Document 3NDorQVyxQ3qgGKZnvZeqK5pn

'720 CHAPTER 37 1949 Guide (drift eliminators) -are attached at regular intervals from top to bottom, these louvers extend outward and upward at an angle of 45 to 50 deg. In most designs the top edge of each louver extends above the bottom edge of the one above. These louvers serve the same function as a louver fence around a spray pond, namely to stop the water drops carried by the-air beyond-the open area of the tower, and to control the quantity of air permitted to pass through the tower. The efficiency of a deck tower is improved primarily by increasing length `or height, or both, within limits; the length and height increase the-area of tower exposed to the wind. The improvement is not directly propor tional to the change made in either case. 1 Neither does a certain percentage SprayApparatus ' 721' towers -are ilong and high in proportion to width and1 must-, be-securely anchored to prevent uplift or overturning during high winds; ; High pump-; irig requirements. (30 to 60 ft) and total dependence upon atmospheric caprice, especially wind (quantity and direction), are disadvantages; - Due to new uses and growth of demand-in recent years requirements for; water-cooling equipment have become increasingly varied and. exacting, necessitating refinements and specialized adaptations. The principal de mand for large water-cooling systems in recent years has come from the, petroleum industry and steam power plants. Eefrigeratiqn, air condi tioning, and engine-jacket cooling service today employ s large,percentage of the medium sized and small water-cooling towers installed. MECHANICAL DRAFT TOWERS The mechanical draft tower consists usually of a vertical shell constructed of wood, metal, transite, or masonry. Water is distributed near the top, Fio. 5. Sprat Filled Atmospheric Cooling Tower -change of one dimension make an equal improvement in efficiency on two .equal towers of different original lengths or''heights. Since the range of efficiency varies through wide limits, it is impracticable to attempt to list data here on the area required per unit quantity of water. Improved ' efficiency due to added height is obtained at the expense of additional pumping head and increased weight per unit of area, whereas improvement ' gained by greater length or width will increase the area and consequently 4 the, foundation required. , - ; Drift' loss in a properly designed deck tower is considerably less'than 'in the spray pond, but the drift nuisance may be considerable and for'this . reason atmospheric deck towers are unsuitable for downtown building . rppfs,, locations adjacent to buildings, or near expensive mechanical equip' ment in industrial plants. They must .be located in an open area, broad side to the prevailing wind. They are' inefficient with less than 3 mph ' wind velocity and with wind directions other than broadside.'! These > Fig. 7. Forced Draft Cooling Tower uniformly over the area, and falls to the collecting basin in the bottom, passing through air which is being circulated in the tower from1 bottom -W top by forced or induced draft fans, or which is circulated horizontally in crossflow towers-by induced draft fans. > In vertical towers the air passes counterflow to the water and is in. con-, tact with the,hottest water just before leaving the tower; hence a given quantity of: air picks up more heat than the average eqiial; quantity ofrair on natural,draft equipment. This permits the water to ;be'. cooled'with'- the least quantity of air required by any type of cooling equipment.' As' movement of air through the towers is obtained by power-consuming finsf it is essential that this air quantity and the draft loss.be reduced to a: mini mum so asto secure low operating cost. ' , . The inside of a mechanical draft tower may be spray filled, i.e., ithie water surface is presented to the air by filling the entire inside, of the structure with water droplets from the spray nozzles, or if may be packed With.'wopd.