Enhancement of mass transfer from particles by local shear‐rate and correlations with application to drug dissolution

Abstract

We analyze hydrodynamic enhancement of mass (or heat) release rate from small spherical particles within fluid flows from local flow shear-rate, with application to drug dissolution. Combining asymptotic theories in the high/low shear Peclet number limits in Stokes flow with 205 carefully-developed computational experiments, we develop accurate correlations for shear enhancement of Sherwood/Nusselt number (Sh/Nu) as a function of shear Peclet and Reynolds number (S * , Re S ). The data spanned S * from 0 to 500 and Re S from 0 to 10. In Stokes flow our correlations are highly accurate over the entire S * range, whereas for finite Re S < 1 accuracy is good for S * up to a few thousand. Shear enhancement results from highly three-dimensional spiraling flow created by particle spin. We develop a model for particle slip velocity that is inserted into the Ranz/Marshall correlation to show that shear-rate enhancement strongly dominates convection, a result important to drug dissolution. K E Y W O R D Sconvective enhancement, dissolution, drug dissolution, particle heat transfer, particle mass transfer, shear enhancement

Computational Modeling of Drug Dissolution in the Human Stomach

“…These quantities represent the relative flow strength over the pill and the local diffusive mass flux, respectively. We have found that if there is substantial relative flow motion over the pill surface, the wall shear rate and the mass flux are indeed correlated not only globally as shown in the previous studies ( Abrahamsson et al, 2005 ; Bai and Armenante, 2009 ; Wang and Brasseur, 2019 ), but also locally as shown in the present study. It is observed, however, that if there is little relative motion between the pill and the flow, like the neutrally buoyant pill, the mass flux (concentration gradient) is almost independent of the wall shear rate.…”

“…This suggest that the positive correlation between the wall shear rate and the mass flux may only be valid for the pills heavier than the medium. This may be an important finding because many dissolution models have been derived from the correlation between the mass flux and the wall shear stress or wall shear rate ( Abrahamsson et al, 2005 ; Bai and Armenante, 2009 ; Wang and Brasseur, 2019 ).…”

Numerical method to characterise capsule membrane permeability for controlled drug delivery

“…Here, the obtained value of D m is close to 6:75 Â 10 À10 m 2 =s, which is expectedly small. The flow around the capsule induced by stirring is expected to enhance the release rate due to convection, 25,33,34 but not to significantly increase the intrinsic permeability of the capsule membrane.…”

Mass transfer from a sheared spherical rigid capsule

“…They have proposed Sherwood number correlations as a function of the blockage ratio. Recently, Wang and Brasseur [8] studied numerically mass transfer from a freely rotating sphere in shear flow and have proposed correlations valid over a wide range of the Péclet number. All these studies, and others summarized in Ref.…”