Interfacial geometry and its effect on the estimation of binary gas diffusivities in an isothermal Stefan column

Moreno, Marimar; Moreno, Isamaris; Jaime, María del Sol; Maisonet, Shayra G.; Ramı́rez, Carlos A.

doi:10.1080/00986445.2020.1770233

Cited by 7 publications

(2 citation statements)

References 18 publications

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“…In recent years, we have addressed this gap in scientific knowledge by reporting our efforts to quantify the various Stefan column end effects and their impact on the gas diffusivity estimates. These studies clearly show that factors such as column nonisothermality, 68 sweeping gas stream Reynolds number (dimensionless ratio of fluid inertial to viscous forces) and column aspect ratio (gas phase height to column inside diameter), 69 liquid phase composition, 70,71 and interfacial shape and curvature 72 must be rigorously accounted for in the diffusivity calculations to minimize estimation errors. Our findings to date have hopefully made Stefan column researchers aware of some of the common pitfalls the analyst may find when estimating binary gas diffusivities from experimental interfacial descent versus time data.…”

Section: Chloroform Synthesis and Its Uses In Medicine And Chemical E...mentioning

confidence: 94%

Lipids, Chloroform, and Their Intertwined Histories

Ramirez

2022

Substantia

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Lipids and their fatty acid constituents, in particular, have been the subject of academic and industrial research initiatives since their isolation by Michel-Eugène Chevreul in 1813. Fatty acids can be saturated or unsaturated, their physical properties depending on the aliphatic chain length and degree of saturation. They constitute the building blocks of many lipid groups, such as triglycerides and phospholipids; are key additives in commercial foods, pharmaceuticals, and cosmetics; and can cross cell membranes. Chloroform was synthesized in 1831 by Samuel Guthrie and has had a tortuous history of interactions with mankind: from an anesthetic in obstetrics, dentistry, and surgery, to being labeled as a potential carcinogen in the 1970s. It has also had important nonmedical applications, such as in chemical engineering mass transfer systems designed to estimate binary gas diffusion coefficients. Although chemically dissimilar, lipids and chloroform intertwined their scientific paths through the work of Jordi Folch and associates in the 1940s-1950s, in which many lipid-based brain molecules were isolated and characterized. This article outlines the separate histories of lipids and chloroform, and those research initiatives in which they have acted synergistically. The narrative covers the interplay of chemical compounds with different historical backgrounds, but with physical properties which continue to foster their modern-day interaction.

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Section: Chloroform Synthesis and Its Uses In Medicine And Chemical E...mentioning

confidence: 94%

Lipids, Chloroform, and Their Intertwined Histories

Ramirez

2022

Substantia

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“…[23] As part of our research program on Stefan column operation and D AB estimation, we have addressed issues such as thermal effects, [24] sweep stream Reynolds number, [25] multicomponent liquid phases, [26][27][28] and curvature effects at the liquid-gas interface. [29,30] A better understanding of transport phenomena in the Stefan diffusion column has certainly emerged from these efforts. The present proofof-concept device attempts to minimize the gas-phase end effects which occur in the Stefan column, while giving the researcher an opportunity to tailor its geometry to shorten experimental diffusion times.…”

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confidence: 99%

A steady two‐dimensional cylindrical mass transport model to determine binary gas diffusivities: A proof‐of‐concept theoretical development

Ramírez

2024

Can J Chem Eng

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Binary gas diffusivities, DABs, are key parameters in the analysis of many chemical engineering processes. Significant efforts to estimate diffusivities experimentally were made by Josef Stefan in the 19th century, who designed a column with liquid A at the bottom overlaid by a gas phase through which gas A diffused. His studies led to the determination of DABs for many gas pairs (B is commonly air), and to the development of alternate mass transport systems. The present proof‐of‐concept theory describes a steady two‐dimensional (2D) diffusion model consisting of a vertical cylinder thinly coated on its inner surfaces with either a sublimating or evaporating species A. The gas‐phase mass conservation partial differential equation is rendered dimensionless and solved by separation of variables. The theoretical molar flow rate of species A at the top of the cylinder, calculated analytically, can be equated to the experimental rate of mass loss from the coated walls, ultimately leading to DAB. The solution of the steady 2D diffusion model is explored in terms of the cylinder aspect ratio (height/radius), showing that the latter quantity can be tailored to obtain preselected sublimation rates of A. The interplay of the radial and axial diffusion mechanisms is also demonstrated as a function of geometry. Finally, the model's use in analyzing a projected sublimation/evaporation–diffusion experiment is discussed. This is the first time that a steady 2D diffusive transport model has been proposed to estimate DABs from experimental data.

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