“Salt in a porous matrix” sorbent and sawdust as air driers for ventilation systems

The processes of moisture desorption by a sorbent-drier of the type of “salt in a porous matrix” and sawdust in convective flow, as well as under the acoustoconvective action, have been investigated. It has been shown that at a flow velocity of 31 m ⁄ sec the sorbent has a rather prolonged drying stage with a constant rate, and at a flow velocity of 13 m ⁄ sec this drying stage ends faster. It has been established that the velocity of the convective flow strongly influences the drying process of the sorbent, and the action of the acoustic field therewith produced no marked effect on the drying process. Moisture desorption from sawdust proceeds with a variable rate, and its intensity markedly increases under the action of the acoustic field. The influence of acoustic vibrations on the rate of moisture removal has a nonmonotonic character. The kinetics of the process of humidification of the sorbent-drier has been investigated. On the basis of the investigations made, a basic circuit for ventilating closed rooms by dried air with the use of sawdust or an IK-011-1 sorbent-drier has been proposed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 252–257, March–April, 2009.     

Kinetics of microwave drying of a free-flowing organic material

The kinetics of drying of a dense buckwheat layer in a microwave electromagnetic field of frequency 2.45 GHz has been investigated for different amounts of the material charged into a working chamber. Analysis of the kinetics curves has shown that the drying of the material studied is divided into the periods of heating, drying with a constant rate, and drying with a decreasing rate. The influence of the power supplied as well as the mass and dimensions of a sample on the rate of its drying has been investigated and a formula for calculating this rate has been obtained. It has been established that, in the process of drying of a disperse material, the amount of microwave energy converted into heat energy depends not only on the mass of a sample, but also on the thickness and area of its surface layer. Generalized equations for calculating the moisture content in a layer of a free-flowing material and its temperature have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 123–127, May–June, 2006.     

Experimental investigation of the acoustic-convective drying of unhusked Korean rice

Experiments on determination of the kinetic curves of drying of unhusked Korean rice have been conducted on two (small-and large-scale) acoustic-convective dryers of capillary-porous materials of the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences. Different regimes of drying were used. The characteristic time of drying to a prescribed final humidity has been determined; the absence of the influence of the scale factor on the kinetics of drying of rice has been shown. The coefficient of moisture conductivity of rice has been evaluated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 652–655, July–August, 2008.     

Mechanical properties of a colloidal body in the process of its transformation into a capillary-porous one as a result of drying

The changes in the mechanical properties of a colloidal body in the process of its transformation into a capillary-porous one as a result of drying have been investigated by the example of casein. The rheological properties of casein were experimentally investigated by the method of mechanical Fourier spectroscopy. The mass loss and the shrinkage of this biopolymer were measured at different rates of conductive drying determined by the drying temperature. A macrokinetic model has been constructed. As the kinetic parameter, the relative mass loss was selected. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 442–449, May–June, 2008.     

Investigation of the process of drying of a system of connected capillaries in an acoustic-convective field

A study has been made of the process of drying of a model specimen with a system of capillaries connected via a slot space; the specimen is located in an intense acoustic-convective field. The film-dropwise mechanism of extraction of water from the specimen’s system of capillaries has been video-recorded. It has been established that the difference of the acoustic pressures in the external flow and inside the cavity of the specimen is one motive force of this process. It has been shown that a vortex gas motion pulsating with the frequency of the acoustic field and under whose action the liquid breaks down into droplets is formed in the capillaries—slot space system in the acoustic-convective regime. Such phenomena have not been observed in the convective regime of drying. The influence of the frequency and amplitude of oscillations of the acoustic field on the rate of drying of the specimen has been studied. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 6, pp. 1097–1101, November–December, 2008.     

Experimental study of the high-temperature thermomechanical drying of wood

The results of an experimental study of the thermomechanical drying of cylinder-shaped wood by the depressurization method are presented. The high rate of the process of thermomechanical drying with a good quality of dried articles has been confirmed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 69–74, January–February, 2009.     

A kinetic approach to the rheology of inhomogeneous systems with account for the interaction of disperse-phase particles

By measuring the optical characteristics of a flow the rheology of a viscous non-Newtonian fluid — an aqueous solution of hydrolyzed polyacrylonitrile — has been studied. The loss of stability by the system with chaotic fluctuations of transparency has been established. A kinetic model, as well as kinetic equations that describe the flow of heterogeneous systems, have been suggested. It is expected that this approach will be used in calculations in oil-and gas production and filtration of non-Newtonian systems in porous media. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 90–97, November–December, 2006.     

Reaction kinetics and mechanical properties in the reactive brazing of copper to aluminum nitride

Aluminum nitride (AlN) is an attractive substrate material for electronic packaging applications because of its high thermal conductivity and electrical resistivity. However, improved metallization of aluminum nitride is required for reliable conductivity and good adhesion to the ceramic substrate. In this study, the kinetics, microstructure, and mechanical strength of Ag–Cu–Ti/AlN reaction couples have been studied in the temperature range of 900–1,050 °C and hold time range of 0–1.44 × 10⁴ s using a eutectic silver–copper filler alloy containing titanium within the range of 2–8 wt%. The product layer thickening kinetics has been observed to change from a linear to non-linear thickening mechanism with the increase in holding time and temperature. At shorter hold times at a fixed temperature, the interfacial product layer followed a linear thickening kinetics. With the increase in the hold time, the thickening kinetics of the interface followed a non-linear thickening behavior. The non-linear thickening mechanism has been approximated as a parabolic thickening mechanism. The interface has been found to be rich in the reactive metal (Ti) content. The mechanical strength of the brazed joints has been analyzed using four-point bend tests. The strength of the brazed joints initially increased and then decreased with an increase in the hold time at a fixed temperature. A maximum strength of 196 MPa has been obtained for a brazed joint heated at 1,000 °C for 2,700 s containing 2 wt% Ti in the filler alloy. It was observed that the sample with the maximum strength had a discontinuous interface.     

Modeling and kinetics study of microwave heat drying of low grade manganese ore

During the industrial-scale smelting process of manganese ore, blast may occur due to the high moisture content of the ore, and drying pretreatment of the manganese ore is needed in the aspects of safety. In the present paper, microwave drying experiments were conducted under different particle size distributions and different microwave power conditions to explore the basic theory of microwave drying characteristics and kinetics of manganese ore, and the experimental data were fitted and analyzed by using thin-layer drying dynamics model. Results indicated that with the increase of the particle size and the microwave power of the manganese ore, the microwave drying rate increased, and accompanied with a promoting on the drying efficiency. For describing the microwave drying process of manganese ore, diffusion approach model was adopted among the commonly used thin-layer drying kinetic models. Based on Fick's second law, it can be seen that the surface diffusion coefficient increased from 4.27 × 10⁻¹³ m²/s to 8.24 × 10⁻⁸ m²/s with the increase of particle size from a particle size range of 0.012–0.095 mm to a particle size range of 4.2–5.0 mm. Clearly, the particle size has a significant influence on microwave drying efficiency.     

Kinetics,mechanism and modelling of microstructural evolution during thermomechanical processing of a 15Cr–15Ni–2.2Mo–Ti modified austenitic stainless steel

The paper discusses the kinetics, mechanism and modelling of the microstructural evolution of a 15Cr–15Ni–2.2Mo–0.3Ti modified austenitic stainless steel (alloy D9) during dynamic recrystallization (DRX). The experimental methodology included different hot working operations employing industrial equipment such as forge hammer, hydraulic press and rolling carried out in the temperature range 1,173–1,473 K to various strain levels. The kinetics of DRX has been investigated employing modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. It has been found that the value of Avrami exponent varies in a close range of 1.17–1.34 which implies that D9 exhibits growth controlled DRX. Optical metallography has revealed that nucleation of DRX grains occurred along the prior grain boundaries by bulging mechanism. Microstructural characterization has shown that a significant correlation between microstructural features and processing parameters exists. However, this interrelation is ambiguous and fuzzy in nature. Therefore an artificial neural network model has been developed to predict the microstructural features, namely fraction of DRX and grain size, at different processing conditions. A good correlation between experimental findings and predicted results has been obtained. An instantaneous microstructure, therefore, can be designed in order to optimize the process parameters based on microstructural evolution.     

Kinetic features of optically stimulated luminescence in aluminum nitride powder

Room-temperature optically stimulated luminescence (OSL) response in UV-irradiated aluminum nitride (AlN) powders has been studied. Excitation of AlN powder by UV photons with energies within 3–5 eV gives rise to an intense afterglow that is related to isothermal quenching of recombination processes involving shallow donor centers. It is established that a useful OSL response separated on the background of this recombination afterglow represents a superposition of two components with decay kinetics order b = 1.0–1.2 and 1.7–2.1. Superlinear UV-dose dependences of the OSL light sum have been measured and the corresponding coefficients for each component have been analyzed in comparison to the available published data.     

Certain regularities of the kinetics of moisture and heat exchange in drying of moist materials

Methods of calculation of the kinetics of drying of moist materials for the period of the falling rate are considered; they are based on the characteristics of the kinetics of drying: the relative drying rate and the generalized and relative drying times. Miscellaneous  Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 6, pp. 1102–1110, November–December, 2008.     

Thermophysical Properties of Nitrogen from a New Potential Energy Surface Using the Mason–Monchick Approximation

A recent N₂–N₂ potential has been used to calculate the second virial, viscosity, and diffusion coefficients. Calculations have been done up to the first quantum correction for virial coefficients and the second-order kinetic theory approximation for transport coefficients. The Mason–Monchick approximation (MMA) has been used for the calculation of collision integrals and, via a numerical analysis, a common intersection point has been found for reduced cross sections and collision integrals of different orientations. This regularity has been interpreted with the aim of the orientation dependence of the potential energy and different types of collisions between molecules. The overall agreement of the calculated second virial coefficient with experiment is reasonable but suggests that a slight re-scaling of the potential would be beneficial. In the case of transport properties, calculated and experimental results show an average deviation of about 1.6% and 0.7% for viscosity and relative diffusion coefficients, respectively.     

Kinetics and Apparatus-Technological Arrangement of Convective Drying of Disperse Polymer Materials

The laws of internal mass transfer under deep drying of granular polymers depending on their state have been considered. From the point of view of the system approach, the general problem of their drying kinetics has been decomposed into two basic levels: a micro- and a macroscopic one, and, in accordance with this, the questions of mathematical modeling have been analyzed. The experimental data on the diffusion and sorption properties and longitudinal mixing of the solid phase are presented and recommendations on the apparatus arrangement of the process are given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 51–60, May–June, 2005.     

Influence of direct electric current on the processes of contact fusion in the bismuth-tellurium system

We have investigated contact fusion (CF) in the Bi-Te binary system with a complex state diagram under different programs of heating the contact of specimens in the current and currentless regimes. CF at temperatures below the fusion temperature of the lowest eutectics has been revealed. It has been established that the known state diagram of the Bi-Te system is metastable and, depending on the contact heating rate, the CF processes proceed differently. It has been shown that the values and directions of the direct current passed through the contacts of Bi and Te specimens can control the phase-formation processes and the CF kinetics. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 34–41, November–December, 2005.     

Influence of granulated blast furnace slag on the reaction,structure and properties of fly ash based geopolymer

Ground granulated blast furnace slag (GBFS) has been used to alter the geopolymerisation behaviour of fly ash. The influence of varying amount of GBFS (5–50%) on the reaction kinetics has been studied using isothermal conduction calorimetry. It was observed that the reaction at 27 °C is dominated by the GBFS activation, whereas the reaction at 60 °C is due to combined interaction of fly ash and GBFS. The reaction product of geopolymerisation has been characterised using X-ray diffraction and scanning electron microscopy–X-ray microanalysis. Alumino–silicate–hydrate (A–S–H) and calcium–silicate–hydrate (C–S–H) gels with varying Si/Al and Ca/Si ratio are found to be the main reaction products. Coexistence of A–S–H and C–S–H gel further indicates the interaction of fly ash and GBFS during geopolymerisation. Attempt has been made to relate the microstructure with the properties of the geopolymers.     

Rehydration ratio of fluid bed-dried vegetables

Fluid-bed drying of vegetable pieces has been investigated. The vegetables used have been potatoes, parsley roots, celery roots and carrots of various dimensions. Starting water content was: potatoes 78%, parsley roots 85.1%, celery roots 93.6%, and carrots 88.6%. Temperatures of fluidisation have varied from 60‡ to 100‡C at velocities of 0.71 ms^-1. The goal has been to obtain dry vegetables with 6% to 10% water content and of good rehydration quality. Experimental data (bed height, gas temperature and velocity, pressure drop over the bed, drying time) have been measured and relevant values have been calculated. The results have shown that drying of vegetables in a fluidized bed produces dry vegetable pieces of excellent quality in a much shorter time than in continuous belt-dryers which are generally used     

Dissipative self-organization of a single layer of ferrosuspension particles in a high-frequency magnetic field of different polarization

Structural transformations in a plane layer of spherical soft-magnetic particles on exposure to a rotating elliptically polarized field whose plane of polarization is perpendicular to the layer’s plane have been studied by the molecular-dynamics method. The influence of the concentration of the particles and the polarization of the field on the kinetics of aggregation and the equilibrium form of disperse structures has been studied in the high-frequency limit. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 2, pp. 345–352, March–April, 2008.     

Dehydration kinetics of the microporous zirconosilicate elpidite

The dehydration kinetics of natural elpidite, Na₂ZrSi₆O1₅ · 3H₂O, have been studied by isothermal (110–254°C) and nonisothermal (20–600°C) thermogravimetry. The process comprises two steps. In the first step, 50% of the water is released according to a first-order rate law with a rate constant k ₁ = 10^{8.9 ± 0.2} exp[(−98740 ± 3100)/RT] s⁻¹ (R = 8.314 J/(mol K)). The second dehydration step cannot be described by a simple kinetic law. The effective activation energy for this step (76.5 kJ/mol) has been evaluated from the temperature dependence of its initial rate. The results on the dehydration kinetics of elpidite are discussed in relation to the structural transformations of the framework and the hydrogen bonds formed by the water molecules in the zeolite channels.     

Application of modified nanoporous materials in ascorbic acid adsorption

In this study, three types of mesoporous materials Santa Barbara no. 15 (SBA-15), carbon mesostructured by KAIST (CMK-3), and modified carbon mesostructured by KAIST (modified CMK-3) were prepared and their capability as sorbents for vitamin C (ascorbic acid) adsorption from aqueous solutions was compared with each other. Cetyltrimethylammonium bromide (CTAB) was used for surface modification of CMK-3. The structures of different adsorbents were characterized by X-ray diffraction (XRD) and N₂ adsorption measurements, and the functionalization of CMK-3 was proved by XRD technique. The adsorption isotherms, sorption kinetics as well as the effects of some parameters such as pH value of the vitamin solution, adsorption time, and the initial vitamin concentration on the adsorption capacity of the analyte on CTAB/CMK-3 were investigated. It was found that the ultimate capacity of the adsorbents varied in the order CTAB/CMK-3?>?CMK-3?>?SBA-15. Langmuir and Freundlich isotherm models have been used to fit equilibrium data for CTAB/CMK-3. The equilibrium data were best represented by the Langmuir isotherm. Kinetic studies were performed and it was determined that the sorption kinetics of vitamin C was truly described by a pseudo-second-order kinetic model.