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

THE EVAPORATOR. 91 always in the form of a volute, nor grouped together, but each item of surface (some 8 to 10 items) separately fitted to the inside of the evaporator-casing, instead of to the inside of the door. A short description has also been given of the most material points requiring con- sideration in the various types of heating surfaces put in evaporators. 51. It is now usual to describe the heating surface of the evaporator (and, indeed, the cooling surface of the condenser) by the number of square feet of the outside surface of the coils or tubes used. As this is the subject of calculation, the following Table K gives the outside surface (in square feet) of various diameters of tube per foot length. TABLE K.—Outer Surface in Square Feet of Tubes pee 1 foot Length. Outer Diam. of Tubes in Inches. 0 JS i i 4 8 4 1 0 0-0327 0-0654 0-0982 0-1309 0’1636 0-1903 0-2291 1 0-2618 0-2945 0-3272 0-3600 0'3927 0-4254 0-4581 0'4909 2 0-5236 0-55(53 0'5890 0’6218 0’6545 0-6872 0-7200 0-7527 3 0’7854 0-8181 0’8508 0-8836 0-9163 0’9490 0-9817 1-0145 4 1-0472 1-0799 1-112G 1-1454 1-1781 1-2108 1-2435 1-2763 5 1-3090 1-3417 1-3744 1-4072 1-4399 1-4726 T5053 1-5381 Size and Thickness of Coils. 52. The size or diameter of the coil is also an important matter. Tubes that are small are apt to have a more adherent scale than tubes of large diameter, as the ex- pansion and contraction of the outer circumference when at work is greater in the large diameter, which enables it therefore to crack off the scale. Another reason for preferring a large diameter is that it reduces the length