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Froehlich, F. R. (ed.) / The Wisconsin engineer
Volume 13, Number 4 (June 1909)

Brownlee, Frank R.
Comparative efficiencies of power plants with special reference to the efficiency of a superheated steam pipe-line,   pp. 246-261


Page 246


The WlTisconsin Engineer.
COMPARATIVE EFFICIENCIES OF POWER PLANTS
  WITH SPECIAL REFERENCE TO THE EFFICIENCY
  OF A SUPERHEATED STEAM PIPE-LINE.
                  FRANK R. BROWNLEE. '08.
  All machines or mechanical apparatus for either doing
work or transforming energy have an efficiency less than
unity. The difference between the energy expended and the
useful work done, or the loss, is usually consumed either in
overcoming friction or in doing work on bodies surrounding
the machine from which no useful work is received.  It can
be seen that where more than one machine or operation is
used in a series in a power transforming plant the efficiency
of the entire series must necessarily be low.
  The total efficiency of any power plant is the product of
the efficiencies of the individual machines and transmissions.
Taking a simple steam power plant for lighting purposes as
an example, the total efficiency from the coal to the electric
light is rarely if ever, above one per cent. The reason for
this is that each step taken in the process of generating elec-
tricity in itself reduces the efficiency, and the combination of
a large number of steps taken, necessarily reduces the total
value. In the example taken, the total efficiency is com-
prised of seven individual efficiencies. Starting with the
coal the efficiencies to be considered are boiler, furnace,
steam pipe-line to the engine, engine (considered from
both thermal and mechanical point of view), generator, elec-
tric transmission, and motor or lights.
  The efficiency of each step depends upon the losses taking
place in that step. The furnace efficiency depends upon the
coal, grate, and flue-gas losses. The kind of coal and its
combustion, whether complete or incomplete, is a large factor
in the furnace efficiency. The grate design and size must be
accurately worked out to suit the draft and other conditions
246S


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