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MODELLING of VORTICAL HEAT TRANSFER IN SCRAPED SURFACE HEAT EXCHANGERS
Author(s) -
HÄRRÖD MAGNUS
Publication year - 1990
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.1745-4530.1990.tb00061.x
Subject(s) - heat transfer , thermodynamics , dynamic scraped surface heat exchanger , mechanics , heat transfer coefficient , laminar flow , heat exchanger , flow (mathematics) , radius , chemistry , dispersion (optics) , materials science , critical heat flux , physics , optics , computer security , computer science
Heat transfer experiments have been performed in pilot plant scraped surface heat exchangers, using starch pastes and water as model products. When the flow was vortical, the backmixing effects were considered using the plug flow and axial dispersion model; the true surface heat transfer coefficients and axial dispersion coefficients were determined from temperature measurements. These coefficients were modelled and the following variables were considered: rotational speed, viscosity, flow rate, number of blades, radius ratio and heat transfer direction. Using these models, the overall heat transfer coefficients and the axial temperature profiles can be predicted quite precisely for SSHEs over a wide range of operating conditions. the first blade improved the heat transfer coefficients while additional blades did not; and heat transfer was higher when the radius ratio was 0.5 than when it was 0.75. the differences between previously proposed models are explained. The most favorable flow pattern in SSHEs occurred when the flow was vortical, but close to the transition point to laminar flow.