GAS-PRESSURE DROP AND HEAT DISPERSION IN A LAYER OF FIBROUS MATERIAL

The pressure drop and effective radial heat conductivity have been mea sured in fibrous layers of insulation materials exhibiting unisotropic stratified structure. Both quantities have been found to vary with th e two principal orientations of strata in the fibrous material with re spect to the direction of the flow. Pressure losses have been successf ully interpreted in terms of the Ergun equation, valid for beds of par ticulate solids, applying the concept of the equivalent diameter to th e fibrous material. The equivalent diameters were correlated with the void fraction of the material, allowing direct use of the Ergun equati on for calculation of the energy losses. The heat dispersion has been found detectably unisotropic but, for technical purposes, the problem may be solved on the basis of an isotropic model with an error of abou t 20%. A correlation of the effective thermal conductivity of the mate rial for this case also has been presented. The effective heat conduct ivities were correlated as Peclet numbers, using the effective 'partic le' diameter as the scale length both in the Peclet and the Reynolds n umber. The effective 'particle' diameters for the fibrous materials we re obtained by fitting the Ergun equation to pressure drop vs. gas vel ocity data. A joint plot of the Peclet vs. Reynolds number, interpreti ng the effective thermal conductivities of layers of fibrous material as well as particulate beds, suggests that the adopted approach is als o physically meaningful. The results presented represent a contributio n to the process of thermally self-sustained curing of adhesive in the manufacture of fibrous insulating materials.