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Performance of a Scraped‐Surface Heat Exchanger Under Ultra High Temperature Conditions: A Dimensional Analysis
Author(s) -
CUEVAS ROBERTO,
CHERYAN MUNIR,
PORTER VER L.
Publication year - 1982
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1982.tb10136.x
Subject(s) - nusselt number , reynolds number , laminar flow , mechanics , turbulence , thermodynamics , heat transfer coefficient , heat exchanger , dynamic scraped surface heat exchanger , chemistry , dimensionless quantity , rotational speed , materials science , heat transfer , critical heat flux , physics , classical mechanics
Performance characteristics of a pilot‐scale scraped‐surface heat exchanger (Contherm Model 6 × 2) under UHT operating conditions were evaluated. Outlet temperature and overall heat transfer coefficient (U) were significantly affected by rotational speed of the blades, mass flow rate of feed, feed inlet temperature, steam pressure and solids content of the model low‐acid liquid food (soy extracts). The scraping action of the blades greatly improved the performance up to about 350 rpm; higher blade speeds had little or no effect and sometimes decreased U values. Application of dimensionless models showed that the effect of axial Reynolds number (Re A ) on the Nusselt number was more significant in the turbulent regime (Re A > 1800), while rotational Reynolds number above 10 5 had a significant effect at all values of Re A between 1200 and 3700. At very high values of the Taylor number (> 10 10 ) when laminar axial flow conditions prevailed, Nusselt number decreased with increase in rotational Reynolds number.