. Applied thermodynamics for engineers. altitude to chimney draft ? (See Problem 12, ChapterXIII.) 138 APPLIED THERMODYNAMICS 16. Circulating water pumped from a surface condenser to a cooling tower loses4| per cent of its weight by evaporation and is cooled to 88° F. If the loss is madeup by city water at 55°, fed continuously, what is the temperature of the waterentering the condenser ? 17. Steam at 100 lb. absolute pressure and 500° F. is used in an open feed-waterheater to warm water from 60° to 210°. How much water will be heated by 1 steam ? 18. Steam at 150 lb. absolute pressure,
. Applied thermodynamics for engineers. altitude to chimney draft ? (See Problem 12, ChapterXIII.) 138 APPLIED THERMODYNAMICS 16. Circulating water pumped from a surface condenser to a cooling tower loses4| per cent of its weight by evaporation and is cooled to 88° F. If the loss is madeup by city water at 55°, fed continuously, what is the temperature of the waterentering the condenser ? 17. Steam at 100 lb. absolute pressure and 500° F. is used in an open feed-waterheater to warm water from 60° to 210°. How much water will be heated by 1 steam ? 18. Steam at 150 lb. absolute pressure, 2 per cent wet, passes through a super-heater which raises its temperature to 500° F. How much heat was added to eachlb. of steam ? 19. 20,000 lb. of steam at 150 lb. absolute pressure, 2 per cent wet, are super-heated 200° in a separately-fired superheater of efficiency. What weight of coal,containing 14,000 B. t. u. per lb., will be required ? CHAPTER XYII DISTILLATION —FUSION—LIQUEFACTION OF GASESVacuum Distillation. Fig. 288. WATER OUTLET Art. 591. —Still. 591. The Still. Figure 288 represents an ordinary still, as used forpurifying liquids or for the recovery of solids in solution by applied heat evaporates the liquid in A, which is condensed at H B. All of the heat ab- sorbed in A is given up atB to the cooling water;the only wastes, in theory,arise from radiation. Con-ceive the valve c to beclosed, and the space fromthe liquid level d to thisvalve to be filled with satu-rated vapor, no air beingpresent in any part of theapparatus. Then w^hen thevalue c is opened, a vacuum will gradually be formed throughout thesystem, and evaporation will proceed at lower and lower temperatures. Since the total heat of saturated vapor decreases with decrease ofpressure, evaporation will thus be facilitated. In practice, however, theapparatus cannot be kept free from air; and, notwithstanding the opera-tion of the condenser, the vacuum would soon
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