Immersion speed

Figure 26.23 Interpretation of fluid holding phenomena on vertical plates immersed in solution to a depth of 15 mm (indicated by the dotted line on each plate) and then raised to a depth of 5 mm corresponding force loop plots with fluid holding times of (A) 0 s, (B) 57 s, and (C) 115s were calculated from a constant immersion speed of 300 mm/s.

Figure 6.18 shows the results obtained for sweeps using 3, 6, and 12 cm/s immersion speeds. However, at immersion speed 5 cm/s the immersion takes about 1 s and approximately 25 measurement points were recorded for evaluation. 

Figure 6.18. Shape of the immersion curve for various immersion speeds.

All the other approaches, including the head-to-tail methods and full-immersion (OH-first), have the common drawback that the immersion time in the second solution is practically hmited (<15 min under the experimental parameters selected in this work). For the head-to-tail method, this is because the immersion speed can only be varied between 2.5 pimls to 2.5 mm/s. The full-immersion (OH-first) method has a limitation because an elongated immersion (>1 h) of the HO(CH2)iiSH precoated film in the second solution (0.01 mM CH3(CH2)iiSH) results in a loss of the hydrophobicity gradient as a result of the displacement of adsorbed HO(CH2)iiSH by CH8(CH2)ii-SH. Thus, for the full-immersion (OH-first) method the immersion time in the second solution needs to be a compromise between the full saturation of sites and the maintenance of a hydrophobicity gradient (10 min was selected in this work). In contrast, full-immersion (CHs-first) suffered virtually no corresponding displacement in... 

The automated capillary rise technique has been employed to carry out various dynamic advancing and receding contact angle measurements (54) at different immersion speeds ranging from 0.008 to 0.9 mm/min. This technique has also been utilized to study both dynamic advancing and receding contact angles on dry, pre-wetted, and soaked fluorocarbon FC-722 (3M Inc.) surfaces (55). Such measurements reveal that the... 

Immersion-type extractors have been made continuous through the inclusion of screw conveyors to transport the soHds. The Hildebrandt immersion extractor (18) employs a sequence of separate screw conveyors to move soHds through three parts of a U-shaped extraction vessel. The helix surface is perforated so that solvent can pass through the unit in the direction countercurrent to the flow of soHds. The screw conveyors rotate at different speeds so that the soHds are compacted as they travel toward the discharge end of the unit. Alternative designs using fewer screws are also available. 

As the vessel is only about half filled with slurry, the disks become coated with the cake when immersed, the cake is dewatered when the disks emerge from the slurry, and scraped or blown off, by reverse blow, into the central conveyor which takes the cake to one end of the vessel. The planetary action and the slow movement of the disks through the feed slurry ensure exceptionally good homogeneity of the cake which is critically important for good dewatering characteristics the typical speed of rotation of the planetary system of shafts is from 0.8 to 1 rpm. 

The speed of the pickle reaction is also dependent on the concentration and temperature of the pickle, the degree of agitation of either the metal part or the pickle solution, the alloy being pickled, and the acid used. Pickling solutions may be appHed by either spray or immersion techniques. However, because of the noxious fumes emitted, there must be adequate ventilation. Sometimes, particularly when spraying techniques are used, an enclosure to contain the fumes and mist is employed. 

In addition, dimensional analysis can be used in the design of scale experiments. For example, if a spherical storage tank of diameter dis to be constmcted, the problem is to determine windload at a velocity p. Equations 34 and 36 indicate that, once the drag coefficient Cg is known, the drag can be calculated from Cg immediately. But Cg is uniquely determined by the value of the Reynolds number Ke. Thus, a scale model can be set up to simulate the Reynolds number of the spherical tank. To this end, let a sphere of diameter tC be immersed in a fluid of density p and viscosity ]1 and towed at the speed of p o. Requiting that this model experiment have the same Reynolds number as the spherical storage tank gives... 

The advantage of such dipping apparatus is that the insertion and removal of the chromatogram is performed at a uniform speed and the time of immersion can be set as necessary. Interfering ripple marks", such as are observed on manual dipping, do not occur. Care must be taken, however, to clean off the back of the... 

Aerodynamics deals with the flow of gases, particularly air, and the interaction with objects immersed in the flow. The interaction takes the form of an aerodynamic force and moment exerted on the object by the flow, as well as heat transfer to the object (aerodynamic heating) when the flow velocities exceed several times the speed of sound. 

Optimum depth of immersion depends on pitch-line speed. Deep immersion is permissible at low speeds because power losses from churning are low, but at moderate speeds the immersion depth should not be more than three times the tooth height. At the highest speeds, only the addenda of the teeth need be submerged (Figure 52.8). 

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