Effect of infrared irradiation on drying characteristics of wet porous materials

We studied infrared drying characteristics of wet porous materials by compa rison with the convective drying characterisaics, and our attention was foc used on the factors influencing their characteristics. By selecting three k inds of membrane filters, we examined the influences of the mean pore diame ter and the spectral distribution of irradiation power as variables using a far-infrared heater and a near-infrared heater. The differences between th e infrared and convective drying characteristics (drying rate, sample tempe rature, water content distribution) were experimentally obtained, and the i nfluence of mean pore diameter of the sample on its drying characteristics was observed only in infrared drying but in convective drying. By measuring the diffuse transmittance of the membrane filter in consideration of the d rying process, we deliberated that infrared radiation penetrating into the drying sample was absorbed directly by the water in the voids, and that the water vaporized there.