Calculation of temperature waves in kurums

The article indicates the relevance of the study of heat transfer processes in kurums. Boundary value problems of vertical temperature change in kurums and in the underlying rock base are solved, when the temperature on the surface of kurums changes according to a given periodic law, which simulates daily and seasonal temperature fluctuations. The cases when the rock base is a heat-conducting medium and permafrost are considered. Some regularities of temperature propagation along the depth are revealed.

Application Analysis of Medium Temperature Solar Refrigeration System in Civil Buildings

The lithium bromide absorption refrigeration system with medium temperature solar collector as driving heat source was built, and the refrigeration performance of the system was tested and analyzed. The medium-temperature solar collector adopts all-glass vacuum solar collector tube with heat-conducting oil as medium, and the inside of the vacuum tube is composed of heat-conducting medium flow channel on the sunny side and aluminum silicate insulation cotton on the backlight side. Through test and analysis, the medium temperature solar collector of the system can provide stable heat source, and the maximum temperature of solar heating can reach above 150°C in sunny weather and about 80°C in cloudy days. The generator driving heat of the system is stable and efficient. The driving heat of lithium bromide absorption refrigerator is higher than 200 MJ/h, and can reach 300 MJ/h in some periods. The COP of the system can be kept above 0.6 during stable operation, but when the driving temperature of the generator is higher than 80°C, the COP of the system basically does not increase with the increase of the driving temperature.

Heat-Exchange Surface Calculation of Heat-Conducting Medium and Grain Trashed Heap

Для энергосбережения при сушке зерна в контактно-конвективной сушилке предлагается использовать тепло охлаждающей жидкости двигателя внутреннего сгорания. Жидкость поступает в трубки контактно-конвективной сушилки. Трубки теплоносителя расположены наклонно под углом 40° параллельно друг другу по всей ширине сушилки. Над ними, в шахматном порядке – паросборники. Над паросборниками установлен плавающий разравнивающий транспортёр, который изменяет своё положение в зависимости от объёма зерна в контактно-конвективной сушилке. Рассмотрена отдельная зерновка, движущаяся по поверхности трубки теплоносителя. В результате нагрева зерновки происходит её отпотевание – появление влаги на поверхности зерновки. Произведён теплотехнический расчёт поверхности теплообмена теплоносителя и зернового вороха, определено количество тепла, передающегося зерновому вороху в результате контактного теплообмена. Установлено, что использование тепла охлаждающей жидкости двигателя внутреннего сгорания в контактно-конвективной сушилке приводит к энергосбережению при сушке зерна. For energy saving at grain drying in contact-convection drier it is proposed to use heat of cooling liquid of internal combustion engine. The liquid enters the tubes of the contact-convection drier. Heat carrier tubes are set at an angle of 40 ° parallel to each other along the full width of the drier. There are steam headers staggering above them. An amphibious leveling carrier is installed above the steam headers which changes its position depending on the volume of grain in the contact-convection drier. Separate caryopsis moving along surface of heat-conducting medium tube is considered. As a result of the heating of the caryopsis its sweating occurs – the appearance of moisture on the surface of the caryopsis. Thermotechnical calculation of heat-exchange surface of heat-conducting medium and grain trashed heap is performed, amount of heat transferred to grain trashed heap as a result of contact heat exchange is determined. It has been found that using the cooling liquid heat of the internal combustion engine in the contact-convection drier leads to energy saving when drying grain.

Derivation of the Criterion Heat Transfer Equation for the Bakery Oven Heat Generator by Numerical Three-Dimensional Modeling

Рассмотрены вопросы передачи тепла в хлебопекарной печи от теплогенератора к вторичному холодному теплоносителю – воздуху, особенностью которого является высокая влажность. Передача тепла от теплогенератора к вторичному теплоносителю – сложный процесс. Несмотря на то, что по этой тематике написано много работ и проведено множество исследований, вопрос остаётся до сих пор не полностью изученным. Критериального уравнения, с помощью которого можно было бы определить числа Нуссельта для условий теплоотдачи к влажному теплоносителю, проходящему через шахматный пучок теплообменника, в источниках не представлено. С помощью трёхмерного численного моделирования воспроизведена виртуальная работа теплогенератора, в результате по полученным данным было выведено новое критериальное уравнение и получены коэффициенты теплоотдачи (α), позволяющие в конструктивном методе расчёта теплообменных аппаратов определить площадь теплоотдачи для условий влагосодержания в теплоносителе в интервале d = 0,1…0,6 кг влаги на 1 кг воздуха (в хлебопекарной печи другие условия влагосодержания не используются). Предлагаемое уравнение существенно повышает точность расчёта площади теплоотдачи самого теплогенератора, поскольку учитывает влияние влажности на процесс теплоотдачи. The issues of heat transfer in the bakery oven from the heat generator to the secondary cold heat-conducting medium, the peculiarity of which is high humidity are considered. Heat transfer from the heat generator to the secondary heat-conducting medium is a complex process. Despite the fact that many works have been written on this topic and many researches have been carried out, the question remains still not completely understood. The sources do not provide a criterion equation by which the Nusselt numbers can be determined for the heat transfer conditions to the humid coolant passing through the staggered bundle of the heat exchanger. Using three-dimensional numerical modeling the virtual operation of the heat generator was reproduced, as a result according to the obtained data a new criterion equation was derived and heat transfer coefficients (α) were obtained allowing in the constructive method of calculating heat exchangers to determine the heat transfer area for moisture content conditions in the heat carrier in the range d = 0.1...0.6 kg of moisture per 1 kg of air (other moisture content conditions are not used in the bakery oven). The proposed equation significantly increases the accuracy of calculating the heat dissipation area of ​ ​ the heat generator itself since it takes into account the influence of humidity on the heat transfer process.

The thermoelastic contact problem for wavy surfaces with a heat-conducting medium in interface gaps

This paper presents a study on the thermoelastic contact between a wavy surface and a flat surface in the presence of a heat-conducting interstitial medium in interface gaps. The influence of applied mechanical and thermal loads on the deformation of the gaps is taken into account. The contact problem is reduced to a system of singular integro-differential equations for a temperature jump across the gaps and the height of the gaps. Solutions are obtained for the cases of thermoinsulated and heat-conducting gaps. It is shown that, in contrast to the thermoinsulated gap model, the use of the heat-conducting gap model makes it possible to construct a physically correct solution of the contact problem. It is revealed that the wavy interface with heat-conducting gaps exhibits thermal rectification. The effects of the medium’s thermal conductivity, the pressure and heat flow magnitudes and the waviness amplitude on the effective thermal contact resistance and the level of thermal rectification are analysed.

Numerical investigation of a new class of waves in an open nonlinear heat-conducting medium

The paper contributes to the problem of finding all possible structures and waves, which may arise and preserve themselves in the open nonlinear medium, described by the mathematical model of heat structures. A new class of self-similar blow-up solutions of this model is constructed numerically and their stability is investigated. An effective and reliable numerical approach is developed and implemented for solving the nonlinear elliptic self-similar problem and the parabolic problem. This approach is consistent with the peculiarities of the problems — multiple solutions of the elliptic problem and blow-up solutions of the parabolic one.