External chambers

Fig. 4. Schematic of a hemodialyzer. The design of a dialyzer is close to that of a sheU and tube heat exchanger. Blood enters through an inlet manifold, is distributed to a parallel bundle of fibers, and exits into a coUection manifold. Dialysate flows countercurrent in an external chamber the blood and dialysate are separated from the fibers by a polyurethane potting material. Housings are typically prepared from acrylate or polycarbonate. Production volume is...

One rather unusual design comprises a mixing system with two external chambers (Fig. 31). The nitrator is connected with both sides of each chamber, in each of which a propeller stirrer is rotated at 200-400 r.p.m. The speed of rotation and cross-sections of the chambers are so selected as to enable the whole of the nitrator contents to make one round within one minute. 

For a simple derivation of the dissipation function, consider an isothermal composite system with three compartments consisting of two external chambers (I and II) and a membrane compartment (m) in between. The volumes of the compartments are constant (dl = dVu = dVm = 0). The Gibbs relations for the compartments are... 

External chambers, such as welded jackets, can provide a means for both heating and cooling from external sources such as steam generators or circulating baths. These jackets are themselves pressure vessels and have the same design considerations as the inner vessel. 

The laboratory system used in these studies was developed from the experience on sediment/algae interactions with a modified two-chambered device (Ahlf et al., 1986). The system is made of a central chamber connected with 6 external chambers and separated by membranes of 0.45 pm pore diameter (Figure 5-4). The volume of the central chamber is litres and each of the external chambers contains 250 ml. Either solution or suspension can be inserted into the central chamber in each... 

Cold on-column injection employs the direct introduction of the sample as a liquid into the oven-thermostatted column inlet or precolumn without prior vaporization in a heated external chamber [40,42,43,69,81]. The sample is subsequently vaporized from the liquid layer formed in the column inlet or precolumn. Cold on-column injection is the only technique in which the composition of the sample introduced into the column is identical to the original sample composition. Discrimination is virtually eliminated and quantification of components of different volatility is facilitated. Sample... 

The scheme of the jet vortex mill is shown in Fig. 1. The gas under high pressure is injected tangentially through flat nozzles located in the external chamber wall. Coarse particles with low velocities are injected through the orifice in the center of the upper cover of JVM. It is reasonable to carry out the injection of a raw by an ejector through a spiral channel (volute) that provides uniform solid feeding on a circle of a small radius Ri. However, because of the cylindrical zone with radius Rp in the chamber center is zone of rarefaction, the raw can be put into the chamber also by means of a pouring feeder. Coarse particles are accelerated by... 

For this kind of case, a modification of the dilution method is being developed. Instead of using an external fixed-geometry measurement chamber, a suitable part of the process, e.g. a stretch of pipe, is used. A radiation detector is mounted on the outside of the pipe, and a tracer emitting sufficiently hard gamma radiation is used. As sufficient mixing can be achieved by injecting upstream the separator the radiation level found will be strictly proportional to the concentration and thus inversely proportional to the true flow rate. 

A generic multipurpose fluidized bed is illustrated in Figure 2 (1). The soHds are contained in a vessel and gas is introduced into the system via a distributor, which is typically a drilled plate at the bottom of the vessel. A plenum chamber is provided below the distributor plate. The height of the soHds level above the distributor is called the bed height, and the vertical space above the bed height is called the freeboard. A splash zone may exist as a transition between the bed and freeboard. Cyclones, located either in the freeboard or external to the vessel, are used to remove soHds from the gas stream. Diplegs can return entrained soHds directly to the bed. 

One design for a low temperature convection furnace shown in Figure 4 utilizes an external circulating fan, heating chamber, and duct system. The fan draws air (or a protective atmosphere) from the furnace and passes through the external heating chamber and back into the furnace past the work. This system minimizes the chance that the work receives any direct heat radiation. In theory it is less efficient because the external blower, heating chamber, and ductwork add external surfaces that are subject to heat losses. 

Vehicle Fa.ctors. Because knock is a chemical reaction, it is sensitive to temperature and reaction time. Temperature can in turn be affected either by external factors such as the wall temperature or by the amount of heat released in the combustion process itself, which is directiy related to the density of the fuel—air mixture. A vehicle factor which increases charge density, combustion chamber temperatures, or available reaction time promotes the tendency to knock. Engine operating and design factors which affect the tendency to produce knocking are... 

The second class of grinding equipment is used to prepare dispersions. Typical of this class are baU and pebble mills, ultrasonic mills, and attrition mills. SoHds, eg, sulfur, antioxidants, accelerators, and zinc oxide, are generaUy ground on this equipment (see Size reduction). BaU mill action is assisted in some mills by a combination of dispersion circulation by an external pump and mechanical osciUation of an otherwise fixed nonrotary mill chamber. Where baU mill chambers are rotated it is necessary to experimentally estabHsh an optimum speed of rotation, the size and weight of the baU charge, and ensure the mills do not overheat during the grinding period. 

Alpha counting is done with an internal proportional counter or a scintiUation counter. Beta counting is carried out with an internal or external proportional gas-flow chamber or an end-window Geiger-MueUer tube. The operating principles and descriptions of various counting instmments are available, as are techniques for determining various radioelements in aqueous solution (20,44). A laboratory manual of radiochemical procedures has been compiled for analysis of specific radionucHdes in drinking water (45). Detector efficiency should be deterrnined with commercially available sources of known activity. 

External recirculation is the movement of the heated air within the bay to an external duc t, where this air mixes with inlet air, and the mixture serves as the cooling fluid within the bay. Inlet air does not have direct access to the tube bundle an adequate mixing chamber is essential. Recirculation over the end of the exchanger is illustrated in Fig. 11-48. Over-the-side recirculation also is used. External recirculation systems maintain the desired low temperature of the air crossing the tube bundle. 

FIG. 11-48 External recirculation with adequate mixing chamber. [Hydrocar-hon Vrocess, 59, 148-149 (October 1980).]... 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

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