Sizing Methods

Vents are usually sized on the assumption that the vent flow is  

The first two cases represent the smallest and largest vent sizes required for a given rate at increased pressure. Between these cases, there is a two-phase mixture of vapor and liquid. It is assumed that the mixture is homogeneous, that is, that no slip occurs between the vapor and liquid. Furthermore, the ratio of vapor to liquid determines whether the venting is closer to the all vapor or all liquid case. As most relief situations involve a liquid fraction of over 80%, the idea of homogeneous venting is closer to all liquid than all vapor. Table 12-3 shows the vent area for different flow regimes. 

These systems are called tempering (i.e., to prevent temperature rise after venting) systems because there is sufficient latent heat available to remove the heat of reaction and to temper the reaction at the set pressure. The vent requirements for such systems are estimated from the Leung s Method [31,32]  

Type of flow Required vent area as a multiple of all vapor vent area 

The first derivative of Equation 12-22, denoted by the subscript s, corresponds to the heating rate at the set pressure, and the second derivative, denoted by subscript m, corresponds to the temperature rise at the maximum turnaround pressure. Both derivatives are determined from an experiment (e.g., in the PHI-TEC or VSP). 

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Plan defects are the most sensitive to a disorientation of the ultrasonic beam and are therefore the most difficult for sizing. If the defect is perpendicular to the direction of propagation, the sizing method by successive falls of 6 dB will give a correct dimension estimation of the... 

BIRAC (A.M.), SAGLIO (R.) and FRAPPIER (J.C.), Improvement of sizing methods by ultrasonic focalised probes. Proceedings of a specialist meeting-Nuclear Science and Technology, Ispra, 1983. 

Because the cells can intermpt the optical path in random orientations, individual scattering intensities are not proportional to cell volume. However, because thousands of cells of each type pass through the flow cell, the effects of orientation can be averaged To a first approximation HCT and platelet crit (PCT), the percentage of blood sample volume occupied by platelets, is proportional to the sums of the scattering intensities of the ted cells and platelets, respectively. MCV can be computed from HCT and RBC, whereas MPV can be computed from PCT and PLT. The accuracy of MCV deterrnined by this method is tied to the RBC accuracy, as is the case for the manual MCV method. Ortho Instmments Corporation s ELT-8 uses these counting and sizing methods. 

Sizing methods for pilot-operated pressure relief valves are in accordance with the accepted formulas described above, utilizing the appropriate discharge coefficients and effective orifice areas as recommended by the valve manufacturer. The following points should be noted ... 

As seen in Chapter 7, the operation of bateh erystallizers is inherently unsteady-state. Transient values oeeur of the major operating variables sueh as slurry density, supersaturation, temperature and mean partiele size. Methods of operational eontrol sueh as by use of seeding and temperature programming were also eonsidered in detail. 

Comparison of Results From Four Particle Size Methods. 

This account of the kinetics of reactions between (inorganic) solids commences with a consideration of the reactant mixture (Sect. 1), since composition, particle sizes, method of mixing and other pretreatments exert important influences on rate characteristics. Some comments on experimental methods are included here. Section 2 is concerned with reaction mechanisms formulated to account for observed behaviour, including references to rate processes which involve diffusion across a barrier layer. This section also includes a consideration of the application of mechanistic criteria to the classification of the kinetic characteristics of solid-solid reactions. Section 3 surveys rate processes identified as the decomposition of a solid catalyzed by a solid. Section 4 reviews other types of solid + solid reactions, which may be conveniently subdivided further into the classes... 

TTiere are several particle sizing methods, all based upon sedimentation and Stokes Law. If a particle is suspended in a fluid (which may be gas, or any liquid), the force of resistance to movement by the particle will be proportional to the particle s velocity, v, and its radius, r, vis-... 

Many solid-liquid reactions are likely to benefit from the careful selection of the reactant (particle size, method of manufacture, etc.). Many reaction-crystallization systems may benefit from the use of seed crystals (see Section 5.4). 

Dow Chemical Co. (1973) The Dow Safety Guide, a reprint from Chemical Engineering Progress (AIChE). Duxbury, H. A. (1976) Loss Prevention No. 10 (AIChE) 147. Gas vent sizing methods. 

DL Black, MQ McQuay, MP Bonin. Laser-based techniques for particle-size measurement a review of sizing methods and their industrial applications. Prog Energy Combustion Sci 22(3) 267-306, 1996. 

A number of alternative sizing methods are available, and these are described in Table 8. The American Association of Pharmaceutical Scientists, Inhalation Focus Group conducted a comprehensive review of available methods, which was published in a series of articles identified in the last column of the table. All of the methods described either have been or are currently employed in the development of aerosol products. However, at this time only the inertial samplers, cascade impactors and impingers appear in compendial standards and in regulatory guidelines [44-46], Other methods such as thermal imaging are also under development and may give complementary size information to the current methods. 

In this chapter we introduce relief fundamentals and the steps in the relief design procedure. Relief sizing methods are covered in chapter 9. 

Both vent sizing methods for gases and dusts require values for the deflagration indexes, KG or KSt. We discussed the experimental procedure to determine these values and also provided tables of typical values for gases and dusts in chapter 6. 

A sizing method similar to the one recommended above is proposed by Schmidt and Giesbrecht (2001), based on experimental work done at BASF in Germany. 

It is recommended to choose the automatic step-size method AUTO and to set a small value of l)Tmm and a large value for l)Tm/ If the results are good, try to improve the speed by increasing both parameters. Sometimes the resulting curves are not smooth if l>imj is too high. In most cases, good results are obtained with AUTO and l>imm set to about 1/1000 of the smallest time constant. 

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