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

THE DISTILLING CONDENSER. I 37 It may be admitted (1) at, (2) below, or (3) above, the ordinary atmospheric pressure. The most convenient pressure is (1). In this case the gained steam at ordinary atmospheric pressure simply enters the tubes at the ordi- nary atmospheric pressure (valve at (A) is really not a necessity), is condensed into water, which falls into the bottom pan, and flows to where it is desired. In case (2), if the secondary steam or vapour enters the tubes beloio atmospheric pressure, a pump must be used to suck away the water from (B), which causes a sucking action at (A), so that the valve at (A) will have to be regulated by hand, as the low pressure inside the tubes (T) varies. In case (3) also the valve at (A) will need occasional regu- lation, and a valve will be needed at (B) to keep up the pressure in the tubes (T). Put shortly, the system of working at ordinary atmospheric pressure, as in case (1), accommodates itself at once to an automatic working between evaporator and distiller, which can hardly be said of cases (2) and (3). 5. When the distilled water is required for boiler feed, it is usually specified that it shall be delivered from the apparatus at a temperature not exceeding 150°, other- wise it could not be satisfactorily measured. (6 ) For Cold Distilled Water—Drinking Water. 7. Let us now examine the type of distiller required to produce the distilled water cold. 8. It differs from the distiller for feed-water chiefly in the form of surface—that is to say, a cooling surface has to be added for cooling the water. This may be con- veniently provided by having a set of cooling tubes placed under the condensing tubes, as shown in Fig. 18.