Last Updated: 11/8/07
Extended
Surface Heat Transfer
(Fins, Heat Sinks, etc.)
Air-Cooled Franklin Engine
The cooling fins on this 1910
4-cylinder, air-cooled Franklin automobile engine
run longitudinally along the cylinders, not radially as in more modern air-cooled cylinder designs. Perhaps the
Air-Cooled Radial Aircraft Engine
The Curtiss-Wright R-3350 Turbo-Compound Engine had 5850
ft2 (543 m2) of fin surface area to help get rid of waste
heat! The silver-colored device at
the left is one of the three Power Recovery Turbines (PRT). The exhaust streams from six
cylinders were directed to each of the three turbines, which extracted
additional energy. Jim Buckel took
this photo
at the Sun & Fun Museum in Lakeland,
Air-Cooled Rotary Aircraft Engine
The
fins on the two 80 hp Le Rhone 9C rotary
engines powering this French Caudron G.4
World War I light bomber and reconnaissance aircraft are much less dramatic
than those on the R-3350 above.
They didn’t need to be.
In a rotary engine (as opposed to a radial), the crankshaft is
stationary and the rest of the engine rotates at the same speed as the
propeller! With such high air
velocities and resulting convection coefficients, long fins were not needed to
dissipate the heat.
Air-Cooled
Motorcycle Engine
If you would like to include radiative as well as
convective heat transfer in your analysis of the extended surface heat transfer
from this 1.45 liter air-cooled engine, note that the fin sides are a black,
matte finish, while the fin tips are highly polished and reflective! Looks great!
Bristle-Fin Surface on Condenser Tubes
Bristle fins applied to the outside surface of these
condenser tubes greatly increase the surface area exposed to ambient air.
Extended Surface Heat Transfer in Computers
Pentium 3 processor and attached heat sink
Pentium 4 processor (under the aluminum heat sink) with (green) cooling air shroud in place
Pentium 4 with
cooling shroud raised to show heat sink and fan drawing air through it.
The Trans-Alaska Pipeline Passive Cooling System
Extended
surface heat transfer devices (cooling fins) are
very prominent at the condenser end of the heat pipes that are part of the
vertical support members along the Trans-Alaska
Pipeline. Some 380 miles of
pipeline in the north are insulated and
buried, a few miles with active refrigeration, most without. Further south, where the heat generated
overcoming fluid friction in the pipeline could cause thawing of the permafrost
and possible structural damage to the pipeline, the pipeline is elevated on vertical support
members. There are two heat
pipes for each vertical support member. The heat pipes (actually they are
Perkins tubes, a type of thermosyphon, because they use gravity rather than
capillary action in a wick for the return flow of the condensate to the
evaporator end) are designed so that during the winter they remove as much heat
as possible from the area around the base of the VSM’s. During the summer, the working
fluid (anhydrous ammonia) sits idle at the bottom of the tube. Essentially the heat pipe acts as
a thermal “diode” actively promoting heat transfer upward in the
winter and inhibiting downward heat transfer in the summer. The idea is to chill the permafrost so
thoroughly during the winter that it will remain solid through the following
summer. The winter and summer
operation of the heat pipes is shown here in schematic
form. More technical details
about the TAP may be found at the Alyeska website and
more about heat pipes may be found in An Introduction to Heat Pipes: Modeling,
Testing and Applications, by G.P. Peterson, Wiley (1994).
NOTE: Links to Web Sites
external to the
The stegosaurus graphic above
is from: Farlow, J.O., Thompson, C.V., and Rosner, D.E., “Plates of the
Dinosaur Stegosaurus: Forced Convection Heat Loss Fins?” Science, 192, No. 4244, pp. 1123-25,
June 1976.
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