ISSN Online: 2377-424X
ISBN Print: 0-89116-299-2
International Heat Transfer Conference 7
INVESTIGATION OF SURFACE TENSION AND GRAVITY EFFECTS IN FILM CONDENSATION
Abstrakt
Horizontal integral-fin tubes are widely used
for condensation of refrigerants and organic
fluids. Beatty and Katz developed a gravity
drained model to predict the condensation
performance of such tubing. Our work evaluated a
"spine-fin" condensing surface, for which the
gravity drained model predicted a substantial
improvement over conventional integral-fin tubing.
The spine-fin surface geometry was machined on the
surface of a 51 mm diameter block and tested with
R-12. Surprisingly, its performance was 40% below
the predicted value. A vertical, longitudinal-fin
surface was tested and its performance was 300%
higher than predicted by the gravity drained
model. Due to these discrepancies, the scope of
the work was redirected to explain the unexpected
test results. An analytical model, based on
surface tension drainage, was formulated and
applied to the test data on the longitudinal
finned surface. This model predicted the
performance within 10%. We therefore conclude
that a gravity drained model is not appropriate
for enhanced surfaces of the integral or spine-fin
varieties.