Page 468 - Bird R.B. Transport phenomena

448 Chapter 14 Interphase Transport in Nonisothermal Systems

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Fig. 14.7-2. Correlation of heat transfer data for film condensa-
tion of pure vapors on vertical surfaces. [H. Grober, S. Erk, and
U. Grigull, Die Grundgesetze der Warmeubertragung, 3rd edition,
Springer-Verlag, Berlin (1955), p. 296.]

Equations 14.7-4 to 7 are summarized in Fig. 14.7-2, for convenience of making calcula-
tions and to show the extent of agreement with the experimental data. Somewhat better
agreement could have been obtained by using a family of lines in the turbulent range to
represent the effect of Prandtl number. However, in view of the scattering of the data, a
single line is adequate.
Turbulent condensate flow is very difficult to obtain on horizontal tubes, unless the
tube diameters are very large or high temperature differences are encountered. Equa-
tions 14.7-2 and 3 are believed to be satisfactory up to the estimated transition Reynolds
number, Re = W /LJJL, of about 1000, where w T is the total condensate flow leaving a given
T
tube, including the condensate from the tubes above. 7
The inverse process of vaporization of a pure fluid is considerably more complicated
than condensation. We do not attempt to discuss heat transfer to boiling liquids here, but
refer the reader to some reviews. 28

7
W. H. Me Adams, Heat Transmission, 3rd edition, McGraw-Hill, New York (1954), pp. 338-339.
H. D. Baehr and К Stephan, Heat and Mass Transfer, Springer, Berlin (1998), Chapter 4.
8