Visualization of liquid-vapor phase change phenomena in impulse technology
2006 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 5, no 6, 15-21 p.Article in journal (Refereed) Published
This paper addresses two unresolved aspects in the physics of impulse technology. In our initial study, we used a modified laboratory platen press to investigate contact phenomena at the interface between the wet web and the hot press. We replaced the heated press platen with a preheated glass plate and used high-speed photography to visualize the interfacial interactions. The results confirm that little or no steam is formed before the point of maximum applied load for contact times typical of industrial pressing operations (25 ms). Steam generation during the nip compression phase could be observed only for pulse lengths well beyond-those encountered in industrially relevant impulse press nips (250 ms). In a complementary study, flashing phenomena were investigated in STFI's FlashLab, an experimental facility for the study of phase-change phenomena in water-saturated porous media. Model experiments under well-defined conditions showed that delamination can be prevented by an appropriate unloading strategy. Moreover, we observed that flashing-assisted displacement dewatering occurred when the hydraulic pressure was released. We discuss its significance for impulse pressing efficiency in this report. Application: Insights from this study will help in the further development and possible commercialization of impulse drying systems.
Place, publisher, year, edition, pages
2006. Vol. 5, no 6, 15-21 p.
operating window, delamination
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-15763ISI: 000238443000003ScopusID: 2-s2.0-33745794630OAI: oai:DiVA.org:kth-15763DiVA: diva2:333805
QC 201005252010-08-052010-08-052011-01-21Bibliographically approved