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Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Volumes per year:

various

Year 2006

DOI: 10.1615/IHTC13.p10

DETERMINATION OF FLOW PHENOMENA AND MASS TRANSFER COEFFICIENTS IN NON-NEWTONIAN FLOW

G. Zheng
Institute for Food Technology, Food Process Engineering, University of Hohenheim, Stuttgart, Germany

P. Gschwind
Institute for Food Technology, Food Process Engineering, University of Hohenheim, Stuttgart, Germany

V. Kottke
Institute for Food Technology, Food Process Engineering, University of Hohenheim, Stuttgart, Germany

ABSTRACT

Numerous flows show a non-Newtonian flow behavior. The majority shows a shear-thinning behavior, which is to be investigated here in detail. The aim of this work is to establish a method to analyze flow and transport phenomena in various geometry for non-Newtonian media. As working material a transparent shear-thinning liquid is used, which corresponds well to a simple Ostwald-de Waele' approach (Methocel K 15 M, n < 1).
Through a variation of the concentration of the added material, the viscosity can be adjusted in a wide range, which is interesting for numerous foods. The viscosity is measured with a rotational viscometer. Through addition of a dye the mixing behavior of different structures can be investigated.
For the experimental determination of the local and integral mass transfer a measuring method is used based on convective mass transfer with a coupled chemisorption of an anionic dye (Acidol-Blau 3 GX) to polyamide. The technique gives the mass transfer distribution as color density distribution. It is possible to analyze flat surfaces by coating with polyamide chromatography sheets, with polyamide membranes or to build the surface to be analyzed from polyamide. Therefore also highly complex technical surfaces can be analyzed.
The evaluation of the measurements is carried out with remission photometric measurements, image processing with a scanner or ccd-camera. As an example, flow and transport phenomena in flat channels with spacers, as they are typical for membrane processes with viscous media and small duct dimensions or for static mixers, are investigated and presented.