Document 9265xRG2rxkLZRaZ6gD1KRz7

w American Society of Heating and Ventilating Engineers Guide, 1937 pig. 3. It will suffice here to note that heating is generally accomplished by passing the water through dosed hot water heaters or by injectin, steam into the water circuit; cooling, by passing the water through clos^ coolers or over refrigerating coils in a Baudelot chamber. Often in a cooling and dehumidifying application, the refrigerating coils are located, within the washer chamber. Washers are sometimes arranged in two or more stages to cool through long ranges or to increase the over-all effidency of heat transfer between air and the cooling or heating medium (water, brine, etc.). A multi-stage washer is equivalent to a number of washers in series arrangement. Each stage is in effect a separate washer. Usually the catalog capadty of a washer is expressed in cubic feet o[ air per minute and is based upon an air velocity of 500 feet per minute through the gross cross-sectional area of the unit above the water level in its tank. At this rating spray type washers handle about 2J4 gpm of DIAPHRAGM VALVE Fio. 3. Air Washer with Spray Water Heating Arrangement water per bank per square foot of area, that is, about 5 gpm per bank per 1000 cfm. These proportions of air, water, area, and velority may be departed from to meet the needs of some particular job, but certain limiting relationships should be observed. Two of the more important items are: o. Choose a washer for air velocities above approximately 300 fpm and below approximately 600 fpm. Velocities outside this range are likely to result in faulty elimination of entrained moisture. b. When a high saturating efficiency is required, select a two or three bank spray type unit, having a total water capacity of not less than 15 gpm per 1000 cfm. For a single stage air washer, a 15 F drop in wet-bulb temperature of the air passing through the washer is about the maximum that should be anticipated. For greater decrease in wet-bulb temperature, multi-stage washers should be-utilized. A rise of 6 F should be the calculated maxi mum for the spray water. Brine has been utilized as a cooling medium in place of water in air washers to obtain low outlet temperatures impossible with water. How ever, proper elimination of brine spray carry over into the duct work is much more difficult than with water. A greater number of air deflections should be used in the eliminators, and the air velocity maintained at a minimum. The area of a washer may be dictated by space limitations outside, the 12--Humidification, Dehumidipication and Water Cooling washer, such as headroom, or by space requirements inside washer, sucli as face area needed by a bank of cooling coils. The length of a washer is determined by the number of spray banks, or scrubber plates, and if cooling coils are installed in the unit, by the number of banks of coils. Roughly, a spray space of about 2 ft 6 in. in length is required for each bank of sprays, (the leaving eliminators require about 1 ft 6 in., entering eliminators about 1. ft). The resistance to air flow through an air washer varies with the type of eliminators, number of banks of sprays, direction of spray, air velocity, type of scrubber plates, size and type of cooling coils if located in the washer. Manufacturers should be consulted to obtain the resistance for a particular installation. apparatus for direct industrial humidification Apparatus for industrial air conditioning may be divided into two distinct groups, namely, (1) humidifiers for increasing the moisture con tent of the air and for producing cooling by evaporation and (2) dehu midifiers for removing moisture from the air and for producing cooling by contact with water or surfaces at a lower temperature than the air. Strictly speaking, humidity control alone, whether it involves humidi fication or dehumidification, is not air conditioning. To be entitled to this classification according to the definition in Chapter 44, the process should include the simultaneous control of temperature, humidity and air motion. Industrial humidifiers may be divided into the following general types, according to the method of operation: (1) Direct, which spray into the room; (2) Indirect, which introduce moistened air; and (3) Combined direct and indirect. Spray Generation Spray generation is obtained by (1) atomization, (2) impact, (3) hydraulic separation, and (4) mechanical separation. Atomization involves the use of a compressed air jet to reduce the water particles to a fine spray. With the impact method, a jet of water under pressure impinges directly on the end of a small round wire. Where hydraulic separation is employed, a jet of water .enters a cylindrical chamber and escapes through an axial port with a rapid rotation which causes it immediately to separate in a fine cone-shaped spray. In the mechanical separation process, water is thrown by centrifugal force from the surface of a rapidly revolving disc and separates into particles suf ficiently small to be utilized in certain types of mechanical humidifiers. Spray Distribution Spray distribution is obtained by (1) air jet, (2) induction, and (3) fan propulsion. The air jet which generates the spray in atomizers also carries the spray through a space sufficient for its distribution and-evaporation, and this method of distribution is termed air jet. Where distribution is obtained by induction, the aspirating effect of an impact or centrifugal spray jet is utilized to induce a current of air to flow through a duct or casing, and 221 v/