Characterizing liquid-vapor phase change phenomena in impulse technology with resistivity probes.

The article presents a study on the dynamic detection of liquid-vapor change of wet paper webs undergoing impulse pressing. Resistivity probes made from thin copper wires insulated with high-temperature polymeric material. Results showed that probe was not affected by the fiber network and that trials with low applied pressure and long residence times exhibited the propagation of a vapor front through the sheet. Subsequent impulse pressing showed, on the other hand, the detection of steam inside the sheet manifested upon unloading of the hot nip closest to the heated surface.