Manipulation of meniscus rise for in situ multiphase nuclear magnetic resonance spectroscopy

Published

April 8, 2025

Author(s)

Veruska Malave, Newell Moser, Edward Garboczi, Mark McLinden, Jason Widegren, Christopher Suiter

Abstract

Our earlier work demonstrated that nuclear magnetic resonance (NMR) spectroscopy is a viable technique for in situ analysis of vapor–liquid equilibria (VLE) of fluid mixtures and that inserting a capillary into the NMR sample tube allows the simultaneous collection of separate liquid- and vapor-phase spectra for composition determination. This is the result of a thin film of liquid wicking up due to capillary forces into the vapor space, which was not possible with the undisturbed meniscus in the absence of a capillary. The present study investigates the meniscus rise (i.e., capillary action) effect in detail. We use three-dimensional (3D) computational fluid dynamics to investigate the flow regime of the liquid wicking in the NMR tube considering the flow as inviscid, low-viscosity laminar, or viscous-laminar. Thus, we can predict the liquid-volume fraction as a function of the capillary diameter and fluid properties. These results are compared to, and validated against, x-ray computed tomography experiments, which provided detailed (8 µm resolution) 3D imaging of the meniscus of decane in an NMR tube. Phase determination of liquid and vapor cyclopentane in an NMR spectrometer provided additional validation, although integrated over a 10-mm high detection volume. Both meniscus height and thickness are significant variables to modify; thus, in situ VLE studies with NMR can be improved. We demonstrate that the prediction of the effect of capillary geometry on NMR signals for liquid and vapor phases of a pure compound can be used for rapid optimization in NMR VLE measurements.

Citation

AIP Advances

Pub Type

Journals

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Keywords

Nuclear magnetic resonance (NMR), multiphase flows, surface tension, meniscus rise, computational fluid dynamics (CFD), X-ray computed tomography (XCT).

Citation

Malave, V. , Moser, N. , Garboczi, E. , McLinden, M. , Widegren, J. and Suiter, C. (2025), Manipulation of meniscus rise for in situ multiphase nuclear magnetic resonance spectroscopy, AIP Advances, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959436 (Accessed April 13, 2025)