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ISSN Online: 2377-424X

ISBN Print: 0-89116-909-1

International Heat Transfer Conference 9
August, 19-24, 1990 , Jerusalem, Israel

HEAT TRANSFER OF NON NEWTONIAN FLUIDS YIELD EFFECT AND APPLICATION TO SCRAPED SURFACE HEAT EXCHANGERS

Get access (open in a dialog) DOI: 10.1615/IHTC9.1060
pages 57-60

要約

The results presented here concern the flow between an annular space (with or without rotation of the inner cylinder), the external wall being heated withe a constant heat flux φ.
1) For Poiseuille flow (laminar regime, no rotation) a yield leads to axial velocity profiles which are favorable to heat transfer, the wall shear rate being enhanced. We have determined local heat transfer coefficient.
2) So as to eliminate this undesirable effect, it is sufficient to impose a radial velocity gradient by means of a slight rotation, the stress being everywhere above the yield value. Heat transfer is then greater and we another correlation (for the so called Couette Poiseuille flow).
3) Finally, when the Taylor's number is large enought, heat transfer is substantially enhanced by Taylor's cells. We propose a third correlation.
This geometry bears a direct relationship to that of scraped surface heat exchangers. For this type of apparatus, the rotor is equiped with blades. Our visualization studies have shown that the flow is basically unmodified. The positive effect of these blades on heat transfer is non-negligible but remains limited.