Handbook of Turbomachinery Second Edition Revised - Ventech!

This process began in the 1920s, although at least one major U.S. utility
continued to use 50 Hz until the 1940s [5].
By the year 2001, the design and manufacturing capabilities of
manufacturers have resulted in nuclear steam turbines of 1500 Mw in
capacity at 1,500rpm (see Fig. 5).
STEAM TURBINE THERMODYNAMIC CYCLES
A basic understanding of the thermodynamics of the steam turbine is
essential to understanding the how a steam turbine is designed, operated,
and maintained. There is a controlled and continual drop of both pressure
and temperature as the working steam expands through the turbine flow
path. As the pressure is reduced, the steam specific volume and volumetric
flow increase. The pressure, temperature, and moisture content of steam
control the efficiency of the process and impose severe performance
requirements on turbine components [6].
Review of Thermodynamic Principles
Historical Developments
The importance of thermodynamics in the history of technology cannot be
overstated. Bernal has said: ‘‘The central and most far-reaching discovery in
the physical science of the nineteenth century was that of the conservation of
energy—the first law of thermodynamics’’ [7]. The second law of
thermodynamics was discovered by Sadi Carnot. In 1824, in Re´flexions
sur la puissance motrice du feu et sur les machines propre a` developper cette
puissance, Carnot outlined the second law as a theoretical limit on the
efficiency of reversible cycles. Carnot also discovered the first law and a
value for the mechanical equivalence of heat in 1830, but those were
unpublished and lost in his notes until their rediscovery in 1878.
Rudolf Clausius generalized Carnot’s work and by so doing began
formal thermodynamics. Clausius pointed out in 1850 that ‘‘It is impossible
to construct a device which, when operating in a cycle, will produce no effect
other than the transference of heat from a colder to a hotter body.’’
The final acceptance of the new views was due to the work of two
academic scientists, William Thompson (Lord Kelvin), in his paper ‘On
the Dynamical Equivalent of Heat’ and Herman Ludwig Ferdinand
Helmholtz in his paper ‘On the Conservation of Force’, who fitted them
into the accepted scheme of classical physics and almost succeeded in
obscuring the fact that a great revolution in human thought had been
achieved [11].
Copyright © 2003 Marcel Dekker, Inc.