Appeal No. 1999-0404 Page 10
Application No. 08/580,256
51 showing that ribs 53 have height H and have rib spacing S .r r
Figure 6 is a section view of wall 51 showing that notches 54
have an angle between opposite notch faces 56 of ( and are
impressed into ribs 54 to a depth of D .
n
Chiang teaches (column 3, line 52, to column 4, line 24)
that for optimum heat transfer consistent with minimum fluid
flow resistance, a tube embodying the present invention and
having a nominal outside diameter of 20 mm (3/4 inch) or less
should have an internal enhancement with features as described
above and having the following parameters:
a. the rib helix angle should be between five and 45
degrees, or
5°#"#45°;
b. the ratio of the rib height to the inner diameter of
the tube should be between 0.015 and 0.03, or
0.015#H /D #0.03;
r 2
c. the number of ribs per unit length of tube inner
diameter should be between 10 and 24 per centimeter (26
and 60 per inch);
d. the angle of incidence between the notch axis and the
[helical ribs] longitudinal axis of the tube should be
less than 15 degrees, or
2<15°
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