A review of heat transfer models of nanoporous silica aerogel insulation material

Abstract

In this paper, the development of effective thermal conductivity models for nanoporous silica aerogel insulation materials is summarized. In the first part, heat transfer characteristics of nanoscale gaseous/solid/radiative heat transfer inside aerogel insulation material are introduced. Then, the existing theoretical models, empirical models, and numerical methods for the thermal conductivity of each heat transfer mode are reviewed and analyzed. After that, the advances in effective thermal conductivity models for the nanoporous silica aerogel materials as well as their composite insulation materials after the addition of opacifiers and reinforced fibers are presented. Next, the authors previous work is taken as an illustration of a procedure for establishing an effective thermal conductivity model of an aerogel insulation material from nano- to macro-scale. A brief introduction to the application of molecular dynamics in the simulation of aerogel materials is also given. In the end, further researchneeds are indicatedfor the nanoporous silica aerogel insulation materials. These include: the coupled heat transfer behavior at the gas–solid contact interface, the influence of scale/interfacial effects on the thermal conductivity of nanoscale solid particles, and the effect of different influencing factors on the total heat transfer performance. Such studies could provide help in accurately predicting the thermal conductivity as well as optimizing the insulation performance for the aerogel material and could provide guide for the design of new type aerogel insulation material which can be used in industry such as aeronautics and astronautics, thermal insulation, building, chemical industry and so on.