Draft Construction

Fan power consumption is the major operating cost and can be counterbalanced in part by greater investment in natural draft construction. In the majority of process applications, fen-operated towers are preferred. Very large installations such as those in power plants employ chimney assisted natural draft installations. A limited use of atmospheric towers is made in areas where power costs are especially high. 

Bishop D (1994) The professionals view of the Heal A and Safety Commission s draft Construction (Design and Management) Regulations. Construction Management and Economics, vol 12 pp 365-372. 

Data Collection and Analysis Pertinent to the PA s Development of Guidelines for Procurement of Highway Construction Products Containing Recovered Materials, EPA Contract 68-01-6014, Draft, Vol. 1, Issues and Technical Summary, Franklin Associates, Ltd., and Valley Forge Laboratory, Inc., July 6, 1981. 

By viriue of its vertical construction, the turbo-type tray dryer has a stack effect, the resulting draft being frequently sufficient to operate the dryer with natural draft. Pressure at points within the dryer is maintained close to atmospheric, as low as 0.1, usually less than 0.5 mm of water. Most of the roof area is used as a breeching, lowering the exhaust velocity to settle dust back into the dryer. 

H is placed at the highest available level (Note 5) and connected with the tubes 7, 7, and K in such a manner as to secure a pressure of liquid sufficient to more than balance the steam pressure (Note 6). E and F are specially constructed condensers of unusual length (160 cm. and 85 cm., respectively) and bore (40 mm.) made from large glass tubing and rubber stoppers (Note 7). I he top of condenser E is connected to a good draft chamber. 

Enclosure roof doors that are directly susceptible to fume drafts must be positioned beneath the roof overlapping the opening. Rising fume will then strike, deflect, and disperse within the enclosure, instead of leaking through door clearances. The rest of the roof construction must be tightly sealed. 

I would like to thank Dr. Geraint O. Thomas (Centre for Explosion Studies, Department of Physics, University of Wales, Aberystwyth, UK) for offering to write Chapter 4. He prepared the first draft, but due to a sabbatical in Japan and other research commitments, he was unable to write the revisions. However, he did make constructive comments and suggestions on the revisions that I wrote. In addition, I would like to thank the following other individuals who provided me with technical data and other assistance based on their knowledge of flame arresters and combustion science and technology G. Binks (IMI Amal), R. Butler (Enardo). K. Chatrathi... 

Natural and forced-draft cooling towers are generally used to provide the cooling water required on a site, unless water can be drawn from a convenient river or lake in sufficient quantity. Seawater or brackish water can be used at coastal sites, but if used directly will necessitate more expensive materials of construction for heat exchangers. 

Drafts, condensation on windows, ice damming, excessive noise from outdoors or equipment operation, and rooms that are cold in winter and hot in summer will diminish comfort in a home. Air-sealed construction, improved insulation, high-performance windows, right-sized, efficient hcating/cooling distribution systems, and mechanical ventilation commonly found in energy-efficient homes all work together to effectively eliminate these problems. 

Figure 12-123B-2. Wear strip construction on induced draft fan for dirty gases. The inertia of suspended dust particles carries them toward the backplate or centerplate where the wear plate withstands the abrasion normally affecting the blade. (Used by permission Bui. 2-5100. The Howden Fan Co.)...

Draft tubes, 309, 313 Drive and gears, 306, 308 Impeller, location, 322 Impeller types, 290, 291-295 Materials of construction, 307 Motor horsepower, actual, 307, 318 Shaft, 306... 

Aeration towers are often simply constructed wooden towers with or without the benefit of a forced-air draft, over which the well water is distributed. Typically, the tower holds 8 to 10 trays, each with a 3- to 4-inch (7.6-10.2 cm) bed depth of volcanic lava or coke media to provide the total 30 to 36" (76-91 cm) depth required. The lava or coke acts as a catalyst for the further precipitation of iron and manganese salts. These salts can be readily oxidized provided there is sufficient alkalinity present. If in doubt, ensure a minimum of 120 to 150 ppm total alkalinity (T Aik or M Aik) as CaC03. 

The constructed wetland was composed of the two tanks connected in series the one is the aerobic tank and the other is the anaerobic/anoxic one (Figure 1). The former tank could remain aerobic owing to the continuous supply of air through the natural draft system (Figure 2) whose driving force for airflow was the temperature difference between the... 

Figure 2. The natural air draft system installed inside the aerobic tank of the constructed wetland.

Eulerian two-fluid model coupled with dispersed itequations was applied to predict gas-liquid two-phase flow in cyclohexane oxidation airlift loop reactor. Simulation results have presented typical hydrodynamic characteristics, distribution of liquid velocity and gas hold-up in the riser and downcomer were presented. The draft-tube geometry not only affects the magnitude of liquid superficial velocity and gas hold-up, but also the detailed liquid velocity and gas hold-up distribution in the reactor, the final construction of the reactor lies on the industrial technical requirement. The investigation indicates that CFD of airlift reactors can be used to model, design and scale up airlift loop reactors efficiently. 

It is a pleasure to acknowledge stimulating discussions with Richard Cushman and Boris Zhilinskii, who introduced the author to this interesting field. He is particularly grateful to ZhiUnskii for constructive comments on an initial draft, which led to substantial improvements to the chapter. 

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