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Browsing Статті КТ by Author "Gabrinets, Vladimir A."
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Item Modeling of Temperature Fields in a Solid Heat Accumullators(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2016) Belimenko, Serhii S.; Ishchenko, Volodymyr O.; Gabrіnets, Volodymyr O.; Gabrinets, Vladimir A.EN: Purpose. Currently, one of the priorities of energy conservation is a cost savings for heating in commercial and residential buildings by the stored thermal energy during the night and its return in the daytime. Economic effect is achieved due to the difference in tariffs for the cost of electricity in the daytime and at night. One of the most common types of devices that allow accumulating and giving the resulting heat are solid heat accumulators. The main purpose of the work: 1) software development for the calculation of the temperature field of a flat solid heat accumulator, working due to the heat energy accumulation in the volume of thermal storage material without phase transition; 2) determination the temperature distribution in its volumes at convective heat transfer. Methodology. To achieve the study objectives a heat transfer theory and Laplace integral transform were used. On its base the problems of determining the temperature fields in the channels of heat accumulators, having different cross-sectional shapes were solved. Findings. Authors have developed the method of calculation and obtained solutions for the determination of temperature fields in channels of the solid heat accumulator in conditions of convective heat transfer. Temperature fields over length and thickness of channels were investigated. Experimental studies on physical models and industrial equipment were conducted. Originality. For the first time the technique of calculating the temperature field in the channels of different cross-section for the solid heat accumulator in the charging and discharging modes was proposed. The calculation results are confirmed by experimental research. Practical value. The proposed technique is used in the design of solid heat accumulators of different power as well as full-scale production of them was organized.Item Percolation Threshold for Elastic Problems: Selfconsistent Approach and Padé Approximants(Springer International Publishing, Switzerland, 2018) Andrianov, Igor V.; Starushenko, Galina A.; Gabrinets, Vladimir A.EN: Self-consistent approximation and Padé approximants are used for calculation of percolation threshold for elasticity problem.Item Refinement of the Maxwell Formula for Composite Reinforced by Circular Cross-Section Fibers. Part I: Using the Schwarz Alternating Method(Springer Link, 2020) Andrianov, Igor I.; Awrejcewicz, Jan; Starushenko, Galina A.; Gabrinets, Vladimir A.EN: The effective properties of the fiber-reinforced composite materials with fibers of circular cross section are investigated. The novel estimation for the effective coefficient of thermal conductivity refining the classical Maxwell formula is derived. The method of asymptotic homogenization is used. For analytical solution of the periodically repeated cell problem, the Schwarz alternating process is employed. The principal term of the refined formula coincides with the classical Maxwell formula. On the other hand, the refined formula can be used far beyond the area of applicability of the Maxwell formula. It can be used for dilute and non-dilute composites. It is confirmed by comparison with known numerical and asymptotic results.Item Refinement of the Maxwell Formula for Composite Reinforced by Circular Cross-Section Fibers. Part II: Using Padé Approximants(Springer Link, 2020) Andrianov, Igor I.; Awrejcewicz, Jan; Starushenko, Galina A.; Gabrinets, Vladimir A.EN: The effective properties of the fiber-reinforced composite materials with fibers of circle cross section are investigated. The novel estimation for the effective coefficient of thermal conductivity refining the classical Maxwell formula is derived. The method of asymptotic homogenization is used. For an analytical solution of the periodically repeated cell problem the Schwarz alternating process (SAP) was employed. Convergence of this method was proved by S. Mikhlin, S. Sobolev, V. Mityushev. Unfortunately, the rate of the convergence is often slow, especially for nondilute high-contrast composite materials. For improving this drawback we used Padé approximations for various forms of SAP solutions with the following additive matching of obtained expressions. As a result, the solutions in our paper are obtained in a fairly simple and convenient form. They can be used even for a volume fraction of inclusion very near the physically possible maximum value as well as for high-contrast composite constituents. The results are confirmed by comparison with known numerical and asymptotic results.