Shelf Types

All types of compressors will benefit if suction drums are part of the inlet system design. However, as a practical consideration, it would be difficult to justify a drum on small spared compressors, particularly the off-the-shelf type. If the compressor is in critical service, even when spared and/or replacement cost is deemed significant, suction drums should be considered. 

Sublimation temperatures are in the range of —10 to —40°C and corresponding vapor pressures of water are 2.6-0.13 mbar. Cabinet tray dryers are the most commonly used type. The trays are lifted out of contact with hot surfaces so the heat transfer is entirely by radiation. Loading of 2.5 lb/sqft is usual for foodstuffs. Drying capacity of shelf-type freeze dryers is 0.1-1.0kg/(hr)(m2 exposed surface). Another estimate is 0.5-1.61b/(hr)(sqft). The ice surface has been found to recede at the rate of 1 mm/hr. Freeze drying also is carried out to a limited extent in vacuum pans, vibrating conveyors, and fluidized beds. Condensers operate as low as —70°C. 

Batch units are frequently cylindrical shelf-type dryers equipped with heating and cooling coils or plates. Designs for belter heal input, that is, spikes or expanded metal sheet that penetrate the frozen mass or movable heated shelves compressing the frozen materials, have met with some success. 

Rotatins-Shelf Type The patented Roto-shelftype (Fig. ll-55c) features (1) a large heat-transfer surface provided over a small floor space and in a small building volume, (2) easy floor cleaning, (3) non-hazardous machinery, (4) stainless-steel surfaces, (5) good control range, and (6) substantial capacity by providing as needed 1 to 10 shelves operated in parallel. It is best suited for thick-cake production and burden materials having an indefinite solidification temperature. Sohdification of liquid sulfur into 13- to 19-mm- (Vt- to thick... 

In operation, this shelf type of converter was manually controlled by regulation of the cold air valves between the catalyst shelves with minute to minute observations of pyrometers by the operator of each converter. The largest of these converters apparently could produce about SO pounds of phthalic anhydride per 24 hours on good days. A boiling mercury controlled converter of approximately the same overall dimensions can produce 1800 pounds of phthalic anhydride per 24 hours, and one operator can control about eight or more of these machines. ... 

Only very little knowledge exists concerning the quantitative carbonate production, export and its accumulation on continental shelves. Two shelf types, carbonate-rich and carbonate-poor shelves, are distinguished by Milliman and Droxler (1996). 

Their areas amount to 15 and 10-10 km, respectively (Hay and Southam 1977). However for the two shelf types well-constrained estimates of how much carbonate is produced are missing. In the context of shelves it may be important to separate two other specific bioherms which could have a great potential in shallow-water carbonate production. These are sedimentaiy carbonates exclusively built up by the calcareous green algae Halimeda in tropical latitudes (e.g. Roberts and Macintyre 1988) and extensive biotic cold-water carbonate reefs or banks as described above for mid to high latitudes. For Halimeda bioherms total carbonate production and accumulation is about 1.510 mol yr (Table 9.1) while the estimates for open shelves given by Wollast (1994) and Milliman and Droxler (1996) do not differentiate a... 

Natural Convection, Static Bed, or Shelf-Type Dryers.307... 

FIGURE 14.3 Shelf-type dryer with separate collector. (From Wibulswas, P. and Niyomkarn, C., Reg. Workshop on Solar Drying, CNED-UNESCO, Manila, Philippines, 1980, p. 1.)... 

Selcuk et al. [5,123] describe the simulation of a shelf-type dryer. Close [124] worked out the simulation of an air-type solar drying system equipped with gravel-bed heat storage using a 10-node discretized model for the heat storage and forward finite difference technique for solving the equation system. Imre et al. [25,125] presented a simnlation of solar dryer for alfalfa. 

Dryer. A shelf-type dryer with hot air circulation with a temperature control range of 392°F (200°C) or more is recommended. 

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