Abstract
The article analyzes temperature fields over foam concrete samples reinforced by PET fibers. The samples are developed at the Votkinsk branch of Kalashnikov Izhevsk State Technical University. The effectiveness of reinforced PET fibers has already been proven, but so far, the effect of PET reinforcement on the thermophysical properties of foam concrete has not been well studied. In the laboratories of the Technical University in Zvolen, Slovakia (TUZVO), the heat transfer is analyzed using natural convection by heating reinforced foam concrete samples. The method of holographic interferometry is used, which allows to visualize temperature fields in real time. Temperature fields arising above the samples are displayed and recorded by a Mach-Zehnder interferometer using the «living boundary» method throughout the entire length of the interference fringes. A method for calculating the parameters of heat transfer by analogy with the heating of a flat plate has been proposed. Qualitative and quantitative analyzes of holographic interferograms of the temperature fields are carried out. The local heat transfer parameters are calculated: the heat transfer coefficient α and the heat conductivity coefficient λ. It has been established that the samples of foam concrete reinforced by PET fibers made in Russia have a higher heat resistance and better insulation than foreign analogues.
Highlights
The article analyzes temperature fields over foam concrete samples reinforced by PET fibers
The samples are developed at the Votkinsk branch of Kalashnikov Izhevsk State Technical University
Temperature fields arising above the samples are displayed and recorded by a Mach-Zehnder interferometer using the «living boundary» method throughout the entire length of the interference fringes
Summary
Функциональная зависимость температуры от величин состояния окружающей среды, длины модели, длины световой волны и количества темных полос от положения неоднородной области определяется в соответствии с [7] по формуле:. Где T(x,y) – расположение температур, температура в соответствующем интерференционном порядке; T∞ – температура воздуха в контрольной области; p∞ – давление в данной области; s – интерференционный порядок; λ – длина световой волны; l – длина модели. Значение локального (местного) коэффициента теплоотдачи αx зависит от многих факторов, например, от типа жидкости, скорости потока, формы поверхности, положения наблюдаемой области или разницы температур поверхности и воздуха [8]. Значение локального коэффициента теплоотдачи можно рассчитать по формуле [9]: x v. Где λ – коэффициент теплопроводности (определяется температурой поверхности); Tx – температура поверхности модели в положении x. Если температура газа (или жидкости) над плитой соответствует t∞ , то согласно закону Ньютона-Рихмана о плотности потока тепла [11]:. Из уравнения (6) можно рассчитать неизвестный коэффициент теплопроводности плиты:
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