Page 7 - Entrophy Analysis in Thermal Engineering Systems

xii Preface

is his inequality with no adequate mention of what he meant by entropy and
how he discovered it.
Despite entropy remains as a gray area (it is not as clear as many other
concepts deduced from natural laws), today entropy-based analysis has fre-
quently been employed as a design tool in a wide range of applications.
Often, second law-based studies present entropy calculations but without
any constructive use of such calculations. It is natural to ask: What is the goal
of entropy-related calculations? Is entropy generation always an indication
of losses, for instance, in a power cycle, fluidized bed, boiler, hydrogen pro-
duction plant, chemical reaction, condenser? Do we need to be always con-
cerned about the growth of entropy? Are there specific circumstances where
entropy-related calculations may yield meaningful results? The primary
objective of this book is to highlight the limitations of the application of
entropy in engineering and clarify when a second law analysis may lead to
rewarding results.
The journey of the present book begins with an overview of the funda-
mental thermodynamic concepts in the opening chapter. It is then followed
by a brief historical sketch of Thermodynamics in Chapter 2, which illumi-
nates its evolution as well as the contributions of many ingenious men to the
advancement of the subject during the 19th century. More importantly, a
careful examination of several sources reveals that the tutorial method of
the second law and entropy could be much easier had it followed the same
path as it was discovered and presented by the founders. The current method
of teaching the second law, inherited not from the original founders but
those authors who developed first textbooks on Thermodynamics in the late
19th and early 20th century, skips important steps, for instance the role of the
ideal gas law in the investigation of Carnot, Thomson, and Clausius.
A detailed discussion on the shortcomings of the common tutorial
method of entropy is presented in Chapter 3. Specifically, the demonstration
technique of the Carnot’s corollaries that rests on philosophical reasoning is
shown to suffer from certain issues. The common derivation method of
Carnot efficiency and introduction of the absolute temperature scale with-
out a proper background is critically reviewed. A simple but effective
method is then proposed to ease understanding the connection between
the chain of concepts like Carnot efficiency, entropy, reversibility, and
absolute temperature. The discussion will advance in Chapter 4 where
the main task is to clarify the phenomenon of entropy increase and to show
the direct connection between the phenomena of heat transfer and entropy
generation.