| 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 524 | DD | .~.~ Longitudinally extending {2} |
| DIG 525 | | .~.~.~ Helical {1} |
| DIG 526 | DD | .~.~.~.~> Spine or loop fins |