Papers by Keyword: Irreversible Thermodynamics

Abstract: In this analysis, the variable configuration requires a variable distribution. This takes account of the areas offered by the valves and resistance gazodynamic coefficients. All at once the law of efficiency variation describes the variation of the power law. Cycle behavior was analyzed for the following values of the pressure drop coefficient on admission: 5%, 10%, 20% and 40%. For the calculations is necessary to determine the dimensionless heat developed by combustion. I used the following values: for the pressure drop coefficient on admission I use ψ_a=10 % and for the share of gazodynamic on the suction route conductance in total conductance I use .With this configuration imposed and with (dimensionless heat developed by combustion) resulted: (mean indicated pressure cycle) ; η_v = 0,876 (cylinder filling coefficient) ; α = 1,515 (excess air coefficient) and η_i = 0,499 (indicated cycle efficiency) ; (dimensionless indicated power ); (dimensionless heat taken combustion gas) ; (dimensionless heat taken environment). After numerical analysis result a maximum efficiency with relatively low dissipation.

Abstract: The irreversibility of ferroelectric phase transitions has been studied by using the irreversible thermodynamics. The thermal hysteresis of first-order ferroelectric phase transitions and the polydomain structure of ferroelectrics can be explained on the basis of the principle of minimum entropy production. A conclusion has been derived that the thermal hysteresis is not an intrinsic property of a system in which a first-order ferroelectric phase transition occurs. The finiteness of the systems surface is connected with the thermal hysteresis.

Abstract: Based on the irreversible thermodynamics, a irreversible thermodynamic description of domain occurrences in ferroics such as ferroelectrics, ferromagnetics and ferroelastics was given. The ferroic domain structures occur at the ferroic phase transitions from the prototype phases to the ferroic phases. The processes of transition are stationary state processes so that the principle of minimum entropy production is satisfied. The domain occurrences are a consequence of this principle. The time-spatial symmetry related to the domains and their occurrences was also expounded.

Abstract: Based on the irreversible thermodynamics theory, the kinetic of BaSiO₃ solid-solid reaction has been constituted and then the equations were applied to BaSiO₃ solid synthesis reaction. The calculation results showed that the reaction was under control of reaction at 1207K.

Abstract: In this work we show that the volume velocity, ρυ , rather than the local centre of mass velocity should be used in continua. We use the volume continuity equation to define the volume frame of reference in the multicomponent, compressible continua. The volume velocity (material velocity) is a unique frame of reference for all internal forces and processes, e.g., the mass diffusion. No basic changes are required in the foundations of linear irreversible thermodynamics except recognizing the need to add volume to the usual list of extensive physical properties undergoing transport in every continuum. The volume fixed frame of reference allows the translation of the Newton’s discrete mass-point molecular mechanics into continuum mechanics and the use of the Cauchy linear momentum equation of fluid mechanics and Navier-Lamé equation of mechanics of solids. Our proposed modifications of Navier-Lamé and energy conservation equations are selfconsistent with the literature for solid-phase continua dating back to the classical interdiffusion experiments of Kirkendall and their subsequent interpretation by Darken in terms of diffusive volume transport. We do show that the local diffusion processes do not change the centre of mass of the system and that the internal stress depends on the gradient of the local volume velocity only.