Volume 28, Issue 4

The conventional means of thermal optimization (TO) suffers from complications in simultaneously optimizing a number of parameters which govern the process. This is particularly severe when thermal-fluid flow phenomena are involved, for example, optimization of electronic cooling devices. In order to revolutionize the means of optimizing a system involving both thermal and fluid flow phenomena, a new entropy generation minimization (EGM) method is developed utilizing the second law of thermodynamics which implies that the minimization of entropy generation is equivalent to thermal optimization. In this study, both TO and EGM are performed on the design of packages of parallel boards with discrete block heat sources. The board spacing for minimum entropy generation agrees very well with that calculated by maximizing the thermal conductance induced by both heat transfer and viscous friction.

Non-equilibrium phenomena within a turbulent binary mixture undergoing a phase transition are modelled based on the one fluid, homogeneous approach. The set of governing evolution equations is given and the averaged basic balance laws are considered. The continuum under consideration consists of two constituents of which the first is undergoing a phase transition (vaporisation, cavitation, flashing, condensation) during the flow with turbulent transport of mass, heat and momentum. Starting from the Clausius-Duhem inequality for the recoverable specific entropy, several thermodynamical relationships for equilibrium and non-equilibrium fields are developed. The relaxation-retardation constitutive model for turbulent, phasic and diffusive fluxes are described. It is shown that the resulting model uncovers a few known two-phase models of turbulence and also the classical relaxation models as limiting cases.

All adsorption systems which have to deal with technology and environment are systems which are not in equilibrium. They are only on their way to achieving a certain adsorption equilibrium. Therefore, knowledge of the time evolution of adsorption systems should be of fundamental importance. However, the overwhelming majority of the published papers report on experimental and theoretical studies of adsorption equilibria. This is probably why the theories of adsorption equilibria are at present much more advanced than the theories of time evolution of non-equilibrium adsorption systems. The theories of the kinetics of gas adsorption/ desorption on/from flat solid surfaces provide a very impressive illustration. On both the experimental and theoretical side, one finds a level far behind that characterizing current studies of adsorption equilibria. One can still observe controversies concerning the fundamentals of adsorption/desorption kinetics. The present review reports on the most recent achievements in the theoretical description of both isothermal adsorption kinetics and kinetics of thermodesorption, achieved by applying the Statistical Rate Theory.