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

8o SEA WATER DISTILLATION. (a) A fixed pressure outside the coils, say | lb. per square inch. Practically atmospheric pressure. (&) A fixed proportion of evaporation and brine to the feed-water, say, from every U lbs. of feed-water supplied, 1 lb. is to be evaporated and | lb. brine, making the brine in salinity. (c) A fixed time for the evaporation, say 1 lb. of gained steam to be generated per hour (i.e., f of the feed). (tZ) A fixed temperature for the inlet feed-water, say 150°. 28. Suppose we compare the three primary pressures of 10 lbs., 25 lbs., and 75 lbs. per square inch, work- ing upon the basis mentioned in the preceding section. Different makers of evaporators have different rules to work by for estimating the square feet of surface required for a given evaporation in a given period of time. Much may influence them in arriving at what they consider a proper surface. Thus they may, and probably do, take into consideration what quantity of water has been evap- orated by their evaporator on experimental occasions. Various matters have to be considered besides the bare question of the pressure of the steam inside the coils to settle the amount of coil surface to allow for a specified output of gained steam, and no rule can be fixed to apply to every kind of evaporator that is made. Experience can alone guide one as to the proper amount of surface, or square feet of coil surface, as it is usually termed. 29. Let us, therefore, assume that in the case above given, with a particular make of evaporator, the con- ditions of working are as specified in section 27, and that 1 ton of steam lias to be generated from, say, 1| tons of sea water per hour, and for the purpose of com-