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INFLUENCE OF FLOW REGIMES ON TEMPERATURE HETEROGENEITIES WITHIN A SCRAPED SURFACE HEAT EXCHANGER
Author(s) -
DUMONT ERIC,
VALLE DOMINIQUE DELLA,
FAYOLLE FRANCINE,
LEGRAND JACK
Publication year - 2000
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2000.tb00512.x
Subject(s) - heat exchanger , mechanics , thermodynamics , plate heat exchanger , work (physics) , materials science , heat transfer , dynamic scraped surface heat exchanger , flow (mathematics) , plate fin heat exchanger , heat transfer coefficient , critical heat flux , physics
ABSTRACT In industrial applications, fluids processed in scraped surface heat exchangers often show large temperature heterogeneities at the exchanger outlet. Our study deals with the thermal evolution of model fluids, Newtonian and non‐Newtonian in heating or cooling conditions and allows us to link the phenomena of appearance and disappearance of temperature heterogeneities with the changes in the flow pattern within the exchanger. Based on literature data dedicated to scraped surface heat exchangers as well as to annular spaces without blades, we have shown that thermally homogeneous products can be obtained when Taylor vortices appear in the exchanger. Studies done on the exchanger with and without blades show that the thermal behavior is basically the same for both geometries but with a difference in critical Taylor numbers value for change in heat transfer regime. The presence of blades promotes the appearance of instabilities at lower values of generalized Taylor number (Ta g = 10 with blades; Ta g = 39 without blades). It shows as well, that the value of critical Taylor number in scraped surface heat exchanger closely depends upon the flow‐rate even for very low values for Re axg (Re axg < <1).