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[en] The Gibbs condition is used to consider, how different phases can be obtained by surface effects. A new argument is given, why broken continuous symmetry gives rise to long range correlations. Finally it is argued that mixed KMS-states are unstable under changes on the surface. (Author)
[en] The purpose of this paper is to show which are the basic requirements for a valid modeling of thermal processes. Developing numerical models is not an end purpose. It is only a way of solving an engineering problem and thus, it is important to know what are the basic requirements which must be satisfied. The mathematical model will be valid only when the requirements of feasibility, consistency, stability, conservation, convergence and accuracy are fulfilled. We must be aware of these requirements also when we interpret the numerical solution in order to dissociate between the behavior of the process which has been modeled and the influence of the numerical schemes. These is extremely important to avoid solutions which are grid dependent or which have numerical instability. (author)
[en] In Bru (2002 J. Phys. A: Math. Gen. 35 8969), we present a general method of superstabilization corresponding to the addition of the 'forward scattering' interaction to some non-superstable model. Here we complete the thermodynamic study done in this paper and we prove that the 'standard' thermodynamic behaviour of the non-superstable model is preserved in its superstabilized form in the grand-canonical ensemble. In particular, the Bose condensation phenomena persist in the new Bose gas. Moreover, this method ensures the strong equivalence for the new superstabilized model between the canonical and grand-canonical ensembles in the thermodynamic limit (Georgii H-O 1994 Probab. Theory Related Fields 99 171-95) and then it gives another way to analyse the canonical (infinite volume) Gibbs state of the first non-superstable model
[en] Heat pumping is a highly energy-efficient technology that could help reduce energy and environmental problems. The efficiency of a heat pump greatly depends on the individual and integral performance of the components inside. In this study, heat pump performance is investigated with a special focus on heat exchangers. Experimental data obtained from comprehensive heat pump measurements performed at the Austrian Institute of Technology (AIT) were analyzed with the help of thermodynamic models developed for this purpose. The analysis shows that the performance of heat exchangers varies widely resulting in substantial COP differences among the heat pumps. The models and methodology developed in this study are found capable of extracting useful information from measurement data quickly and accurately and could be useful for the industry. - Research highlights: → A heat pump database has been analyzed focussing on the influences of heat exchangers on COP. → It was shown that an empirical equation could excellently correlate experimental COP data with relevant parameters. → It was found that heat exchanger design alone caused 15-20% difference in COP.
[en] The authors' elaboration of atmospheric radiative transfer processes in the theoretical framework of local irreversible thermodynamics is applied to study integral entropy production theorems for the global earth-atmosphere system. In detail it is shown that, with the inclusion of radiant absorption and emission being decisive effects for long-term climate variations, global evolution criteria can be formulated quite generally and applied to typical meteorological-climatological conditions. For our specific system in which radiant phenomena and Fourier-type heat conduction are combined, the validity of the Glansdorff-Prigogine general evolution condition is discussed. This principle is applied as a basis to derive a sufficient thermodynamical stability criterion for Budyko-Sellers type energy balance models. With given simplifications so-called kinetic or diffusive potentials characterizing Lyapounov-stability can be formulated. This analysis is used to discuss the limiting case of an isothermal gray (and especially a black) body whose entropy production becomes a minimum in stationary states. We notice too, how Paltridge's former hypothesis of a climate having a maximum production of entropy can be interpreted in this thermodynamical connexion
[en] We present a general theorem restricting properties of interfaces between thermodynamic states and apply it to the spin glass excitations observed numerically by Krzakala and Martin and separately by Palassini and Young in spatial dimensions d=3,4. We show that such excitations, with interface dimension ds< d, cannot yield regionally congruent thermodynamic states. More generally, zero density interfaces of translation-covariant excitations cannot be pinned (by the disorder) in any d but rather must deflect to infinity in the thermodynamic limit. Additional consequences concerning regional congruence in spin glasses and other systems are discussed
[en] Previously the five dimensional S1-rotating black rings have been superposed in a concentric way by some solitonic methods, and regular systems of two S1-rotating black rings were constructed by the authors and then Evslin and Krishnan (we called these solutions 'black di-rings'). In this place we show some characteristics of the solutions of five dimensional black di-rings, especially in thermodynamic equilibrium. After the summary of the di-ring expressions and their physical quantities, first we comment on the equivalence of the two different solution sets of the black di-rings. Then the existence of thermodynamic black di-rings is shown, in which both isothermality and isorotation between the inner black ring and the outer black ring are realized. We also give detailed analysis of peculiar properties of the thermodynamic black di-ring including discussion about a certain kind of thermodynamic stability (instability) of the system.
[en] Highlights: • The application of control actions to green technologies has been simulated. • Energy consumption of green technologies can be reduced even more. • The efficiency of green technologies can be raised. • Environmental concerns can be diminished. • The sustainability of the planet can be increased. - Abstract: Reducing environmental emissions is one of the challenges that human being has to overcome. It can only be reached with a proper energetic efficiency and management of the processes that exist in the society nowadays. Several academic works have mentioned that raising the efficiency of a process it also increases sustainability and in turn decreases the environmental impact. One process that requires much attention is the cooling and heating of buildings; this process contributes to the major part of the electric bill, in particular, if a conventional and old air conditioning is used as commonly occurs in many countries. In recent years there have been developed new alternatives that are used in few countries, such as the earth–air heat exchanger, where air is passed through a heat exchanger buried a few meters below the ground. The heat exchanger takes advantage of the well-known difference between the temperature of the surrounding air and the temperature of the ground for cooling or heating the air that is subsequently injected into the buildings. This process requires less energy, then in the present work is thought that a PID (Proportional, Integral and Derivative) controller can be applied to an earth–air heat exchanger to reduce even more the energy consumption. Therefore, a simulation of a thermodynamic model of an earth–air heat exchanger was done and used along with a PID controller, to estimate savings in energy consumption. The results show that the energy consumption can be reduced up to 87% with the PID control, hence the efficiency of the process is increased as well as the sustainability of the planet and thus the environmental concerns are diminished
[en] Verlinde has suggested that the gravity has an entropic origin, and a gravitational system could be regarded as a thermodynamical system. It is well-known that the equipartition law of energy is invalid at very low temperature. Therefore, entropic force should be modified while the temperature of the holographic screen is very low. It is shown that the modified entropic force is proportional to the square of the acceleration, while the temperature of the holographic screen is much lower than the Debye temperature TD. The modified entropic force returns to the Newton's law of gravitation while the temperature of the holographic screen is much higher than the Debye temperature. The modified entropic force is connected with modified Newtonian dynamics (MOND). The constant a0 involved in MOND is linear in the Debye frequency ωD, which can be regarded as the largest frequency of the bits in screen. We find that there do have a strong connection between MOND and cosmology in the framework of Verlinde's entropic force, if the holographic screen is taken to be bound of the Universe. The Debye frequency is linear in the Hubble constant H0. (geophysics, astronomy, and astrophysics)
[en] The nonconventional thermodynamical approach to subatomic physics is described with large nonequilibrium effects taken into account by introducing the temperature continuum O≤T<∞. The approach is an expansion of the classical fluctuation theory and chemical-reaction formalism. A large body of problems in low- and high-energy nuclear physics is solved in the framework of super-nonequilibrium thermodynamics. 30 refs., 2 figs., 1 tab