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740 CHAPTER 33 1952 Guide Count and Discoloration Methods of Testing Air Filters, by F. B. Rowley and R. C. Jordan (A.S H.V.E. Transactions, Vol. 47, 1941, p. 29). A.S.H.V.E. Research Report No. 1187--Economical Air Velocities for Mechan ical Air Filtration, by F. B. Rowlev and R. C. Jordan (A.S.H.V.E. Transactions, Vol. 47, 1941, p. 391). A.S.H.V.E. Research Report No. 1218--Overloading of Viscous Air Filters Dur ing Accelerated Tests, by F. B. Rowley and R. C. Jordan (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 437). The Dust-Free Space Surrounding Hot Bodies, by H. H. Watson (Transactions of the Faraday Society, Vol. 32, 1936, Pt. 2, p. 1073). A New Electrostatic Precipitator, by G. W. Penney (Electrical Engineering, Jan uary, 1937, p. 159). Electrostatic Precipitation for Aircraft, by Howard E. Corbitt and Norman J. Clark (Aero Digest, December, 1940, p. 132). Cleaning of Air and Gas by Thermal Repulsion, by Samuel C. Blacktin (Journal, Society of Chemical Industry, 68, 1939, p. 334-8, 69, 1940, p. 153-4). . Pointers on Selecting Equipment for Industrial Gas Cleaning, by C. E. Miller (Chemical arid Metallurgical Engineering, 45, March, 1938, p. 132-5). Electrical Precipitation, by W. A. Schmidt and E. Anderson (Electrical Engineerng, 67, August, 1938, p. 332-r338). Electrostatic Precipitation for Cleaning Industrial Gases, by H. W. Wagner (Fuel Economist, 10, 1935, p. 895-9, 942-5, 971-3); , Dust Precipitation, by M. Pauthenier and Mme. Moreau-Hanot (Electrician, US, August 10, 1934, p. 187-9). Alternating Current Precipitators for Sanitary Air Analysis; II; Acid Formation in Electric Precipitators, by W. G. Hazard and Tomoyoshi Ishikawa (Journal of Industrial Hygiene, October, 1932, p. 367-70). Electrical Precipitation, by A. W. Simon and L. C. Kron (Electrical Engineering, 61, February, 1932, p. 93-5); The Mathematical Theory of the Cottrell Electric Precipitator, by. A. W- Simon (Iron and Steel Engineering, 6, 1929, p. 143-6). Progress in the Art of Electrical Precipitation Since 1900, by P. E. Landolt (Trans actions, American Electrochemical Society, 51, 1927); Some Factors and Principles Involved in the Separation and Collection of Dust, Mist and Fume from Gases, by Evald Anderson (Transactions, American Institute of Chemical Engineers, 16, 1924, Pt. 1, p. 69-86). Electrical Precipitation of Solids from Smelter Gases, by Ross B. Rathbun (Trans actions, American Institute of Electrical Engineers, 41, 1922, p. 815). Electrical Engineering Features of the Electrical Precipitation Process, by G. H. Horne (Transactions, American Institute of Electrical Engineers, 41, 1922, p. 808). Characteristics of Unit Dust Collectors, by Arthur C. Stern; Jack Baliff, Arthur E. Perina, Robert Crowley, Benjamin Feiner and Arthur A. Urbano (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, May, 1946, p. 117). Agglomeration of Smoke, Fog or Dust Particles by Sound, by H. W. St.Clair (Industrial and Engineering Chemistry, November, 1949). Ultra Sonics, by Ludwig Bergmann, translated by H. Stafford Hatfield (John Wiley & Sons, New York 1946). Ultra Sonics, by Benson Carlin (McGraw Hill Book Co., Inc. New York, 1949). CHAPTER 34 SPRAY APPARATUS Air Washers, Humidification with Air Washers, Dehumidification and Cooling with Air Washers, Well and Water Main Temperatures, Apparatus for Direct : Humidification, Unit Humidifiers, Water-Cooling Towers, Water Use and Conservation, Rivers and Lakes, Spray Cooling Ponds, Atmos pheric and Mechanical Draft Cooling Towers, Mechanics of At mospheric Water-Cooling, Design Conditions, Water-Cooling Tower Design, Selection of 'Water-Cooling Towers, ' Operation and Maintenance AIR humidification is effected by the vaporization of.water, and always requires heat from some source. This heat may be added to the water prior to the time vaporization occurs, or it may be secured by a transformation of sensible heat of the air being humidified to latent heat as the vapor is added to the air. The thermodynamics of the process are discussed in Chapter 3. The removal of moisture from air. may, or may not, involve the removal of heat from the air-vapor mixture. With-spray equipment, dehumidification of air always necessitates the removal of heat. AIR WASHERS An air washer , consists essentially of a chamber or casing in which is provided a spray nozzle system, a tank at the bottom of the chamber for collecting the spray water as it falls, and an eliminator section at the leaving end of the chamber for removal of drops of entrained moisture from the delivered, air. Air is drawn through the casing of the washer, . where it comes into intimate contact with the spray water;' A heat trans fer takes place between the air and water, resulting in either humidifica tion or dehumidification of the air, depending upon the method of operation and the relative temperatures of air and spray water. To prevent backlash of spray ahead of the washer chamber, and to aid in more uniform air distribution, inlet diffusion plates or eliminator baffles, where necessary, are provided in the air entrance end of the air washer. Inlet diffusion plates are used when the air flow and water.spray -are in the same direction; eliminator baffles of special design are.used .where one. or more of the water sprays opposes the air flow. At the out let. end of the washer suitable flooded eliminator plates are used. These plates, for the removal of entrained moisture, usually cause four to six changes in direction of the air flow. Figs. 1 and 2 show the essential construction features of conventional air washers. Intimate contact between the air and the water is secured (I) by breaking the -water into fine drops; (2) by passing the air over sur faces continuously wetted by water; or (3) by a combination of the two. The. wetted surfaces in an air washer may be of fiber glass, metal or scrubber plate construction. Scrubber plate types of washers are generally used to wash reclaimable products from the air, and are composed of several baffle type plates located across the air stream. Water is supplied at the top of the washer to spray over these plates. ' In the case of the fiber glass or metal surfaces, the water spray is usually rather coarse and at 741