Conjugaisons finies et milieux continus en relativité générale

We present here the main elements of a mechanics of relativistic continua relying upon a concept of 《finite conjugacy》 between two relativistic motions described by two unit vector-fields u and u' defined on two different relativistic manifolds $\text{M}$-and $\text{M}$'.This purely relativistic, global, and intrinsic theory leads, together with a new approach of the deformation tensors in relativity, to a differential system of equations for the conjugacies which is neither under-determined nor over-determined. A rough study of the propagation of the conjugacy-waves shows then that it is advisable to consider the notion of a finite conjugacy as a satisfying relativistic extension of the classical and tridimensional notion of a finite deformation in mechanics, and to identify the spatial conjugacy-waves obtained with the ordinary acoustic waves.Drastic particularizations of the space-times $\text{M}$ and $\text{M}$', of the motions u and u', of the admissible types of conjugacies and of the elastic behaviour of the continua under study allow to recover, as very important but particular cases, the tridimensional non-relativistic theory of elasticity for finite deformations and non-linear behaviour, as well as the main theories of relativistic elasticity already proposed by Mmes Choquet-Bruhat and Lamoureux-Brousse, Rayner, Carter and Carter-Quintana, Grot-Eringen…. The obtained system of equations generalizes also to the finite case some aspects of the infinitesimal theory of Weber and Papapetrou.     

Efficacité des techniques de régénération d'eau pour une usine de fabrication de papier intégrée sans effluent. Analyse exergétique

Water regeneration efficiency for pulp and paper plant. Exergy analysis. The water network of a pulp and paper mill is contaminated by a large number of components which are brought into the system as wood constituants or process additives. Keeping the contaminant concentrations below certain limits, to safeguard paper quality and process runnability, must be part of any systems closure strategy. This can be achieved by purging contaminants using well known separation techniques such as evaporation, freeze crystallization and membrane filtration. The purpose of this study was to compare the thermodynamic efficiency of these techniques by means of an advanced exergy analysis. The contaminated stream was modelled using key components for both organic and inorganic contaminants. The activity coefficients were calculated using the Chen algorithm. The approach developed by Brodyanski, Sorin and Le Goff was used to determine the exergy efficiency. This analysis shows that freeze crystallisation is the most efficient technique when the exergy of the output stream is considered as a useful effect. When only the useful work obtained by separation is considered, membrane separation becomes the most efficient process. The analysis of the process incorporating a separation operation produces the actual efficiency. This example illustrates the advantage of using exergy methods to determine the efficiency of processes based on different physico-chemical phenomena.     

Réflexions sur lʼavenir de lʼénergie nucléaire,de la France dʼaujourdʼhui au monde de demain : IIe à IVe générations

The recent events at the Fukushima power plants (PP) have brought to light key issues which have to be discussed concerning the position of nuclear energy in the energy mix, in the context of global warming, of waning petroleum resources, of an increasing world population, and of its industrial development. These questions are addressed here from the viewpoint of physical facts; and, without proposing definite choices, this article aims to provide information on the equipment required to benefit from the fission chain reaction, while explaining the possible incidents and accidents, and the possible hidden military misuse of nuclear matter. Specific issues, such as risk assessment and risk management, will be considered, under the constraints of dealing with international non-proliferation safeguards and France energy resources independence. A special emphasis will be given on the fuel cycle, on the variety of time scales involved, and on the requirements of developing the next generation of nuclear power plants, and more specifically the fast breeder option. The lessons to be drawn from the Fukushima accident, resulting mainly from the residual power of used fuel and the loss of cooling source, are outlined, and the consequences to be drawn about the various relevant time scales are emphasized.     

MODICS. Généralisation de la méthode d'optimisation systémique aux systèmes thermiques avec échangeurs imposés

We present here the generalization of the systemic optimization method for complex thermal installations, based on the thermal integration, that was the subject of a previous publication in the October 1995 (n^o 406) issue of the Revue Générale de Thermique. The proposed method allows to distinguish component irreversibilities, that are linked to the internal functioning of a component alone, independently of the rest of the considered system, and systemic irreversibilities that can only be modified by changing the configuration of the system. It constitutes a tool for design engineers, the originality and the power of which are to give them systemic insights on the installation under study.The general method MODICS is obtained by mixing on the one hand the previously described method and on the other hand an analogous approach adapted to the case when heat exchangers are imposed. The article details the totality of procedures to follow to implement this method and gives various examples.     

Transfert thermique pour la condensation du R123, du R134a et de leurs mélanges,en écoulement forcé entre deux plaques planes horizontales. Etude numérique.

Heat transfer for forced convection condensation of R123, R134a and their mixtures flowing between two horizontal parallel plates. Numerical study. Film condensation of pure and binary mixtures flowing between parallel plates is treated numerically. The coupled equations of mass, momentum, species and energy conservations for the two phases are solved with an implicite scheme. In this study, we retained the pressure forces, the liquid and vapor interfacial shear stress, the Dufour effect, the inertia and enthalpy convection terms, the turbulence in the two phases and the variation of the physical properties with the temperature and concentration. The results obtained for the condensation of refrigerants R123 and R134a, show strong influence of the composition of mixture on the mean heat transfer coefficient and the total pressure loss. The calculated mean Nusselt number is in good agreement with the experimental correlations of Mochizuki and Inoué [6] and Akers and Rosson [24]. A new correlation for the mean heat transfer for forced convection condensation of pure refrigerants R123 and R134a and their mixtures between horizontal flate plates is proposed.