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

THE EVAPORATOR. 79 24. Hie details of this small type of apparatus, call it a boiler, evaporator, generator, or what you like, will be gone into in a subsequent chapter, when we deal with the working of the apparatus generally, after having explained all its parts. This small apparatus is complete in itself__ that is, it includes a small distilling condenser, and, when required for producing drinking water, a small filter. The water is thus produced, not only of special purity, but also cold and of the best quality for drinking. The apparatus is suitable for domestic use. (C) Heating Surface—Generally. 25. It will now be convenient to pass on to the subject of coil or tube surface—that is, the amount of heating surface required for certain productions under certain conditions of working. This is affected by the pressure of the steam inside the coil, perhaps more than by any- thing else. 26. It will be remembered that the intensity of steam heat i.e., the sensible heat of steam «increases and de- creases, according as the pressure rises and falls. The higher the pressure, the hotter (sensibly) is the steam, in its gaseous state, and this increase or decrease, as the case may be, of “ sensible ” heat is counterbalanced by a decrease or increase of the “ latent ” heat that is emitted as the steam is reduced into a state of water. On the amount of ‘ sensible ” heat of the steam inside the coil, above the sensible heat of the sea water outside the coil, depends the amount of coil surface that is required. 27. To explain this, with a view to showing how to calculate the amount of heating surface, it is best to start with a basis, or a certain state or condition of things, thus :—