THE PURPOSE. The service life duration of wooden tangent towers used on overhead transmission lines with a voltage of up to 35 kV depends on the quality of lumber drying and subsequent impregnation. The drying of tangent tower workpieces is currently carried out by atmospheric or convective methods and is the longest and one of the energy-consuming stages of their production. At the same time, there are promising electrotechnological drying installations that can reduce the duration and improve drying quality at comparable specific energy costs. Such installations include vacuum high-frequency complexes, the wide introduction of which is complicated by a number of unresolved scientific and technical problems like optimizing vacuum high-frequency drying modes and ensuring electromagnetic field uniformity in long workpieces. The purpose of this article is to obtain mathematical tools that simultaneously describe the cross-effects of electromagnetic phenomena and heat and mass transfer processes in long-sized lumber and contribute to the further solution of these problems. METHODS. The positions of the theory of electromagnetic field, heat mass transfer and heat mass exchange, methods of mathematical modeling were used for this purpose. Also the results of previous studies of electromagnetic field distribution in the cross-section and longitudinal sections of the working chamber loading are taken into account. RESULTS. А one-dimensional mathematical model is obtained. It describes the influence of electromagnetic wave distribution along the length of tangent towers and external medium parameters on the temperature and moisture content in the material. This model is characterized by the possibility of using simple algorithms for analyzing differential equation systems based on the finite differe nce method and requiring less initial data on the drying material properties. CONCLUSION. The obtained by using the proposed model and the method of its analysis the numerical study results are compared with the available experimental data. Based on this comparison it is concluded that the obtained model is adequate and more effective relative to other existing models of vacuum high-frequency drying. Generally, further use of the presented mathematical toolkit to optimize the design and modes of vacuum-high-frequency complexes in the task of drying wooden tangent towers will increase the reliability of overhead transmission lines.

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The article discusses possible options for a low-temperature induction heating system (LTIHS) of flat metal products in a traveling electromagnetic field. The problem of calculating eddy currents, active and reactive powers induced in a heated flat object, as well as electromagnetic forces acting on the object moving it in a given direction, is posed and solved. A mathematical model has been developed that takes into account the dependence of the influence on the main parameters of the electromagnetic field of the following factors: geometric dimensions of the air gap between the poles of the magnetic circuit and the heated flat body; the longitudinal edge effect caused by the open circuit of the magnetic circuit of the inductor, as well as the transverse edge effect associated with the appearance of the longitudinal components of eddy currents in a heated flat object. The solution of particular problems of LTIHS in one- and two-dimensional formulation allows them to be simplified and to perform calculations for various design variants of induction heating devices with a traveling electromagnetic field, using a one-dimensional model that explicitly takes into account the features of electromagnetic processes in the systems under study.

The consumption and temperature of hot water produced by boiler units are calculated using such a quantity as the consumption of the consumed network water. The formulas represent functional dependencies connecting the obtained values not only with the consumption of heating water, but also with the consumption of hot water supplied for recirculation, for own needs and for the needs of the fuel economy. They take into account the losses of network and hot water. The formulas are obtained as a result of the joint solution of the equation for the total consumption of hot water and the equation for its partial costs.