Operable Ranges

Investigating column performance starts with heat and material balance calculations, which generate liquid and vapor flows and properties. The fluid foaming characteristics and corrosivity are also determined. Typically, the calculations are done on a computer simulator, which generates liquid and vapor flows as well as physical properties, such as densities, viscosities, and surface tension. 

The next step is to determine the flooding vapor velocity, which is a function of the vapor and liquid flow rates and their densities. The design vapor velocity is then calculated by multiplying the flooding vapor velocity by a flood factor such as 0.85. The vapor velocity is based on the vapor volumetric flow and the net flow area between the trays, that is, the column cross-sectional area minus the area blocked by the downcomers. With known vapor velocity, vapor flow, and fraction of the column cross section occupied by the downcomers, the net area can be calculated. The total area is then calculated, from which the tray diameter is determined. The actual column diameter is obtained by rounding off the tray diameter to the next larger standard size. The vapor velocity is then adjusted to the new diameter to calculate the expected flood factor. 

At this point most of the column and tray parameters have been tentatively deter- 

A liquid entraimnent check is also usually made to ensure that it does not exceed acceptable limits. The fractional entraimnent is a function of liquid and vapor flows and densities and of the flood factor. The column should not be operated at high fractional entraimnent since this reduces the tray efficiency. 

In the following section many of these factors are discussed quantitatively based on general correlations. 

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Temperatures operating range-Power supply -Overall dimensions -Mass -... 

Fig. 10. Economic operating range of extractors. Superscripts a and b are constants.

Fig. 5. Static pressure vs oudet velocity for a specific airfoil fan, where the dashed lines define the quiet operating range of an airfoil fan.

The way a pilot plant is designed affects its cost, operabiUty, and effectiveness. AH operating ranges may not yet be fully defined at the initial design stage, but a reahstic preliminary range is required before the design is commenced, as is a clear definition of the pilot plant s purpose. 

RO, primarily used ia the dairy iadustry, is expanding iato other areas of food processiag. RO can be used for a variety of operations, ranging from wastewater treatment and material recovery to clarification and concentration. Material recovery is advantageous for two reasons. By recovering valuable products, eg, proteias, from waste streams, profits can be iacreased while costs for waste disposal decreased. An excellent review of the different apphcations ofRO ia food processiag is available (9). 

The term in equation 42 is called a Souders-Brown capacity parameter and is based on the tendency of the upflowing vapor to entrain Hquid with it to the plate above. The term E in equation 43 is called an E-factor. and E to be meaningful the cross-sectional area to which they apply must be specified. The capacity parameter is usually based on the total column cross section minus the area blocked for vapor flow by the downcomer(s). Eor the E-factor, typical operating ranges for sieve plate columns are... 

A turbine flowmeter consists of a straight flow tube containing a turbine which is free to rotate on a shaft supported by one or more bearings and located on the centerline of the tube. Means are provided for magnetic detection of the rotational speed, which is proportional to the volumetric flow rate. Its use is generally restric ted to clean, noncorrosive fluids. Additional information on construction, operation, range, and accuracy can be obtained from Holzbock (Instruments for Measurement and Control, 2d ed., Reinhold, New York, 1962, pp. 155-162). For performance characteristics of these meters with liquids, see Shafer,y. Basic Eng., 84,471-485 (December 1962) or May, Chem. Eng., 78(5), 105-108 (1971) and for the effect of density and Reynolds number when used in gas flowmetering, see Lee and Evans, y. Basic Eng., 82, 1043-1057 (December 1965). 

The compressors operating range is between two major regions as seen in Fig. 10-74, which is a performance map of a centrifugal compressor. These two regions are. surge, which is the lower flow limit of... 

Smaller, high-pressure compressors that do the same job will reduce foundation proolems but will have greatly reduced operational range. 

Uses of Ejectors For the operating range of steam-jet ejectors in vacuum applications, see the subsection Vacuum Systems. ... 

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