Equivalent opening size

Spunbonded fabrics are effective filters in that they are layered stmctures of relatively fine fibers, the three-dimensional stmcture of which creates a torturous path. Even relatively thin spunbonded fabrics (eg, 0.2—0.25 mm) present a significant challenge to the passage of soil fines and are suitable for use in some filtration appHcations. The porosity of geotextile fabrics is classified by means of several procedures such as flux (volume flow/area per time) and equivalent opening size (EOS), which is a measure of the apparent pore size of the openings in the fabric. The flux measures the porosity to Hquid water, and the EOS measures the porosity to soHd particles of a known diameter. Literature is available on limitations of particular styles of fabrics within an apphcation (63). 

Equivalent Circular Perimeter diameter (ECPD), 18 147-148 Equivalent conductance, 3 416 Equivalent opening size (EOS), 17 488 Equivalent patent information searches, 18 236-237... 

Roughly equivalent to a powder which would pass through a No. 325 sieve (325-mesh, 54p.m average opening size) and be retained on a No. 400 sieve (400-mesh, 45 p.m average opening size). 

A cascade impactor consists of a series of orifices, of decreasing opening size, which lie ahead of collecting plates (see Figure 2.22). For each orifice size, particles that are too large to remain with the gas stream are deposited onto the collection plates. With each subsequent stage, smaller and smaller particles are trapped and collected. Since the collection is due to sedimentation, the results are usually reported in terms of equivalent aerodynamic diameter. Since each size fraction is collected on a separate collection plate, they are available for individual chemical analysis. Cascade impactors are applicable to the collection and classification of particles down to about 10 nm and up to about 25 pm (aerodynamic diameter) [128,129]. 

Further distinction has to be made between conventional filtration of fine particle less than 10 pm in diameter, and microfiltration. It would be unusual for the filtration of such particles on a conventional fiher cloth to be described as ndcrofiltratian. Thus microfihration is constituted by the filtration of small particles and by the medimn which is used for the filtration. Conventional fihration is undertaken on filter cloths with a very open structure, see Chapter 4, whereas membrane fihration is usua% concerned with fihration enq>loying membrane media where the equivalent pore size is of the order of 10 pm, or less. These definitions are, however, becoming less distinct as it is now possible to obtain conventional fihration equ ment employing membrane-type fiher media, as discussed in Chapter 4, and crossflow microfilters enqploying conventional filter cloth. 

Although it has been common practice to specify the pressure loss in ordinary valves in terms of either equivalent length of straight pipe of the same size or velocity head loss, it is becoming more common to specify flow rate and pressure drop characteristics in the same terms as has been the practice for valves designed specifically for control service, namely, in terms of the valve coefficient, C. The flow coefficient of a valve is defined as the volume of Hquid at a specified density that flows through the fully opened valve with a unit pressure drop, eg, = 1 when 3.79 L/min (1 gal /min) pass through the valve... 

The te.st is carried out by using an apparatus shown in Figure 11.8, consisting of a closed test chamber in which talcum powder can pass through a sieve having square openings of 75 fim, and is held in suspension by an air current. The amount of talcum powder is supplied at 2 kg per cubic metre size of the test chamber. The enclosure under lest is placed inside the chamber and is connected to a vacuum pump which maintains, inside the enclosure, a differential pressure equivalent to not more than a 200 mm eolumn of water. 

The amount of heat absorbed by a vessel exposed to an open fire is markedly affected by the size and character of the installation and by the environment. These conditions are evaluated by the following equivalent formulas, in which the effect of size on the heat input is shown by the exponent of A, the vessel wetted area, and the effect of other conditions, including v essei external insulation is included in a factor F [33] ... 

In open rod bundles, transverse flow between subchannels is detectable by variations in hydraulic conditions, such as the difference in equivalent diameter in rod and shroud areas (Green et al., 1962 Chelemer et al., 1972 Rouhani, 1973). The quality of the crossflow may be somewhat higher than that of the main stream (Madden, 1968). However, in view of the small size of the crossflow under most circumstances, such variation generally will not lead to major error in enthalpy calculations. The homogeneous flow approximation almost universally used in subchannel calculations appears to be reasonable (Weisman, 1973). The flow redistribution has a negligible effect on the axial pressure drop. 

The sieve is made of a wire mesh cloth of standard sizes held in place by a circular metal frame. The diameter of the sieve ranges from 4 to 18 in., and the height may vary from 1 to 2 in. Three popular sieve series are used the Tyler Series, the first commercial laboratory screens the U.S. Standard Series and the U.S. Alternative Series. Both the U.S. Alternative Series and the Tyler Series designations use the approximate number of opening per linear inch. However, the U.S. Standard Series is the preferred designation and is recommended by the International Standards Organization (ISO). Table 15.3 shows the U.S. Sieve Series and Tyler Series equivalents for a selected number of screens. 

Novel general expressions were developed for the description of the behaviour of the height equivalent of a theoretical plate in various chromatographic columns such as unpacked (open capillary), packed with spherical nonporous particles and packed with spherical porous adsorbent particles. Particles may have unimodal or bimodal pore size distribution. The expression describing the mass balance in open capillaries is... 

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