Appeal No. 1999-0404 Page 9
Application No. 08/580,256
Notch axis a is inclined at angle 2 from ribs 53. Tube 10
N
has an internal diameter D as measured from
2
the internal surface of the tube between ribs.
Figure 3 of Chiang is an isometric view of a portion of
wall 51 of heat transfer tube 50 depicting details of surface
enhancement 52. Extending outward from wall 51 are a
plurality of helical ribs 53. At intervals along the ribs are
a series of notches 54. The notches 54 are formed in ribs 53
by a rolling process. The material displaced as the notches
are formed is left as a projection 55 that projects outward
from each side of a given rib 53 around each notch 54 in that
rib. The projections have a salutary effect on the heat
transfer performance of the tube, as they both increase the
surface area of the tube exposed to the fluid flowing through
the tube and also promote turbulence in the fluid flow near
the tube inner surface. Figure 4 is a plan view of a portion
of wall 51 of tube 50 showing ribs 53 disposed on the wall at
rib spacing S . Notches 54 are impressed into the ribs at
r
notch interval S . The angle of incidence between the notches
n
and the ribs is angle 2. Figure 5 is a section view of wall
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