ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
A Study of Macroscopic Physical Meaning of Entropy
摘要
At present, it is still a challenging work to give an adequate answer to the question of what is the
macroscopic physical meaning of entropy, just as Prigogine said, "...entropy is a very strange concept
without hoping to achieve a complete description...". Hence, the microscopic interpretation of entropy,
instead of its macroscopic interpretation, is usually presented in most textbooks and literatures. However, it
has no help for the analysis and design of thermal systems. In this study, a combined system that consists of
a simple compressible thermodynamic system and its environment is taken into consideration and the
balance equations of the unavailable energy of the system for reversible heat and work interactions are
developed respectively to discuss the macroscopic physical meaning of entropy, which is summarized as
followings: (1) The entropy of a system represents its unavailable energy during reversible heat interaction
between the system and its environment only, that is, the reversible work interaction has no influence on the
entropy of the system; (2) The entropy transfer by heat transfer is of the same dimension of the heat capacity
and consequently the entropy transfer is the unavailable energy transfer per unit environmental temperature;
(3) Understanding the physical meaning of the entropy, which is a property of the system, must be related to
the environmental temperature. Hence, the environmental temperature serves as the role of an auxiliary line
as in solving geometrical problems to help clarify the macroscopic physical meaning of entropy.