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HEATING VENTILATING AIR CONDITIONING GUIDE 1943 ;it to approximately the wet-bulb temperature of the surrounding atmos phere. The end view of a typical evaporative condenser is shown in Fig. 8. The fan draws the air over a finned tube condenser which is kept wet by a water spray. The discharge refrigerant gas from the compressor enters the top of the condenser coil and the liquid refrigerant is drained from the bottom of the coil into a liquid receiver and then circulates through the remaining portion of the system in the usual way. The water is circulated through the spray nozzles and the level is maintained in the sump by means of a float valve. The eliminator plates Table 7. Pressure Losses in Dichlorodifluoromethane Discharge or Hot Gas Fines3 '_ Capacity Btu per Hour Pressure Drop in Pounds per Square Inch per 100 Ftb Line Sizes, Inches 10,000 15,000 20,000 25,000 . 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 125,000 150,000 175,000 200,000 250,000 300,000 400,000 500,000 600,000 800,000 1,000,000 1.250.000 1.500.000 2,000,000 .H 2.3 4.9 8.5 H 1.0 2.0 , 3.4 5.3 7.5 H lH 0.6 1.0 . 1.7 ` 0.6 2.6 0.9 3.6 1.2 6.4 9.8 2.1 3.1 4.4 6.0 8.0 10.2 1H 0.5 r 0.7 1.0 1.3 . 1.9 2.5 3.1 3.8 6.0 8.5. 11.6 lH 2H 2H *-1 0.5 0.7 0.9 1.1 1.4 1.7 2.6 3:8 5.1 6.7 10.4 0.5 0.7 1.0 ;1.3 1.7 0.6 2.6 : 0.9 3.7 1.2 ' 6.7 2.2 10.5 3.5 -- cOCnb o 3H 3H 0.5 0.9 1.5 0.7 2.1 1.0 3.8 1.8 5.8 2.9 9.5 4.4 6.4 11.3 Soft annealed copper tubing up to and including outside diameter and larger. mTsoutside diameter. Hard copper pipe H in. . ^Length of tubing includes the average number of fittings. are placed in the path of the water-air mixture so as to remove the entrained water. The air leaving the unit is almost completely-saturated, so that care must be taken in locating discharge ducts1 to prevent con densation. Evaporative condensers are available in sizes up to, 100 tons or more. These units use only a small portion of the watef required for a water cooled condenser. The water is vaporized by the: heat of the refrigerant so' that each pound of water used extracts approximately 1000. Btu from the refrigerant, whereas, under standard'rating conditions where the water temperature rise is 20 F, each pound of. water extracts only 20 Btu 492 CHAPTER 25. REFRIGERATION from the refrigerant. Including the water lost by entrainment in the discharge air, by overflow and stand-by evaporation, the water used is about 3 to 5 per cent of the amount that would be required for a'water cooled condenser. The evaporative condenser requires more maintenance, occupies greater space (must be located where air is available), and has a higher first cost than the water cooled condenser, but where the use of water is restricted or expensive, the evaporative condenser has become widely accepted. Compared with a water cooled condenser and cooling tower, which com- Table 8. Pressure Losses in Dichlorodifluoromethane Liquid Refrigerant Lines Capacity Btu per Hour 100.000 125,000 * 150,000 175,000 200,000 225,000 250,000 275,000 300.000 325,000 350,000 375,000 400,000 450,000 500,000 550,000 600.000 700,000 800,000 900,000 1,000,000 1,200,000 1,400,000 i.600;ooo "" 1,800,000 2,000,000 2,200,000 Pressure Drop in Pounds per Square Inch per 100 FTa Pipe Sizes. Inches H iH m 1M 0.6 0.9 1.3 1.8 2.3 0.6 *2.9 0.8 3:6 1.0 4.3 1.2 5.1 1.4 5.9 1.6 6.9 1.8 7.9 2.1 9.0 2.3 0.8 2.9 1.0 3.5 1.3 4.3 1.5 0.7 5.0 1.8 0.8 6.7 2.4 1.1 8.7 3.1 1.4 3.9 i.7 4.7 6.7 9.0 . 2.1 . 3.0 4.0 5.1 6.3 7.9 9.2 . Length of tubing includes the average number of fittings. bination uses about the same quantity of water, the evaporative con denser has the advantage of lower cost and smaller space requirements. EVAPORATORS AND COOLERS The types of coolers used-in connection with air conditioning work-fall into three general groups. The first, is the direct cooling of water; the second, direct cooling' of air; and the third, cooling of brine for circulation in a closed system, which can cool either water or air. One method of the direct cooling of water is to install direct-expansion coils in the spray chamber so that the-water sprayed:into the air- comes in direct contact 493