Measurement of Thermo-Radiation Characteristics of Spectral-Selective Materials for Space Structures Designs

The research demonstrates the relevance of creating the technologies of application of spectral-selective coatings of materials, intended for open space structures designs and the development of methods of control of their thermo-radiation characteristics. It is noted that under other equal conditions, the temperature of the surface of a structure in the vacuum of the outer space is determined by the ratio of the absorption coefficient of solar radiation to the emission factor of the surface. The aim of the work is to demonstrate the perspective of calorimetric measurements of thermo-radiation characteristics without vacuuming the volume of the measuring chamber, substantiating the structure and characteristics of the equipment for these studies, carrying out an experimental verification of the method and equipment on the real samples of materials for space technology. The possibility of using the calorimetric method for measuring the emission factor without vacuuming the volume of the measuring chamber, taking into account the heat transfer from the radiator to the surface of the sample through the air layer, is substantiated. The structure of the corresponding apparatus is recommended and the ratio of the geometric dimensions of the working chamber, in which the boundary distortion due to heat transfer through the air is insignificant, and the correction for conductive heat exchange can be easily calculated, is defined. The method of measurement and the description of the test stand on the basis of thermoelectric heat exchangers and absolute solar radiation receiver, which are intended to determine the absorption coefficient of solar radiation, are given. A brief description of the technology of coating Al + TiO2 layered structure and the measured values of emission factor and absorption coefficient of samples with such coating is given. It is shown that the ratio of the absorption coefficient of solar radiation to the emission factor for a two-layer coating is significantly lower than the similar value obtained for its individual components. It is established that by changing the ratio of thickness of layers of Al and TiO2 it is possible to reduce the ratio of coefficients to the value that provides an acceptable level of temperature of the surface of the spacecraft

Measurement of Thermo-Radiation Characteristics of Spectral-Selective Materials for Space Structures Designs

The research demonstrates the relevance of creating the technologies of application of spectral-selective coatings of materials, intended for open space structures designs and the development of methods of control of their thermo-radiation characteristics. It is noted that under other equal conditions, the temperature of the surface of a structure in the vacuum of the outer space is determined by the ratio of the absorption coefficient of solar radiation to the emission factor of the surface.The aim of the work is to demonstrate the perspective of calorimetric measurements of thermo-radiation characteristics without vacuuming the volume of the measuring chamber, substantiating the structure and characteristics of the equipment for these studies, carrying out an experimental verification of the method and equipment on the real samples of materials for space technology.The possibility of using the calorimetric method for measuring the emission factor without vacuuming the volume of the measuring chamber, taking into account the heat transfer from the radiator to the surface of the sample through the air layer, is substantiated. The structure of the corresponding apparatus is recommended and the ratio of the geometric dimensions of the working chamber, in which the boundary distortion due to heat transfer through the air is insignificant, and the correction for conductive heat exchange can be easily calculated, is defined. The method of measurement and the description of the test stand on the basis of thermoelectric heat exchangers and absolute solar radiation receiver, which are intended to determine the absorption coefficient of solar radiation, are given.A brief description of the technology of coating Al+TiO2 layered structure and the measured values of emission factor and absorption coefficient of samples with such coating is given. It is shown that the ratio of the absorption coefficient of solar radiation to the emission factor for a two-layer coating is significantly lower than the similar value obtained for its individual components. It is established that by changing the ratio of thickness of layers of Al and TiO2 it is possible to reduce the ratio of coefficients to the value that provides an acceptable level of temperature of the surface of the spacecraft.Показана актуальність створення технологій нанесення спектрально-селективних покриттів матеріалів, призначених для конструкцій космічної техніки, які розкриваються, та розвитку методів контролю їх терморадіаційних характеристик. Зазначено, що при інших рівних умовах, температура поверхні конструкції у вакуумі космічного простору визначається відношенням коефіцієнта поглинання сонячної радіації до коефіцієнта випромінювання (емісії) поверхні.Метою роботи є показ перспективності калориметричних вимірювань терморадіаційних характеристик без вакуумування об’єму вимірювальної камери, обґрунтування структури і характеристик обладнання для цих досліджень, проведення експериментальної перевірки методу і устаткування на реальних зразках матеріалів для космічної техніки.Обґрунтована можливість застосування калориметричного методу для вимірювання коефіцієнту емісії без вакуумування об’єму вимірювальної камери при врахуванні теплопередавання від випромінювача до поверхні зразка крізь шар повітря. Рекомендована структура відповідної апаратури і визначене співвідношення геометричних розмірів робочої камери, за яких крайові спотворення внаслідок теплопередавання крізь повітря є несуттєвими, а поправка на кондуктивний теплообмін може бути легко розрахована.Наведено методику вимірювань і опис випробувального стенду на базі термоелектричних перетворювачів теплового потоку і абсолютного приймача сонячного випромінювання, які призначені для визначення коефіцієнта поглинання сонячного випромінювання.Наведено стислий опис технології нанесення покриття шаруватої структури Al+TiO2 та виміряні значення коефіцієнта емісії і коефіцієнта поглинання сонячного випромінювання зразків з таким покриття. Показано, що відношення коефіцієнта поглинання сонячної радіації до коефіцієнта емісії для двошарового покриття істотно нижче аналогічного значення, отриманого для його окремих компонентів. Встановлено, що зміною співвідношення товщини шарів Al і TiO2 можна забезпечити зниження величини відношення коефіцієнтів до значення, яке забезпечує допустимий рівень температури поверхні космічного апарату

Dynamics of interfacial interaction between components during mixing

The effect of mechanical action on the mixing and whipping of a mixture of components contributes to the establishment of a three-dimensional sponge-mesh continuous structure of the gluten framework, as it determines the elastic and elastic properties of the medium and is relevant in the dispersion of gas in a liquid. The purpose of the work was to establish the relationship between the gas retention capacity of the medium and the energy consumed for the hydration of the components. The experiments performed the task of determining the gas retention capacity of the medium with variable parameters of the height of the liquid phase from the intensity of mixing, the time of the transient processes of the formation of the full volume of the gas-liquid medium, the time of the transient process of the dispersed gas phase. The difference in levels before the gas phase generation and the stirring mode determines the value of gas retention capacity. Therefore, it was concluded that it is expedient to completely destabilise the steady-state regimes by changing the modes of action of the working body in the flow system. An additional impact on the system is the change of hydrodynamic regimes due to the unstable dynamics of the dispersed gas phase generation. The generation of this phase means the presence of energy costs for the interfacial surface establishment, which must be considered in the overall energy balance. In addition, a part of the gas phase, which existed and continues to exist in the new regime after mixing, enters the transient regime. Therefore, the most effective mixing occurs in case of compliance with the shifted mode of dosing components in a suspended state and the mechanical impact of the working body. Considering the tasks and conditions for mixing the dough, the requirements for the design of the mixer are determined, and it is established that the supply of components should last at least 45 seconds. During this period, there is hydration and a reduction in energy consumption. Such an approach intensifies mass transfer and biochemical processes under conditions of thermodynamic equilibrium with appropriate desorption bonds of the dissolved part of the gas phase and liquid, which covers a new method of mixing and allows further use in the design calculations of working chamber