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

THE EVAPORATOR. 71 To meet this requirement, we have primary steam at 10 lbs. pressure, with a latent heat of 946 units and a sensible heat of 239°, so that (if no advantage is taken of the heat left in the primary water after the primary steam has imparted its latent heat) we shall have an economy of 1,134 -i- 946 = 1'2—that is, 1'2 economy. If, however, we utilise the heat left in the primary water from 239° down to, say, 212°—that is, use 27° of it (239° - 212° = 27°)—the economy will then be improved as follows:— 946 the latent heat of steam at 10 lbs. pressure. 27 the sensible heat left in the primary water (239- 212 = 27). ____ 1 973 B.T.U. total heat. So that 1,134 4- 973 = 1166—i.e., 1’166 economy. Or, if the sensible heat left in the primary water is further used, so as to reduce it from 239 to, say, 150, the economy will be further improved as follows :— 946 the latent heat as before (10 lbs. pressure). 89 the sensible heat left in the primary water (239 - 150 = 89). ------ ■ 8 1,035 B.T.U. total heat. So that the economy will then be 1,134 1,035 = 1’096 —i.e., 1-096 economy, or 1'096 lbs. (weight) of primary steam to obtain 1 lb. (weight) of secondary steam. 12. Now, take the primary steam at 25 lbs. pressure, and compare it with the 10 lbs. pressure in last section. There will still be the 168° of sensible heat to provide for, also the latent heat of 966° also, making a total, as