| 165 / | HD | HEAT EXCHANGE |
| DIG 327 | DD | THERMOSYPHONIC HAVING VERTICAL AIR DRAFT PASSAGE {3} |
| DIG 337 | DD | .~ Heating or cooling means entirely surrounded by air draft passage forming casing {3} |
| DIG 338 | | .~.~ Nested or concentric members define annular air draft passage and heating or cooling conduit {1} |
| DIG 339 | DD | .~.~.~> With baffle |