PERPINDAHAN PANAS HYBRID PHOTOVOLTAIC DAN THERMOELEKTRIC GENERATOR DENGAN HOT MIRROR

Heat transfer is the transfer of energy from one area to another due to the temperature difference between these areas. Wasted heat energy can be converted into electricity using (TEG) between the hot and cold sides. If the temperature difference is more significant, the efficiency may increase along with the operating temperature of the TEG-type material. So in this study, the author will calculate the heat transfer that occurs in Photovoltaic (PV), Thermoelectric Generator (TEG), and Hot Mirrors by utilizing thermal energy light produced from Muxindo LED bulbs with 10 Watt, 15 Watt, and 20 Watt power. The results of this study indicate that by using 10, 15, and 20 Watt LED bulbs for free convection heat transfer, the power generated from each point increases because it passes through several obstacles from objects that experience a decrease in temperature to PV and TEG, with the characteristics of the displacement. The movement of molecules from the medium importance follows convection heat at every point of transfer in the intermediate substance. The most significant power generated from radiant heat transfer is about 0.1873 Watt. It occurs on the surface of the fresnel lens using a 20 Watt LED bulb with the characteristic that the radiation propagates in a straight line and does not require an intermediate medium to transfer heat from one substance to another. The most significant conduction heat transfer power, 0.2453 Watt, occurs in Fresnel Lens using a 20 Watt LED bulb with heat transfer characteristics in solid objects.

Influence of washing on textile material thermal properties under exposure of an open flame and heating ele-ment heat flow

Elevated temperatures are factors causing harm to human health and life. To ensure protection, various personal protective equipment is used, which includes special protective clothing. The article discusses the heat-shielding indicators of the safety of textile material. In order to determine the heat-shielding properties of the material, various types of exposure are used – convective heat from a heating element and an open flame. Fabrics of various raw materials and surface density are used for sewing special protective clothing. Five clothes were selected for the research. The research was held under the exposure of an open flame and convective heat of heating element with a comparable heat flux density equal to 80 kW/m². Also, research was held under influence of multiple wash cycles on radiant heat transfer index and heat transfer index.

A Novel Model Concerning the Independence of Emissivity and Absorptivity for Enhancing the Sustainability of Radiant Cooling Technology

Radiant cooling technology is a sustainable technology for improving built environment. The past research only studied the performance (e.g., radiant heat flux) based on Kirchhoff’s law while the accuracy and its reasons were seldom analyzed. In order to study the mechanism deeply, a new model of radiant heat transfer is derived theoretically which considers emissivity and absorptivity independently. This model is validated by the experimental data then applied in a reference case for further analysis. The analyzing methods of sensitivity and relative deviation are performed to investigate the reasons for the errors. The results of sensitivity analysis show that it is about 20% − 40% more sensitive for the emissivity to the heat flux than the absorptivity. Furthermore, the deviation of the heat flux can reach up to 20% when the absorptivity is in the range from 0.4 to 0.9. This deviation is close to the estimated error range of 21.8% in the past studies. Therefore, the discussion based on the theoretical analysis, shows that the errors in past studies are highly due to the oversimplified preconditions for applying Kirchhoff’s law and they ignored the impact of surface absorption. Additionally, the validation in the previous experiments was highly coincidence, since they neglected the key independent tests of the absorptivity and radiant heat flux. Comprehensively, the new model is valuable to provide a more reliable solution for analyzing the radiant heat transfer and for the future design of an independent test of radiant heat flux.

Preface

Preface for the STS37 XXXVII Siberian Thermophysical Seminar JoP volume XXXVII Siberian STS37 XXXVII Siberian Thermophysical Seminar S. V. Alekseenko, D. M. Markovich, D. Ph. Sikovsky Kutateladze Institute of Thermophysics, Lavrentyev str., 1, 630090 Novosibirsk, Russia e-mail: [email protected], [email protected] The Siberian Thermophysical Seminar is traditionally held in the Akademgorodok of the city of Novosibirsk at Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, since 1960. In 2021, the Seminar was dedicated to the Year of Science and Technology of the Russian Federation and the 60th anniversary of the first human flight into space. The organizing committee sincerely hopes that the XXXVII Siberian Thermophysical Seminar helped to attract young scientists to solve urgent scientific problems, and stay in the Novosibirsk Academgorodok and at the Institute of Thermophysics left many positive emotions and pleasant impressions. The present Seminar covered the following topics: turbulent flows in single-phase media; heat transfer enhancement; transfer processes in physical and chemical transformations including combustion; aerogasdynamics and thermophysics in space applications; hydrodynamics, heat and mass transfer, and wave processes in multiphase media; heat and mass transfer during phase transitions; thermophysical problems of power engineering, energy efficiency, and energy-saving; thermal physics of micro- and nanosystems, processes in rarefied gases and plasma; thermophysical properties of substances and radiant heat transfer; heat transfer and hydrodynamics in technological processes and environmental protection; calculation fundamentals and constructing principles of energy systems based on the effect of superconductivity. The proceedings contain 171 papers grouped by topics. The Scientific Committee of the Seminar highly appreciates the great work of the editorial board and reviewers in preparing this volume. We would like to express our sincere gratitude to all authors for their research contributions, and also to the organizers of the Seminar for their valuable spadework. List of Editorial Committee, Organizing Committee are available in this pdf.

Thermal effect of a fire on a steel beam with corrugated wall with fireproof mineral-wool cladding

This paper reports a study into the possibility of applying a simplified approach, recommended by standards for conventional steel beams, to determine the heating temperature under the conditions of a fire in relation to steel I-beams with a corrugated wall. The research is predetermined by the limitation of methods that make it possible to determine the heating temperature of this type of beam in a fire using engineering methods with a small amount of calculations. Technical data on steel beams with cladding have been considered for calculation, the features of heat impact of fire on them have been analyzed, a calculation procedure has been devised, the estimation schemes have been built, and the calculations have been performed. Data on the temperature distribution in the cross-sections of beams with and without cladding were obtained by using a simplified method recommended by standards and the refined method based on a finite-element method. Mathematical models have been constructed for calculations that describe the effect of a standard temperature regime of fire on the distribution of temperature in each minute in the cross-sections of steel beams with and without cladding. The models have been described on the basis of the differential equation of thermal conductivity, boundary conditions of the third kind, which take into consideration convective and radiant heat transfer. It was established that the mineral wool cladding of the beam with a corrugated wall is a reliable fire protection agent. The heating temperature of the beam does not reach a critical value of 500 °C in 60 minutes, which provides the class of this beam with the most stringent requirements for its fire resistance in accordance with the classification in line with the acting norms in Ukraine. The simplified method, recommended by the current standards of the European Union and Ukraine, could be effectively used to analyze the fire resistance of these beams and is the basis of the procedure for the estimated assessment of the fire resistance of these structures

Analytical Solution of Problems about the Radiative and Radiative–Conductive Stationary Heat Transfer in a Medium with an Arbitrary Dependence of the Scattering and Absorption on Frequency Boundary Conditions

We defined a method for the analytical solution of problems on stationary radiative and radiative–conductive heat transfer in a medium with an arbitrary frequency dependence of absorption and scattering near its boundary. We obtained formulas for the heat conductance of the remote surface and the thickness of the radiative–conductive relaxation of the medium. We determined characteristics of radiant heat transfer from the medium to free space such as the radiation spectrum, the radiation temperature and the medium outer boundary temperature. In addition, we solved the problem on the radiative–conductive heat transfer from one of two parallel surfaces to another with a medium between them.

Investigating the radiation-convective heat exchange of a metal-ceramic plate

The paper presents the experimental data on heat exchange during thermo-cyclic interaction of a flame jet with a thermal barrier ceramic coating. Cooling due to radiant heat transfer into the environment allows organizing heat exchange in such a way that when a flow of combustion products with a temperature of 1500 °C flows onto the sample, the temperature on the surface of the TBC does not exceed 1200 °C. The thickness of TGO after 1500 thermal cycles was 9.5 microns

Modeling of a temperature field for extruder body

The paper considers the process of induction heating of the extruder body, the temperature of which determines the degree of heating of the polymer mixture in the zone of loading the dry mixture. A mathematical model of this process is formulated taking into account radiant heat transfer in the gap between the inductor and the case. An iterative numerical-analytical method is proposed for solving the corresponding nonlinear boundary value problem of housing heating, at the first iteration of which a linear boundary value problem is solved (without taking into account radiant heat transfer). At the subsequent stages, a nonlinear boundary value problem is solved. The iterative method is based on the application of integral transformations of the linear part of the problem, followed by an iterative scheme for finding a nonlinear problem. This scheme is based on the algorithms for the equivalent simplification of the expressions obtained by solving the problem. The results of mathematical modeling of the corresponding algorithms are presented.

Experimental assessment of the influence of radiant heat transfer on the transition of a crown fire to settlements

Проведены экспериментальные исследования влияния лучистого теплообмена на переход верхового лесного пожара на постройки IV и V степеней огнестойкости. Лесной верховой пожар моделировался горением штабеля древесины с интенсивностью тепловыделения, близкой к интенсивности при реальных пожарах. Получена зависимость изменения плотности теплового потока от расстояния до кромки горения. Экспериментально определены температура воздуха с подветренной стороны пожара и плотность выпадения искр в зависимости от расстояния. Проверена эффективность защиты растворами ретардантов деревянных строений от возгорания при лучистом теплообмене между факелом пламени пожара и объектом защиты. Crown fires are the main threat of the combustion transfer from the forest to objects located in it. Fire services dealing with forest fires face the problem how to protect these objects from forest fires. It is proposed to treat the object with retardant solutions before a forest fire approaches. To assess the effectiveness of such tactics for fire protection of objects when exposed to a heat flow from the combustion front there were carried out experiments on large-scale crown fire models. A crown fire is simulated with a pile of wood with a heat release rate of ≈ 13 MW m. The wind is generated by fans, its speed is close to the speed at which a forest fire occurs. Measurements of the heat flux density, medium temperature, and the density of sparks falling downwind of the fire front at different distances and heights were carried out. Calculations were carried out to assess the impact of heat flow on buildings of IV-V degrees of fire resistance. The results obtained are compared with experimental data and they are in good agreement. There have been determined the distances from the fire front at which the fire protection with retardant solutions is effective for structures of IV-V fire resistance degrees at radiant heat exchange.