Stirrer shaft

Viscoelastic Measurement. A number of methods measure the various quantities that describe viscoelastic behavior. Some requite expensive commercial rheometers, others depend on custom-made research instmments, and a few requite only simple devices. Even quaHtative observations can be useful in the case of polymer melts, paints, and resins, where elasticity may indicate an inferior batch or unusable formulation. Eor example, the extmsion sweU of a material from a syringe can be observed with a microscope. The Weissenberg effect is seen in the separation of a cone and plate during viscosity measurements or the climbing of a resin up the stirrer shaft during polymerization or mixing. 

I. The Hershberg stirrer, shown in part in Fig. 2, provides very efficient agitation of this or other pasty mixture. Two glass rings are sealed to the end of a stirrer shaft at right angles to one another, and each is threaded with B. and S. No. 18... 

A heavy nichrome wire twisted into 4 loops (similar to an egg beater) was found to be very satisfactory. The two ends of the wire, extending several inches beyond the loops, were pushed into a piece of glass tubing for the stirrer shaft. 

High agitation and aeration cause major problems such as foaming, which may lead the fermentation vessel to unknown contamination. Antifoam cannot be always added for the reduction of foam it may have inhibitory effects on the growth of microorganisms, so the simplest devices have rakes mounted on the stirrer shaft and located on the surface of the fluid. 

The simplest devices have rakes mounted on the stirrer shaft located on the surface of the liquid. A more sophisticated device is the Funda-foam system , in which the foam is destroyed by centrifugal forces. The nutrient solution held in the foam flows back into the bioreactor, and the air released from the foam leaves the vessel. 

Foam in the bioreactor is troublesome it can reduce the oxygen transfer rate (OTR). Antifoam is use to prevent foam formation. However, excess antifoam may cause growth inhibition in the course of fermentation. The simplest device is known as a foam breaker, which is mounted on the stirrer shaft located on the surface of liquid. It is a flat blade. 

Wooden hatch covers may support and encourage growth, particularly of fungi, and powders, caked onto the stirrer shaft and lid, moistened with condensation and not biocidally protected, can also become colonised by micro-organisms. 

Sand as diluent to prevent caking, 22,98 Sandmeyer reaction, 24, 22 Saponification, of ethyl linoleate, 22, 78 of ethyl linolenate, 22, 84 of natural oils, 22, 75, 79, 82 of Ji-nitrobenzyl acetate, 24, 81 Screen, protective, 22, 97 Seal, rubber tube, for stirrer shaft, 21, 40... 

This disc holder is rotated at the end T of the stirrer shaft in place of the wire I basket in (ii) above. 

Fig. 5.10 Computer-assisted extraction kinetics-measuring apparatus for highly stirred phases (A) high-speed stirrer (B) stirrer shaft (C) sample inlet (D) Teflon stirring har (E) Teflon phase separator (F) water hath (G) flow-cell (H) spectrophotometer (I) peristaltic pump (J) chart recorder (K) A/D converter (L) clock (M) minicomputer (N) dual-floppy disk drive (O) printer, (P) plotter. (From Ref. 16.)...

Fig. 3.23. Conductivity cell with phial magazine Q containing phials and magnetic pusher. The electrode assembly E is that shown in Fig. 3.22. S is a stirrer shaft with a propeller at one end and a glass-enclosed magnet N at the other. The stirrer shaft is held in position by the PTFE bearings Tf Tf, and Tf and the glass tube spacer G Th ha. thermocouple pocket and B a magnetic breaker for the phial P. The propeller, driven by the rotating magnet M, pumps the cell contents around the loop L, so that when P is broken there is very fast mixing.

Stirring is continued until the mass has set solidly it is desirable for a channel to exist around the stirrer shaft to facilitate the subsequent decomposition. 

Stirring Device — The lid shall be equipped with a stirring device (Fig F13), mounted in the center of the lid and carrying two two-bladed metal propellers. A stirrer shaft may be coupled to the motor by a flexible shaft, or a suitable arrangement of pulleys... 

Cole-Parmer Instrument Co. Chicago, IL. Alternatively, a variable-speed shop drill may be used with a standard stirrer shaft. 

Mechanical stirrer (shaft, blade, bearing, motor)... 

A magnetic stirrer is unsatisfactory. The submitters used a glass-blade stirrer at 300 r.p.m. The stirrer shaft must be rigidly attached to the motor because the reaction mixture becomes very thick during the addition of oxalyl chloride. 

In (b), the pi numbers and 7ho T as well as ye/yn, have to be added (7 = din /dT). Besides this, completely other phenomena can occur (e.g., creeping of a viscoelastic liquid on a rotating stirrer shaft opposite to gravity—the so-called Weissenberg effect) that require additional parameters (in this case g) to be incorporated into the relevance list. 

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