SURFACE CONDENSERS. 101 
outside diameter, placed inside of tubes of varying diameters. With a 5/8-inch 
tube, about 4 feet long, placed inside of a tube about 114-inch inside diameter, a 
temperature rise of 60° F. was obtained. By placing this same 5/8-inch tube 
inside a tube 2-inch inside diameter, a temperature rise of 100° F. was obtained 
with the same steam pressure and the same conditions of test. This showed con- 
clusively that the steam space surrounding the 5/8-inch outside diameter tube was 
a most important factor. 
The author then ran a series of tests with varying velocities of water and, much 
to his amazement, obtained a heat transfer of about 2,750. An apparatus was 
then built having about one hundred tubes, 5/8-inch outside diameter, with the 
conventional tube layout, and this apparatus was tested exhaustively by the engi- 
neers at the Annapolis station in both vertical and horizontal positions, these 
results showing a heat transfer of about 1,000. This clearly proved the advantage 
of having ample steam space between the tubes, so it was decided to design a 
surface condenser with tubes spaced well apart at the entering rows and to gradually 
decrease this spacing to normal at the point where the condensate left the tubes. 
The experiments on the various appliances showed that it was a serious mistake 
to fill up an enclosure with as many tubes as it could hold and call this a proper 
surface condenser design, as nothing could be gained by having the steam or con- 
densed vapor traverse a mass of tubes after it had been condensed. Why not 
endeavor to produce a design whereby a maximum inlet area between the tubes 
could be obtained, so that with a volume of steam corresponding to a vacuum of 
281% inches we would have a velocity of about 100 feet per second or less? Instead 
of the conventional method of blocking up the entrance area between the tubes 
and thereby suffering a loss due to unnecessary resistance, which reacts on the tur- 
bine and causes an unnecessary loss in efficiency, and permitting the steam to 
travel through a bank of tubes after it had already been condensed and allowing 
the cold circulating water to cool the condensate unnecessarily “‘as it does in all 
condensers of ordinary design,” it was decided to reduce the depth of the bank 
of tubes to about half of that ordinarily used and to permit the condensate to be 
drained from said bank of tubes at its maximum temperature, “which should be 
approximately that of the temperature corresponding to the temperature of the 
vacuum.” 
Realizing the great value of reducing the volume of air and non-condensable 
vapors, a liberal cooling chamber was provided of efficient form, this chamber 
also to condense any vapors that remained and the condensate from this chamber 
to fall into the common condensate space, where it would be removed at the bottom 
of the shell. When used for battleships or the like this air-cooling space was 
enlarged, thereby providing about 40 per cent of the total tube surface. This 
enabled the outer portion of the condenser to serve as a primary condenser and the 
so-called air-cooling space a secondary condenser. 
Thus, when the turbines are operating at less than full load, ‘“‘and particularly 
at steam capacities below half that of full load,” the primary condenser can do all 
the work and retain its heat in the condensate instead of falling over a bank of 
