Roll cells

The cell used (Fig. 16) is an undivided, so called Swiss-roll cell (Figs. 16 and 17) with a Ni mesh anode and a steel cathode. 

Fig. 17. Schematic diagram of the flow system used for batch and continuous oxidation of DAS (Diacetone-L-sorbose) with a swiss roll cell with an anode area of 3 m2...

Swiss Roll Cell This cell has been developed in Switzerland [89]. A commercial application is one oxidation step at a NiOOH anode in alkaline solution for the vitamin C production [22]. Mesh electrodes of stainless steel (cathode 1) and nickel (anode 3) are rolled up together with spacers of polypropylene mesh (2,4) on the central current feeder (5) and mounted in a cylinder (cells up to 1 m diameter, 200 m active area). The electrolyte streams axially through the cell. 

Flow near the interface that is influenced by gradients of interface tension is called Marangoni convection. It may have further modes [27]. Thus, a low Marangoni convection in an interface, which results from small concentration differences, may be increased to a strong flow in the shape of rolling cells by mass transfer. These rolling cells transport liquid out of the... 

Third, turbulent transport is represented as a succession of simple laminar flows. If the boundary is a solid wall, then one considers that elements of liquid proceed short distances along the wall in laminar motion, after which they dissolve into the bulk and are replaced by other elements, and so on. The path length and initial velocity in the laminar motion are determined by dimensional scaling. For a liquid-fluid interface, a roll cell model is employed for turbulent motion as well as for interfacial turbulence. 

Fig. 6. (a) The flow pattern assumed in the physical model for the motion near the wall, (b) A more realistic flow pattern of the motion, (c) The roll cell pattern near the wall in a section normal to the main direction of flow. 

S. Roll Cell Models for Turbulent Mass Transfer... 

Fig. 8. Roll cell model (a) stream lines in a frame of reference moving with the average liquid velocity (b) stream lines in a fixed frame of reference.

For laboratory scale conversions a simple beaker-type cell (Fig. 1) is convenient When lower current densities have to be applied or in big scale operations 21,26) the Swiss-roll cell is of advantage. The latter cell (Fig. 2) contains a rolled-up sandwich, consisting of an anode and cathode sheet and a separator net. This allows a high electrode area applied in a small cell volume, which results in the low current densities necessary for efficient electrolyses at the nickel hydroxide electrode. 

Fig. 2 Swiss-roll -cell, arrangement of the electrodes 1 Steel net cathode 2,4 Polypropylene net as insulating separator 3 Nickel net anode 5 Current feeder...

The Swiss-roll cell is commercially available from Dr. Robertson, P. M., Haldenstr. 9, 8185 Winkel, Switzerland... 

A special construction, called Swiss-Roll cell [13] (Fig. 22.12), is used for the application of the NiOOH electrode in the oxidation of primary alcohols to carboxylic acids. 

Figure 22.12 Swiss-Roll cell for the applications of NiOOH electrodes (1 = steel net cathode 2 + 4 = polypropylene net 3 = nickel net anode 5 = current feeder).

The three-dimensional, fully parabolic flow approximation for momentum and heat- and mass-transfer equations has been used to demonstrate the occurrence of these longitudinal roll cells and their effect on growth rate uniformity in Si CVD from SiH4 (87) and GaAs MOCVD from Ga(CH3)3 and AsH3 (189). However, gas expansion in the entrance zone combined with flow obstructions, such as a steeply sloped susceptor, can also produce... 

Mercury represents a serious environmental risk, and the study of removal of mercury from wastewater has received considerable attention in recent years. Mercury concentration was usually reduced by deposition on a cathode with high surface area. Removal of mercury is studied using extended surface electrolysis which reduces the level of mercury to below acceptable concentrations of 0.01 ppm in wastes by employing a Swiss roll cell with a cadmium-coated, stainless-steel cathode. An industrial cell with a fluidized bed electrode has also been studied. Graphite, as an efficient porous electrode, has been used to remove traces of mercuric ions form aqueous electrolyte solutions. In order to apply the electrochemical method for some effluents, it is necessary to use sodium hypochlorite to convert elemental mercury and less soluble mercury compounds to water-soluble mercuric-chloride complex ions. 

For cells that lack IR loss-increasing membranes, the Swiss-roll cell design (Ibl, 1975) may be the answer. Two metal foils act as electrodes and are separated by two insulating plastic masks that act as turbulence promoters. This cell gives large area and low IR. It is shown in Fig. 11.6. 

Fig. 11.6. Swiss-roll cell. (Reprinted from G. Kreysa, in Ulmann s Encyclopedia of Industrial Chemistry, Vol. 49, p. 200,1985, with permission from Wiley-VCH.)...

Polyacene PC (CH3CH2)4N+BF4- 2.5 V Coin cells Jelly-rolled cells — >1,000,000 Page 207... 

Activated carbon PC (CH3CH2)4N+BFC 2.5 V Jelly-rolled cells — — Page 213... 

Swiss-roll cell — This cell was developed in Switzerland in 1982, and it is used on industrial-scale in case of the NiOOH electrode for the oxidation of primary alcohols to carboxylic acids, as, e.g., in vitamin C production. The electrolyte solution flows axially through the cell (see Figure), which is made up of rolled meshes of the nickel net anode and steel net cathode, separated from each other by polypropylene spacers, around the central current feeder rod. 

Because of the rotation of the Earth and because of the warm equatorial and cool polar regions, the atmosphere divides itself into six regions (roughly corresponding to the climatic zones). These atmospheric regions are called the northern and southern Polar, Ferrel, and Hadley cells (so called because they are roll cells ) see Figure 3.2. This division of the atmosphere tends to slow the mixing... 

As Er is increased further to around 10 in 8CB (at 37°C), there is a roll-cell instability involving (a) a periodic modulation of the director field in the vorticity direction and (b) a cellular flow. The rolls cells are parallel to the primary flow direction (Pieranski and Guyon 1974) (see Fig. 10-19). These transitions in the director field have been both predicted from the Leslie-Ericksen theory (Manneville and Dubois-Violette 1976 Larson 1993) and... 

Figure 10.19 Velocity field (a) and director pattern (b) in roll cells that form in a tumbling nematic initially oriented in the vorticity direction of a shearing flow. (From Larson 1993, with permission from the Journal of Rheology.)...

Other quasi-periodic textures have been reported, including birefringent stripes parallel to the flow direction (Gleeson et al. 1992). A low-shear-rate stripe texture observed in PBG solutions can be attributed to roll cells (Larson and Mead 1993), similar to those... 

---