11,290 research outputs found
Thermodynamic Bond Graphs and the Problem of Thermal Inertance
It is shown that an isolated thermal inertance does not obey the second law of thermodynamics. Consequently, such an element should not be used in physical systems theory. To eliminate the structural gap in the thermal domain of current physical systems theory, a new framework is introduced using Bond Graph concepts. These Thermodynamic Bond Graphs are the result of synthesis of methods used in thermodynamics and in mechanics
“Constructal Theory: From Engineering to Physics, and How Flow Systems Develop Shape and Structure”
Constructal theory and its applications to various fields ranging from engineering to
natural living and inanimate systems, and to social organization and economics, are
reviewed in this paper. The constructal law states that if a system has freedom to morph
it develops in time the flow architecture that provides easier access to the currents that
flow through it. It is shown how constructal theory provides a unifying picture for the
development of flow architectures in systems with internal flows (e.g., mass, heat, electricity,
goods, and people). Early and recent works on constructal theory by various
authors covering the fields of heat and mass transfer in engineered systems, inanimate
flow structures (river basins, global circulations) living structures, social organization,
and economics are reviewed. The relation between the constructal law and the thermodynamic
optimization method of entropy generation minimization is outlined. The constructal
law is a self-standing principle, which is distinct from the Second Law of Thermodynamics.
The place of the constructal law among other fundamental principles, such
as the Second Law, the principle of least action and the principles of symmetry and
invariance is also presented. The review ends with the epistemological and philosophical
implications of the constructal law
Panel I: Connecting 2nd Law Analysis with Economics, Ecology and Energy Policy
The present paper is a review of several papers from the Proceedings of the Joint European Thermodynamics Conference, held in Brescia, Italy, 1–5 July 2013, namely papers introduced by their authors at Panel I of the conference. Panel I was devoted to applications of the Second Law of Thermodynamics to social issues—economics, ecology, sustainability, and energy policy. The concept called Available Energy which goes back to mid-nineteenth century work of Kelvin, Rankine, Maxwell and Gibbs, is relevant to all of the papers. Various names have been applied to the concept when interactions between the system of interest and an environment are involved. Today, the name exergy is generally accepted. The scope of the papers being reviewed is wide and they complement one another well
Hawking Radiation and Analogue Experiments: A Bayesian Analysis
We present a Bayesian analysis of the epistemology of analogue experiments
with particular reference to Hawking radiation. First, we prove that such
experiments can be confirmatory in Bayesian terms based upon appeal to
'universality arguments'. Second, we provide a formal model for the scaling
behaviour of the confirmation measure for multiple distinct realisations of the
analogue system and isolate a generic saturation feature. Finally, we
demonstrate that different potential analogue realisations could provide
different levels of confirmation. Our results provide a basis both to formalise
the epistemic value of analogue experiments that have been conducted and to
advise scientists as to the respective epistemic value of future analogue
experiments.Comment: 25 pages, 5 figure
What we cannot learn from analogue experiments
Analogue experiments have attracted interest for their potential to shed
light on inaccessible domains. For instance, `dumb holes' in fluids and
Bose-Einstein condensates, as analogues of black holes, have been promoted as
means of confirming the existence of Hawking radiation in real black holes. We
compare analogue experiments with other cases of experiment and simulation in
physics. We argue---contra recent claims in the philosophical literature---that
analogue experiments are not capable of confirming the existence of particular
phenomena in inaccessible target systems. As they must assume the physical
adequacy of the modelling framework used to describe the inaccessible target
system, arguments to the conclusion that analogue experiments can yield
confirmation for phenomena in those target systems, such as Hawking radiation
in black holes, beg the question.Comment: 27 pages, 2 figures; forthcoming in Synthes
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