Flow parameter

Locational considerations include both surficial location and screened interval, ie, the sampling depth. The surficial location is selected based on whether the sample is to represent background quaUty or quaUty at the location of contamination, or potential leak location. In selecting the surficial location, the groundwater flow parameters, velocity and direction, are assumed to be known from other monitoring wells or borings already completed. 

Drops coalesce because of coUisions and drainage of Hquid trapped between colliding drops. Therefore, coalescence frequency can be defined as the product of coUision frequency and efficiency per coUision. The coUision frequency depends on number of drops and flow parameters such as shear rate and fluid forces. The coUision efficiency is a function of Hquid drainage rate, surface forces, and attractive forces such as van der Waal s. Because dispersed phase drop size depends on physical properties which are sometimes difficult to measure, it becomes necessary to carry out laboratory experiments to define the process mixing requirements. A suitable mixing system can then be designed based on satisfying these requirements. 

Maximum allowable values of the capacity parameter are for a flooding condition and are designated C,i,f. Experimental values have been correlated against a dimensionless flow parameter Flg as shown in Fig. 14-25. The flow parameter represents a ratio of liquid to vapor kinetic energies ... 

For distillations, it is often of more interest to ascertain the effect of entrainment on efficiency than to predic t the quantitative amount of liquid entrained. For this purpose, the correlation shown in Fig. 14-26 is useful. The parametric curves in the figure represent approach to the entrainment flood point as measured or as predicted by Fig. 14-25 or some other flood correlation. The abscissa values are those of the flow parameter discussed earher. The ordinate values y are fractions of gross hquid downflow, defined as follows ... 

Figure 14-25 also provides a means for estimating whether spray or froth might prevail on the tray. As can be seen, low values of the flow parameter Flg,. s for vacuum fractionators, can lead to the spray regime. 

The abscissa scale term is the same flow parameter used for plates (dimensionless) ... 

Referring to Fig. 14-48, the intersection of the capacity parameter and the flow parameter lines gives a pressure drop of 0.38 inches H20/ft packing. (The same result is obtained from the Kister/Gill chart. Fig. 14-49.)... 

Efficiency and capacity for the trays, the random packing, and the structured packing decline with a rise in flow parameter. 

Figure 22 gives his backup capacity data for his selection graph (Figure 23). It is easy to see why he preselects packing over trays for a flow parameter of less than 0.1 for example.

The flow process in an injection mould is complicated by the fact that the mould cavity walls are below the freezing point of the polymer melt. In these circumstances the technologist is generally more concerned with the ability to fill the cavity rather than with the magnitude of the melt viscosity. In one analysis made of the injection moulding situation, Barrie showed that it was possible to calculate a mouldability index (p.) for a melt which was a function of the flow parameters K and the thermal diffusivity and the relevant processing temperatures (melt temperature and mould temperature) but which was independent of the geometry of the cavity and the flow pattern within the cavity. 

Estimating the amount of material ejected through the break in the time that it being released with consideration for the flow parameters and the pressure driving the discharge. 

Flow parameter specified is one of mass flow, velocity, or pressure. Usually mass flow or velocity is taken, as these values are known for air supplies. 

Figure 8-139. Entrainment comparison sieve trays vs. bubble caps for 24-in. tray spacing. Note BCT = Bubble Cap Tray ST = Sieve Tray FP = Flow Parameter. Used by permission, Fair, J. R., Petro-Chem Engineer, Sept. (1961), p. 45, reproduced courtesy of Petroleum Engineer International, Dallas, Texas.

Fya = Vapor flow parameter based on active area, defined by Fva = Va Pv /2 or... 

FP = flow parameter, dimensionless HETP = height equivalent of a theoretical plate, in. 

Figure 9-17 plots flood capacity versus flow parameter. The FP values of 0.4-0.7 are estimated by Kister, el al. [136] in absence of data. The plots show that for low and moderate pressures the flood capacity factor versus FP correlates the effects of liquid rate and pressure on the optimized tray capacity [136]. At higher pressures an additional effect of pressure on capacity shows a decline of optimized tray capacity. 

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