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Local heat transfer coefficients in a model “falling film” scraped surface exchanger
Author(s) -
Azoory S.,
Bott T. R.
Publication year - 1970
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450480405
Subject(s) - heat transfer coefficient , penetration (warfare) , heat transfer , thermodynamics , heat exchanger , materials science , mechanics , dynamic scraped surface heat exchanger , falling (accident) , intensity (physics) , mass transfer coefficient , mass transfer , critical heat flux , physics , mathematics , optics , medicine , environmental health , operations research
Utilization of an accurate technique to measure the local heat transfer coefficient in thin falling film scraped surface exchangers yields results which indicate that the local heat transfer coefficient is dependent on N 0.5 and, above a certain rotational speed, independent of axial flow rate. Both of these observations are in agreement with the theoretical penetration model. The results, however, are generally lower than would be expected from the theory, and as a result, heat transfer may be described by the penetration model in combination with an empirical factor, f. This term is based on the liquid physical properties and gives a measure of the intensity of cross sectional mixing within the liquid, i.e.\documentclass{article}\pagestyle{empty}\begin{document}$$ h = 8.74\left( {c_p \cdot \rho \cdot k \cdot N} \right)^{1/2} \cdot \frac{1}{f} $$\end{document}where f , is defined as\documentclass{article}\pagestyle{empty}\begin{document}$$ f = \frac{{Pr}}{{500}} + 3.50 $$\end{document}