Enclosure

In the standard method, the metal enclosure (called the air chamber) used to hold the hydrocarbon vapors is immersed in water before the test, then drained but not dried. This mode of operation, often designated as the wet bomb" is stipulated for all materials that are exclusively petroleum. But if the fuels contain alcohols or other organic products soluble in water, the apparatus must be dried in order that the vapors are not absorbed by the water on the walls. This technique is called the dry bomb" it results in RVP values higher by about 100 mbar for some oxygenated motor fuels. When examining the numerical results, it is thus important to know the technique employed. In any case, the dry bomb method is preferred. 

Figure 5.1 The reaction of A and B groups at the ends of two different chains. Note that rotations around only a few bonds will bring A and B into the same cage of neighboring groups, indicated by the broken line enclosure.

Another option available with rotary vacuum dmm filters is fiiU enclosure. This enables operation under nitrogen or other atmospheres, for reasons such as safety, prevention of vapor loss, etc. Enclosure may also be used to prevent contamination of the material being filtered or to confine the spray from washing nozzles. The rotary dmm filter also can be enclosed in a pressure vessel and operated under pressure. 

Other designs squee2e the cake between two permeable belts or between a screw conveyor of diminishing diameter, or pitch, and its permeable enclosure. The available filters which use mechanical compression can be classified into four principal categories, ie, membrane plate presses, tube presses, belt presses, and screw presses. 

Most continuous pressure filters available (ca 1993) have their roots in vacuum filtration technology. A rotary dmm or rotary disk vacuum filter can be adapted to pressure by enclosing it in a pressure cover however, the disadvantages of this measure are evident. The enclosure is a pressure vessel which is heavy and expensive, the progress of filtration cannot be watched, and the removal of the cake from the vessel is difficult. Other complications of this method are caused by the necessity of arranging for two or more differential pressures between the inside and outside of the filter, which requires a troublesome system of pressure regulating valves. 

A furnace is a device (enclosure) for generating controlled heat with the objective of performing work. In fossil-fuel furnaces, the work appHcation may be direct (eg, rotary kilns) or indirect (eg, plants for electric power generation). The furnace chamber is either cooled (waterwaH enclosure) or not cooled (refractory lining). In this article, furnaces related to metallurgy such as blast furnaces ate excluded because they ate coveted under associated topics (see... 

H. C. Hottel and E. S. Cohen, "Radiant Heat Exchange in a Gas-EiUed Enclosure," paper presented at ASME/AIChE Joint Heat Transfer Conference, University Park, Pa., Aug. 1957, AIChE Paper No. 57-HT-23. 

If the kiln may be considered an enclosure bounding an isothermal gray gas of emissivity, S, with two bounding surfaces consisting of reradiating walls of area, and of bed soHds (the radiation sink) of area, then the expression for R becomes (19)... 

Inclusion compounds open up a wide area of applications (1,2,17—28). An important aspect in this connection is the specific microenvironment created by the host enclosure of the guest which exerts an influence on the physical, spectroscopic, chemical, and other properties of the guest. 

Enclosure also changes the redox properties of a compound, its color, and other physical properties (1,2). On this basis nonlinear optical materials, luminescence markers, controlled light switches, and other high-tech devices might be designed and prepared (15,17,137). 

Options. Traditional control options for overexposure are material substitution, process change, containment, enclosure, isolation, source reduction, ventilation, provide personal protection, change work practices, and improve housekeeping. A simple way of looking at selection of control options is to find the cheapest option that results in the desired amount of exposure reduction. It is not actually that simple, however, because the various options differ in ways other than cost and degree of control. Some of the other factors to consider in selection of control options are operabiUty, rehabiUty, and acceptabihty. 

Operability. Hidden costs may result from changes in the way a process operates as a result of a control. For example, enclosure and isolation may diminish the abiUty of workers to observe the process. Upsets and dismptions resulting from this loss of intelligence are expensive and generate resistance to the use of these controls, no matter how effective. 

Aerosols (qv) are very finely divided sprays having droplet diameters of l ndash 30 p.m. They are used almost entirely as space sprays for appHcation to enclosures, particularly against flying insects. Aerosols are most conveniendy appHed by the familiar Hquefted gas dispersion or bomb but can be generated on a larger scale by rotary atomi2ers or twin duid atomi2ers. 

Uses. Sound-absorbing materials are frequendy used to reduce reverberation, or the persistence of sound in a space after generation of the sound ceases to reduce focused reflections from concave surfaces to prevent echoes, or delayed sound reflections from distant surfaces and to prevent the buildup of sound by multiple reflections within rooms and other enclosures. Sound-absorbing materials also are used to reduce the transmission of noise from one location to another by multiple reflections from sound-reflecting surfaces. 

Sound-Absorptive Blankets. Sound-absorptive blankets of fiber glass or mineral wool are not usually considered damping materials, but when fastened to sheet metal machine enclosures they can provide some useful damping in addition to sound absorption. 

The minienvironment approach to contamination control has been increasing in use. A minienvironment is a localized environment created by an enclosure that isolates the product wafer from contamination and people (48). Another approach is using integrated processing, where consecutive processes are linked in a controlled environment (32). Both requite in situ sensors (qv) to measure internal chamber temperatures, background contamination, gas flow rates, pressure changes, and particularly wafer temperature (4). 

G. L. Wiser, "Sierracin Glass/Plastic Composite Wiadshields," presented at Conference on Transparent Materialsfor Aerospace Enclosures, U.S. Air Eorce and University of Dayton, June 25, 1969. 

J. B. Olson, "Design, Development and Testing of a Lightweight Bird-Proof Cockpit Enclosure for the E-111," presented at The Conference on Aerospace Transparent Materials and Enclosures, Long Beach, Calif., Apr. 24—28,1977. 

R. W. Wright, "High Strength Glass in Service—A Status Report," presented at The Conference on Aerospace Transport Materials and Enclosures, Tech. Report AFML-TR-76-54, Atianta, Ga., 1975. 

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