The natural phenomenon of thunderstorm activity is one of many causes of a forest fire. Thunderstorms cause especially intensive fire danger situations within remote areas and highlands. As a rule, a cloud-to-ground lightning discharge is the fire source. The present study is based on the research results of electrical overloads in supply networks. Physical and mathematical formulation and numerical solution for the problem of a coniferous tree (pine) ignited by a cloud-to-ground lightning discharge are presented. The problem is considered in a cylindrical coordinate system in two-dimensional formulation. The features of current passage and heat transfer taking into account the reactive wood localization are investigated. The Joule-Lenz’s law is used to calculate heat production in a tree trunk. Parametric analysis has been conducted and tree trunk ignition conditions have been determined in a typical range for the influencing parameters of negative and positive discharges.

Abstract. The opportunity analyses of using the thermosyphons as the main elements in the systems of thermal regime supplying has been conducted under the conditions of their usage in power transformers on thermal stations. Mathematical modeling of jointly proceeding processes of conduction, forced convection and phase transitions (evaporation and condensation) of coolant in the thermosyphon of rectangular cross section has been carried out. The problem of conjugated conductive-convective heat transfer was formulated in dimensionless variables "vorticity/stream function/temperature" and solved by finite difference method. The effect of the heat flux density supplied to the bottom cover of the thermosyphon from a transformer tank on the temperature drop in the steam channel was shown based on the analysis of numerical simulation results (temperature fields and velocities of steam). The parameters of energy-saturated equipment of thermal stations were found to be controlled by an intensification of heat removal from the top cover surface of the thermosyphon.

Global warming promotes the acceleration forces all countries to reduce fossil energy sources and increase renewable energy sources with the development of environmentally friendly resource-saving technologies. The vast territory of Russia is permafrost or has seasonally frozen soils. The use of renewable energy sources, especially solar energy sources, is especially important for such territories.The article presents the experimental results of the operating modes of a pilot industrial solar hot water supply system with two vacuum tube collectors after snow pollution or icing of pipe surfaces. This technique is used to measure the hourly values of thermal energy from the conversion of solar radiation by collectors with polluted and cleaned collector surfaces on a sunny day after snowfall or icing. The average hourly value of solar insolation (with contaminated surfaces and after their cleaning) is obtained by integrating the meter recordings on the incident heat flux from the sun (by 600 values each) at an interval of 6 seconds. It is found that when the collector pipe surface is iced, the decrease in the thermal energy supply is maximum and amounts to 36.96 %. In other cases it varies from 8.51 to 13.47 %.

No abstract

РАЗРУШЕНИЕ СТРОИТЕЛЬНЫХ МАТЕРИАЛОВ (КИРПИЧ, БЕТОН, ГРАНИТ) ПРИ ВЫСОКОТЕМПЕРАТУРНОМ ТЕПЛОВОМ ВОЗДЕЙСТВИИ ГЕТЕРОГЕННЫХ СТРУЙ В статье представлены результаты экспериментального исследования разрушения некоторых строительных материалов высокотемпературными гетерогенными струями продуктов сгорания твердых топлив. Актуальность исследования обусловлена необходимостью обеспечения безопасности зданий и сооружений специального назначения при экстремальных тепловых воздействиях на элементы их конструкций. Целью работы являлось установление основных закономерностей разрушения неметаллических конструкционных материалов (кирпич, бетон, гранит) при воздействии на них высокотемпературных гетерогенных струй продуктов сгорания твердых топлив и разработка на их основе физической модели процесса. Для проведения экспериментов использовался газодинамический стенд, позволяющий варьировать давление торможения потока; в качестве характеристик выбраны величины массовой скорости разрушения материала и глубины образующихся кратеров. Получены зависимости массовых скоростей разрушения и глубин кратеров от давления торможения в сравнении с аналогичными данными для стали. Приведены данные по расчетам величин напряжений в приповерхностном слое материала. Предложена физическая модель процесса разрушения неметаллических конструкционных материалов, основанная на превышении возникающих в приповерхностном слое материала напряжений предела прочности материала.Ключевые слова: строительные материалы; гетерогенная струя; газодинамический стенд; параметры струи; массовая скорость разрушения; предел прочности материала; напряжения на границе раздела.Для цитирования: Немова Т.Н., Рекунов В.С., Цветков Н.А. Разрушение строительных материалов (кирпич, бетон, гранит) при высокотемпературном тепловом воздействии гетерогенных струй // Вестник Томского государственного архитектурно-строительного университета.The paper presents the research results of the building material destruction due to hightemperature evaporation of heterogeneous solid-fuel combustion products. The aim of this work is to determine basic laws of destruction of non-metallic constructional materials (brick, concrete, granite) under the influence of high-temperature evaporation of heterogeneous solidfuel combustion products and develop a physical model of the process. A gas-dynamic setup is used to conduct the experiments, which allows to vary the stagnation pressure. The destruction rate of the material and the depth of resulting craters are chosen as characterization parameters. (кирпич, бетон, гранит) Разрушение строительных материалов