The structure of supercritical fluid free‐jet expansions

Khalil, Imane; Miller, David R.

doi:10.1002/aic.10285

Cited by 43 publications

(27 citation statements)

References 14 publications

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“…We have previously studied the free-jet expansion of supercritical CO 2 from orifices using a numerical time marching Lax-Wendroff method, incorporating a real gas equation of state for CO 2 with both repulsive and attractive corrections to ideal gas. For the orifice sources, we have reported reasonable agreement between experimental and calculated properties of the expansion with source pressures up to 200 bar and temperatures up to 70 o C [1,2,3]. In this paper, we extend the free-jet studies to expansions from small tubular capillary sources.…”

Section: Introductionsupporting

confidence: 58%

“…Our previous studies of supercritical CO 2 free-jet expansions from an orifice source and impacting a flat plate [2,3] used an isentropic calculation from the reservoir to the exit of the orifice, followed by a two-step predictor corrector numerical time-dependent method known as the two-step Lax-Wendroff method to solve for the axisymmetric flow field in the supersonic as well as the subsonic regions of the expansion [5]. The partial differential equations for the axisymmetric free-jet supersonic expansion are :…”

Section: Numerical Calculationsmentioning

confidence: 99%

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The Free-Jet Expansion of Supercritical CO2 from a Capillary Source

Khalil¹,

Miller²

2005

AIP Conference Proceedings

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In this paper we present computational and experimental results for the expansions of supercritical CO 2 from capillary sources, and compare them with similar expansions from orifices of the same diameters, with source pressures up to 100 bar and temperatures up to 70 o C. The expansions impact a vertical flat plate near ten diameters along the centerline. The subsonic flow from stagnation source conditions to the capillary exit is calculated as a quasi-onedimensional viscous flow to exit Mach number = 1 conditions, and then a time marching, two-step predictor corrector Lax-Wendroff axisymmetric method is used to calculate the two-dimensional supersonic expansion, shock structure, and subsonic flow against the flat plate. Experimentally we have made shadowgraph measurements of the shock structure, and temperature and pressure measurements at the flat plate. We find very good agreement between our calculations and experiments for both the capillary and orifice sources for flow rate and shock structure, quantitatively characterized by the Mach disk location as a function of source conditions and flat plate location. The differences between the two types of sources and the non-ideal fluid effects are significant, and well reproduced by the calculations. While we have good agreement for the flat plate pressure profiles for expansions from the orifice source, the agreement is not as good for the expansions from the capillary sources. The experiments show that the pressure profiles at the flat plate are significantly different for the two sources, even when scaled to the same mass flow rate or to the same source exit sonic pressure.

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Section: Introductionsupporting

confidence: 58%

Section: Numerical Calculationsmentioning

confidence: 99%

The Free-Jet Expansion of Supercritical CO2 from a Capillary Source

Khalil¹,

Miller²

2005

AIP Conference Proceedings

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“…The RESS/REHPS process has been modeled by many researchers in the literature; for example, refer to Debenedetti, 40 Reverchon and Pallado, 43 Franklin et al, 53 Hirunsit et al, 54 Khalil and Miller, 55 and Weber and Thies. 45,46 Therefore, only a skeletal description of the model is presented here and the analysis is limited to conditions close to those employed in our experiments.…”

Section: Models For Ress/rehps Deagglomerationmentioning

confidence: 99%

Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high‐pressure suspensions

To¹,

Davé²,

Yin³

et al. 2009

AIChE Journal

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Deagglomeration of suspensions of alumina and titania nanopowders (i.e., nanoparticle aggregates) via rapid expansion of supercritical suspensions (RESS) or high-pressure suspensions (REHPS) was studied. The size distribution of fragmented nanopowders was characterized by online Scanning Mobility Particle Spectrometer (SMPS) and Aerodynamic Particle Sizer (APS), and by offline Scanning Electron Microscopy (SEM). SMPS and SEM measurements indicate that the average agglomerate sizes were well below 1 lm, consistent with the length scales observed in our complementary RESS/REHPS mixing experiments using alumina and silica nanopowders. The APS measurements, on the other hand, were affected by reagglomeration during sampling and yielded an agglomerate size range of 1 to 3 lm. Analysis of the RESS/ REHPS process through compressible flow models revealed that both the shear stress in the nozzle and the subsequent impact of the agglomerates with the Mach disc in the free expansion region can lead to micron or sub-micron level deagglomeration. V

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“…They proposed that a divergentconvergent capillary could be more suitable for the RESS process than a convergent nozzle. Dea et al [26] investigated the growth of magnetic thin films using carbon dioxide RESS expansion, following the 2D work of Khali et al [24]. They applied a quasi-one dimensional analysis to thermal properties on the jet centerline, and a kinematic model for the particle formation, which was based on bimolecular collisions.…”

Section: Introductionmentioning

confidence: 99%

“…Separate continuity equations were used for air and CO 2 . Khali et al [24] studied the structure of supercritical jet expansion for in viscid, adiabatic pure carbon dioxide flow impacting on a flat plate, but particle formation was not considered. They solved an axisymmetric Euler equation with the Redlich-Kwong equation of state [25], using a two-step Lax-Wendroff finite difference method.…”

Section: Introductionmentioning

confidence: 99%