Entropy: Thermodynamics – Energy – Environment – Economy

Entropie - ISSN 2634-1476 - © ISTE Ltd

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La Société Française de Thermique a pour objectif le développement et le rayonnement des sciences thermiques et énergétiques et de leurs applications. Cette année 2025, le 33e Congrès Français de Thermique s’est déroulé du 3 au 6 juin 2025 à Chambéry sur le thème Thermique, Energies renouvelables et Territoires.

We describe a new nodal simulation approach, and a corresponding theoretical model, to quantify thermal conduction through the solid phase in three-dimensional fibrous networks, with the impact of fiber-to-fiber thermal contact resistances. We demonstrate that the solid thermal conductivity can be calculated by a master curve, based solely on geometric parameters of the medium, particularly in the case of low-connectivity. This provides a powerful predictive tool to be applied to the study of real insulation materials, to develop in particular optimization strategies based on structural parameters.

Measuring temperature fields in semi-transparent media requires the knowledge of optothermal properties. While current techniques are well established for isothermal thin films, they remain unexplored for thick films with temperature gradients. This study proposes to generalize current methods to thick media by combining transmittance measurement based on transmission heterodyne photothermal imaging (TPHI) and optothermal modeling. In this work, we demonstrate the validity of our model, followed by the measurements of thermotransmittance and thermoreflectance coefficients for 3 different materials.

Local Climate Zones (LCZs) classify urban areas based on their morphology and thermal properties. Using the WUDAPT Level 0 methodology, this study develops an LCZs map for Lyon by leveraging satellite imagery and open-source tools. The process involves collecting training data, performing classification, and validating results. The LCZs map reveals Lyon’s diverse urban structures, offering valuable insights for climate studies and sustainable urban planning. This study highlights the utility of LCZs datasets in addressing challenges posed by urbanization and climate change.

The behavior of pool fires and the ignition risk of unburnt gases are analyzed in a reduced-scale model of a ventilated historic chamber. Experiments were carried out with various pool diameters and air exchange rates to examine fire behavior in a confined environment. The results show that fire behavior varies depending on the combustion regime. The risk assessment, based on a global approach, indicates that the largest pool fire presents a high ignition risk, while the smallest remains below the ignition threshold. This study provides perspectives for fire safety in historic buildings.

In this article, after reminding the present definition of the term « heat », its evolution is summarized with focusing on the mode of heat conduction. The notion of heat has been discussed from antiquity either in East or West. First based on a sensation of hot or cold, the notion of heat for a long time has been confused with that of temperature. Two types of theories have been simultaneously developed, substantialist theories and mechanistic theories. The progression of these two types of theories has been reported from antiquity to present times. At the beginning was the Aristotelian categorization, then the phlogiston theory and, after the theories of caloric and ether for which heat is a substance but, it is shown that as soon as antic times the motion of matter corpuscles also has been associated to heat. Nevertheless, many researchers at the end of the 18th century and the beginning of 19th did not want to take sides, as did Fourier, who has formalized heat conduction in his pioneering work and who is the reference. The corpuscular interpretation is by now accepted and has followed the physics evolution especially with the quantum mechanics. So, heat conduction is associated with particle interactions and with atomic vibrations in solids. In this context, the use of the phonon quasi-particle has contributed to a large part to the present developments.

In the research on the origin of life, topics that can be considered reasonably shared by the generality of researchers are initially identified. The application of these principles to the results obtained with the mathematical model for the simulation of aggregative processes developed by the authors (and the subject of previous publications) leads to the conclusion that the primordial formation of self-replicating structures is difficult to reconcile with deterministic aggregative dynamics in the classical sense. Regardless of the extent to which the process is governed by chance or by aggregative codes written in the laws of chemistry, no conventional causality is likely. Indeed, when the model is applied to the simulation of aggregative processes in the absence of guiding elements (that is code-carrying agents, also capable to promote catalytic effects) as is likely to have been the case in the prebiotic world, the repetitive and ordered formation of sufficiently complex structures implies an entropy deficit that is difficult to justify in a classical context. Only one way out seems possible: the existence of information sets that affect the evolution of the system according to modalities other than those that depend on the flow of perceived time. The possibilities offered by quantum mechanics and its most recent interpretations are con-sequently investigated to try to shed some light, at the level of particle physics, on this enigmatic and unconventional con-jecture.