Horizontal collectors

Sediment deposition. Horizontal surfaces collect particles primarily by sedimentation deposition, sometimes referred to as fallout . These can provide valuable information relating to exposure for horizontal surfaces in the field such as water and ground. Most studies measuring spray performance within the application area, and/or outside this area by drift, include horizontal collectors. The most common types of such collector include flat papers, cards and plates. Water- and oil-sensitive papers have been widely used for looking at the uniformity of spray coverage, coefficient of variation, droplet densities and approximate droplet size within a spray block. 

Vertical surfaces collect spray primarily by impaction. Plants and other entities with a vertical component will collect some material by impaction, and typically also by deposition, as discussed in the previous section. While horizontal collectors will tend to collect all or most material that falls out on to them, vertical collectors will have collection efficiencies that are more closely related to their physical characteristics, especially collector diameter. The SDTF used a-cellulose cards oriented perpendicular to the ground and strings made of cotton or Teflon in its field studies to assess spray volumes at locations above the ground. Many other researchers have used strings for assessing airborne spray volumes in drift studies. ... 

The largest SWRO plant in North America, which obtains source water fiom beach wells, is the 15,000-m /day water supply facility for the Pemex Salina Cruz refinery in Mexico. This plant also has the largest existing seawater intake wells—three Raimey-type horizontal collectors with capacities of 15,000 m /day each. Key considerations for the selection of the type of intake most suitable for the site-specific conditions of a given SWRO plant and guidelines for the development of subsurface intakes for seawater desalination plants are discussed elsewhere (AWWA, 2007 Wright and Missimer, 1997 Voutchkov, 2004a). 

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. 

Primary steam separators These devices are located horizontally, immediately above the top drum waterline and use baffles or chevrons and dry pipe collectors, or cyclone or centrifugal action to radically change the steam flow, resulting in the heavier water and contaminants separating out from the steam. 

Both horizontal and vertical cross-flow separators require spreaders and collectors to uniformly distribute water flow through the plates For this reason, it is suggested that Eq. 8 be modified to indude a 75% spreader efficiency term ... 

In gravity settling separation, the particle-laden gas is fed horizontally into a large expansion chamber. The enlargement of the cross section of the flow stream significantly reduces the gas velocity. The particles settle downward on the collection surface or hopper collectors at the bottom of the chamber. The decrease in the gas stream velocity reduces the reentrainment of collected particles and increases the residence time of the particles so that they may have sufficient time to settle by gravity. 

Fig. 22. Horizontal apparatus for the chlorination of ferrosilicon 1 - furnace 2 -filling device 3 - condensers 4 - screws 5 - abscheider 6 -tube for the withdrawal of solid chlorides 7 - collector.

A flat-plate solar collector is 1 m square and is inclined at an angle of 200 with the horizontal. The hot surface at 160°C is placed in an enclosure which is evacuated to a pressure of 0.1 atm. Above the hot surface, and parallel to it, is the transparent window which admits the radiant energy from the sun. The hot surface and window are separated by a distance of 8 cm. Because of convection to the surroundings, the window temperature is maintained at 40°C. Calculate the free-convection heat transfer between the hot surface and the transparent window. 

One way to reduce the free-convection heat loss in a horizontal solar collector is to reduce the pressure in the space separating the glass admitting the solar energy and the black absorber below. Assume the bottom surface is at 120°C and the top surface is at 20°C. Calculate the pressures that are necessary to eliminate convection for spacings of 1, 2, 5. and 10 cm. 

For the study of liquid distribution along the height of the foam column section, foam collectors or a system of electrodes situated on various levels can be used [68], The most correct values of the local foam expansion ratio can be obtained only using horizontal porous electrodes. 

In the oscillating hopper sample divider [23] ](Figure 1.29), the feed hopper is pivoted about a horizontal axis so that it can oscillate while emptying. Two collectors are placed under the hopper outlet so that the powder falls into them alternately so that at each step the sample is halved. The contents of one box are retained so that at each step the weight of the sample is halved. The oscillating paddle sample divider (Figure 1.30) works in a similar way. 

Air spaces between two Inclined parallel plates are commonly encountered in tlal-plaie so lar collectors (between the glass cover and the absorber plate) and the double-pane skylights on inclined roofs. Heat transfer through an inclined enclosure depends on the aspect ratio H L as well as the till angle 6 from the horizontal (Fig. 9-25). 

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