Example 3-12 Type Specific Speed

The majority of centrifugal pumps have performance curves with the aforementioned profiles. Of course, special design pumps have curves with variations. Eor example, positive displacement pumps, multi-stage pumps, regenerative turbine type pumps, and pumps with a high specific speed (Ns) fall outside the norm. But you ll find that the standard pump curve profiles are applicable to about 95% of all pumps in the majority of industrial plants. The important thing is to become familiar with pump curves and know how to interpret the information. 

The theory of dimensionless groups of Section 7.2, Basic Relations, also applies to fans and compressors with rotating elements, for example, Eqs. (7.8)-(7.10) which relate flow rate, head, power, speed, density, and diameter. Equivalent information is embodied in Table 7.5. The concept of specific speed, Eqs. (7.11) and (7.12), also is pertinent. In Figures 7.21 and 7.25 it is the basis for identifying suitable operating ranges of various types of compressors. 

Evaluate the pump chosen for the installation. Check the specific speed of a centrifugal pump using the method given in Example 6.20. Once the specific speed is known, the impeller type and approximate operating efficiency can be found from Fig. 6.12. 

A mass spectrometer provides an example of a molecular beam, in this case a beam of molecular ions. Molecular beams are used in many studies of fundamental chemical interactions. In a high vacuum, a molecular beam allows chemists to study the reactions that take place through specifically designed types of collisions. For example, a crossed-beam experiment involves the intersection of two molecular beams of two different substances. The types of substances, molecular speeds, and orientations of the beams can be changed systematically to give detailed information about how chemical reactions occur at the molecular level. Chemists also have learned how to create molecular beams in which the molecules have very little energy of motion. These isolated, low-energy molecules are ideal for studies of fundamental molecular properties. 

Having chosen the test mixture and mobile diase composition, the chromatogram is run, usually at a fairly fast chart speed to reduce errors associated with the measurement of peak widths, etc.. Figure 4.10. The parameters calculated from the chromatogram are the retention volume and capacity factor of each component, the plate count for the unretained peak and at least one of the retained peaks, the peak asymmetry factor for each component, and the separation factor for at least one pair of solutes. The pressure drop for the column at the optimum test flow rate should also be noted. This data is then used to determine two types of performance criteria. These are kinetic parameters, which indicate how well the column is physically packed, and thermodynamic parameters, which indicate whether the column packing material meets the manufacturer s specifications. Examples of such thermodynamic parameters are whether the percentage oi bonded... 

As you assemble this information, focus on providing as much specific information as possible. If you re writing about your skills as an administrative assistant, for example, in addition to listing your typing speed and accuracy, list specific word processing programs you re proficient in using, such as Microsoft Word, WordPerfect, and so forth. 

The potential volume involved and our assessment of the property benefit of Celcon in the application were sufficient to justify a lab program whose objective was to develop a polymer or modify the extrusion process so that Celcon would extrude at comparable or faster speeds than the material being used. After some nine months of effort an extrusion die was designed that permitted extrusion speeds of 450 feet per minute while making tubing with the tolerance specifications established by the customer. The foregoing is an example of a type of process development work described in the preceding paper. 

Usually catalysts and enzymes are very specific and will only speed up one particular reaction. For example, one enzyme in the blood will only catalyse one type of reaction and will not affect other reactions. Therefore a blood clotting enzyme reacting at the site of a cut will not be affected by a clot dissolving enzyme at a different site. The reactions are very specific. 

The first necessary condition [6.21] to be taken into account in all particularization cases is the use of general mixing parameters (factors related to the geometry of agitation, the properties of liquid media, the type of agitators and rotation speed) as well as the use of the specific factors of the studied application. For example, in the case of suspended solid dissolution, we can consider the mass transfer coefficient for dissolving suspended solids, the mean dimension of the suspended solid particles, and the diffusion coefficient of the dissolved species in the liquid. 

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