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MODELLING of the MEDIA‐SIDE 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.tb00057.x
Subject(s) - heat transfer , nusselt number , thermodynamics , mechanics , materials science , dynamic scraped surface heat exchanger , laminar flow , heat transfer coefficient , heat exchanger , plate heat exchanger , ntu method , heat transfer enhancement , critical heat flux , chemistry , turbulence , reynolds number , physics
The heat transfer on the media‐side and in the tube wall of scraped surface heat exchangers was investigated when the product was heated with steam or cooled with water. The heat transfer coefficients found experimentally were 15% higher than predicted with the Nusselt theory for steam condensation, and 30% lower than predicted with a traditionally recommended model for cooling with water. New, much better models for the media‐side heat transfer were developed. the choice of model for the media‐side affects a subsequent modelling of the heat transfer on the product‐side. When the product‐flow was laminar in the scraped surface heat exchangers, the heat transfer was controlled mainly by the resistance on the product‐side; while the resistance on the media‐side was very small. Vortical flow decreased the resistance on the product‐side considerably and made the choice of material in the tube wall important from a heat transfer point of view.