The Transformation of Heat in an Engine Page: 3 of 34
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N.A.C.A. Technical Memorandum No. 509
The efficiency coefficient given above, sometimes colled
the economic coefficient, is not well adapted to express the rat-
ing of a heat engine. From the standpoint of thermodynamics
this coefficient can never equal 1. In order to follow the heat
transformation in the engine and obtain an expression for its
efficiency coefficient based on the possibilities of a perfect
(free from heat losses) engine, a rating known as the thermody-
namic efficiency coefficient is used. This is the ratio between
the work of the actual engine Ln and the work of the perfect
(free from heat losses) engine L. That is,
Sthermodyn. = L 1,
and since the loss of work between the perfect and the actual
engine is Lv = L - Ln, the proportion of the work lost is
= L = 1- lthermodyn.
That is, a knowledge of the thermodynamic efficiency coefficient
gives at once the proportion of the work to be won, the differ-
ences between it and its limiting value 1, and the degree of
work loss of the heat engine. The aim must be to make the value
of ( as small as possible. The smaller (, the better the
mechanical construction of the engine, the more appropriate has
been the means employed to meet in' its construction the ends
indicated by theeretical considerations to attain maximum effi-
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Neumann, Kurt. The Transformation of Heat in an Engine, report, April 1929; (digital.library.unt.edu/ark:/67531/metadc279532/m1/3/: accessed February 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.