气体稀薄及扩散效应对气凝胶隔热材料传热的影响研究

Nano-porous aerogel materials have been used widely in high temperature insulation field. Most investigation on porous insulation materials is limited to effective thermal conductivity of materials. Gas in high temperature side expands and diffuses to low temperature side, enhances heat transfer, increases back temperature of materials and makes heat insulation performance worse. The effect of gas diffusion on heat transfer performance of nanoporous insulation materials is numerically studied by adding a source term in one-dimensional transient heat conduction equation. Investigations of intrinsic permeability and gas apparent permeability on transient heat conduction are implemented. A model relating the permeability is established to predict the back temperature of porous media. Gas moves faster in materials with large permeability which causes the back temperature increase, and makes heat insulation performance of materials worse. In addition, large-density materials with low permeability decrease the velocity of gas diffusion, and improve heat insulating performance. Nano-porous aerogel insulation materials with large density and small particle size can be employed in engineering.The present study provides guidance for design of porous insulation materials.