Wire mesh

No standard equations have been developed for pressure drop through wire mesh because the mesh 

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Impingement demister systems are designed to intercept liquid particles before the gas outlet. They are usually constructed from wire mesh or metal plates and liquid droplets impinge on the internal surfaces of the mist mats or plate labyrinth as the gas weaves through the system. The intercepted droplets coalesce and move downward under gravity into the liquid phase. The plate type devices or vane packs are used where the inlet stream is dirty as they are much less vulnerable to clogging than the mist mat. 

Mesh beds of knitted wire mesh, plastic, or glass fibers are used for the removal of Hquid particulates and mist. They will also remove soHd particles, but win plug rapidly unless irrigated or flushed with a particle-dissolving solvent. 

Other types of RPC have been proposed but are not in industrial use as of this writing. These include a reciprocated wire-mesh packing (188), a reciprocating screen-plate (205), and the multistage vibrating disk column (MVE)C) developed in Japan (189,206,207). These types of RPC may be useful for gas—hquid contact as well as Hquid-Hquid contact. 

Paper Production and Properties. During the paper production process, the wood pulp is mixed into an aqueous slurry, which is poured onto a continuously moving wire mesh and drained by gravity. Additional water is then squee2ed out of the paper by a felt web pressed from above. This pressed side, referred to as the felt side, has smaller, finer fibers and is therefore smoother. It is also the preferred printing side. 

Constmction and dem olition (C D) debris is a potentiahy large source of recyclables. However, as of 1995, generation rates and ferrous scrap content were not weh estabUshed and estimates were highly variable. Eerrous materials in C D debris are typicahy reinforcing bars, wire mesh, and stmctural steel. Some of the scrap is sold for recycling once concrete is effectively removed and the scrap is sized to specification (17). 

Electrodes. AH of the finished silver electrodes have certain common characteristics the grids or substrates used in the electrodes are exclusively made of silver, although in some particular cases silver-plated copper is used. Material can be in the form of expanded silver sheet, silver wire mesh, or perforated silver sheet. In any case, the intent is to provide electronic contact of the external circuit of the battery or cell and the active material of the positive plate. Silver is necessary to avoid any possible oxidation at this junction and the increased resistance that would result. 

In another appHcation expanded polystyrene foam panels, 1.2 x 2.4 m, are faced with a wire mesh and mounted ia a metal channel bolted to a coacrete slab. These panels are then sprayed on both sides with plaster, which is anchored to the wire mesh and forms the iaterior and exterior surfaces. Roof and iaterior partitioas provide low cost housiag for mild climates. 

Knitted wire mesh serves as an effective entrainment separator when it cannot easily be foiiled by sohds in the liquor. The mesh is available in woven metal wire of most alloys and is installed as a blanket across the top of the evaporator (Fig. ll-122d) or in a monitor of reduced diameter atop the vapor head. These separators have low-pressure drops, usually on the order of 13 mm [ M in) of water, and collection efficiency is above 99.8 percent in the range of vapor velocities from 2.5 to 6 iti/s (8 to 20 ft/s) [Carpenter and Othmer, Am. nsi. Chem. 

Steam-heated air is the usual heat-transfer medium employed in these dryers, although combustion gases may be used also. Temperatures above 600 K are not usually feasible because of the problems of lubricating the conveyor, chain, and roller drives. Recirculation of air is in the range of 60 to 90 percent. Conveyors may be made of wire-mesh screen or perforated-steel plate. The minimum practical screen opening size is about 30 mesh. 

Conveyors may be of parallel-chain, mat, slat, woven wire-mesh belt, or cast-alloy type. Automatic tensioning devices are used to maintain belt tension during heating and cooung. The product may rest directly on the conveyor or on special supports built into it. RoUer-conveyors are used for large pieces. Flame curtains are provided for sealing the ends and for protection of special treating atmospheres. 

Entrainment Due to Gas Bubbling/Jetting through a Liquid Entrainment generally hmits the capacity of distiUation trays and is commonly a concern in vaporizers and evaporators. Fortunately, it is readily controllable bv simple inertial entrainment capture devices such as wire mesh pads in gravity separators. 

Lm. The coarseness results from the relatively low power dissipation per mass on distillation trays. This means that it is relatively easy to remove by a device such as a wire mesh pad. Over 50 percent is typically captured by the underside of the next higher tray or by a turn in the piping leaving an evaporator. Conversely, though small on a mass basis, the smaller drops are extremely numerous. On a number basis, more than one-half of the drops in the lower curve are under 5 [Lm. These can sei ve as nuclei for fog condensation in downstream equipment. 

FIG. 15-45 Second ScLeiLel extractor witL horizontal baffles and no wire-mesh packing between stages. [Repiinted with peimission of Am. Inst. Chem. Eng. J.,2, 74 (1956)]. 

Filters for mists and droplets have more open area than those used for dry parhcles. If a filter is made of many fine, closely spaced fibers, it will become wet due to the collected liquid. Such wethng will lead to mathng of the fibers, retenhon of more liquid, and eventual blocking of the fiter. Therefore, instead of fine, closely spaced fibers, the usual wet filtrahon system is composed of either knitted wire or wire mesh packed into a pad. A looser filtrahon medium results in a filter with a lower pressure drop than that of the filters used for dry parhculates. The reported pressure drop across wire mesh mist eliminators is 1-2 cm of water at face velocihes of 5 m sec T The essenhal collechon mechanisms employed for filtrahon of droplets and mists are inertial impachon and, to a lesser extent, direct intercephon. 

Behning, F.P., Schum, El.J., and Szanca, E.M., Cold-Air Investigation of a Turbine with Transpiration-Cooled Stator Blades, IV—Stage Performance with Wire-Mesh Shell Blading, NASA, TM X-2176, 1971. 

Performance of Wire Mesh Demisters , Bulletin 635, Otto H. York Co., Inc. 

Security arrangements should be such as to prevent tampering or vandals. Fencing should be of robust wire mesh which does not obstruct ventilation. 

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