104 SURFACE CONDENSERS. 
to the pound. Figuring the heat transfer for this trial, we find that it is in the neighbor- 
hood of 500 to 540 British thermal units. 
The great discrepancy between this figure and that obtained on the first test can 
hardly be explained as deterioration. But, in view of the many assumptions made in 
the first test, it is safe to conclude that its results are misleading and that the lower heat 
transfer figure, as obtained in the second test, is more nearly representative of the true 
performance of the condenser. 
However, a heat transfer of something over 500 British thermal units is commend- 
able performance and compares with the results obtained from other well-designed con- 
densers. 
ProFessor Epwarp M. Bracc, Member:—Perhaps some of you will remember 
that yesterday I said that, judging from the lines that are produced in our shipyards, 
only a small number of the designers are familiar with the work that has been carried 
on in naval tanks, and the statement in the concluding paragraph of this paper allows 
me to take a whack at the marine engineer. 
If the marine engineers were familiar with the literature of their profession, this 
lack of understanding need not have existed, because as early as 1906 Professor Weighton 
wrote for the Institute of Naval Architects a paper describing some valuable tests made 
upon an experimental condenser. This condenser was small, to be sure, having only 
about roo square feet of surface, and was run in connection with a small triple-expansion 
engine of the marine type. The temperature of the inlet water was varied from 45° 
to 70°. The speed of the water through the tubes varied from about 1 foot per second 
up to 6 feet per second, and the output of the engine was varied so that the square feet 
of cooling surface per horsepower varied from 0.5 to 1.5. At that time the advantage 
was clearly shown of leading off the condensate to one side and preventing it from dripping 
down through the tubes. It was clearly shown that the efficiency of the cooling surface 
increased directly with the velocity of the water, and that in order to have the tubes: 
act efficiently the velocity of the steam across them should be sufficient to remove any 
blankets of air that tended to form at that place. 
I think that the shipyards should provide their designers with easy access to the 
literature of their profession, because there is really no excuse for the designers continuing 
on in the same old path for the last twenty-five years. 
I had occasion to take those results as they are presented by Professor Weighton 
and to work them over, and I have been able to simplify them and use them in my 
classes as a basis for condenser design. You may be interested to know that the results 
obtained from the test of this condenser with 8,000 square feet of cooling surface checks 
in very closely with the results obtained from Weighton’s experimental condenser with 
roo square feet of surface. One quantity very convenient for tabulating results is the 
surface-section ratio. I think no mention is made of that in this paper. If we reduce 
all condensers to one pass, then the surface-section ratio is the ratio of the outside surface 
of one tube to the cross-sectional area of that tube for the passage of water. Of course 
this ratio has a large value; it varies from 1,000 up to 3,000. Ordinarily in marine work 
we use a ratio of about 2,000, but for land practice, where water is expensive and in some 
cases difficult to get, we try to save all we can in that direction by using as high a ratio 
aS 3,000. 
I see in Plates 43 and 44 that enough data are given to work out the surface-section 
