Document NeOez6k1pdgyXQprJx38K20dp

640 CHAPTER 36 ' I 1946 'Guide attic, permitting air to flow from the hall below. Outdoor air, which enters the house through open windows, is drawn into the attic through the grilles, and is discharged outside by the fan. An attic stairway may be used in place of the grilles. It is essential that the roof and the attic walls be free from air leaks. Boxed-in fans are units in which the fan is installed within the attic in' a box or housing directly over a central ceiling grille, or in a bulkhead enclosing an attic stair. The fan may be connected by a duct system to the grilles in individual rooms. Outdoor air entering through the windows of the rooms below is discharged into the attic space and escapes to the outside through louvers, dormer windows, or screened openings under the eaves. Another version of the attic fan is the window fan for use when attic application is not feasible or no attic is available. Supplied with a perforated or expanded metal enclosure and mounted in either the upper or lower window section, this fan is easy to install or move to another location. The locations of the fan, the outlet openings, and grilles should'be selected after consideration of the room and attic arrangements in order to give uniform. air distribution in the individual rooms served. If the outlet for the air is not on the side away from the' direction of the pre vailing wind as in the case of the boxed-in fan, openings should be provided on all sides. Kitchens should be separately ventilated because of the fire hazard, and to prevent the spread of cooking odors. The window fan may be located in a hall or an unused bedroom. Noise of operation is more of a problem with the window fan than with the attic type, although care should be taken to locate either type of fan so that occupants are not disturbed. These fans range in capacity from 3000 to 30,000 cfm. The window type usually does not exceed 8000 cfm, while the most generally used attic type ranges from 8000 to 16,000 cfm. Power consumption is under 50 watts an hour per 1000 cfm of rated output for the 8000 cfm fan and larger while the watts input for smaller. fans is greater than this figure. Improved results can be secured with the window fan by closing off parts of the house where ventilation is not desired. REFERENCES 1--Prepared by-a Joint Committee of the American Society of Refrigerating Engineers, American Society of Heating and Ventilating Engineers, Refrigerating Machinery Association, National Electrical Manufacturers' Association, and Air Conditioning Manufacturers' Association (A J5JI E. Circular No. 13-42). 2"Standard Method of Rating and Testing Self-Contained Air Conditioning Units for Comfort Cooling prepared by a Joint Committee of the-American Society of Refrigerating Engineers, American Society of Heating and Ventilating Engineers, Refrigerating Machinery Association, Notional Electrical Manu facturers' Association, and Air Conditioning Manufacturers' Association (A.S.R.E. Circular No. 16). 3~Defined in Proposed A.S.R.E. Standard Methods of Rating and Testing Forced-Circulation Air Coolers for Commercial and Industrial Refrigeration (A.S.R.E. Circular No. 25-43).' , 4~Code of Minimum Requirements for Comfort Air Conditioning (A.S.H.V.E. Transactions, VoI. 44, 1938, p. 27). Reprints of this code are available at $0.10 a copy. 5--Concerning Conservation of Underground Water with Suggestions for, Control, by Noel E Porter (A.S.H.V.E. Transactions, Vol. 47, 1941, p. 309). *--Comfort Cooling with Attic Ventilating Fans, by G. B. Helmrich and G. H. Tuttle (A.S.H.V^E Transactions, Vol. 40, 1934. p. 155). A.S.H.V.E. Research Report No. 979--Study of Summer Cooling in the Research Residence for the Summer of 1933. by A. P. Kratz and S. Konzo (A.S.H.V.E. Trans-' actions, Vol. 40. 1934. p. 167). A.S.H.V.E. Research Report No. 1198--The Effect of Attic Fan Opera tion on the Cooling of a Structure, by W. A. Hinton and A. F. Poor (A.S.II.V.E. Transactions, Vol. 48, 1942. p. 145). The Installation and Use of Attic Fans, by W. H. Badgett (Agricultural and Mechanicai College of Texas, Bulletin No. 52, 1940). CHAPTER 37 Spray- -Apparatus Air Washers, Humidification with Air Washer, Apparatus for Direct Humidification, Air Dehumidification with Washers, Well and Water Main Temperatures, Atmospheric Water Cooling Equipment, Selection of Water Cooling Equipment, Design Wet-bulb Temperatures for Water Cooling,. Cooling Ponds, Spray Towers, Cooling Tower Design, Cooling Tower Performance, Winter Freezing 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 Air washers may be used as either humidifiers or 'dehumidifiers de pending upon the method of operation and the temperature of the spray water. The functions of an air washer are to regulate the moisture and heat content of air passing through it and, although not so effective as . air filters, to remove dust and dirt from the air. The construction of commercial air washers is indicated in Figs. 1 and 2. Any air washer consists essentially of a chamber through which the air passes in intimate contact with water. The lower portion of the washer chamber serves as a sump for the spray water. Contact between the air and the washer water is secured: (1) by breaking the water into a very fine mist, (2) by passing the air over: surfaces which are continuously wetted by water, or (3) by a combination of water sprays and wetted plates. Scrubber-plate types of washers are used largely to wash, heavy reclaimable products from the air, and are generally composed of one to three eliminator-type baffle scrubber plates across the air stream. Water is supplied at the tops of the scrubber plates by flooding nozzles placed across the top of the washer. Spray washers have one or more banks of water atomizing nozzles placed in the air stream above the level of the water in the sump. The direction of the water sprays may be against the air stream, with the air stream, or with one bank spraying with the air stream and one against it: The number of ' nozzles required depends upon their design, the quantity of air handled, and the arrangement of the nozzles. . Scrubbers generally consist of eliminator-type baffle plates placed in the air. stream to cause several reversals of the direction of air flow. The scrubber plates are more effective as air cleaners than as humidifiers. All 'washer chambers should have inlet diffuser plates to aid in producing more uniform air flow through the washer spray chamber. These inlet vanes-also aid in preventing spray water from being thrown into the air duct ahead of the washer. However, if the water spray opposes the air flow, the ordinary perforated diffuser plate is not sufficient, and specially designed eliminator baffles must be used to prevent spray from passing into the air inlet duct. At the outlet end of the washer suitable flooded / 641