Document x1LnNYJ6w4z8ky30xZvwEmD2G

Dichlorodifluoromethane System: Power requirements, Cooling tower fan Cooling tower pump 17.8 bhp 30.2 Total 48.0 bhp , Power for cooling tower system = l?^hg^XJ|0hr = 53J0() ^ The water cooler in a dichlorodifluoromethane system of the surface type renUi additional pumping head other than the friction drop through the cooler, which i problem is estimated to be 10 ft. The total pumping head is, therefore, 75' + io Power required for the chilled water system will be, 1200 gpm X 8.34 lb per gallon X 85 ft head _ o, . -------- 33,000-ft lb X-0.T5-pump efficiency - -P 34.3 bhp X 0.746 X 1200 hr 0.80 motor efficiency = 38,300 kwhr. Thus, the total power required by the auxiliary equipment will be 53,700 + 38,300 = 92,000 kwhr. The 92,000 kwhr at 2 cents per kwhr will cost The power cost of refrigeration, from Question 4, is The total annual power cost, using a dichlorodifluoromethane system, is Steam Ejector System: Power requirements, Cooling tower fan Cooling tower pump 35.6 bhp 47.8 Total 83.4 bhp Power for cooling tower systems = 83.4 bhp X 0.746 X 1200 hr 0.80 motor efficiency = 93,300 kwhr. In the flash tank or water cooler of the steam ejector system, the water is at a r. corresponding to the chilled water temperature required. In this case it is at 46 f, corresponds to an absolute pressure of 0.1532 lb per sq in. or 0.3118 in. Hg. This inc. the pumping head on the chilled water circulating pump by 14.7 -- 0.15 = 14.55 lb square inch, or 33.5 ft. The total pumping head is, therefore, 75.0 + 33.5 = 108.5 1200 gpm X 8.34 lb per gallon X 108.5 ft head _ .,, _ 33,000 ft-Ib X 0.75 pump efficiency _ P' 43.7 bhp X 0-746 X 1200 hr _ ,Q ann , . 0.80 motor efficiency , w r. The total power required by the auxiliary equipment is 93,300 + 48,800 = 142,100 kwhr. The 142,100 kwhr at 2 cents per kwhr will cost The cost of the steam, from Question 5, is J2.84Z 1,929 The total annual power cost, using a steam ejector system, is $4,771 These calculations indicate that for the assumptions made, both the dichlorodiflu methane system and the steam-ejector system would cost 2.6 cents per ton-hour' operate. In order to obtain a complete analysis it would be necessary to compare' fixed charges which include interest, depreciation, obsolescence, and maintena These are customarily computed at 15 per cent of the initial cost per annum. To cost must be added the cost of refrigerant make-up per year. In the steam system is negligible, but in the dichlorodifluoromethane system it may be approximate from lA to of the refrigerant charge per year. 182 Chapter 11 HUMIDIFICATION and dehumidification .. n,,.hrrs Atmospheric Water Cooling Equipment, Cooling Air o ' Wet-Bulb Temperature, Cooling Ponds, Natural OfiDecliType Towers,Mechanical Draft-Towers*Winter Freezing- EmilPM ENT for humidifying and dehumidifying is of varied character nd its functions will be discussed in this chapter. An air washer is Vfally a chamber in which air is brought in intimate contact with eSSfei-1 the object being (a) to wash the air or (6) to regulate the moisture ^vV t of the air and at the same time wash it. The air comes in contact the water by passing it through water sprays or by passing it over tfeces wetted by a continuous flow of water; hence the classification: SraV, scrubber, and combination spray and scrubber type washers. A Washer chamber may be constructed of wood, or stone, but it is most ofteji1 constructed of sheet metal. The lower portion of it is specially designed as a tank to receive the water dropping through the chamber and to serve as a reservoir from which the water may be recirculated. It is desirable that air leaving a washer contain no water in suspension. For this reason eliminators are provided at the washer outlet. These may be in the form of plates or baffles upon which the free moisture is deposited as the air is deflected through several changes from its original direction of flow. In some washer units steel wool filter sections serve as eliminators. However, specially designed plates are used more gener ally'than other devices because they offer the least resistance to the flow of'air, while still performing effectively the function of free moisture elimination. They also have the advantage of acting as scrubber surfaces when'flooded. '.` It is essential to uniform performance in a washer, that air enter evenly flis'tnbuted over the washer inlet. To insure this, a perforated plate or .-eliminator plates are installed at the inlet. Eliminator plates are now 'more*'generally used. They serve a second purpose in preventing the escape bf spray through the washer inlet. JVafer is supplied to scrubber type units through flooding nozzles. The `Sl^ojy of these nozzles varies with the manufacturer although a fair ' 5 gpm may be used. The nozzles are spaced on one-foot centers across;the top of the washer over the scrubber plates.