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MODELLING of LAMINAR 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.tb00060.x
Subject(s) - dynamic scraped surface heat exchanger , heat transfer , laminar flow , thermodynamics , heat transfer coefficient , mechanics , heat exchanger , convective heat transfer , plate heat exchanger , churchill–bernstein equation , ntu method , chemistry , materials science , micro heat exchanger , nusselt number , critical heat flux , turbulence , reynolds number , physics
Heat transfer experiments with starch pastes have been performed in pilot plant scraped surface heat exchangers (SSHE). Effects of the following variables were considered in the modelling of the laminar heat transfer: rotational speed; viscosity, flow rate, number of blades, radius ratio and heat transfer direction. The poor radial mixing restricted the heat transfer coefficients. When the radius ratio increased, the heat transfer rate increased. This was probably due to increasing mixing effects from the blades. the flow rate and the heat transfer directions did not affect the heat transfer coefficients. The scatter in the heat transfer coefficients was considerable, due to unstable flow conditions in the SSHEs. However, the scatter was reduced, compared with previous investigations, by the use of a static mixer after the SSHEs, since the radial temperature differences were eliminated. Better design of rotor and blades may improve the performance of SSHEs operating with laminar flow.