Thermal insulation at room temperature. Physical basis

The vast majority of modern insulating materials are lightweight porous materials, within which heat transfer takes place by both conduction and radiation. The semi-transparent nature of some of these materials, even at room temperature, has prompted a large number of studies and necessitated a rethinking of the traditional treatment of these materials, as well as a reconsideration of the terminology used to describe their properties. Basic studies on the functioning of insulating materials have focused on gaining a better understanding of heat and mass transfer by natural and forced convection, and by radiation in semi-transparent porous media. They have also extended to the study of the influence of surrounding factors on performance: the influence of humidity and thermomigration, and the influence of the diffusion of interstitial gases different from air (aging). Studies begun initially in relation to special applications, such as cryogenics, space, nuclear engineering, etc., have been progressively extended to common products and to temperatures close to ambient temperature. This knowledge has made it possible to model the operation of insulators and predict their performance as a function of their thermophysical parameters and application conditions. Modeling has been an important lever in improving products and optimizing application conditions.