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Kot V.A.,A. V. Luikov Heat And Mass Transfer Institute
Journal of Engineering Physics and Thermophysics | Year: 2016

An N-fold integration of the heat-conduction equation for a space bounded from the inside has been performed using a system of identical equalities with definition of the temperature function by a power polynomial with an exponential factor. It is shown that, in a number of cases, the approximate solutions obtained can be considered as exact because their errors comprise hundredths and thousandths of a percent. The method proposed for N-fold integration represents an alternative to classical integral transformations. © 2016, Springer Science+Business Media New York. Source

Sychevskii V.A.,A. V. Luikov Heat And Mass Transfer Institute
International Journal of Heat and Mass Transfer | Year: 2015

In the present work we show that in drying of colloidal capillary-porous materials the processes of heat and mass transfer are usually accompanied by the processes of deformation and development of stresses. Application of the Euler approach, which is connected only with the account of small deformations, to description of the occurring processes is erroneous. The stressed-strained state should be described on the basis of the Lagrange approach with account for large displacements and deformations of material. In this connection, we present a physical-mathematical model of the process of drying colloidal capillary-porous materials in curvilinear coordinates in the tensor form. A variational formulation of the problem and its solution by the method of finite elements are presented. The results of calculations and regularities obtained on their bases are given. Special attention is paid to the fact that the developed model and calculation techniques can form a theoretical basis for designing devices of experimental determination of stresses in materials. © 2015 Elsevier Ltd. All rights reserved. Source

Chorny A.,A. V. Luikov Heat And Mass Transfer Institute | Zhdanov V.,University of Rostock
Chemical Engineering Science | Year: 2012

Turbulent mixing with fast chemical reaction was modeled in the confined jet flow at large Schmidt number (Sc~1000). The Reynolds-Averaged-Navier-Stokes approach was employed to describe the turbulence-chemistry interaction. Numerical results were validated against data obtained by the two-color planar laser-induced fluorescence method. Based on these data the dissipation rates of the mixture fraction and the product reaction concentration were calculated. Their comparison showed essential differences both in dynamics and values. The influence of different-order finite-difference schemes for scalar gradient determination and of the noise-signal ratio on the dissipation rates was estimated. More accurate higher-order schemes caused both noised and corrected dissipation rates to increase. Eliminating the noise leveled essentially the order-effect of finite-difference schemes. The analysis of the mixing models was demonstrated that the mixing model with the constant mechanical-to-scalar time ratio R and the Multi-Time-Scale model overestimated the mixture fraction variance σf in comparison with experiment. To predict the dissipation in the jet flow at Sc~1000 the low-Reynolds-number effects were considered: in the transport equation for σf the ratio R and the turbulent Schmidt number Scσ were the functions of turbulent Reynolds number. The accuracy of the used standard k-ε model was improved by coordinating the values of the model constants Cμ and Cε2 with the jet velocity decay and the expansion radius (Cμ=0.06 and Cε2=1.87). The examination of the known reaction rate models for the gas flow (Sc~1) (the segregation intensity approach, the EDC-model or the PDF method) showed that the reaction rate was overestimated by these models in comparison with the one obtained from the measurements in the liquid flow. The proposed modification of the EDC-model took into account the specific micromixing in vortex structures of flow at Sc≫1. © 2011 Elsevier Ltd. Source

Kashevsky S.B.,A. V. Luikov Heat And Mass Transfer Institute
Computational Materials Science | Year: 2010

This paper presents computational studies of the dissipative self-organization of a system of soft magnetic particles in a drying thin layer of polymer solution set under a rotating magnetic field. The structure transformations during the layer drying is modeled for different situations including constant/increasing viscosity, regard/disregard of the hydrodynamic interactions, slow or fast drying with respect to the structure formation. All these factors are found influential on the final pattern of the particles distribution in the settled polymer film. © 2010 Elsevier B.V. All rights reserved. Source

Kalitko V.A.,A. V. Luikov Heat And Mass Transfer Institute
Journal of Engineering Physics and Thermophysics | Year: 2010

On the basis of experience in the commercial operation of tire-shred steam thermolysis in EnresTec Inc. (Taiwan) producing high-grade commercial carbon, liquid pyrolysis fuel, and accompanying fuel gas by this method, we have proposed a number of engineering solutions and calculated-analytical substantiations for modernization and intensification of the process by afterburning the accompanying gas with waste steam condensable in the scrubber of water gas cleaning of afterburning products. The condensate is completely freed of the organic pyrolysis impurities and the necessity of separating it from the liquid fuel, as is the case with the active process, is excluded. © 2010 Springer Science+Business Media, Inc. Source

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