Mass Transfer to a Rotating Disk

A new model for turbulent heat and mass transfer in the wall region is developed. It is based on the energy dissipation rate concept. The energy dissipation rate, which is a parameter characterizing turbulent heat and mass transfer, is evaluated using the hydrodynamic properties of the flow in the wall region. Applicability of the proposed model is examined using the experimental data and correlations for flows on a flat plate, wall jets and flows on a rotating disk. Satisfactory agreement is found between the proposed model and the available experimental data and correlations.

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“…with the experimental data obtained by Ellison and Cornett[16] and Lal et al[17]. It is seen fromFigure 7that Eq.…”

supporting

confidence: 70%

Heat and Mass Transfer in the Wall Region of Turbulent Flows

Kawase

Umeno

1993

Chemical Engineering Communications

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“…If the disk is infinitely large and the interracial concentration is uniform, the concentration profile is independent of the r and 0 directions, and the convective diffusion equation in dimensionless form at steady state becomes 0" -ScHO' = 0 [15] with the boundary conditions…”

Section: Theoreticalmentioning

confidence: 99%

Experimental Mass Transfer at a Forced‐Convective Rotating‐Disk Electrode

Yen

Wang

Chapman

1992

J. Electrochem. Soc.

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The mass transfer at a rotating-disk electrode with an external forced convection has been studied in this paper. The mass-transfer factor of the forced-convective rotating disk suitable for Schmidt numbers greater than 1 is presented. The limiting currents of the ferricyanide reduction at various forced-flow strength and rotating speeds were measured experimentally and used to estimate the mass transfer at the forced-convective rotating disk. It is found that the experimental results agree very well with the values calculated theoretically.The fluid flow and mass transfer (or heat transfer) near a rotating disk in the presence of an external forced flow is an interesting problem worthy of investigation. There are two limiting cases of this flow type. One is the flow induced by a rotating disk, which is well known in electrochemistry, and the other is the axisymmetrical flow with stagnation on a planar wall. Both have been applied extensively in many fields I-~"The solution of fluid flow induced purely by a rotating disk was first obtained by yon K~rm~n ~ and later by Cochran 6. The works of yon K~rm~n and Cochran have stimulated numerous authors to study fluid flow near a rotating disk by using various methods. The relevant heat or mass transfer to a rotating disk has been studied extensively. The asymptote derived by Levich I is suitable for high Schmidt numbers. Corrections to this asymptote were presented by Sparrow and Gregg 7, Newman 8, and Liu and Stewart ~, respectively, so they can be applied to moderate and low Schmidt numbers. Generally, the experimental data were found to have good agreement with the theoretical values for laminar flow 1~ As for transition (3 x 105 < Re < 106) and turbulent flows (Re > 106), most of the studies were experimental approach and correlations applied to various regions of Reynolds numbers are available in the literature 12,14,15.On the other hand, the impinging jet on a flat plate is also an interesting flow which can provide "uniform accessibility" at its center spot for heat or mass transfer similar to that on a rotating disk. Because of this property it receives the same attention as the rotating disk. From the results in the literature 4' 16-19, it is concluded that the local transfer rate depends on the Reynolds number of the fluid in the nozzle, the Schmidt number of the diffusing species, the nozzle height, and the radial position on the plate. The dependences on these parameters are somewhat different in the stagnation and wall-jet regions on the impinged plane 4'~-I~. The flow pattern in the nozzle also plays an important role in heat or mass transfer of an impinging jet. Scholtz and Trass 16 considered an impinging jet with a parabolic velocity distribution. In addition to the theoretical and experimental examinations of fluid flow, the local mass-transfer coefficients:/l~have been calculated theoretically and compared with the experimental data for the airnaphthalene system. It was pointed out that even at equal Reynolds numbers, the mass transfer observed for a...

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“…-23- Substitution of these two expressions into equation (6) gives Q 0.6,,1. 8 (11) constant defined in equation (32) the number of electrons transferred The Reynolds number dependence of the radial shear stress.…”

Section: Rementioning

confidence: 99%

“…, Tien and Campbell [5], Ellison and Coronet [6], and Chin and Litt [7]. For the transition region Mohr and …”

mentioning

confidence: 99%