General flow pattern

Strong buoyancy dominates the flow of the fire. Turbulence and pressure cause the ambient to mix (entrainment) into the fire plume. Momentum and thermal buoyancy 

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Bubble generators are commercially available which will produce small neutrally buoyant soap bubbles for use in the visualization of the general flow patterns in rooms. The bubbles are about 3 or 4 mm in diameter and are filled with a lielium/air mixture. In practice, it is difficult to make the bubbles truly... 

Fully developed nonisothermal flow may also be similar at different Reynolds numbers, Prandtl numbers, and Schmidt numbers. The Archimedes number will, on the other hand, always be an important parameter. Figure 12.30 shows a number of model experiments performed in three geometrically identical models with the heights 0.53 m, 1.60 m, and 4.75 m." Sixteen experiments carried out in the rotxms at different Archimedes numbers and Reynolds numbers show that the general flow pattern (jet trajectory of a cold jet from a circular opening in the wall) is a function of the Archimedes number but independent of the Reynolds number. The characteristic length and velocity in Fig. 12.30 are defined as = 4WH/ 2W + IH) and u = where W is... 

Figure 3.15 Generalized flow pattern map boiling in horizontal tubes. (From Dukler and Taitel, 1991b. Copyright 1991 by University of Houston, Houston, TX. Reprinted with permission.)...

Fig. 6.18 Comparison of general flow patterns for planar and axisymmetric, finite-gap, stagnation flow.

Figure 3 General flow pattern of liquid in a gas continuous rotor.

Figure 5.2 Sketch of generalized flow patterns for cases of unconfined and confined settling.

In Fig. 14.1 (top panel) the impact from the initialization on the horizontal winds is illustrated. The modifications are generally less than 0.1 m/s and over large areas less than 0.02 m/s, both for hydrostatic and non-hydrostatic data. The corrections are thus small and could not be expected to violate the general flow pattern. Note that the corrections seem to be very small in relation to the corresponding errors in Fig. 14.1 (middle and bottom panels), which is a bit misleading as the latter results from integrated errors. 

General flow patterns in bulk storage containers... 

Because mass flow bins have stable flow patterns that mimic the shape of the bin, permeabihty values can be used to calculate critical, steady-state discharge rates from mass flow hoppers. Permeabihty values can also be used to calculate the time required for fine powders to settle in bins and silos. In general, permeabihty is affected by particle size and shape, ie, permeabihty decreases as particle size decreases and the better the fit between individual particles, the lower the permeabihty moisture content, ie, as moisture content increases, many materials tend to agglomerate which increases permeabihty and temperature, ie, because the permeabihty factor, K, is inversely proportional to the viscosity of the air or gas in the void spaces, heating causes the gas to become more viscous, making the sohd less permeable. 

Approximate prediction of flow pattern may be quickly done using flow pattern maps, an example of which is shown in Fig. 6-2.5 (Baker, Oil Gas]., 53[12], 185-190, 192-195 [1954]). The Baker chart remains widely used however, for critical calculations the mechanistic model methods referenced previously are generally preferred for their greater accuracy, especially for large pipe diameters and fluids with ysical properties different from air/water at atmospheric pressure. In the chart. 

The cross-flow plate (Fig. 14-16 ) utilizes a hquid downcomer and is more generally used than the counterflow plate (Fig. 14-16Z ) because of transfer-efficiency advantages and greater operating range. The liquid-flow pattern on a cross-flow plate can be controlled by placement... 

Many times solids are present in one or more phases of a solid-hquid system. They add a certain level of complexity in the process, especially if they tend to be a part of both phases, as they normally will do. Approximate methods need to be worked out to estimate the density of the emulsion and determine the overall velocity of the flow pattern so that proper evaluation of the suspension requirements can be made. In general, the solids will behave as though they were a fluid of a particular average density and viscosity and won t care much that there is a two-phase dispersion going on in the system. However, if solids are being dissolved or precipitated by participating in one phase and not the other, then they will be affected by which phase is dispersed or continuous, and the process will behave somewhat differently than if the solids migrate independently between the two phases within the process. 

A distinc tion is to be drawn between situations in which (1) the flow pattern is known in detail, and (2) only the residence time distribution is known or can be calculated from tracer response data. Different networks of reactor elements can have similar RTDs, but fixing the network also fixes the RTD. Accordingly, reaction conversions in a known network will be unique for any form of rate equation, whereas conversions figured when only the RTD is known proceed uniquely only for hnear kinetics, although they can be bracketed in the general case. 

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. 

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