Axial plates

Fig. 36. (a) Single poppet valve (b) combined inlet—outlet axial plate valve. 

The axial plate height is related to the apparent axial dispersion coefficient by 2 Da... 

Figure 6.13 Comparison of the plots of the reduced axial plate height vs. the reduced flow velocity obtained (a) by PFGNMR and (b) using a conventional chromatographic method. Column packed with 50 m particles of porous C18 silica. The lines shown are the best fits of the experimental data (symbols) to the correlations suggested by Giddings (x = 1), Huber (x = 0.5), and Horvath and Lin (x = 0.33). In either case, the best fit of the data to the Knox equation coincides with that to the Horvath and Lin correlation. Reproduced with permission from U. Tallarek, E. Bayer, G. Guiochon, J. Am. Chem. Soc., 120 (1998) 1494 (Fig. 6). 1998 American Chemical Society.

Figure 7. Normalized retention time and reduced axial plate height of 5 nmol NE as a function of radial position for a new column. Flow rate - 1.0 mL mln. The dashed lines are the estimated position of the column walls. (Reproduced from ref. 13. Copyright 1988 American Chemical Society.)...

In Chapter 4 the development of axisymmetric models in which the radial and axial components of flow field variables remain constant in the circumferential direction is discussed. In situations where deviation from such a perfect symmetry is small it may still be possible to decouple components of the equation of motion and analyse the flow regime as a combination of one- and two-dimensional systems. To provide an illustrative example for this type of approximation, in this section we consider the modelling of the flow field inside a cone-and-plate viscometer. 

The nonuniformity of drop dispersions can often be important in extraction. This nonuniformity can lead to axial variation of holdup in a column even though the flow rates and other conditions are held constant. For example, there is a tendency for the smallest drops to remain in a column longer than the larger ones, and thereby to accumulate and lead to a locali2ed increase in holdup. This phenomenon has been studied in reciprocating-plate columns (74). In the process of drop breakup, extremely small secondary drops are often formed (64). These drops, which may be only a few micrometers in diameter, can become entrained in the continuous phase when leaving the contactor. Entrainment can occur weU below the flooding point. 

Pulsed Columns. The efficiency of sieve-plate or packed columns is increased by the appHcation of sinusoidal pulsation to the contents of the column. The weU-distributed turbulence promotes dispersion and mass transfer while tending to reduce axial dispersion in comparison with the unpulsed column. This leads to a substantial reduction in HETS or HTU values. 

For the scaled-up column, suitable baffle plates are required to control axial mixing. For the final column layout the equipment vendor (Ghtsch Process Systems Inc.) should be consulted. 

Sugar-beet cossettes are successfully extracted while being transported upward in a vertical tower by an arrangement of inclined plates or wings attached to an axial shaft. The action is assisted by staggered guide plates on the tower wall. The shell is filled with water that passes downward as the beets travel upward. This configuration is employed in the BMA diffusion tower (Wakeman, loc. cit.). 

Basic types of extruders include axial end plate, radial screen, rotary cyhnder or gear, and ram or piston. For a review, see Newton [Powder Technology Pharmaceutical Processes, Chuha et al. (eds.), Elsevier, 391 (1994).]... 

As the final part of the repair proeess, the expander underwent a trial assembly at the repair faeility. The aetual job assembly and disassembly fixtures were used during the trial assembly. No signi-fieant problems were eneountered and internal elearanees were to speeifieations. As the assembly bed plate at the repair faeility did not exaetly duplieate the user s baseplate, there was some eoneern that readjustment would be required in the field to obtain elearanees. To faeilitate the field assembly proeess, appropriate pins and fixtures were manufaetured to hold axial and eoneentrie positions of the diffuser and stator as they were in die repair shop. The entire expander trial assembly was eompleted one mondi ahead of sehedule. 

The solute is distributed largely over 4-vn plates in the column and thus, as (n) is large, the differential temperature between plates is negligible, and so the heat conducted axially along the column will be very small compared with that conducted radially to the walls and from the system. 

Example 2.6 The bobbin shown in Fig. 2.16 has been manufactured by sliding the acetal ring on to the steel inner and then placing the end-plate in position. At 20°C there are no stresses in the acetal and the distance between the metal end-plates is equal to the length of the acetal ring. If the whole assembly is heated to 1(X)°C, calculate the axial stress in the acetal. It may be assumed that there is no friction between the acetal and the steel. The coefficients of thermal expansion for the acetal and the steel are 80 x 10 °C and 11 X 10 °C respectively. The modulus of the acetal at 100°C is 1.5 GN/m. ... 

In large industrial installations, the latter is the most common arrangement. The burner has a profile plate that controls the rate of combustion air. The warm air delivery fan may be either centrifugal or axial. 

Plate-mounted An axial flow fan mounted in an orifice or spigot-... 

Aitemativeiy, the beam end couid have compiete rotational restraint and no transverse displacement, i.e., clamped. However, a third boundary condition exists in Rgure D-3 just as in Figure D-2. That is, an axial condition on displacement or force must exist in addition to the conditions usually thought of as comprising a clamped-end condition. Note that the block-like device at the end of the beam prevents rotation and transverse deflection. A similar device will be used later for plates. Whether all of the three boundary conditions can actually be enforced depends on the order of the differential equation set when (necessarily approximate) force-strain and moment-curvature relations are substituted in Equations (D.2), (D.4), and (D.7). 

Erosion corrosion of pump impellers, casings and wear plates can be very troublesome. Positive-displacement pumps create much less turbulence than centrifugal or axial-flow pumps and should be used where possible in critical... 

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