Swirl motion

Insert with channels to provide high velocity swirl motion at nozzle exit... 

The rotating-disk CVD reactor (Fig. 1) can be used to deposit thin films in the fabrication of microelectronic components. The susceptor on which the deposition occurs is heated (typically around lOOOK) and rotated (speeds around 1000 rpm). A boundary layer is formed as the gas is drawn in a swirling motion across the spinning, heated susceptor. In spite of its three-dimensional nature, a peculiar property of this flow is that, in the absence of buoyant forces and geometrical constraints, the species and temperature gradients normal to the disk are the same everywhere on the disk. Consequently, the deposition is highly uniform - an especially desirable property when the deposition is on a microelectronic substrate. 

In those cases where stirring for short periods is necessary, this may usually be accomplished by gentle rotation of the vessel thus imparting a swirling motion to its contents. If the vessel cannot conveniently be moved, a hand-operated stirrer constructed entirely of glass (compare Fig. II, 10,4 and Fig. II, 10, 2) will be found satisfactory provided the glass loop is not too large. 

Helical screws normally function by pumping liquid from the bottom of a tank to the liquid surface. The liquid then returns to the bottom of the tank to fill the void created when fresh liquid is pumped to the surface. A rotating helical screw positioned vertically in the centre of an unbaffied cylindrical tank produces a mild swirling motion in the liquid. Since the liquid velocity decreases towards the tank wall, the liquid at the wall of an... 

Only a movie filmed at the impossible rate of about 1016 frames a second would show the swirling motion. 

Fluoride-related health hazards are associated with the use of fluoride-contaminated water for drinking and cooking. This corresponds only to 2-4 L per capita per day. Fluoride removal in rural areas in LDCs, where centralized water treatment and distribution facilities are unavailable, should consequently be carried out at a household level and the system applied should be simple and affordable. In this regard, tea bag POU system becomes handy. Although this kind of system has not been specifically reported for water defluoridation, it has been tested for arsenic [37,107], It is therefore a short-term potential technique worth considering. In this technique, adsorption medium is placed in a tea bag-like packet, which is subsequently placed in a bucket of water to be treated. To ensure faster defluoridation kinetics, the bag should be swirled inside the water. It therefore operates like a batch reactor and hence requires a relatively longer adsorption time to achieve the permissible levels. Since the swirling motion is supposed to be human-powered, the technique would require a material with very fast kinetics or very fine adsorption media. 

When, however, the diameter is increased above 10 cm., the speed of the flames is affected by the coming into play of another factor, namely, convection. This is noticeable with the fastest moving flames in tubes 10 cm. m diameter, the visible effect being a turbulence of the flame front. This is essentially a swirling motion in a direction nearly normal to the direction of translation of the flame front, which, as in tubes of smaller diameter, progresses at a uniform speed for about 150 cm. before backward and forward vibrations are set up. This swirling motion appears ab initio, and is due to rapid movement of the hot gases from below upwards by convection. In tubes of comparatively small diameter (5 to 9 cm.) this rapid movement is suppressed. 

In a 1-1. round-bottomed flask are placed 66 g. (0.33 mole) of glucose monohydrate (Note 1) and 302 g. of 95 per cent acetic anhydride (280 cc., 2.81 moles). To this mixture three small drops of concentrated sulfuric acid are added from a medicine dropper (Note 2). The glucose is kept in partial suspension by shaking the flask with a swirling motion the reaction starts almost immediately. If the temperature of the mixture approaches the boiling point, the flask is momentarily immersed in a pan of cold water. Within ten to fifteen minutes nearly all the glucose will have dissolved and the temperature of the reaction mixture will ha ve risen nearly to 100°. The flask is loosely stoppered and is healed on a steam bath for two hours. Then about 200 cc. of mixed acetic acid and acetic anhydride is removed by distillation under reduced pressure (Note 3). 

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