| 165 / | HD | HEAT EXCHANGE |
| DIG 510 | DD | HAVING HEAT EXCHANGE SURFACE TREATMENT, ADJUNCT OR ENHANCEMENT {7} |
| DIG 518 | | .~ Conduit with discrete fin structure {5} |
| DIG 519 | DD | .~.~> porous or mesh |
| DIG 520 | DD | .~.~> Internal and external {1} |
| DIG 522 | DD | .~.~> Transverse fins spaced along conduit {1} |
| DIG 524 | DD | .~.~> Longitudinally extending {2} |
| DIG 528 | DD | .~.~> Fin and conduit of diverse materials |