A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

142 SEA WATER DISTILLATION. contact therewith) must be such that the circulation, as it passes in between the tubes, is able to absorb all the latent heat of the steam or vapour inside the tubes, and further to reduce its temperature when condensed. 14. Suppose, therefore, that per hour 1 ton (2,240 lbs.) of steam has to be condensed into water—i.e., hot water at 212°—and that such water has to be cooled to 150°; and that the circulation water is to enter the distiller at not less than 75°. Each pound of secondary steam (at atmospheric pressure) must part with 966 B.T.U. to the circulation water, in order to be reduced to a liquid. If, therefore, the circulation water is specified to have an inlet temperature of 75°, and it is convenient for such circulation water to be discharged at, say, 125°, a difference of 50° between its inlet and outlet (125 - 75=50), the pro- portion of circulation water to the condensed secondary steam will be as follows :— As 50 : 966 :: 1 : 19’3 tons of circulation water to 1 ton of gained steam. If, however, the distilled water is cooled down from 212° to 90° (15° above 75°, the inlet temperature of the circulation water), then the ratio will be as follows :— As 50 : 966+212- 90—1,088 :: 1 : 2T8 tons (nearly) of circulation to 1 ton of distilled water. 15. If 145° is the temperature of the circulation water at its outlet, the ratios will be— As 145 - 75=70 : 966 :: 1 : 13’8 tons of circulation to 1 of distilled water, or As 145-75=70 : 966 + 212-90= 1,088 :: 1 : 15*5 tons of circulation to 1 of distilled water at 90°.