The Surface Diffusion of High Temperature Vapors in Porous Alumina

Jacobson, Nathan; Opila, Elizabeth J.; Searcy, Alan W.

doi:10.1007/978-1-4612-5180-4_3

Cited by 2 publications

(2 citation statements)

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“…As formulated, the capillary-flow mechanism applies only to liquid imbibition. However, the discovery of a surface flow (13)(14)(15)(16)(17)(18) that is different from ordinary and Knudsen diffusions (see later) raises the intriguing possibility that the mechanism may also apply to gaseous imbibition. It is found that surface diffusion can occur in parallel with Knudsen diffusion and that, in common with the capillary-flow mechanism, it is independent of the bulk-pressure driving force (14).…”

Section: Introductionmentioning

confidence: 99%

“…The fact that nonleaker emissions of VOCs correlate poorly with bulk-pressure driving force suggests that the ratio is high and that capillary flow may be dominant in the pinch points. Similarly, the relative importance of capillary and Knudsen flows through a pinch point is given by the ratio ß2/8µ _ 3 cos kRTV/2 DkAPb(M/RT) ~16pAPh \~2M ) (17) The fact that surface flow can exceed Knudsen flow (16,17) suggests that the above ratio can be larger than unity under conditions of practical interest.…”

Section: Introductionmentioning

confidence: 99%

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Capillary-flow mechanism for fugitive emissions of volatile organics from valves and flanges: model development, experimental evidence, and implications

Choi¹,

All²,

Overcash³

et al. 1992

Environ. Sci. Technol.

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Experimental and model results are presented to show that the so-called "nonleaker" emissions of volatile organics from valves and flanges probably proceed by a capillary mechanism. A capillary-flow model is formulated based on theoretical consideration and field data, and equations are derived which permit a test of the model under laboratory conditions. Model predictions are shown to be confirmed by an experimental study of emission from a valve. The results suggest some practical steps for reducing fugitive emissions of VOCs from valves and flanges: (1) the use of nonwetting and low surface energy packing and containment materials, (2) the use of a resilient, nonswelling or nonshrinking packing material, (3) the damping of vibrations and temperature or pressure cyclings, and (4) the application of a compressive stress just sufficient to produce small pore sizes in the packing but insufficient to harm the resiliency and life span of the packing.

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