Properties research of highly porous cellular heat-shielding materials


Аuthors

, Netelev A. V.*, Salosina M. O.**, M.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: netelev@mai.ru
**e-mail: salosina.m@yandex.ru

Abstract

The article presents the results of a study of the structure of highly porous cellular heatshielding materials Duocel ERG®, RVC with a density of 20, 60 and 80 pores per inch. The technology for the production of highly porous cellular materials is based on the pyrolysis process of a polyurethane foam matrix pre-impregnated with phenol-formaldehyde resin. To impart specific properties, various inorganic materials can be sprayed onto the matrix. Heat transfer in cellular materials is described by four processes: conductive thermal conductivity through a solid frame, thermal conductivity through the gas phase in cells, heat exchange due to convection in the gas phase, and radiative heat exchange in a porous structure. The conductive thermal conductivity of a rigid frame of a highly porous cellular material is usually represented as a set of thermal resistances of rods and nodes with different geometry forming the structure of the material. When simulating radiation heat transfer, a complex structure of a highly porous cellular material is considered as a kind of continuous semitransparent medium that emits, absorbs and scatters electromagnetic radiation. Thus, the internal structure of the material has a significant effect on the effective thermal conductivity of the material. The object of research is the geometry of an individual cell of a highly porous cellular material. The studies were carried outusing an OLIMPUS SZX2-ZB16 stereoscopic microscope. More than 200 high-contrast photographs of cells and their elements were obtained. The photographs obtained made it possible to clarify the statistical data on the number, shape, size of the cells and the representative elements that form them. Defects of the cellular structure and its elements were revealed. On the basis of the obtained statistical data, graphs of the distribution of the geometric parameters of the structural elements of the samples RVC-20, RVC-60 and RVC-80 were constructed. The graphs allow us to conclude that the geometric parameters of the elements are random with a distribution law close to normal. The collected statistics will make it possible to analyze the physical processes occurring in the material and more reasonably approach the choice of a mathematical model of heat and mass transfer. This article is the first in a group of articles devoted to the study of the characteristics of highly porous cellular materials.

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