfactant is found to greatly affect both micellar properties and contaminant solubilization. The partitioning of the solute is found to be independent of surfactant concentration, but increases with solute concentration. The results show that contaminant partitioning is controlled primarily by enthalpic contributions.

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PubMed1997

Effect of the Spreading Coefficient on Three-Phase Flow in Porous Media

A pore-level network model has been developed to study the effect of spreading coefficients on three-phase flow through porous media. This model combines the morphological description of the pore space with pore-level displacement physics to model capillarity-controlled, immiscible gas invasion of a porous medium initially saturated with water and oil. Three displacement events are involved during gas invasion, namely, direct water drainage, direct oil drainage, and double drainage. Direct oil drainage and double drainage involve oil mobilization and consequently lead to oil recovery. Direct water drainage event is preferred over double drainage if the spreading coefficient is highly negative. The residual oil saturation to gasflood starting after a waterflood is higher for nonspreading oils than for spreading oils. In spreading oils, it is not a function of the spreading coefficient. In nonspreading oils, the residual oil saturation increases with the magnitude of the spreading coefficient. The residual oil saturation to gasflood is also a function of the initial oil saturation; it increases as the initial oil saturation increases. The increase is higher for nonspreading oils. The gas-oil capillary pressure is not a function of the liquid saturation alone, as is commonly presumed. It is a function of the spreading coefficient and the initial oil saturation, as well.

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