Overflow principle

Volume metering is predominantly realized by overflow principles. If, for instance, an excess volume is filled into a bucket, the liquid level lowers to its upper edge, thus metering the initial volume to the geometrically defined (smaller) volume of the bucket. In centrifugal microfluidics, the overflow corresponds to an outlet connected to a radially inward position (Fig. 5). 

Figme 14.2 presents the principle of a constant head permeameter. The porous medium layer, of thickness L, is set in the lower tank. The water level in the upper tank is kept constant using an overflow pan. The liquid flows upward inside the porous medium, from bottom-up. The fluid is discharged using the same overflow principle that maintains the water level constant above the porous medium. As the upstream and downstream water levels are constant, the pressure difference AP between the bottom and top of the porous medium is also constant. 

Overflow at the rate of 2700 m (713,000 gal) per day from a zinc-concentrate thickener is treated by ion flotation, precipitate flotation, and untrafine-particle flotation [Nagahama, Can. Min. Metall. Bull., 67, 79 (1974)]. In precipitate flotation only the surface of the particles need be coated with collector. Therefore, in principle less collector is required than for the equivalent removal of ions by foam fractionation or ion flotation. 

Technologically it is important that smart battery packages, featuring power management by electronic devices within the battery package, are becoming a necessity due to the sensitive charging characteristics of Li and Ni-MeHy batteries, it should be noted that the same principles at a fraction of the cost have been successfully applied realized by simple reversal protection and overflow components by the low-cost RAM batteries. 

For the centrifuge it is necessary to position the overflow on the same principle, as shown in Figure 9.3. In this case the radius n of the weir for the less dense liquid will correspond approximately to the radius of the inner surface of the liquid in the bowl. That... 

The principles of fluidisation, discussed in Chapter 6, are applied in this type of dryer, shown typically in Figure 16.25. Heated air, or hot gas from a burner, is passed by way of a plenum chamber and a diffuser plate, fitted with suitable nozzles to prevent any back-flow of solids, into the fluidised bed of material, from which it passes to a dust separator. Wet material is fed continuously into the bed through a rotary valve, and this mixes immediately with the dry charge. Dry material overflows through a downcomer to an integral after-cooler. An alternative design of this type of dryer is one in which a thin bed is used. 

The principle is basically the same as any coffee pot a paper thimble is filled with the substance to be extracted (F) and a loose plug of cotton is placed (E) over the top. The Soxhlet apparatus is attached to a flask containing the proper solvent (if the solvent is not given in the formula, then usually you must find a solvent in that either the desired substance or the impurities are insoluble in). Attach a condenser to the Soxhlet tube (B). The solvent is boiled causing vapor to rise and pass through the holes (C) into the condenser where it is turned back into liquid. The liquid drops down into the thimble and solvent When the solvent level exceeds the top of the riser tube (D) the solvent overflows back into the boiling flask (G) and the process is recycled or continuous. 

In industrial fluidized bed reactors, the bed height is commonly fixed by an overflow weir. Thus, as the gas velocity, U, increases from Umf, the apparent bed density decreases. An important design principle for the gas distributor is to ensure its sufficient pressure drop for a uniform gas distribution, i.e., without gas channeling, and stable bed operation. Specifically, the total pressure drop across both the distributor and the bed should be in an increasing trend with an increase in the gas velocity. Suppose that the pressure drop across a perforated distributor, Apdistnbuior, with a total orifice area of Ao can be expressed by... 

Flow across the tray. The classical hydraulic model implies that liquid flows across the tray by building up a liquid head on the tray, and when this head exceeds the weir height it overflows it. This mechanism is valid in principle when liquid is the continuous phase, but in the spray regime, vapor is the continuous phase and the liquid is present as drops in the vapor space (Figs, 6,25d, 6.26c, and 6.276). In... 

The reactor has tubes Z5 to 4 m long and 10 to 20 cm in diameter filled with catalyst The catalyst, maintained by a grid, overflows at the top and bottom of the actual tubular zone. The operating principle of this type of equipment implies limitations in teims of maximum unit production capacity. 

Overflow theory The overflow theory (F. L. Liebermann et al., 1970) (7) is based on the principle that retention of sodium already exists as a primary event and hence causes an expansion in volume. 

---