Density differences

Fig. 4. Terminal velocities in air of spherical particles of different densities settling at 21°C under the action of gravity. Numbers on curves represent tme (not bulk or apparent) specific gravity of particles relative to water at 4°C. Stokes-Cunningham correction factor is included for settling of fine particles.

Ammonia—water systems operate under moderate pressures and care must be taken to avoid leaks of the irritating and toxic ammonia (qv). Sometimes a third material with a widely different density, eg, hydrogen, is added to the cycle in order to eliminate the need for mechanical pumping. 

Reduction to Liquid Metal. Reduction to Hquid metal is the most common metal reduction process. It is preferred for metals of moderate melting point and low vapor pressure. Because most metallic compounds are fairly insoluble in molten metals, the separation of the Hquified metal from a sohd residue or from another Hquid phase of different density is usually complete and relatively simple. Because the product is in condensed form, the throughput per unit volume of reactor is high, and the number and si2e of the units is rninimi2ed. The common furnaces for production of Hquid metals are the blast furnace, the reverberatory furnace, the converter, the flash smelting furnace, and the electric-arc furnace (see Furnaces, electric). 

FIG. 6-61 Terminal velocities of spherical particles of different densities settling in air and water at 70°F under the action of gravity. To convert fhs to m/s, multiply by 0.3048. (From Lapple, etal.. Fluid and Particle Mechanics, University of Delaware, Newark, 1951, p. 292. )... 

One hundred tubes were taken as the representative sample population and all were integrated for three different density distributions and each at 3 different levels of runaway tubes (few, medium, and many tubes in runaway.) Altogether 900 integrations were performed and the results analyzed. Figure 9.8.1 shows the distribution of observed maximum ATs with the hundred tubes with 5% random packing variation and at beginning of runaways at 486 K wall temperatures. 

In general, when sepiarating two liquids, they must be immiscible and have different spiecific gravities before a separation technique-such as oil/water separation-would be effective. In the case of finely dispersed liquids or finely dispersed solids, if the dispersed material is below one micron in particle size, centrifuging should be considered. The use of centrifugal force on the differing densities of the material can facilitate the separation technique. 

Srratification is a desirable strategy to provide efficient room air condi-noning with much less effort than using the piston strategy. Its mam application in room air conditioning is the thermal replacement method. However, it can also be applied for contaminants without any thermal buoyancy sources that have different density from the room air. Examples of different air distribution methods to create thetma teplacement are presented in Fig. 8.12. 

Pressure differences due to the different densities of the air inside and outside the building (stack effect). 

A very obvious way to change die measurement range and sensitivity of a fluid manometer is by using fluids of different densities. There are only a few suitable liquids with specific gravit> between that of water and mercury. Ethylene bromide has a specific gravity of 2.2 and acetylene tetrabromide 3.0., but they are corrosive. 

Convection The mechanism of heat transfer due to different temperatures, and hence different densities in fluids. It may be natural, dependent only on thermal forces, or forced, when use is made of a rotodynamic device to improve the rate of heat exchange. 

Mixing The process by which fluids of different density are combined naturally or by some mechanical device. One or more of the following mechanisms may produce the mixing process ... 

In order to get a better notion of the scaling relationship between gyration radius and average chain length for different density regimes, it is convenient... 

This exercise would be a good place to compute a charge distribution difference density between the ground stale and the first excited state, and plot it using an available graphics package. 

The correlation energy of a uniform electron gas has been determined by Monte Carlo methods for a number of different densities. In order to use these results in DFT calculations, it is desirable to have a suitable analytic interpolation formula. This has been constructed by Vosko, Wilk and Nusair (VWN) and is in general considered to be a very accurate fit. It interpolates between die unpolarized ( = 0) and spin polarized (C = 1) limits by the following functional. 

The only significance in differentiating between water and liquids of different densities and viscosities is the convenience in having a separate simplified table for water. 

When two free settling particles of different dimensions, D p] and D po and different densities, pp and pp2, fall through a fluid of density, pf, they will attain equal velocities when ... 

The study of Broaddus et al. [7] can be used to develop the following drainage time relation, and is based on fluids of several different densities and viscosities ... 

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