Optimization of Compressed Ceramics Fiber Insulating Layers

Compressed thin layers of ceramic fiber insulation are used as high temperature insulating layers as well as mechanical support for catalyst coated ceramic monoliths in automotive emission control devices. Minimization of energy losses, choice of material and thickness of com- pressed insulating layer are based on knowledge of their thermal physical properties. Currently, consistent meas- urements of materials in a compressed state, as they would be in emission control applications, are absent due to the absence of suitable methods for s,wh tests. A test method was developed for measurement of the thermal conductivity of compressed thin fiber layers. This paper summarizes the results of thermal conductivity and diffu- sivity measurements of 27 compressed fiber alumina -sili- ca -vermiculite materials in the range of 200 -950℃. Thermal physical properties as a function of temperature, density/mechanical pressure, thickness and composition of insulating layers are presented. The whole set of exper- imental data is generalized on 3D surface plots and de- scribed by polynomial functions. The possible heat trans- fer mechanisms governing apparent thermal conductivity of pressed insulation layers are discussed.