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

THE EVAPORATOR. 77 the same at any pressure such steam is generated, or in other words, the “ sensible ” heat plus the “ latent ” heat almost equal the same total heat, at any pressure. (See Table E, p. 33; also Note on p. 49.) The above economy is, of course, quite a different matter from the economy that is obtained by multiple distillation, which is treated of in the chapter on Multiple Distillation. Steady Ebullition. 20. The secondary steam, at whatever pressure it is generated, should rise steadily from the surface of the sea water, and not in gulps, otherwise there will be a tendency to priming—i.e., particles of sea water being blown up with the secondary steam, and carried over with it, so as to impair the good quality of the water condensed from the secondary steam. Baffles are some- times fitted in the steam room to prevent priming, such baffles being of various designs to arrest these particles of sea water, and bring them down again into the sea water. More will be said as to this when the subject of “ brine area ” or “ steam delivery area ” is dealt with. Secondary Steam Valve. 21. The pipe from the evaporator leading the secondary steam away to be condensed is sometimes fitted with a valve. The object of this valve is to regulate the flow of secondary steam, where there is a minus pressure in the condenser. Or such valve may be used to shut off altogether the secondary steam, so as to get up a pressure in the evaporator casing for the purpose of blowing away the brine at intervals, if required. This will, however,