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SCRAPED SURFACE HEAT EXCHANGERS
Author(s) -
HÄRRÖD MAGNUS
Publication year - 1986
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.1745-4530.1986.tb00116.x
Subject(s) - laminar flow , mechanics , mixing (physics) , heat transfer , dynamic scraped surface heat exchanger , flow (mathematics) , heat exchanger , laminar flow reactor , plug flow , axial compressor , heat transfer coefficient , thermodynamics , chemistry , open channel flow , physics , critical heat flux , gas compressor , quantum mechanics
In this literature survey flow patterns, mixing effects, heat transfer and power required for rotation in scraped surface heat exchangers (SSHE) are thoroughly discussed, with the emphasis on assumptions and results, while the principal design of different SSHEs are only briefly discussed. The flow patterns control the desired radial mixing and the undesired axial mixing. the flow in a SSHE can be regarded as the sum of an axial flow and a rotational flow. the axial flow is laminar and the rotational flow is laminar or vortical. With laminar flow the radial mixing is poor, which causes poor heat transfer and allows the axial flow profile to control the residence time distribution. the precise onset of vortical flow in a SSHE is hard to predict. the vortical flow makes the radial mixing very efficient, giving good heat transfer and perhaps plug flow behavior. However, vortical flow also causes axial mixing which reduces the apparent heat transfer coefficient and increases the residence time distribution. The power required to rotate the shaft and blades is mainly determined by the design of the blades.