Plate Heat-exchangers in Modern Waste Heat Recovery Systems of Hot Blast Stoves and Other Metallurgical Equipment

One of the main factors which defines modern economy is energy efficiency, namely, rationality of use of natural resources, first of all fuel resources, their economic use. Energy saving and energy efficiency improvement should be considered as one of the main sources of future economic growth. Keywords: heat recovery system, economic and ecological effect, plate heatexchangers, ribbed panel, laser welding, ribbed panels, heating uni

Dielectric relaxation of the cowle-cowle type and self-similar relaxation processes

In order to describe relaxation processes not obeying an exponential law a model of a self-similar relaxation process is proposed which is described by an equation containing fractional differentiation operators. It turns out that the complex susceptibility corresponding to such a model system has a form which agrees with the known empirical Cowle-Cowle expression. © 1997 Plenum Publishing Corporation

Cole-Davidson dielectric relaxation as a self-similar relaxation process

An effort has been undertaken to understand the nature of one type of non-exponential relaxation, namely Cole-Davidson relaxation. Toward this end, a model of relaxation as a self-similar process is proposed. An equation containing operators of fractional integration and differentiation is obtained and solved, which the relaxation function obeys in this case. © 1997 American Institute of Physics

Dielectric relaxation of water absorbed in porous glass

The dielectric spectroscopy method was applied to the investigation of water absorbed on the inner surface of porous glass. The measurements were done using broad band dielectric spectrometry (BEDS) over a wide range of frequency (20 Hz to 1 MHz) and temperature (-100 °C to +300 °C). The dielectric response was found to be very sensitive to the geometrical micro- and mesostructural features of the porous matrix and the structure and mobility of the water filling the pores. The hindered dynamics of water molecules located within the pores and affected by the surfaces reflect the geometrical structure of the porous matrix. The analysis of the dielectric parameters as a function of the temperature enabled us to characterize the physical parameters of the dielectric spectra over an extended frequency range. © 2001 American Chemical Society

Mechanism of the cooperative relaxation in microemulsions near the percolation threshold

Cooperative dynamics of three-component water-oil-surfactant microemulsions based on sodium bis(2-ethylhexyl) sulfosuccinate surfactant were investigated near the percolation threshold. The measurements were made by means of the time domain dielectric spectroscopy method in the temperature interval 12 °C-40 °C, including the percolation range. The data treatment was carried out in time domain in terms of the macroscopic dipole correlation functions (DCFs) related to the structural and kinetic properties of the system. It is shown that the DCF can be described by the Kohlrausch-Williams-Watts (KWW) expression exp[-(t/τ) ν] (where τ is the relaxation time and ν is the stretched parameter), reflecting the peculiarities of the dipole interactions in a self-similar medium. For a physical interpretation of the phenomenological parameters τ and ν, a generalization of the known model of the cooperative relaxation was made. The model developed was adjusted for a description of the relaxation in microemulsions that have a fractal nature in the percolation region. The results obtained testify that parameters τ and ν in the KWW function are related to the structure of the system and reflect the cooperative behavior of microemulsion droplets near the percolation threshold. It was shown also that the macroscopic law of the relaxation of the KWW type is insensitive to the microscopic details of charge transport in the system and that there is a limited temporal range for the applicability of the stretched law of relaxation in time domain. In order to extend the initial temporal interval of the applicability of the relaxation function the correlation to the KWW term was found

'Thermodynamic' mechanism of catalysis by haloperoxidases

A novel 'thermodynamic' mechanistic rationale of haloperoxidase catalysis is based on the following two assumptions: (i) the role of enzyme consists only in the rapid equilibration between the halogen-containing species originating from halide and hydrogen peroxide; (ii) the interaction between the enzyme and organic substrate is kinetically insignificant and halogenation occurs as a result of the electrophilic attack of the active brominating (Br3 -, Br2 and HBrO) or chlorinating (HClO) species at monochlorodimedon indicative of a higher chloride 'specificity' of chloroperoxidase from C. fumago

Effect of penetration enhancers on the dynamic behavior of phosphatidylcholine headgroups in liposomes

The results of a time-domain dielectric spectroscopy (TDDS) study of the effect of two skin penetration modulators on phosphatidylcholine (PC) bilayer vesicles are presented. The complex dielectric permittivity spectra of PC vesicle suspensions were described as the sum of two processes: the interfacial polarization of the bilayer and the reorientation of the zwitterionic PC headgroups in a plane approximately tangential to the bilayer surface. The influence of two additives (Azone and Transcutol) on the structure and dynamic behavior of PC headgroups of the bilayer vesicles was analyzed in terms of the interconnection of the dielectric spectra Cole-Davidson parameter, β, and the correlation factor, g, of the dielectric relaxation Kirkwood cell model. Analytically, these parameters are connected in the proposed model via the spatial distribution of headgroup dipole nonhomogeneities. In terms of the physical modulation of the polar surface phase, it appears that these additives can behave either as enhancers or as retarders. Their activity in this respect depends on the concentration of additive and temperature. © 2000 American Chemical Society