Wiper Blades Research Articles

Properties of the seawater‐air interface. Dynamic surface tension studies1

The properties of the seawater‐air interface were studied by laboratory measurement of the dynamic surface tension of seawater and of samples of artificial seawater on which films of oleic and stearic acid were spread. A commercially available, automatic recording apparatus was used, consisting of a modified Langmuir trough with motor‐driven surface wiper blades, a Wilhelmy plate surface tension electric microbalance, and a recorder.Comparison of the shape of the dynamic surface tension‐surface area curves of original seawater samples with those of artificial ones showed that the “expanded‐” type surface film, produced by surface spreading of oleic acid, serves as an adequate model of conditions at the real seawater‐air interface. This model and its surface tension dynamics could be used, in addition to chemical analytical data, as a quantitative measure of the state of the seawater‐air interface and its role in controlling the transport of gases and other soluble materials between the atmosphere and the oceans.

Studies of lubricated rubber friction: Part 2: Optical techniques applied to practical problems

The development of optical interferometry for examining lubricated rubber contacts was described in Part 1 of this article. Part 2 focuses attention on the application of optical techniques to some commonly encountered rubber devices such as fluid seals, wiper blades and road tyres.

On the computation of mass transfer rates at rotating cylindrical electrodes with wiper blades

On the computation of mass transfer rates at rotating cylindrical electrodes with wiper blades

Continuous activation in a rotating bipolar electrode cell—I via control of the surface oxide thickness

A recently developed rotating bipolar electrode cell, equipped with wiper blades, is described as a continuous activator of the electrode surface; the thickness of the oxide film is easily controlled and at a particular potential the rate of processes occurring on the oxide film can be greatly increased. Furthermore, at a particular current density the reaction potential can be significantly altered, and the products of electrolysis changed. The oxygen evolution reaction and the competing Kolbe dimerization reactions, taking place at Pt in aqueous acid electrolyte, provide specific illustrations of the operating principles.

Continuous activation with a rotating bipolar electrode—II: Via impurity stripping

The ability of a rotating bipolar electrode, equippied with wiper blades, to continuously activate the electrode surface by stripping of adsorbed impurities is demonstrated for the inhibition of oxygen reduction at Pt by copper. The results show that the poisoning effect of such impurities can be avoided, and that the electrode can be maintained at high activity under conditions where ordinarily complete passivation would occur. A theoretical analysis of the continuous effect is also presented, and indicates that the continuous activation effect is most likely to be effective when the rate of impurity adsorption is under diffusion control.

Concentrating, refining and purification by means of rotating bipolar electrode cell

The use of a ‘rotating bipolar electrode’ (RBE) cell to achieve a transfer of a substance (copper) from solutions of low concentration to high concentration is described. The RBE cell employed consists of a central, rotating, cylindrical electrode, surrounded by axial wiper blades which form three compartments through which the electrode surface passes during rotation. An outer electrode in each compartment governs the potential of the rotating electrode, and copper is deposited on the electrode surface in two of the compartments, and stripped in the other. Stripping can be achieved by either electrochemical or chemical means. Very high compartment concentration ratios (>250) can be achieved and sustained by using cells with more than two compartments. The process can be operated with conditions thermo-dynamically more advantageous than possible with conventional cells. Typical costs for a RBE cell process are given.

The rate of mass transfer at a rotating cylindrical electrode with wiper blades

AbstractA theoretical analysis of mass transfer at a rotating cylindrical electrode with wiper blades yields the dimensionless equation where w is the number of the symmetrically located wiper blades, d is the wiper blade thickness and R1 is the radius of the wiped electrode. NuR, ReR and Sc are defined in terms of the cell and electrolyte parameters. Experimental evidence via the reduction of oxygen and ferrocyanide ions indicates that mass transfer rates can thus be predicted at no more than ±5% inaccuracy for Sc>200. The two‐wiper blade system is shown to effect an increase in mass transfer rates by a factor of 7‐8 with respect to a rotating cylindrical electrode without wiper blades.

The rate of mass transfer at a rotating cylindrical electrode with wiper blades

AbstractA theoretical analysis of mass transfer at a rotating cylindrical electrode with wiper blades yields the dimensionless equation where w is the number of the symmetrically located wiper blades, d is the wiper blade thickness and R1 is the radius of the wiped electrode. NuR, ReR and Sc are defined in terms of the cell and electrolyte parameters. Experimental evidence via the reduction of oxygen and ferrocyanide ions indicates that mass transfer rates can thus be predicted at no more than ±5% inaccuracy for Sc > 200. The two‐wiper blade system is shown to effect an increase in mass transfer rates by a factor of 7–8 with respect to a rotating cylindrical electrode without wiper blades.

The extrusion of liquids between highly elastic solids

This paper surveys some of our more recent work on the extrusion of liquid films between a glass and a rubber surface. By producing optically smooth spheres and cylinders of rubber it has been possible to study the thickness and contour of the liquid film trapped between the surfaces by optical interferometry. When the surfaces are brought together in normal approach a bell of liquid is trapped at the centre of the contact region and gradually extruded until the surfaces are almost parallel and a film of the order of a few tens of nm is formed. Further extrusion or tangential sliding thus provides a means of determining the viscosity of the liquid film. For films thicker than 50 nm the viscosity is essentially the same as the bulk. If the liquid contains a low concentration of ions the liquid film collapses for thicknesses less than about 40 nm. If, however, the ion concentration is adequate (e.g.an aqueous solution of SDS or KCl) and if the ions are appropriately adsorbed on to the surfaces electrical double layers may be formed which are capable of supporting a contact pressure of the order of 10 to 100 kPa (0.1 to 1 atm). The film thickness is reduced ( a ) if the contact pressure is increased and ( b ) if the ion concentration is increased since in the latter case the ‘centre of gravity’ of the charge is moved closer to the surfaces. At the lower pressure range the film thickness is of order 25 nm (250 Å) but even in this case the viscosity is comparable with the bulk viscosity. Evidently there is little ordering of the liquid by surface forces. Thinner films appear to show an increase in resistance to shear but this may be the result of contact between asperities. Similar observations have been made using synovial fluid and saliva and it is suggested that many body fluids which contain free ions are able to provide modest boundary lubrication by the charged double-layer mechanism. The paper concludes with a discussion of the behaviour of windscreen wiper blades both in the absence and in the presence of liquid films.

A small laboratory model, wiped‐surface heat exchanger for chilling and texturating shortenings

AbstractA miniature Votator type, wiped‐surface heat exchanger for chilling and texturating shortening has been described.The package unit, mounted on a table about 2×4 ft. in dimensions, fitted with casters for mobility, needs only to be plugged into an electrical outlet for operation, operates at fat feed‐rates of 10 to 80 lbs. per hour, with an integrated 3/4 ton Freon refrigeration unit capable of holding the chilling unit to ±1°F, in the range −30°F, to +60°F., 4‐step pulley agitator drives on both chilling and texturating units giving 330 to 1170 r.p.m. speed range, aluminum alloy chilling and texturating units, fat and air Flowrators with needle valve control, free‐swinging wiper blades, and a few other minor features that lead to smooth operation.The unit has been found useful in our laboratory to process various types of shortenings for research purposes, to supply special shortenings to prospective customers for evaluation, and to check the operation of the plant Votators.

Surface contamination control with uranium rolling operations.

The problems encountered during uranium rolling were found to be more of a technical nature than one of great health hazard. The considerations for enriched uranium were found to be essentially the same as for normal uranium except for the magnification of specific activity levels. Strip heating of uranium and rollers resulted in the least amount of contamination spread, with the exception of wiper blades. Heating uranium in an oil bath prior to rolling resulted in the second least contamination spread, and salt bath and furnace heat methods resulted in the greatest amount of contamination spread. Work clothing issue and change room facilities reduce contamination to personnel as well as confining contamination activity within the plant. Personnel must be monitored for contamination as they leave the area both as a health check and also to indicate a trend on operating controls. It has been found that waste water from such areas has not exceeded the drinking water tolerance providing it has been properly filtered. Contaminated clothing must be processed by laundry facilities segregated from those handling ordinary clothes. Shearing operations created more problems than rolling since the materiall had to be handled longer while it was being sheared. This opcrationmore » results in the greatest external radiation to the body, in addition to creating high airborne contamination, unless adequate ventilation is provided directly at the shears. Contaminated residue had to be placed in containers and disposed of in accordance with AEC and local requirements. Frequent surface monitoring was the key to contamination control. With the exercise of proper contamination and fire control, the hazard encountered by personnel was nil. (auth)« less

The Electrodeposition of Iron‐Molybdenum Alloys

A plating cell was designed to provide a method for the variable rotation of a cylindrical cathode between rubber wiper blades, since wiping the cathode greatly increased the efficiency of the process for plating iron‐molybdenum alloys from a solution containing sodium molybdate, ferric chloride, and sodium pyrophosphate buffered to a pH of 8 with excess sodium bicarbonate. A complete study of the variables showed it possible to electrodeposit alloys which are bright and adherent in thicknesses of a few hundredths of a millimeter. No theoretical treatment is yet available to explain completely this type of deposition.