Volume 39, Issue 1

Abstract. This paper proposes a new point of view in analyzing the optimal Gibbs energy dissipation in growing microorganisms. Small Gibbs energy dissipation in growth would be of biological advantage because less resource is consumed and the biomass yield on these resources could be maximized. It is however not so clear why microorganisms still dissipate considerable amounts of Gibbs energy while growing. Distillation columns are used as a simple qualitative model system in order to gain a qualitative understanding of the question. In both growing microorganisms and continuously operated distillation columns, small energy dissipation values result in small process driving forces and therefore in tentatively slow operation. In microorganisms this entails relatively higher maintenance energy requirements, increasing thereby the resource cost for growth and decreasing the biomass yield. In distillation columns, it results in higher capital and maintenance cost, thereby increasing overall process costs. A simple model is proposed to calculate the biomass yield as a function of Gibbs energy dissipation. It shows that this function goes through a maximum because of maintenance requirements at small dissipations. Experimental data confirm that growing microorganisms dissipate an amount of Gibbs energy that is associated with this maximum.

Abstract. The paper shows that an attainability region of a binary fractionating column depends on two parameters. These parameters are expressed through kinetic coefficients and mixture properties. The paper also considers a problem of finding the maximal productivity of the ternary distillation. Selection conditions for an optimal separation order and expressions for the maximal productivity of this process were obtained.

Abstract. It is well known that, in the absence of external forces, simple non-relativistic fluids involve entropy production only through heat conduction and shear viscosity [De Groot, S. R. and Mazur, P., Non-Equilibrium Thermodynamics, Dover, Mineola, 1984]. In this work, it is shown that a number density gradient contributes to the local entropy production of a simple relativistic fluid using special relativistic kinetic theory. Also, the presence of an external field may cause strictly relativistic contributions to the entropy production, a fact not widely recognized. The implications of these effects are thoroughly discussed.

Abstract. This review paper is dedicated to a description of heat transport at micro and nanoscales from the viewpoint of Extended Irreversible Thermodynamics. After a short survey of the classical heat conduction laws, like those of Fourier, Cattaneo, and Guyer–Krumhansl, we briefly overview the hypotheses and objectives of Extended Irreversible Thermodynamics, which is particularly well suited to cope with processes at short length and time scales. A selection of some important items typical of nanomaterials and technology are reviewed. Particular attention is brought to the notion of effective thermal conductivity: its expression in terms of size and frequency dependence is formulated, its significant increase in nanofluids formed by a matrix and nanoparticles is discussed, the problem of pore-size dependence and its incidence on thermal rectifiers is also investigated. Transient heat conduction through thin one-dimensional films receives special treatment. The results obtained from a generalized Fourier law are compared with those provided by a more sophisticated ballistic-diffusion model. Our survey ends with general considerations on boundary conditions whose role is of fundamental importance in nanomaterials.