Attachment length

The origin of the cylindrical coordinate system is placed at the center of the bath, as shown in Fig. 3.3. The horizontal distance from the side wall is designated by t] =R — r). The distance from the side wall to the nozzle exit, , is varied from 1.75 x 10 to 3.5 x 10 m. The horizontal position at which a peak appears in the gas holdup distribution is designated by a,max and the half-value width by > a,max/2,- These quantities are introduced to represent the horizontal extent of the bubble dispersion region. In the same manner, the peak position and half-value width of the axial mean velocity u are defined. These two representative scales will be discussed in a later section. The attachment length La is defined as the vertical distance from the nozzle exit to the position at which bubbles attach to the side wall. 

The attachment length La was determined from a picture taken with a still camera of a bubbling jet subjected to the Coanda effect. 

Fig. 3.5 Relation between attachment length and gas flow rate...

The average length of the chains attached to aromatic rings (Brown and Ladner, 1960). 

The Mariotte bottle. l he perchlorate guard tube is attached by a length of ordinary rubber condenser tubing to the Mariotte bottle W. This is, in effect, a siphon bottle, and the lead-in tube X is a capillary provided with a tap T,. The bent capillaiy (drawn off slightly at the end) serves as exit tube it is fitted into W by a rubber bung and its level may be adjusted. 

Z-tube. The tube B is made of capillary tubing (3 mm. internal bore) bent into the shape of a Z. It is attached by a length (5 cm.) of very tight-fitting rubber pressure tubing to the tap T, a gla -to-glass join being made inside... 

T for attachment to the angle tube F. The tap T, niay have a length of glass rod fused to it so that it is capable of fine adjustment. The lower (internal) end of the capillary tube G is bent downwards and is also drawn out very slightly. 

The upper outlet for water from the condenser should be above the jacket so as to ensure that the condenser is full of water. If the rubber tube, which carries the waste water to the sink, tends to kink, a short copper spiral, made by winding a length of copper wire round a glass tube, may be slipped over the end attached to the condenser. 

When the boiling point of the liquid is above 140-150°, an air condenser (Fig. II, I, 1, c) may replace the water condenser. If the liquid is inflammable, the conical flask may be replaced by a Alter or suction flask (see Fig. II, 1, 7, c), and a length of rubber tubing leading to the sink is attached to the side tubulure. 

A flask is provided with a long side neck (Fig. II, 25, 1) through which a capillary is inserted and attached externally by a short length of rubber pressure tubing. With this type of connexion there is essentially no contact of hot vapours with the rubber and little or no contamination results. The neck of the flask is preferably fitted with a standard ground joint if attack of the organic vapours on the rubber stopper is likely to occur. 

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