Einfloß einer mechanischen Prallkörperbearbeitung auf die Diffusionsverhältnisse an einer rotierenden Scheibenelektrode

Leitel, E.; Pinkowski, A.; Thiessen, Karsten Peter

doi:10.1515/zpch-1979-0162

Cited by 4 publications

(7 citation statements)

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“…Another explanation for the origin of the critical rotation speed is given by Leitel et al [28] and Caprani et al [16][17][18][19]. The occurrence of one or more critical values of ~ is attributed to partial blockage of the electrode surface by adhesion of particles and removal of adsorbed species at higher rotation speeds.…”

Section: Adhesionmentioning

confidence: 99%

“…The rate of mass transfer of an electrode process can be enhanced via increased convection of the electrolyte, or by introducing turbulence promoters [1], gas bubbles [2,3], and solid particles [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The influence of glass spheres was measured by Leitel et al [4] and Roha [5] for a RDE (rotating disc electrode) and by Smith et al [6] for an electrode in a tube wall. Roha [5] also studied the influence of the particle size and found a weak maximum in the mass transfer when the particle diameter equals the diffusion layer thickness.…”

Section: Introductionmentioning

confidence: 99%

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The influence of suspended particles on the mass transfer at a rotating disc electrode. Non-conducting particles

1990

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Section: Adhesionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The influence of suspended particles on the mass transfer at a rotating disc electrode. Non-conducting particles

1990

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“…Die Veranderung in den Stofftransportverhaltnissen bei feststoffbeladenen Stromungen steht mit den experimentellen Arbeiten an der Versuchsanordnung der rotierenden Scheibenelektrode im Einklang [25]. Die Veranderung in den Stofftransportverhaltnissen bei feststoffbeladenen Stromungen steht mit den experimentellen Arbeiten an der Versuchsanordnung der rotierenden Scheibenelektrode im Einklang [25].…”

Section: Stofftransportgeschwindigkeitunclassified

“…Unter bestimmten experimentellen Bedingungen kommt es jedoch zu einem Ruckgang der Stofftransportgeschwindigkeit[25].Uber den EinfluB der mittleren Stromungsbedingungen auf die Erosion bei Feststoffteilcheneinschlag berichtet Tilly[26]. Bei der SuBgasforderung in der DDR wurden leitungen beobachtet.…”

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Untersuchungen zum Zusammenhang von Stofftransportgeschwindigkeit und Abtragsgeschwindigkeit unter Erosionskorrosionsbedingungen

Leitel

Rübner

Fisch

et al. 1990

Materials & Corrosion

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Die Wechselwirkungen zwischen Strömungsbedingungen, Stofftransportgeschwindigkeit und Abtragsgeschwindigkeit in Zweiphasenströmungen werden bei der Simulation von Erosionskorrosion untersucht. Die Geschwindigkeit und die Beladung der Strömung werden variiert. Zur Bestimmung der Stofftransportgeschwindigkeit dient die Grenzstromtechnik. Die Untersuchungen werden im Redoxsystem Kaliumhexacyanoferrat(II)/Kaliumhexacyanoferrat(III) an einer glatten Platinelektrode durchgeführt. Die Abtragsgeschwindigkeit wird gravimetrisch an den Stählen St 38 und X8 CrNiTi18. 10 in einer wäßrigen Natriumchloridlösung bestimmt. In Zweiphasenströmungen stellt die Stofftransportgeschwindigkeit eine charakteristische Größe für die erosive Beanspruchung dar. Unter bestimmten Bedingungen traten Bistabilitäten sowohl in der Stofftransportgeschwindigkeit als auch in der Abtragsgeschwindigkeit auf.

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“…This description employed since 1979 (14) for concentrated suspensions provides theoretically and experimentally two straight-line segments in t i, ft-~J2 coordinates. We have observed a similar variation law for red blood cell suspensions (15,16), for which we have also shown through diffusion impedance measurements that particles adhere to the electrode (17).…”

mentioning

confidence: 99%

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Caprani

Ficquelmont‐Loïzos

Tamisier

et al. 1988

J. Electrochem. Soc.

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In a previous publication, we studied mass transfer at a rotating disk electrode in "inert" particle suspensions. We now account for the variations of the limiting diffusion current with numerous parameters by different phenomena. These involved either the topography of the interface through adhesion of the particles to the electrode or the mass exchanges in the diffusion layer through changes in the velocity field and/or diffusion coefficient. Each phenomenon, considered separately, gives rise to one or more linear segments for the variations of current with the rotation speed ft, in logarithmic coordinates. Considering all the invoked phenomena, we would expect more segments than the four observed in experimental log I vs. log gt plots. Analyzing the consequences of each phenomenon in the whole f~ range allows one to disregard some of them for certain ft values and to account for most of the experimental results. At low ft values, two predominant phenomena, with antagonistic effects, explain the deviations from the one-phase media behavior: the reduction of the exchange area and the increase of the apparent diffusion coefficient through changes in the size of aggregates along the streamlines. Moreover. for small-size particles or for particle concentrations sufficiently high, deviations from newtonian behavior are also observed. At intermediate and high ~ values, the predominant phenomenon is the variation of the diffusion coefficient with the shear rate. Depending on the ratio of the diffusion layer thickness over the particle size (g/a), two different laws can describe this variation.In the first paper of this series (1), we determined, using an electrochemical method, the influence of several parameters on mass transfer in two-phase media. These parameters are inherent in the particle, the medium, and the rotating disk electrode (RDE). The fact that the influence of each of them is closely dependent on the influence of the others suggests that various phenomena must take place at the interface, with shear rate dependent relative weights.We present here a general model in order to take into account most of our experimental results and to interpret the "particle-wall-flow" interactions which control the mass transfer to the wall.The particles are known to induce discrepancies on mass transfer with respect to the supernatant. Three different approaches have been used in the literature to account for these discrepancies: a hydrodynamic approach, a diffusional approach, and a third approach in which blocking of the exchange area is invoked. The two first approaches disregard the role of the electrode surface, and lead to an increase of mass transfer. The third approach only takes into account the phenomena at the interface and leads to a decrease of mass transfer. This last approach ignores the particle-induced perturbations of the volume-related phenomena.The first and most microscopic approach was employed in the case of the rotating disk electrode (2, 3). It consists in solving with important approximations th...

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Einfloß einer mechanischen Prallkörperbearbeitung auf die Diffusionsverhältnisse an einer rotierenden Scheibenelektrode

Cited by 4 publications

References 0 publications

The influence of suspended particles on the mass transfer at a rotating disc electrode. Non-conducting particles

The influence of suspended particles on the mass transfer at a rotating disc electrode. Non-conducting particles

Untersuchungen zum Zusammenhang von Stofftransportgeschwindigkeit und Abtragsgeschwindigkeit unter Erosionskorrosionsbedingungen

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

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