Elaboration of methods for studying the thermal conductivity coefficient in the circumferential direction of hollow rods

Аuthors

Lu Y. , Reznik S. V., Denisov O. V., Denisova L. V.

Baumann Moscow State Technical University, 105005, Moscow, 2nd Baumanskaya St., b. 5, c. 1

Abstract

Ensuring the dimensional stability of space structures requires accurate prediction of their thermal deformations using modern numerical modeling methods. The greatest challenge is accounting for the anisotropy of the thermal conductivity of composite materials (CM), especially in the directions of maximum temperature differences. For thin-walled rod elements, radial temperature differences are typically insignificant, making longitudinal and circumferential thermal conductivity key parameters in analyzing temperature fields. These characteristics are the ones that most significantly influence temperature distribution during heating of the structure.

The design of space structures is complicated by the fact that the actual thermal properties of a CM can only be determined after the specific component has been manufactured. Standard methods and tools for determining thermal conductivity are unacceptable, as they focus on testing CM in a direction perpendicular to the plane of the reinforcement, using small and not always representative specimens. Manufacturing such specimens from a full-scale rod structure would result in structural damage to the material. Mechanical processing of rod elements to produce flat samples disrupts this integrity, making measurement results unreliable.

The methods for determining the thermal conductivity of anisotropic composites developed at Bauman Moscow State Technical University are based on the generation of temperature fields on elements of full-scale structures during local heating and their mathematical processing using parametric identification methods based on solving inverse heat conduction problems (IHCPs). The methods have been tested on full-scale elements of space structures in the form of anisotropic plates, hollow and solid rods, and open shells. The validity of the methods is confirmed by reference thermal conductivity measurements, while observing the conditions of thermal and geometric similarity.

In this article, the authors assessed the reliability of the results of determining the thermal conductivity of hollow composite rods in the circumferential direction. Hollow rods made of KV quartz glass were used as experimental samples. The tests were carried out in a chamber with still air, ensuring geometric and thermal similarity to the elements of real-life composite material rod structures. Carbon tape was used as a heater. Temperature fields on the sample surfaces were measured with a thermal imager. The experimental data were processed using the IHCP solution program. Good agreement was achieved bet-ween the calculated, experimental, and reference data on the thermal conductivity of KV glass, which can serve as a basis for the practical application of the new method.

Keywords:

thermal conductivity, inverse problem, thermal imajer, reference materials, temperature measurement

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