Characterizing liquid-vapor phase change phenomena in impulse technology with resistivity probes
2006 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 5, no 5, 22-26 p.Article in journal (Refereed) Published
This study used resistivity probes for the dynamic detection of liquid-vapor phase change inside wet paper webs undergoing impulse pressing. The probes were made from thin copper wires insulated with a high-temperature polymeric material (overall diameter-of 50 mu m). The gap between the exposed ends served as the probe tip. The validity of this technique in impulse pressing experiments was demonstrated in two ways: (1) tests with both dry and wet sheets showed that the probe response was unaffected by the fiber network itself; and (2) heated trials with low applied pressure and long residence times (> 1 s) clearly showed the propagation of a vapor front through the sheet, as predicted by theory. Impulse pressing, experiments were subsequently conducted with a platen press under realistic operating conditions (i.e. surface tempera tures up to 300 degrees C, nip residence times of approximately 25 ms, and maximum applied pressure around 4 MPa). Results show that steam was detected inside the sheet only upon unloading of the hot nip for the layers closest to the heated surface.
Place, publisher, year, edition, pages
2006. Vol. 5, no 5, 22-26 p.
operating window, heat
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-15707ISI: 000237867400004ScopusID: 2-s2.0-33745028624OAI: oai:DiVA.org:kth-15707DiVA: diva2:333749
QC 201005252010-08-052010-08-052011-01-21Bibliographically approved