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In this paper, multi-objective optimization of geometric parameters of spirally-cross-corrugated (SCC) tubes is carried out using numerical methods, genetic algorithms (GAs), and artificial neural networks (ANNs). First, the turbulent flow is numerically characterized in various SCC tube geometries using a finite volume method with the realizable k-ε turbulence model. In this approach, the heat transfer coefficient and friction factor f in tubes are calculated. First, two parameters (corrugation pitch-to-diameter ratio ( PR = p / D ) and corrugation depth-to-diameter ratio ( DR = e / D )) are examined in a turbulent flow regime that affects the strength of quadruple longitudinal vortex flows and thermal characteristics. At the final step, using the obtained polynomials for neural networks, multi-objective genetic algorithms (NSGA II) are employed for Pareto based multi-objective optimization of flow parameters in such tubes. This analysis considers two conflicting parameters, f Re and Nusselt number Nu with respect to three design variables, Reynolds number (Re), values of PR and DR . Some interesting and important relationships between the parameters and variables mentioned above emerge as useful optimal design principles involved in the heat transfer of such tubes through Pareto based multi-objective optimization. Such important optimal principles would not have been obtained without the use of a combination of numerical techniques, ANN modeling, and the Pareto optimization.

The oscillating flow of a viscous incompressible fluid in a rigid circular pipe with local constriction has been studied numerically. Fluid viscosity and density of liquid, channel diameter and constriction, as well as amplitude-frequency characteristics of the flow rate are identical to those of the blood flow in the human popliteal artery with stenosis. Reynolds number in the area of stenosis is Re » 5×10³, dimensionless pulsation frequency is Sh = 0.43×10^-3, and normalized constriction of the channel is d = d / D = 0.4. The flow under consideration is characterized by the fact that during one oscillation period the fluid flow rate changes direction four times. This contributes to laminar-turbulent transition when the jet discharges from a contraction throat into the main flow. Qualitative features and quantitative parameters of pulsating flow have been determined including distribution of friction stresses along the channel wall.

A semi-analytical study is performed to examine transient Taylor-Dean flow in a composite annulus within two concentric cylinders partially filled with porous material. In the present model, the circumferential flow is set up as a result of azimuthal pressure gradient as well as the rotation of the two concentric cylinders. The equation governing the flow is rendered non-dimensional and transformed into ordinary differential equation using the well-known Laplace transform technique. The solution is then transformed back to the time domain using the Riemann-sum approximation (RSA) approach. The solution of the steady-state of the present model including the implicit finite difference (IFD) is also computed to validate the result obtained from the RSA approach. It is important to note that the surface resistant force can be controlled by choosing suitable values of β .

Coal mined from the surface or underground is rarely suitable for direct use and requires preparation based on physical and/or chemical methods of removing certain components in order to improve the quality of coal to the required level. High humidity leads to a decrease in the energy efficiency of boiler, so the process of fuel drying is a necessary step in coal preparation, and reducing energy costs for moisture removal is an urgent task. One of the ways of moisture reduction is coal treatment with microwave radiation. As compared with other methods, microwave drying has the following features and important advantages: 1) volumetric heating; 2) selective heating (there is no energy absorption in dried areas); 3) low thermal inertia. However, this method requires high power inputs and there is a need to find energy-efficient processing regimes. In the present work, a drying model has been constructed, the optimal regime of layer drying has been found using the finite element method at the example of brown coal from the Talovsky deposit, and energy costs have been determined.

This study aims to investigate the effect of gas radiation on laminar free convection flow within a square cavity with internal heat generation. The cavity walls are isothermally cooled whereas the inner body is kept constant at a higher temperature. An important finding from this analysis is that radiative contribution plays a major role in the acceleration of the vortexes, providing a homogenizing effect on temperature fields. It is also shown that the optimal level of energy efficiency is achieved if the heater is located at the center of the lower part of the enclosure and when the inclination angle of the enclosure is of π /4.

One of the promising ignition technologies is the plasma thermochemical preparation of pulverized coal for combustion using plasma-fuel systems (PFS). This technology allows increasing the efficiency of fuel application and improving the environmental performance of thermal power plants, as well as eliminating fuel oil, used traditionally to ignite boilers and stabilize combustion of a pulverized coal flame. This paper presents the numerical results on ignition of a pulverized coal flame in a PFS. The plasma-fuel system is designed for oil-free ignition of boilers and stabilization of flame combustion and this is a pulverized coal burner equipped with a plasmatron. In addition to plasmatron electric power and ash content in coal, one of the main operating parameters of PTS, which ensures fuel ignition, is concentration of coal dust in the air mixture, which can be varied over a wide range. The conditions of fuel mixture ignition in the PFS were determined for three above-mentioned operating parameters of PFS using the PlasmaKinTherm program, which combines kinetic and thermodynamic methods for calculating the processes of motion, heating, and thermochemical transformations. The calculations were performed for a cylindrical PFS with a diameter of 0.2 m and a length of 2 m. The coal consumption was 1000 kg/h. The conditions of fuel mixture ignition in the PFS were studied depending on plasmatron power (20-100 kW), coal concentration in the fuel mixture in the range from 0.4 to 1.8 kg of coal per 1 kg of air, and also for three different values of coal ash content (20, 40, and 70%). The main regularities of the process of plasma thermochemical preparation of fuel for combustion have been revealed.

Results of numerical simulation of two-dimensional flows of cellular detonation in plane channels in gas suspensions of submicron aluminum particles (0.6 and 0.3   m) in oxygen are presented. Mixtures with homogeneous and heterogeneous concentrations are considered. A previously developed model of reduced kinetics verified on the basis of the detonation velocity dependence on the particle concentration and extended to heterogeneous mixtures is used. The size and character of detonation cells are found as functions of the particle size and concentration. Problems of detonation propagation in channels with transverse concentration gradients and intermittent distributions of concentration are considered.

The studies of Scotch pine ( Pinus sylvestris L.) needles structure and chlorophylls and carotenoid contents were carried out in four districts of the city of Krasnoyarsk, differing in the level of technogenic load. It was shown, that the length of the needles decreases with an increase in technogenic impact. The width, thickness and cross-section area of the needles and the central cylinder also decrease with an increase in the degree of air pollution. It was found that the cross-section areas of the conducting bundles in the central cylinder, as a rule, are not equal, the differences are 9-12 % and are characterized by high individual variability. No significant correlation was found between the sizes of conducting bundles and the level of technogenic load. The number of resin ducts in needles decreases with an increase in technogenic impact that indicates a decrease in the protection of the assimilation apparatus from damage by pests and diseases. Determination of the content of photosynthetic pigments in pine needles in two districts of the city, differing in the level of pollution, did not show significant differences in the content of chlorophylls and carotenoids. Perhaps this is due to the peculiarities of the weather of this growing season - abundant summer rainfalls prevented the accumulation of pollutants on the surface and inside the needles. The noted changes in the size, anatomical structure and pigment composition of pine needles can be considered as a result of adaptation to growing conditions and weather factors.

The protective forests in Karelia are concentrated mainly (80 %) around water objects. More than 50 % of these forests are presented by Scotch pine ( Pinus sylvestris L.) stands. Modern practice of forestry prefers the simplified felling types oriented on use of natural renewal potential of pine forests because artifical regeneration on stony soils are very complex. On a site of the strip-shelterwood felling (intensity of 35 %) in an uneven-age pine stand of bilberry type in 9 years after the felling three transects consisting of plots of 5 × 5 m with a total length of 1150 m across the clear-cut strips were established for an assessment of natural renewal. Under forest canopy pine undergrowth is presented poorly. At the general frequency of 15 % and average height of 1.2 m its density is less than 0.2 thousand tress per ha, and its condition does not give a hope to expect of growth improvement. The condition of spruce ( Picea A. Dietr.) undergrowth is better: its frequency - 36 %, height - 2.4 m, and density - 0.32 thousand tress per ha. On the cutted strips the pine frequency are 31 %, density and frequency of spruce and birch ( Betula L.) remained almost without changes; the participation of an aspen ( Populus tremula L.) and willow ( Salix L.) are increased sharply. The strip-roads are covered by willow weed ( Chamaenerion angustifolium (L.) Scop.), under the influence of which density and frequency of the conifers is twice lower. On the whole, the frequency and average height of a pine in the middle and at the edges of cutted strips are close. The executed felling did not provide the renewal of coniferous species sufficient for formation of a new forest stand, though emergence in recent years of the small undergrowth of a pine allows to count on his further quantitative increase. The executed assessment of increase in a radial growth of trees on cores showed his insignificance. The obtained results and literary data convince of obligatory need of a scarification of the soil surface during the strip-shelterwood felling execution.

The problem of assessing the balance of accumulated and degraded woody biomass in forest communities, the budget of C, CO₂, H₂O, and Q (energy) in primary virgin forests of different ages of spruce formations in the taiga zone of European Russia is discussed. The studies were carried out in specific biogeocenoses of different dynamic characteristics in the subzones of the northern, middle and southern taiga. The purpose of the research is to study in quantitative and volumetric terms the structural elements of the age series of primary virgin spruce biogeocenoses of different ages of different successional positions, the dynamics of the formation of the stem fraction of wood waste (deadwood), pools and flows of components deposited in the wood of the stem fraction of phytocenoses and tree waste in a single succession series. biogeocenoses of various dynamic characteristics. A cycle of studies was carried out on the trial plots, which made it possible to obtain information about the age structures of forest stands, their dynamic indicators, the volume of trees in the age generations of forest stands, the current tree waste and fallen trees. All volume values of forest stands and wood waste are converted into phytomass. The volumes of C, CO₂, H₂O and Q (energy) deposited in wood and released during its decomposition by wood-destroying fungi were calculated using the formula for mycogenic wood xylolysis. On the example of the spruce biogeocenosis of the middle taiga subzone of the climax phase of dynamics, the mass of carbon, different fractions of wood, presented in a graphic image, was calculated. It has been determined that the volumes of pools and flows of wood components in forest stands and during the decomposition of wood by fungi - destructors are determined by the structural features of the age series of forest stands, the volumes of wood waste in gradations of decomposition stages. A joint analysis of the age structures of forest stands, the structures of current tree waste and deadwood by stages of decomposition helps in a more accurate determination of the dynamic position of forest biogeocenosis in the expanded space of its successional development. In the most stable (climax) virgin spruce forests of the taiga, the values of the balance ratios of accumulation and decomposition of biomass represent an optimal budget model and can be regarded as reference values in comparison with forests of different origin and structural characteristics.