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

__________________________________________________________________________________________________________________________________ ■ ' ____________ __________ _____________________________________________________________ 210 SEA WATER DISTILLATION. casing at practically no pressure at all. The heater shells and interior tube surfaces should be proved to not less than double the maximum working pressure, what- ever that may be in each heater. Surface of Heater. 88. The amount of surface for the heaters is calculated somewhat in the same manner as that already shown foi calculating the amount of surface for evaporator and distiller coils or tubes. The amount of heat available in units per lb. weight of steam and water passing through the tubes is first ascertained, and then the weight of feed- water (in lbs.) that requires to be heated ; the ratio of the one to the other will enable an estimate to be made of the temperature that each lb. of feed-water will be raised to bv its being placed so as to absorb th.© lioat passing through the tubes. The extent of the surface is then estimated on that basis, according to such rules as may have been arrived at by experience with the type of heater used. Materials used for Heaters. 89. The actual surfaces of the heaters are conveniently made of solid-drawn copper tubes. It is well to have the tubes spaced not too close together, as the operation of cleaning has to be considered. The interior of the tubes should be proved to double the maximum working pressure. 90. The tubes are best expanded into gun-metal tube plates, much in the same way as the tubes are fixed in a distilling condenser. 91. The casing or shell of the heater is made of gun- metal, or copper, or steel, as may be desired, rhe covers