Using liquid crystals for analyzing thermofluiddynamical processes in liquids during pressurization
by
Michael Pehl
Technische Universität München, Lehrstuhl für Fluidmechanik und Prozeßautomation, Germany
Coauthors: Franz Werner, Antonio Delgado

Inhomogeneous temperature and velocity fields were caused in liquids due to the procedure of pressurizing. To date this effect mostly has been remained unconsidered in high pressure investigations because of the lack of knowledge and adequate measuring technique. On the other hand processes under pressure may be decisively affected by temperature and motion, e. g. in high pressure treatment processes of foods. In previous studies we have shown, that the liquid crystal measuring technique is an adequate means to visualize temperature and velocity fields at high pressure. The change of the reflected wavelength of TLCs due to pressure is inverse to the effect of temperature. However, a high temperature resolution can be achieved at high pressure and the color changes remain reversible.

In this study encapsulated TLCs of different start temperatures and bandwidths have been used in order to visualize temperature and velocity fields during pressurizing water in an optical cell up to 700MPa. Therewith the decay times of temperature and motion in the liquid after pressurizing have been investigated. First results of the measured decay times depending on the pressurizing rates and the pressure levels will be presented and discussed.

Some additional notes concerning the applicability of the TLC technique in high pressure investigations and the choice of convenient TLCs will be given as well.

Date received: January 29, 1999

Copyright © 1999 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cacp-22.