MEASUREMENT OF CONTRIBUTIONS OF VARIOUS TRANSMISSION TYPES TO RADIATIVE-CONDUCTIVE HEAT TRANSFER IN AIR-FILLED RANDOMLY SCATTERING STRUCTURES

Abstract

Aim. We study the relationship of the structure and properties of materials with their ability to transfer heat in various ways. Methodology. The theory and the results of practical measurements of thermal conductivity components of a randomly scattering structure are compared using two experimental methods and the modification of the radiation properties of samples. Results. The method for measuring the thickness of radiative-conductive relaxation and temperature jump in the medium near the radiation screen, as well as the radiant and conductive components and the total thermal conductivity of the medium, is described. The type of dependence is determined, and the components of thermal conductivity are measured in a wide range of thicknesses during compression of a fibrous canvas, including conductive contributions due to the movement of heat through the air and through the fibers. The change in the radiation contribution to the thermal conductivity due to the metallization of the fiber surface is estimated. Research implications. It is confirmed that different methods for measuring the contributions of the thermal conductivity components of materials give the same result. The conditions of the minimum of the structure thermal conductivity depending on its density are determined. The effect of the metallization of fibers on the thermal conductivity components of the structure is demonstrated.