US PATENT SUBCLASS 165 / DIG 520
.~.~ Internal and external


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

DIG 510  DD  HAVING HEAT EXCHANGE SURFACE TREATMENT, ADJUNCT OR ENHANCEMENT {7}
DIG 518  DD  .~ Conduit with discrete fin structure {5}
DIG 520.~.~ Internal and external {1}
DIG 521  DD  .~.~.~> Pin fins penetrating conduit wall