US PATENT SUBCLASS 165 / DIG 490
.~.~ Noncircular tube cross section (oval, triangular, etc.)

Current as of: June, 1999
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165 /   HD   HEAT EXCHANGE

DIG 454  DD  HAVING SIDE-BY-SIDE CONDUITS STRUCTURE OR CONDUIT SECTION {16}
DIG 471  DD  .~ Plural parallel conduits joined by manifold {15}
DIG 490.~.~ Noncircular tube cross section (oval, triangular, etc.)